Drilling liner cementing method, device and equipment and storage medium

Abstract

The embodiment of the invention provides a drilling liner cementing method, device and equipment and a storage medium. Determining the depths of a leakage risk layer and an overflow risk layer according to the pore pressure equivalent densities and the leakage pressure equivalent densities of different depths; according to the corresponding depths, pore pressure equivalent densities and leakage pressure equivalent densities of the leakage risk layer and the overflow risk layer, an injection scheme of each well cementation fluid is determined; and according to the density and the displacement of each well cementation fluid and the height of the liquid column after the well cementation fluid enters the annulus, the pressure equivalent density of different underground depths after the well cementation fluid enters the annulus is determined. And if the pressure equivalent densities of the different underground depths do not meet the preset conditions, the injection scheme of the well cementation fluid is adjusted until the preset conditions are met, and the well cementation fluid is controlled to be injected into the annulus. According to the method, by considering the pressure density of the leakage risk layer and the overflow risk under the safety density window, the problem of underground leakage or underground overflow in the well cementation process caused by underground complex pressure conditions is solved.

Description

Technical Field

[0001] This application relates to the technical field of oil and gas exploration and development, and particularly to a liner cementing method, device, equipment, and storage medium. Background Art

[0002] As the exploration of oil resources gradually penetrates into deep formations, oil well drilling has entered the stage of deep wells and ultra-deep wells. In this process, due to the complex downhole pressure environment, drilling and completion operations face complex accidents such as lost circulation, well kick, and blowout.

[0003] Existing solutions regulate downhole pressure by considering the balance relationship between bottomhole pressure and formation pressure, and adopting various technical means such as reducing the density of drilling fluid, applying backpressure at the wellhead, and using liner cementing.

[0004] However, due to the complex formation pressure conditions in deep wells and ultra-deep wells, existing solutions cannot cope with the pressure differences in formations at different depths, resulting in problems such as lost circulation or well kick still existing. Summary of the Invention

[0005] Embodiments of this application provide a liner cementing method, device, equipment, and storage medium to solve the technical problem that lost circulation or downhole overflow still exists during cementing due to complex downhole pressure conditions.

[0006] In a first aspect, embodiments of this application provide a liner cementing method, including:

[0007] Obtain the equivalent density of pore pressure and the equivalent density of lost circulation pressure at different depths downhole, and determine the depth of the lost circulation risk layer and the depth of the overflow risk layer according to the equivalent density of pore pressure and the equivalent density of lost circulation pressure at different depths downhole;

[0008] Determine an injection plan for the cementing fluid according to the depth of the lost circulation risk layer, the depth of the overflow risk layer, the equivalent density of pore pressure at the overflow risk layer, the equivalent density of lost circulation pressure at the lost circulation risk layer, and the equivalent density of lost circulation pressure at the overflow risk layer. The injection plan for the cementing fluid includes: the density, volume, and displacement of each cementing fluid;

[0009] Determine the equivalent density of pressure at different depths downhole after each cementing fluid enters the annulus according to the density, displacement of each cementing fluid, and the liquid column height after each cementing fluid enters the annulus;

[0010] In the case where the equivalent density of pressure at different depths downhole does not meet the preset conditions, adjust the injection plan for the cementing fluid until the equivalent density of pressure at different depths downhole meets the preset conditions, and control the injection of each cementing fluid into the annulus according to the injection plan for the cementing fluid.

[0011] Optionally, the cementing fluid includes a flushing fluid, a spacer fluid, a leading cement slurry, a trailing cement slurry, and a displacement fluid;

[0012] Determining an injection plan for the cementing fluid according to the depth of the lost circulation risk formation, the depth of the overflow risk formation, the equivalent density of the pore pressure at the overflow risk formation, the equivalent density of the lost circulation pressure at the lost circulation risk formation, and the equivalent density of the lost circulation pressure at the overflow risk formation, includes:

[0013] Determining the volume of the leading cement slurry and the volume of the trailing cement slurry according to the casing shoe depth, the liner depth, the wellbore diameter, the liner diameter, the depth of the lost circulation risk formation, and the depth of the overflow risk formation;

[0014] Determining the density of the leading cement slurry and the density of the trailing cement slurry according to the equivalent density of the pore pressure at the overflow risk formation, the equivalent density of the lost circulation pressure at the lost circulation risk formation, and the equivalent density of the lost circulation pressure at the overflow risk formation;

[0015] Determining the density of the displacement fluid as the density of the drilling fluid, and determining the density of the flushing fluid and the density of the spacer fluid according to the density of the leading cement slurry and the density of the drilling fluid;

[0016] Determining the displacement of each cementing fluid according to the density of each cementing fluid, the wellbore diameter, and the liner diameter;

[0017] Determining the volume of the flushing fluid, the volume of the spacer fluid, and the volume of the displacement fluid according to the displacement of the flushing fluid, the displacement of the spacer fluid, and a preset time duration.

[0018] Optionally, determining the volume of the leading cement slurry and the volume of the trailing cement slurry according to the casing shoe depth, the liner depth, the wellbore diameter, the liner diameter, the depth of the lost circulation risk formation, and the depth of the overflow risk formation, includes:

[0019] Determining the liquid column height of the leading cement slurry and the liquid column height of the trailing cement slurry according to the casing shoe depth, the liner depth, the depth of the lost circulation risk formation, and the depth of the overflow risk formation;

[0020] Determining the volume of the leading cement slurry according to the wellbore diameter, the liner diameter, and the liquid column height of the leading cement slurry;

[0021] Determining the volume of the trailing cement slurry according to the wellbore diameter, the liner diameter, and the liquid column height of the trailing cement slurry.

[0022] Optionally, determining the liquid column height of the leading cement slurry and the liquid column height of the trailing cement slurry according to the casing shoe depth, the liner depth, the depth of the lost circulation risk zone, and the depth of the kick risk zone includes:

[0023] Subtracting the casing shoe depth from the depth of the lost circulation risk zone to obtain a first liquid column height;

[0024] Subtracting the casing shoe depth from the depth of the kick risk zone to obtain a second liquid column height;

[0025] Determining the liquid column height of the leading cement slurry according to the rule that the liquid column height of the leading cement slurry is greater than the first liquid column height and less than the second liquid column height;

[0026] Subtracting the liquid column height of the leading cement slurry from the difference between the liner depth and the casing shoe depth to obtain the liquid column height of the trailing cement slurry.

[0027] Optionally, determining the density of the leading cement slurry and the density of the trailing cement slurry according to the equivalent density of the pore pressure at the kick risk zone, the equivalent density of the lost circulation pressure at the lost circulation risk zone, and the equivalent density of the lost circulation pressure at the kick risk zone includes:

[0028] Determining the density of the leading cement slurry and the density of the trailing cement slurry according to the following rules:

[0029] The density of the leading cement slurry is greater than the equivalent density of the pore pressure at the kick risk zone, and the density of the leading cement slurry is less than the equivalent density of the lost circulation pressure at the lost circulation risk zone; the density of the trailing cement slurry is greater than the equivalent density of the pore pressure at the kick risk zone, and the density of the trailing cement slurry is less than the equivalent density of the lost circulation pressure at the kick risk zone, to determine the density of the leading cement slurry and the density of the trailing cement slurry.

[0030] Optionally, determining the displacement of each cementing fluid according to the density of each cementing fluid, the wellbore diameter, and the liner diameter includes:

[0031] Determining the displacement of the displacement fluid according to the density of the displacement fluid, the wellbore diameter, and the liner diameter;

[0032] Determining the displacement of the spacer fluid according to the density of the spacer fluid, the wellbore diameter, and the liner diameter;

[0033] Determining the displacement of the leading cement slurry according to the density of the leading cement slurry, the wellbore diameter, and the liner diameter;

[0034] Determine the displacement of the cement slurry tail slurry according to the density of the cement slurry tail slurry, the wellbore diameter, and the liner diameter;

[0035] Determine the displacement of the displacement fluid as the displacement of the cement slurry tail slurry.

[0036] Optionally, the determining the volume of the flushing fluid, the volume of the spacer fluid, and the volume of the displacement fluid according to the displacement of the flushing fluid, the displacement of the spacer fluid, and a preset duration includes:

[0037] Determine the volume of the flushing fluid according to the displacement of the flushing fluid and the preset duration;

[0038] Determine the volume of the spacer fluid according to the displacement of the spacer fluid and the preset duration;

[0039] Determine the sum of the drill pipe volume and the liner volume as the volume of the displacement fluid.

[0040] Optionally, the determining the equivalent density of the pressure at different depths in the wellbore after each cementing fluid enters the annulus according to the density, displacement, and the liquid column height after each cementing fluid enters the annulus includes:

[0041] Determine the static liquid column pressure in the annulus from the wellhead to the depth where each cementing fluid is located according to the liquid column height after each cementing fluid enters the annulus and the density of each cementing fluid;

[0042] Determine the frictional pressure drop in the annulus from the wellhead to the depth where each cementing fluid is located according to the displacement of each cementing fluid, the wellbore diameter, the liner diameter, and the liquid column height after each cementing fluid enters the annulus;

[0043] Determine the sum of the static liquid column pressure and the frictional pressure drop in the annulus from the wellhead to the depth where each cementing fluid is located as the annulus pressure from the wellhead to the depth where each cementing fluid is located;

[0044] Determine the equivalent density of the pressure at different depths in the wellbore after each cementing fluid enters the annulus according to the density of each cementing fluid, the liquid column height after each cementing fluid enters the annulus, and the annulus pressure from the wellhead to the depth where each cementing fluid is located.

[0045] In a second aspect, an embodiment of the present application provides a liner cementing device, including:

[0046] An acquisition module, configured to acquire the equivalent density of the pore pressure and the equivalent density of the lost circulation pressure at different depths in the wellbore, and determine the depth of the lost circulation risk layer and the depth of the overflow risk layer according to the equivalent density of the pore pressure and the equivalent density of the lost circulation pressure at different depths in the wellbore;

[0047] A determination module, configured to determine an injection plan for the cementing fluid according to the depth of the lost circulation risk layer, the depth of the overflow risk layer, the equivalent density of pore pressure at the overflow risk layer, the equivalent density of lost circulation pressure at the lost circulation risk layer, and the equivalent density of lost circulation pressure at the overflow risk layer. The injection plan for the cementing fluid includes: the density, volume, and displacement of each cementing fluid;

[0048] The determination module is further configured to determine the equivalent density of pressure at different depths in the wellbore after each cementing fluid enters the annulus according to the density and displacement of each cementing fluid and the liquid column height after each cementing fluid enters the annulus;

[0049] An adjustment module, configured to adjust the injection plan for the cementing fluid when the equivalent density of pressure at different depths in the wellbore does not meet the preset conditions until the equivalent density of pressure at different depths in the wellbore meets the preset conditions;

[0050] A control module, configured to control the injection of each cementing fluid into the annulus according to the injection plan for the cementing fluid.

[0051] Optionally, the determination module is further configured to determine the volume of the leading slurry of the cement slurry and the volume of the tail slurry of the cement slurry according to the casing shoe depth, liner depth, wellbore diameter, liner diameter, depth of the lost circulation risk layer, and depth of the overflow risk layer;

[0052] The determination module is further configured to determine the density of the leading slurry of the cement slurry and the density of the tail slurry of the cement slurry according to the equivalent density of pore pressure at the overflow risk layer, the equivalent density of lost circulation pressure at the lost circulation risk layer, and the equivalent density of lost circulation pressure at the overflow risk layer;

[0053] The determination module is further configured to determine the density of the displacement fluid as the density of the drilling fluid, and determine the density of the flushing fluid and the density of the spacer fluid according to the density of the leading slurry of the cement slurry and the density of the drilling fluid;

[0054] The determination module is further configured to determine the displacement of each cementing fluid according to the density of each cementing fluid, the wellbore diameter, and the liner diameter;

[0055] The determination module is further configured to determine the volume of the flushing fluid, the volume of the spacer fluid, and the volume of the displacement fluid according to the displacement of the flushing fluid, the displacement of the spacer fluid, and a preset duration.

[0056] Optionally, the determination module is further configured to determine the liquid column height of the leading slurry of the cement slurry and the liquid column height of the tail slurry of the cement slurry according to the casing shoe depth, the liner depth, the depth of the lost circulation risk layer, and the depth of the overflow risk layer;

[0057] The determining module is further configured to determine the volume of the leading slurry of cement slurry according to the wellbore diameter, the liner diameter, and the liquid column height of the leading slurry of cement slurry;

[0058] The determining module is specifically configured to determine the volume of the trailing slurry of cement slurry according to the wellbore diameter, the liner diameter, and the liquid column height of the trailing slurry of cement slurry.

[0059] Optionally, the determining module is further configured to subtract the depth of the casing shoe from the depth of the lost circulation risk layer to obtain a first liquid column height;

[0060] The determining module is further configured to subtract the depth of the casing shoe from the depth of the overflow risk layer to obtain a second liquid column height;

[0061] The determining module is specifically configured to determine the liquid column height of the leading slurry of cement slurry according to the rule that the liquid column height of the leading slurry of cement slurry is greater than the first liquid column height and less than the second liquid column height;

[0062] The determining module is specifically configured to subtract the depth of the casing shoe from the liner depth, and then subtract the liquid column height of the leading slurry of cement slurry to obtain the liquid column height of the trailing slurry of cement slurry.

[0063] Optionally, the determining module is specifically configured to determine the density of the leading slurry of cement slurry and the density of the trailing slurry of cement slurry according to the following rules:

[0064] The density of the leading slurry of cement slurry is greater than the equivalent density of the pore pressure at the overflow risk layer, and the density of the leading slurry of cement slurry is less than the equivalent density of the lost circulation pressure at the lost circulation pressure risk layer; the density of the trailing slurry of cement slurry is greater than the equivalent density of the pore pressure at the overflow risk layer, and the density of the trailing slurry of cement slurry is less than the equivalent density of the lost circulation pressure at the overflow risk layer, to determine the density of the leading slurry of cement slurry and the density of the trailing slurry of cement slurry.

[0065] Optionally, the determining module is specifically configured to determine the displacement of the flushing fluid according to the density of the flushing fluid, the wellbore diameter, and the liner diameter;

[0066] The determining module is specifically configured to determine the displacement of the spacer fluid according to the density of the spacer fluid, the wellbore diameter, and the liner diameter;

[0067] The determining module is specifically configured to determine the displacement of the leading slurry of cement slurry according to the density of the leading slurry of cement slurry, the wellbore diameter, and the liner diameter;

[0068] The determining module is specifically configured to determine the displacement of the trailing slurry of cement slurry according to the density of the trailing slurry of cement slurry, the wellbore diameter, and the liner diameter;

[0069] The determining module is specifically configured to determine the displacement of the cement slurry tail slurry as the displacement of the displacement fluid.

[0070] Optionally, the determining module is specifically configured to determine the volume of the flushing fluid according to the displacement of the flushing fluid and a preset duration.

[0071] The determining module is specifically configured to determine the volume of the spacer fluid according to the displacement of the spacer fluid and a preset duration.

[0072] The determining module is specifically configured to determine the sum of the drill pipe volume and the liner volume as the volume of the displacement fluid.

[0073] Optionally, the determining module is further configured to determine the annular static hydrostatic pressure from the wellhead to the depth where each cementing fluid is located according to the liquid column height of each cementing fluid after entering the annulus and the density of each cementing fluid.

[0074] The determining module is further configured to determine the annular friction pressure drop from the wellhead to the depth where each cementing fluid is located according to the displacement of each cementing fluid, the wellbore diameter, the liner diameter, and the liquid column height of each cementing fluid after entering the annulus.

[0075] The determining module is further configured to determine the sum of the annular static hydrostatic pressure and the annular friction pressure drop from the wellhead to the depth where each cementing fluid is located as the annular pressure from the wellhead to the depth where each cementing fluid is located.

[0076] The determining module is specifically configured to determine the equivalent density of the pressure at different depths in the wellbore after each cementing fluid enters the annulus according to the density of each cementing fluid, the liquid column height of each cementing fluid after entering the annulus, and the annular pressure from the wellhead to the depth where each cementing fluid is located.

[0077] In a third aspect, an embodiment of the present application provides a liner cementing device, including: a memory, a processor;

[0078] The memory stores computer-executable instructions;

[0079] The processor executes the computer-executable instructions stored in the memory, so that the processor executes the above first aspect and / or various possible implementation manners of the first aspect.

[0080] In a fourth aspect, an embodiment of the present application provides a computer-readable storage medium, in which computer-executable instructions are stored, and when the computer-executable instructions are executed by a processor, they are used to implement the above first aspect and / or various possible implementation manners of the first aspect.

[0081] In a fifth aspect, an embodiment of the present application provides a computer program product, including a computer program which, when executed by a processor, implements the above first aspect and / or various possible implementation manners of the first aspect.

[0082] The tail pipe cementing method, device, equipment and storage medium provided by the embodiments of the present application determine the depths of the lost circulation risk layer and the overflow risk layer according to the equivalent density of pore pressure and the equivalent density of lost circulation pressure at different depths; determine the injection scheme of each cementing fluid according to the depths, the equivalent density of pore pressure and the equivalent density of lost circulation pressure corresponding to the lost circulation risk layer and the overflow risk layer; determine the equivalent density of pressure at different depths in the wellbore after each cementing fluid enters the annulus according to the density, displacement of each cementing fluid and the liquid column height after entering the annulus. If the equivalent density of pressure at different depths in the wellbore does not meet the preset conditions, adjust the injection scheme of the cementing fluid until the preset conditions are met, and control each cementing fluid to be injected into the annulus. By considering the pressure density of the lost circulation risk layer and the overflow risk under the safe density window, this method solves the problems of lost circulation in the wellbore or wellbore overflow during the cementing process caused by complex downhole pressure conditions. BRIEF DESCRIPTION OF THE DRAWINGS

[0083] The accompanying drawings herein are incorporated into the specification and constitute a part of this specification, showing embodiments consistent with the present application and used together with the specification to explain the principles of the present application.

[0084] Figure 1 It is a schematic diagram of fluid injection for the tail pipe cementing method provided by the present application;

[0085] Figure 2 It is a schematic flow chart of the tail pipe cementing method provided by the present application Figure 1 ;

[0086] Figure 3 It is a schematic flow chart of the tail pipe cementing method provided by the present application Figure 2 ;

[0087] Figure 4 It is a schematic structural diagram of the tail pipe cementing device provided by the present application;

[0088] Figure 5 It is a schematic structural diagram of the tail pipe cementing equipment provided by the present application.

[0089] Through the above accompanying drawings, specific embodiments of the present application have been shown, and there will be more detailed descriptions hereinafter. These drawings and text descriptions are not intended to limit the scope of the concept of the present application in any way, but to illustrate the concept of the present application to those skilled in the art by referring to specific embodiments. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0090] Exemplary embodiments will be described in detail herein, and examples thereof are shown in the accompanying drawings. When the following description refers to the accompanying drawings, unless otherwise indicated, the same numbers in different drawings represent the same or similar elements. The embodiments described in the following exemplary embodiments do not represent all embodiments consistent with the present application. On the contrary, they are merely examples of devices and methods consistent with some aspects of the present application as detailed in the appended claims.

[0091] As the exploration of oil resources gradually penetrates into deep formations, oil well drilling has entered the stage of deep wells and ultra-deep wells. In this process, due to the complex downhole pressure environment, drilling and completion operations face complex accidents such as lost circulation, well kick, and blowout.

[0092] Existing solutions regulate downhole pressure by considering the balance relationship between bottomhole pressure and formation pressure and adopting various technical means such as reducing the density of drilling fluid, applying backpressure at the wellhead, and using liner cementing.

[0093] However, due to the complex formation pressure conditions in deep wells and ultra-deep wells, existing solutions cannot effectively cope with the pressure differences in formations at different depths, resulting in problems such as formation fracturing or well kick still existing.

[0094] In view of the above problems, the liner cementing method provided by the present application Figure 1 is a schematic diagram of fluid injection for the liner cementing method provided by the present application. As Figure 1 shown. Casing 1 and casing 2 are surface casing and technical casing respectively. First, during the initial stage of drilling, the cementing operation of casing 1 is carried out to seal the annulus between casing 1 and the wellbore with cement slurry to ensure the stability and safety of the wellbore. As the second drilling operation progresses, the formation conditions change, and the cementing operation of casing 2 is carried out.

[0095] In the second-opening cementing stage, casing 2 is run into the well through casing 1 for the cementing operation. After the second-opening cementing is completed, as the drilling operation continues to deepen, when the drilling reaches the target formation, due to the influence of complex formation pressure conditions, a liner needs to be run in for cementing.

[0096] During the liner cementing process, various cementing fluids will be injected in sequence according to the injection plan. The cementing process is as follows: First, the displacement fluid is injected in a turbulent flow injection manner to remove the cuttings in the annulus and the mud cake on the wellbore wall, creating good conditions for the injection of cement slurry. Immediately afterwards, the spacer fluid is injected to form a clear interface between the cement slurry and the displacement fluid to prevent the two from mixing and affecting the curing effect of the cement slurry. Then, it is switched to the plug flow injection and displacement mode, and the leading cement slurry and the trailing cement slurry are injected in sequence to fill the annulus and form a solid cementing structure. Finally, after the trailing cement slurry is injected, the displacement fluid is used to push the trailing cement slurry to ensure that the cement slurry completely enters the annulus from the liner, completing the cementing operation for the ultra-deep formation.

[0097] According to the equivalent density of pore pressure and the equivalent density of lost circulation pressure at different depths, this method determines the depths of the lost circulation risk layer and the overflow risk layer; according to the depths, equivalent density of pore pressure, and equivalent density of lost circulation pressure corresponding to the lost circulation risk layer and the overflow risk layer, it determines the injection plan for each cementing fluid; according to the density, displacement, and liquid column height in the annulus after each cementing fluid enters the annulus, it determines the equivalent density of pressure at different depths in the wellbore after each cementing fluid enters the annulus. If the equivalent density of pressure at different depths in the wellbore does not meet the preset conditions, adjust the injection plan of the cementing fluid until the preset conditions are met, and control the injection of each cementing fluid into the annulus. By considering the pressure density of the lost circulation risk layer and the overflow risk within the safe density window, this method solves the problems of lost circulation or downhole overflow during cementing caused by complex downhole pressure conditions.

[0098] The following uses specific embodiments to elaborate in detail on the technical solution of this application and how the technical solution of this application solves the above technical problems. These several specific embodiments below can be combined with each other, and for the same or similar concepts or processes, they may not be repeated in some embodiments. The embodiments of this application will be described below in conjunction with the accompanying drawings.

[0099] Figure 2 Flow schematic of the liner cementing method provided by this application Figure 1 as Figure 2 shown, this method includes:

[0100] S101. Obtain the equivalent density of pore pressure and the equivalent density of lost circulation pressure at different depths in the wellbore, and determine the depth of the lost circulation risk layer and the depth of the overflow risk layer according to the equivalent density of pore pressure and the equivalent density of lost circulation pressure at different depths in the wellbore.

[0101] Among them, the equivalent density of pore pressure refers to the static pressure generated by the fluid (such as oil, gas, water) in the formation pore space on the wellbore or formation rock. The equivalent density of pore pressure is the conversion of pore pressure into the fluid density at the corresponding depth. For example, the equivalent density of pore pressure of Well No. 001 in the 3000-meter formation is 1.0 g / cm 3 , indicating that in the formation at a depth of 3000 meters, the static pressure exerted by the fluid in the pores (such as oil, gas, or water) is 29.43 MPa.

[0102] The equivalent density of lost circulation pressure refers to the maximum pressure value that the formation rock can withstand without being fractured. The equivalent density of lost circulation pressure is the conversion of the lost circulation pressure into the fluid density at the corresponding well depth. For example, the equivalent density of lost circulation pressure of Well No. 001 in the 3000-meter formation is 1.8 g / cm 3 , indicating that in the formation at a depth of 3000 meters, if the density of the well fluid reaches 1.8 g / cm 3can reach the lost circulation pressure limit of the formation.

[0103] The lost circulation risk zone refers to the area where, within a certain depth range, when the wellbore fluid pressure exceeds the bearing capacity of the rock formation of that layer, the fluid in the wellbore may penetrate or leak into the formation. When the wellbore fluid pressure is greater than the lost circulation pressure of that layer, the well fluid may cause formation fractures or ruptures, resulting in the leakage of well fluid into the underground rock formation, thus generating a lost circulation risk.

[0104] The kick risk zone refers to the area where, within a certain depth range, the pressure of the wellbore fluid column is less than the safe bearing capacity of the formation pore pressure, resulting in the entry of formation fluid into the wellbore.

[0105] The depth of the lost circulation risk zone refers to the depth range of the formation where lost circulation may occur underground. For example, the depth of the lost circulation risk zone is 2000 - 2500 meters, indicating that lost circulation risk may occur in the formation at a depth of 2000 - 2500 meters.

[0106] The depth of the kick risk zone refers to the depth range of the formation where kick of the well fluid may occur in the well. For example, the depth of the kick risk zone is 2800 - 3200 meters, indicating that at a depth of 2800 - 3200 meters in the formation, the pressure in the well may cause a kick.

[0107] The purpose of this step of detecting the equivalent density of pore pressure and the equivalent density of lost circulation pressure at different depths in the wellbore is to evaluate the pressure condition of the underground rock formation and ensure the safety of the drilling operation. And the purpose of this step of determining the depth of the lost circulation risk zone and the depth of the kick risk zone based on the equivalent density of pore pressure and the equivalent density of lost circulation pressure at different depths in the wellbore is to clarify within which depth ranges in the wellbore the wellbore fluid may exceed the safety range, resulting in the occurrence of lost circulation or kick of the wellbore fluid.

[0108] S102. Determine the injection plan of the cementing fluid according to the depth of the lost circulation risk zone, the depth of the kick risk zone, the equivalent density of pore pressure at the kick risk zone, the equivalent density of lost circulation pressure at the lost circulation risk zone, and the equivalent density of lost circulation pressure at the kick risk zone. The injection plan of the cementing fluid includes: the density, volume, and displacement of each cementing fluid.

[0109] Among them, the equivalent density of pore pressure at the kick risk zone refers to converting the formation pore pressure (i.e., the formation fluid pressure) of the kick risk zone into an equivalent fluid density. It represents the fluid density required to balance the pore pressure of that layer. If the density of the cementing fluid is less than the equivalent density of pore pressure at the kick risk zone, the formation fluid may invade the wellbore and cause a kick. For example, the equivalent density of pore pressure at the kick risk zone is 1.20 g / cm 3 , indicating that the density of the cementing fluid needs to be not less than 1.20 g / cm 3 , to effectively seal off the formation fluid.

[0110] The equivalent density of the leakage pressure at the leakage risk zone refers to converting the formation fracture pressure or leakage critical pressure of the leakage risk zone into an equivalent fluid density. It represents the upper limit of the maximum fluid density that the formation can withstand. If the density of the cementing fluid is greater than the equivalent density of the leakage pressure at the leakage risk zone, it may cause the wellbore fluid to leak into the formation (such as fracturing the formation or entering the fractures). For example, if the equivalent density of the leakage pressure at the leakage risk zone is 1.80 g / cm 3 , then the density of the cementing fluid needs to be no greater than 1.80 g / cm 3 to avoid inducing leakage.

[0111] The equivalent density of the leakage pressure at the overflow risk zone refers to the equivalent fluid density corresponding to the leakage critical pressure that the formation can withstand simultaneously in the overflow risk zone (usually characterized by high pore pressure). The equivalent density of the leakage pressure is used to characterize the anti-leakage ability of the overflow risk zone under high pressure, and is used to ensure that the density of the cementing fluid is both higher than the equivalent density of the pore pressure (preventing overflow) and lower than the equivalent density of the leakage pressure (preventing leakage).

[0112] Density refers to the mass per unit volume of the cementing fluid, with the unit of g / cm 3 . A reasonable density ensures that the fluid can provide sufficient pressure to prevent overflow or leakage. For example, the density of the cement slurry fluid is 180 g / cm 3 , which means that during the cementing operation, the density of the cement slurry fluid is 180 g / cm 3 .

[0113] Volume refers to the total amount of the cementing fluid injected, with the unit of cubic meters (m 3 ). For example, the volume of the cement slurry is 100 cubic meters, which means that during the cementing operation, 100 cubic meters of cement slurry need to be injected as the cementing fluid.

[0114] Displacement refers to the amount of the cementing fluid injected per unit time, with the unit of cubic meters per minute (m 3 / min). A reasonable displacement can control the injection rate and prevent excessive pressure caused by too fast fluid injection. For example, the displacement of the cement slurry is 3 cubic meters per minute, which means that during the cementing operation, 3 cubic meters of cement slurry need to be injected into the wellbore per minute through the pumping equipment.

[0115] The purpose of this step is to formulate a suitable cementing fluid injection plan to ensure that during the cementing operation in ultra-deep formations, the pressure in the well will not exceed the safe range, thereby preventing leakage or overflow.

[0116] It is understandable that during the cementing operation in ultra-deep formations, if the pressure of the injected cementing fluid is too high, it may cause the well fluid to exceed the bearing capacity of the overflow risk layer, resulting in overflow; if the pressure is too low, it may cause the well fluid to leak into the loss risk layer, thus affecting the stability of the operation.

[0117] Therefore, by determining the density, volume, and displacement of each cementing fluid, it is possible to ensure that the pressure of the well fluid during the cementing process always remains within a safe range, avoid dangerous situations such as well fluid leakage or overflow, and ensure the smooth progress of the cementing operation.

[0118] S103. Determine the equivalent density of pressure at different depths in the wellbore after each cementing fluid enters the annulus according to the density, displacement of each cementing fluid, and the liquid column height of each cementing fluid after entering the annulus.

[0119] Among them, the annulus includes: the area between the liner and the wellbore wall, and the area between the drill pipe and the upper casing.

[0120] The liquid column height of each cementing fluid after entering the annulus refers to the vertical distance occupied by each type of cementing fluid in the annulus area after being injected into the annulus area during the cementing operation. For example, when the leading slurry of cement slurry is injected into the annulus between the liner and the wellbore wall, the vertical height it occupies is called the liquid column height of the leading slurry of cement slurry; when the tail slurry of cement slurry is injected into the annulus between the liner and the wellbore wall, the vertical height it occupies is called the liquid column height of the tail slurry of cement slurry; when the flushing fluid is injected into the annulus between the drill pipe and the upper casing, the height it occupies is called the liquid column height of the flushing fluid; when the spacer fluid is injected into the annulus between the drill string and the upper casing, the height it occupies is called the liquid column height of the spacer fluid.

[0121] The equivalent density of pressure at different depths in the wellbore after each cementing fluid enters the annulus includes: the equivalent density of pressure generated by each cementing fluid at the loss risk layer, and the equivalent density of pressure generated by each cementing fluid at the overflow risk layer.

[0122] The purpose of this step is to calculate the equivalent density of pressure generated at different depth positions in the wellbore after different types of cementing fluids enter the annulus during the cementing operation.

[0123] It is understandable that first, during the cementing operation, different types of cementing fluids have different densities. The density of the cementing fluid will directly affect the pressure distribution in the annulus area. The greater the density of the fluid, the greater the gravity generated under the same volume, and thus the corresponding increase in pressure in the annulus.

[0124] Secondly, the displacement of different cementing fluids has different flow velocities and flow rates. The magnitude of the displacement determines the filling speed and filling volume of the cementing fluid in the annulus. When the displacement is large, the cementing fluid can fill the annulus faster, thus reaching a higher liquid column height in a shorter time, and further generating a greater pressure. Conversely, when the displacement is small, the filling speed and filling volume of the cementing fluid will decrease accordingly, and the generated pressure will also decrease accordingly.

[0125] Finally, the liquid column height of the cementing fluid after entering the annulus determines the pressure of the liquid column. As the liquid column height increases, the generated pressure also increases.

[0126] Therefore, when calculating the equivalent density of pressure generated by each cementing fluid at different depths underground, multiple factors such as the density, displacement, and liquid column height after entering the annulus of each cementing fluid need to be comprehensively considered.

[0127] In this step, for example, the following formula can be used to determine the liquid column height of each cementing fluid after entering the annulus.

[0128]

[0129] Among them, H C represents the liquid column height of each cementing fluid after entering the annulus; V represents the volume of each cementing fluid, with the unit of cubic meters (m 3 ); A represents the cross-sectional area of the annulus, with the unit of square inches, or cm 2 .

[0130]

[0131] Among them, A represents the cross-sectional area of the annulus, with the unit of square inches, or cm 2 ; D a represents the wellbore diameter, with the unit of inches, or mm; D c represents the liner diameter, with the unit of inches, or mm.

[0132] For example, assuming that the wellbore diameter corresponding to Well No. 001 is 216 mm and the liner diameter is 127 mm, then the annulus cross-sectional area A is 239.4 cm 2 .

[0133] S104. In the case where the equivalent density of pressure at different depths underground does not meet the preset conditions, adjust the injection plan of the cementing fluid until the equivalent density of pressure at different depths underground meets the preset conditions, and control the injection of each cementing fluid into the annulus according to the injection plan of the cementing fluid.

[0134] Among them, the preset conditions include: the equivalent density of pore pressure at the overflow risk layer is less than the equivalent density of pressure at the depth of the well after each cementing fluid enters the annulus, and the equivalent density of pressure at the depth of the loss risk layer after each cementing fluid enters the annulus is less than the equivalent density of loss pressure at the loss risk layer.

[0135] The purpose of judging whether the equivalent density of pressure at different depths in the well after each cementing fluid enters the annulus meets the preset conditions is to determine whether there is a risk of overflow when each cementing fluid passes through the overflow risk layer, or whether there is a risk of loss when the cementing fluid passes through the loss risk layer.

[0136] If the equivalent density of pressure at different depths in the well after each cementing fluid enters the annulus all meet the preset conditions, it indicates that there is no risk of overflow when each cementing fluid passes through the overflow risk layer, and there is no risk of loss when the cementing fluid passes through the loss risk layer. At this time, the injection of each cementing fluid into the annulus can be controlled according to the injection plan of each cementing fluid.

[0137] For example, assume that the equivalent density of pore pressure at the overflow risk layer is 1.5 g / cm 3 , and the equivalent density of loss pressure at the loss risk layer is 1.75 g / cm 3 . After the leading slurry of cement slurry enters the annulus, the equivalent density of pressure at the overflow risk layer is 1.62 g / cm 3 , and the equivalent density of pressure at the loss risk layer is 1.56 g / cm 3 . Then, based on the above information, it can be first determined that the equivalent density of pore pressure at the overflow risk layer, 1.5 g / cm 3 , is less than the equivalent density of annulus pressure of the leading slurry of cement slurry at the overflow risk layer, 1.62 g / cm 3 , and it is determined that the equivalent density of annulus pressure of the leading slurry of cement slurry at the loss risk layer, 1.56 g / cm 3 , is less than the equivalent density of loss pressure at the loss risk layer, 1.75 g / cm 3 . Subsequently, it is determined that the injection plan of the leading slurry of cement slurry meets the preset conditions.

[0138] If the equivalent density of pressure at different depths in the well after any one of the cementing fluids enters the annulus does not meet the preset conditions, it indicates that there is a risk of overflow when the cementing fluid passes through the overflow risk layer, or there is a risk of loss when the cementing fluid passes through the loss risk layer. At this time, the injection plan of the cementing fluid can be adjusted until the equivalent density of pressure at different depths in the well meets the preset conditions, and the injection of each cementing fluid into the annulus is controlled according to the injection plan of the cementing fluid.

[0139] For example, assume that the equivalent density of pore pressure at the overflow risk layer is 1.71 g / cm 3, the equivalent density of the leakage pressure at the leakage risk layer is 1.75 g / cm 3 . After the tail cement slurry enters the annulus, the equivalent density of the pressure at the overflow risk layer is 1.5 g / cm 3 , and the equivalent density of the pressure at the leakage risk layer is 1.64 g / cm 3 . Then, based on the above information, it can be determined that the equivalent density of the pore pressure at the overflow risk layer is 1.71 g / cm 3 is greater than the equivalent density of the pressure of the tail cement slurry at the overflow risk layer, which is 1.5 g / cm 3 , and it can be determined that the equivalent density of the pressure of the tail cement slurry at the leakage risk layer is 1.64 g / cm 3 is less than the equivalent density of the leakage pressure at the leakage risk layer, which is 1.75 g / cm 3 ; Subsequently, it is determined that the injection plan of the tail cement slurry does not meet the preset conditions.

[0140] It can be understood that in downhole operations, each cementing fluid needs to pass through different formations, including the overflow risk layer and the leakage risk layer. To ensure the safety of the operation, it is necessary to separately judge whether the equivalent density of the pressure of each cementing fluid meets the preset safety conditions when passing through the overflow risk layer and the leakage risk layer.

[0141] If a certain cementing fluid does not meet the set conditions when passing through the overflow risk layer, it means that there is a risk of overflow when the cementing fluid passes through the overflow risk layer; or if a certain cementing fluid does not meet the set conditions when passing through the leakage risk layer, it means that there is a risk of leakage when the cementing fluid passes through the leakage risk layer.

[0142] Therefore, when it is determined that the equivalent density of the pressure at different depths in the wellbore after any cementing fluid enters the annulus does not meet the preset conditions, by adjusting the injection plan of the cementing fluid, the injection volume of the cementing fluid can be reasonably controlled and the physical properties of the cementing fluid can be adjusted to ensure the safe progress of the cementing work.

[0143] Optionally, the present application provides a displacement method of each cementing fluid during the injection and displacement process when injecting each cementing fluid into the annulus according to the injection plan of the cementing fluid, including: if the cementing fluid is a flushing fluid and a spacer fluid, a turbulent displacement method is adopted; if the cementing fluid is a leading cement slurry and a tail cement slurry, a plug flow displacement method is adopted.

[0144] It can be understood that in the case where the cementing fluid is a flushing fluid and a spacer fluid, adopting the turbulent displacement method helps to enhance the flushing effect on the drilling fluid and the mud cake on the wellbore wall, improve the flushing efficiency, and ensure the cleanliness of the wellbore wall. In the case where the cementing fluid is a leading cement slurry and a tail cement slurry, adopting the plug flow displacement method helps to improve the displacement efficiency of the cement slurry in the annulus, ensure that the cement slurry can fill the annulus, and thus improve the cementing quality.

[0145] The liner cementing method provided by the embodiments of the present application first determines the depths of the lost circulation risk layer and the overflow risk layer by obtaining the equivalent density of pore pressure and the equivalent density of lost circulation pressure at different depths in the wellbore. Then, based on the depths and pressure data of these risk layers, an injection plan for the cementing fluid is formulated, including the density, volume, and displacement of the cementing fluid. On this basis, according to the density and displacement of the cementing fluid, combined with the liquid column height after the fluid enters the annulus, the equivalent density of pore pressure at each depth in the wellbore is calculated. If it is detected that the equivalent density of pore pressure after a certain cementing fluid enters the annulus does not meet the preset conditions, the injection plan for the cementing fluid will be adjusted until the preset pressure conditions are reached. Finally, according to the adjusted injection plan for the cementing fluid, the injection process of the cementing fluid is controlled to ensure that the equivalent density of pore pressure at different depths in the wellbore meets the requirements. This method effectively solves the problems of lost circulation or overflow in the wellbore during the liner cementing process due to complex downhole pressure conditions by determining the density, volume, and displacement of each cementing fluid and reasonably planning the injection plan for the cementing fluid, ensuring the safety and effectiveness of the cementing operation, and successfully avoiding potential risks such as wellbore instability and wellbore collapse that may be caused by complex pressure formations, thereby comprehensively improving the overall quality and reliability of the cementing operation.

[0146] Figure 3 is a schematic flow chart of the liner cementing method provided by the present application Figure 2 , as Figure 3 shown, on the basis of the Figure 2 embodiment, the liner cementing method is described in detail. The method includes:

[0147] S201. Obtain the equivalent density of pore pressure and the equivalent density of lost circulation pressure at different depths in the wellbore, and determine the depths of the lost circulation risk layer and the overflow risk layer according to the equivalent density of pore pressure and the equivalent density of lost circulation pressure at different depths in the wellbore.

[0148] Among them, the explanation of step S201 is similar to the explanation of step S101 above and will not be elaborated here.

[0149] S202. Determine the volume of the lead slurry of the cement slurry and the volume of the tail slurry of the cement slurry according to the casing shoe depth, liner depth, wellbore diameter, liner diameter, depth of the lost circulation risk layer, and depth of the overflow risk layer. The cementing fluid includes a flushing fluid, a spacer fluid, a lead slurry of the cement slurry, a tail slurry of the cement slurry, and a displacement fluid.

[0150] Among them, the casing shoe depth refers to the depth of the casing shoe in the well. For example, if the casing shoe depth is 3000 meters, it means that the depth of the casing shoe in the well is 3000 meters.

[0151] The liner depth refers to the depth of the bottom end of the liner (i.e., the pipe into which the cement slurry is injected). For example, if the liner depth is 3500 meters, it means the depth of the bottom end of the liner is 3500 meters.

[0152] The wellbore diameter refers to the diameter of the hole formed during the drilling process, with the unit being millimeters or inches. For example, if the wellbore diameter of a certain well is 12.25 inches, it means the diameter of the hole formed during the drilling process is 12.25 inches.

[0153] The liner diameter refers to the outer diameter of the liner. For example, if the liner diameter is 9.5 inches, it means the outer diameter of the liner is 9.5 inches.

[0154] The flushing fluid refers to a liquid used to clean the wellbore, remove sediments or debris on the well wall, ensure smoothness inside the wellbore, and facilitate subsequent injection of cement slurry.

[0155] The spacer fluid refers to a liquid used to separate different liquid layers (such as flushing fluid and cement slurry), preventing different liquids from mixing or reacting.

[0156] The lead cement slurry refers to the first part injected during the injection of cement slurry, usually the uppermost layer of cement slurry, which plays a role in initially sealing the well wall. For example, if the volume of the lead cement slurry is 100 cubic meters, it means 100 cubic meters of cement slurry need to be injected to fill the gap between the liner and the well wall.

[0157] The tail cement slurry refers to the last part of the cement slurry injected during the injection process, usually used to ensure that the cement slurry can completely fill the bottommost area of the annulus. For example, if the volume of the tail cement slurry is 50 cubic meters, it means 50 cubic meters of tail cement slurry are injected to seal the lower annulus.

[0158] The displacement fluid refers to a liquid used to push other liquids (such as cement slurry, spacer fluid, etc.) smoothly into the well, usually used to fill the space inside the casing after injecting the cement slurry to ensure a smooth injection process of the cement slurry.

[0159] It can be understood that parameters such as the casing shoe depth and the liner depth help determine the area where the cement slurry is injected, while parameters such as the wellbore diameter and the liner diameter determine the space for liquid injection. Therefore, by comprehensively considering the casing shoe depth, the liner depth, the wellbore diameter, the liner diameter, the depth of the lost circulation risk layer, and the depth of the kick risk layer, it helps to reasonably determine the volume of the cement slurry, avoid over-injection or under-injection of the cement slurry, and prevent the occurrence of lost circulation or kick phenomena.

[0160] Optionally, the present application provides a possible implementation method, including:

[0161] First step: Determine the liquid column height of the leading slurry and the trailing slurry of the cement slurry according to the casing shoe depth, liner depth, depth of the lost circulation risk zone, and depth of the kick risk zone.

[0162] Among them, the liquid column height of the leading slurry of the cement slurry refers to the length of the cement slurry in the annulus when the cement slurry starts to enter the annulus from the casing shoe (i.e., the lower end of the casing) and flows upward. The unit of the liquid column height of the leading slurry of the cement slurry is meter (m).

[0163] The liquid column height of the trailing slurry of the cement slurry refers to the final liquid column height when the trailing slurry of the cement slurry fills the annulus after injecting the leading slurry of the cement slurry.

[0164] The purpose of this step is to determine the liquid column heights of the leading slurry and the trailing slurry of the cement slurry in the annulus respectively according to the specific depth of the wellbore and the positions of the risk zones.

[0165] It can be understood that the casing shoe depth determines the starting position of the cement slurry injection, while the liner depth limits the termination position of the cement slurry injection. The positions of the lost circulation risk zone and the kick risk zone directly affect the sealing effect of the leading slurry and the trailing slurry of the cement slurry.

[0166] Therefore, by comprehensively considering the casing shoe depth, liner depth, depth of the lost circulation risk zone, and depth of the kick risk zone, it can be ensured that the cement slurry can accurately cover these key areas, form an effective sealing layer, and prevent the overflow of formation fluids or the loss of cementing fluids.

[0167] Second step: Determine the volume of the leading slurry of the cement slurry according to the wellbore diameter, liner diameter, and liquid column height of the leading slurry of the cement slurry.

[0168] Among them, the volume of the leading slurry of the cement slurry refers to the total amount of the leading slurry of the cement slurry injected. For example, assume the leading slurry of the cement slurry is 25m 3 , which means that during a certain cementing operation, 25 cubic meters of the leading slurry of the cement slurry need to be injected.

[0169] In this step, for example, the volume of the leading slurry of the cement slurry can be determined according to the following formula.

[0170]

[0171] Among them, V C1 represents the volume of the leading slurry of the cement slurry, and the unit is cubic meter (m 3 ); D a represents the wellbore diameter, and the unit is inch or mm; D c represents the liner diameter, and the unit is inch or mm; L c1 represents the liquid column height of the leading slurry of the cement slurry, and the unit is meter (m).

[0172] For example, assume that the liquid column height of the leading slurry of the cement slurry is 1,200 meters, the wellbore diameter is 0.216 meters, and the liner diameter is 0.14 meters. Then, based on the above information, the volume of the leading slurry of the cement slurry can be determined to be 25.54 cubic meters using the above formula.

[0173] In the third step, determine the volume of the trailing slurry of the cement slurry based on the wellbore diameter, the liner diameter, and the liquid column height of the trailing slurry of the cement slurry.

[0174] Among them, the volume of the trailing slurry of the cement slurry refers to the total amount of the trailing slurry of the cement slurry injected. For example, assume that the trailing slurry of the cement slurry is 38 m 3 , which means that during a certain cementing operation, 38 cubic meters of the trailing slurry of the cement slurry need to be injected.

[0175] In this step, for example, the volume of the trailing slurry of the cement slurry can be determined according to the following formula.

[0176]

[0177] Among them, V C2 represents the volume of the trailing slurry of the cement slurry, with the unit of cubic meters (m 3 ); D a represents the wellbore diameter, with the unit of inches or mm; D c represents the liner diameter, with the unit of inches or mm; L c2 represents the liquid column height of the trailing slurry of the cement slurry, with the unit of m.

[0178] For example, assume that the liquid column height of the trailing slurry of the cement slurry is 1,800 meters, the wellbore diameter is 0.216 meters, and the liner diameter is 0.14 meters. Then, based on the above information, the volume of the trailing slurry of the cement slurry can be determined to be 38.25 cubic meters using the above formula.

[0179] Optionally, the present application provides an implementation method for determining the liquid column height of the leading slurry of the cement slurry and the liquid column height of the trailing slurry of the cement slurry according to the casing shoe depth, the liner depth, the depth of the lost circulation risk layer, and the depth of the kick risk layer, including:

[0180] In the first step, subtract the casing shoe depth from the depth of the lost circulation risk layer to obtain the first liquid column height.

[0181] It can be understood that the lost circulation risk layer refers to the area where cement slurry leakage may occur during cementing, and the casing shoe is the key part for fixing the casing. Therefore, after subtracting the casing shoe depth from the depth of the lost circulation risk layer, the injection depth range that the cement slurry needs to reach can be clearly defined, which can effectively help determine whether it is necessary to adjust the cement slurry injection strategy to ensure that the cement can seal the wellbore and prevent the risk of lost circulation.

[0182] In this step, for example, the first liquid column height can be determined according to the following formula.

[0183] H1 = h l1 -h lner_hanger

[0184] Wherein, H1 represents the height of the first liquid column, with the unit of meter (m); h l1 represents the depth of the lost circulation risk zone, with the unit of meter (m); h lner_hanger represents the casing shoe depth, with the unit of meter (m).

[0185] For example, in the cementing operation, assuming the casing shoe depth is 2500 meters and the depth of the lost circulation risk zone is 2800 meters, then based on the above information, the height of the first liquid column can be determined to be 300 meters (2800 meters - 2500 meters).

[0186] In the second step, subtract the casing shoe depth from the depth of the kick risk zone to obtain the height of the second liquid column.

[0187] It can be understood that the kick risk zone refers to the area where liquid or gas kick may occur during the drilling process, while the casing shoe is the part where the casing is fixed. By calculating the depth difference between the kick risk zone and the casing shoe, it can help determine whether the cement slurry will kick in this area and ensure the safety of the injection process.

[0188] In this step, for example, the height of the second liquid column can be determined according to the following formula.

[0189] H2 = h p1 -h lner_hanger

[0190] Wherein, H2 represents the height of the second liquid column, with the unit of meter (m); h p1 represents the depth of the kick risk zone, with the unit of meter (m); h lner_hanger represents the casing shoe depth, with the unit of meter (m).

[0191] For example, in the cementing operation, assuming the depth of the kick risk zone is 4000 meters and the casing shoe depth is 2500 meters, then based on the above information, the height of the second liquid column can be determined to be 1500 meters (4000 meters - 2500 meters).

[0192] In the third step, determine the height of the leading slurry of the cement slurry according to the rule that the height of the leading slurry of the cement slurry is greater than the height of the first liquid column and less than the height of the second liquid column.

[0193] Among them, the rule that the height of the leading slurry of the cement slurry is greater than the height of the first liquid column and less than the height of the second liquid column can be understood as that the height of the leading slurry of the cement slurry should be greater than the difference between the casing shoe depth and the depth of the lost circulation risk zone, and at the same time less than the difference between the casing shoe depth and the depth of the kick risk zone.

[0194] The purpose of this step is to ensure that the liquid column height of the leading slurry of the cement slurry can effectively fill the annulus at the depth where the lost circulation risk zone is located, and at the same time prevent excessive injection of the cement slurry to fill the annulus at the depth where the overflow risk zone is located, so as to ensure the effectiveness and safety of the cementing operation.

[0195] It can be understood that by setting the liquid column height of the leading slurry of the cement slurry to be greater than the difference between the casing shoe depth and the depth of the lost circulation risk zone, and at the same time less than the difference between the casing shoe depth and the depth of the overflow risk zone, it can ensure that the cement slurry is evenly distributed in the wellbore, achieving the best cementing effect, preventing leakage or gushing of formation fluids, and ensuring the stability of formation sealing.

[0196] For example, assuming that the first liquid column height is 300 meters and the second liquid column height is 1500 meters, then based on the above information, it can be determined that the liquid column height of the leading slurry of the cement slurry is 1200 meters.

[0197] In the fourth step, subtract the casing shoe depth from the liner depth, and then subtract the liquid column height of the leading slurry of the cement slurry to obtain the liquid column height of the tail slurry of the cement slurry.

[0198] It can be understood that first, subtracting the casing shoe depth from the liner depth is to determine the overall injection range of the cement slurry in the casing. Then, subtracting the liquid column height of the leading slurry of the cement slurry is to clearly exclude the annulus that has been filled by the leading slurry of the cement slurry, ensuring that the tail slurry of the cement slurry can smoothly reach the predetermined area and perform effective cementing.

[0199] Therefore, by comprehensively considering the liner depth, the casing shoe depth, and the liquid column height of the leading slurry of the cement slurry, the injection volume of the tail slurry can be reasonably controlled, ensuring the reasonable distribution of the cement slurry, avoiding insufficient or lost circulation of the cement slurry during injection, thus achieving a good cementing effect and ensuring the stability and safety of the wellbore.

[0200] In this step, for example, the liquid column height of the tail slurry of the cement slurry can be determined according to the following formula.

[0201] L c2 =H - h lner_hanger - L C1

[0202] Wherein, L c2 represents the liquid column height of the tail slurry of the cement slurry, with the unit of meter (m); H represents the liner depth, with the unit of meter (m); h lner_hanger represents the casing shoe depth, with the unit of meter (m); L C1 represents the liquid column height of the leading slurry of the cement slurry, with the unit of meter (m).

[0203] For example, in a cementing operation, assuming the casing shoe depth is 2500 meters, the liner depth is 5500 meters, and the liquid column height of the leading slurry of the cement slurry is 1200 meters, then based on the above information, it can be determined that the liquid column height of the trailing slurry of the cement slurry is 1800 meters, that is, 5500 meters - 2500 meters - 1200 meters = 1800 meters.

[0204] S203. Determine the density of the leading slurry of the cement slurry and the density of the trailing slurry of the cement slurry according to the equivalent density of the pore pressure at the overflow risk layer, the equivalent density of the lost circulation pressure at the lost circulation risk layer, and the equivalent density of the lost circulation pressure at the overflow risk layer.

[0205] It can be understood that, first of all, the equivalent density of the pore pressure at the overflow risk layer requires that the cementing fluid has sufficient suppression ability to prevent formation fluid from entering the annulus and avoid the occurrence of overflow.

[0206] Secondly, the equivalent density of the lost circulation pressure at the lost circulation risk layer requires that the density of the cementing fluid cannot be too high to avoid the loss of the cement slurry into the formation and affect the cementing effect.

[0207] Finally, the equivalent density of the lost circulation pressure at the overflow risk layer requires that the cement slurry shall not exceed the lost circulation pressure of this layer during injection to prevent the loss of the cement slurry due to too high pressure.

[0208] In addition, the leading slurry of the cement slurry, as the first part of the cement slurry injected, its main function is to quickly establish a preliminary cementing barrier to prevent formation fluid from invading the wellbore during the subsequent cementing operation. The trailing slurry of the cement slurry is injected after the leading slurry and is used to further reinforce the cementing barrier, improve the cementing quality, and ensure good bonding between the cement slurry and the wellbore rock.

[0209] Therefore, by reasonably designing the density of the leading slurry of the cement slurry and the density of the trailing slurry of the cement slurry, the requirements of suppressing formation fluid invasion and preventing cement slurry loss can be effectively balanced, thus ensuring the successful progress of the cementing operation.

[0210] Optionally, the present application provides a possible implementation method, including: determining the density of the leading slurry of the cement slurry and the density of the trailing slurry of the cement slurry according to the following rules:

[0211] The density of the leading slurry of the cement slurry is greater than the equivalent density of the pore pressure at the overflow risk layer, and the density of the leading slurry of the cement slurry is less than the equivalent density of the lost circulation pressure at the lost circulation pressure risk layer; the density of the trailing slurry of the cement slurry is greater than the equivalent density of the pore pressure at the overflow risk layer, and the density of the trailing slurry of the cement slurry is less than the equivalent density of the lost circulation pressure at the overflow risk layer, to determine the density of the leading slurry of the cement slurry and the density of the trailing slurry of the cement slurry.

[0212] It is understandable that during the density design of the cement slurry, the pressure characteristics of the overflow risk layer and the lost circulation risk layer need to be comprehensively considered. For the leading cement slurry, its density design needs to be higher than the equivalent density of the overflow risk layer to provide sufficient hydrostatic pressure to inhibit the invasion of formation fluids into the wellbore, thereby effectively preventing the occurrence of overflow. At the same time, to ensure that the leading cement slurry does not fracture the lost circulation risk layer due to excessive pressure during injection, the density of the leading cement slurry also needs to be lower than the equivalent density of the lost circulation pressure of the lost circulation risk layer.

[0213] For the trailing cement slurry, first of all, the density of the trailing cement slurry should be higher than the equivalent density of the pore pressure of the overflow risk layer to ensure that when cementing the annulus below the lost circulation risk layer, sufficient pressure barrier can be provided to prevent formation fluids from entering the wellbore through microfractures or pores. However, to avoid lost circulation at the overflow risk layer with higher pressure, the density of the trailing cement slurry also needs to be lower than the equivalent density of the lost circulation pressure at the overflow risk layer.

[0214] In addition, to ensure the fluid stability during the injection and displacement process and avoid problems such as slurry mixing or channeling caused by density inversion, the density of the leading cement slurry also needs to be less than the density of the trailing cement slurry, thereby forming a density gradient from low to high.

[0215] S204. Determine the density of the displacement fluid as the density of the drilling fluid, and determine the density of the flushing fluid and the density of the spacer fluid according to the density of the leading cement slurry and the density of the drilling fluid.

[0216] Among them, the purpose of determining the density of the displacement fluid as the density of the drilling fluid in this step is to ensure that the displacement fluid will not flow into the annulus during the injection and displacement process and can effectively isolate the cement slurry and the drilling fluid.

[0217] The purpose of determining the density of the flushing fluid and the density of the spacer fluid according to the density of the leading cement slurry and the density of the drilling fluid is to avoid problems such as slurry mixing or density inversion during the injection and displacement process.

[0218] It is understandable that first of all, during the density design of the cementing fluid, the displacement fluid starts to be injected after the injection of the leading cement slurry and the trailing cement slurry is completed. Its main function is to displace the cement slurry and make it fill the annulus. Since the displacement fluid is separated from the cement slurry by a rubber plug, and the rubber plug stops flowing at the end of the injection and displacement and does not enter the annulus, the displacement fluid will not enter the annulus. Therefore, a displacement fluid with the same density as the drilling fluid can be used to avoid fluid flow instability or pressure fluctuations caused by density mismatch.

[0219] Secondly, during the design of the density of the flushing fluid, the main function of the flushing fluid is to clean the wellbore, remove the residual drilling fluid, and provide a clean interface for the cement slurry. To avoid the occurrence of slurry mixing or density inversion during the injection and displacement process (i.e., the fluid layers are reversed, resulting in abnormal fluid flow), the density of the flushing fluid can be reasonably designed based on the density of the leading cement slurry and the density of the drilling fluid.

[0220] In addition, during the design of the spacer fluid, the main function of the spacer fluid is to prevent different fluids from mixing during the injection and displacement process, so as to achieve effective isolation of different fluids. To achieve effective isolation, the density of the spacer fluid can be reasonably designed based on the density of the leading cement slurry and the density of the drilling fluid.

[0221] In this step, for example, the density of the flushing fluid can be determined according to the following formula.

[0222]

[0223] Among them, ρ f represents the density of the flushing fluid, with the unit of g / cm 3 ; ρ c1 represents the density of the leading cement slurry, with the unit of g / cm 3 ; ρ m represents the density of the drilling fluid, with the unit of g / cm 3 .

[0224] In this step, for example, the density of the spacer fluid can be determined according to the following formula.

[0225]

[0226] Among them, ρ s represents the density of the spacer fluid, with the unit of g / cm 3 ; ρ c1 represents the density of the leading cement slurry, with the unit of g / cm 3 ; ρ m represents the density of the drilling fluid, with the unit of g / cm 3 .

[0227] S205. Determine the displacement of each cementing fluid according to the density, wellbore diameter, and liner diameter of each cementing fluid.

[0228] Among them, the purpose of this step is to ensure that during the cementing operation, various fluids are injected into the well at an appropriate displacement, avoiding unstable fluid flow or problems during the injection process.

[0229] It is understandable that the density of the cementing fluid affects its flow characteristics under the action of gravity, while the wellbore diameter and the liner diameter determine the flow space and flow velocity of the fluid in the wellbore. Therefore, by comprehensively considering the density of each cementing fluid, the wellbore diameter, and the liner diameter, it can be ensured that the flow of each cementing fluid in the wellbore is neither too slow to cause low operation efficiency nor too rapid to damage the wellbore structure or affect the cementing quality.

[0230] Optionally, the present application provides a possible implementation method, including:

[0231] In the first step, according to the density of the displacement fluid, the wellbore diameter, and the liner diameter, determine the displacement of the displacement fluid.

[0232] In this step, for example, the displacement of the displacement fluid can be determined according to the following formula.

[0233]

[0234] Among them, Q f represents the displacement of the displacement fluid, with the unit of m 3 / min; D a represents the wellbore diameter, with the unit of inch or mm; D c represents the liner diameter, with the unit of inch or mm; ρ f represents the density of the displacement fluid, with the unit of g / cm 3 ; K represents the fluid consistency coefficient; n represents the fluid flow behavior index.

[0235] In the second step, according to the density of the spacer fluid, the wellbore diameter, and the liner diameter, determine the displacement of the spacer fluid.

[0236] In this step, for example, the displacement of the spacer fluid can be determined according to the following formula.

[0237]

[0238] Among them, Q s represents the displacement of the spacer fluid, with the unit of m 3 / min; D a represents the wellbore diameter, with the unit of inch or mm; D c represents the liner diameter, with the unit of inch or mm; ρ s represents the density of the spacer fluid, with the unit of g / cm 3 ; K represents the fluid consistency coefficient; n represents the fluid flow behavior index.

[0239] In the third step, according to the density of the leading slurry of the cement slurry, the wellbore diameter, and the liner diameter, determine the displacement of the leading slurry of the cement slurry.

[0240] In this step, for example, the displacement of the leading slurry of the cement slurry can be determined according to the following formula.

[0241]

[0242] Wherein, Q c1 represents the displacement of the leading slurry of the cement slurry, with the unit of m 3 / min; D a represents the wellbore diameter, with the unit of inch or mm; D c represents the liner diameter, with the unit of inch or mm; ρ c1 represents the density of the leading slurry of the cement slurry, with the unit of g / cm 3 ; K represents the fluid consistency coefficient; n represents the fluid flow behavior index.

[0243] Fourth step, determine the displacement of the tail slurry of the cement slurry according to the density of the tail slurry of the cement slurry, the wellbore diameter, and the liner diameter.

[0244] In this step, for example, the displacement of the tail slurry of the cement slurry can be determined according to the following formula.

[0245]

[0246] Wherein, Q c2 represents the displacement of the tail slurry of the cement slurry, with the unit of m 3 / min; D a represents the wellbore diameter, with the unit of inch or mm; D c represents the liner diameter, with the unit of inch or mm; ρ c2 represents the density of the tail slurry of the cement slurry, with the unit of g / cm 3 ; K represents the fluid consistency coefficient; n represents the fluid flow behavior index.

[0247] Fifth step, determine the displacement of the tail slurry of the cement slurry as the displacement of the displacement fluid.

[0248] Among them, the purpose of this step is to ensure that the displacement fluid has enough volume to push the cement slurry forward until the cement slurry completely fills the annulus, and the displacement fluid itself can also fully displace the residual drilling fluid in the annulus, so as to achieve effective sealing of the annulus.

[0249] It can be understood that in the cementing operation, the injection of the cement slurry is usually divided into two parts: the leading slurry and the tail slurry. The leading slurry of the cement slurry is the initial part in the process of injecting the cement slurry. Its function is to push the cement slurry to start entering the well and replace other fluids in the wellbore; while the tail slurry of the cement slurry is the last part of injecting the cement slurry, which ensures that the cement slurry completely fills the annulus and effectively seals the wellbore wall. The leading slurry and the tail slurry of the cement slurry together form the entire injection volume of the cement slurry.

[0250] In order to ensure that the displacement fluid can completely replace the original fluid in the well and fully replace other fluids in the annulus, the amount of the displacement fluid needs to ensure that there is enough volume to complete this process.

[0251] Therefore, by determining the displacement of the tail slurry of the cement slurry as the displacement of the displacement fluid, it can be ensured that the displacement fluid effectively pushes the cement slurry forward and completely replaces other fluids in the annulus, thereby ensuring the cementing effect and stabilizing the wellbore.

[0252] In this step, for example, the displacement of the displacement fluid can be determined according to the following formula.

[0253] Q d = Q c2

[0254] where Q d represents the displacement of the displacement fluid, with the unit of m 3 / min; Q c2 represents the displacement of the tail slurry of the cement slurry, with the unit of m 3 / min.

[0255] S206. Determine the volume of the flushing fluid, the volume of the spacer fluid, and the volume of the displacement fluid according to the displacement of the flushing fluid, the displacement of the spacer fluid, and a preset duration.

[0256] Among them, the preset duration can be, for example, 10 min.

[0257] The purpose of this step is to ensure that the injection volume of each cementing fluid can meet the operation requirements.

[0258] It can be understood that the displacement of the flushing fluid determines the effect of cleaning the wellbore during the operation; the displacement of the spacer fluid ensures effective isolation between different fluids and avoids cross-contamination; the preset duration determines the duration of each fluid during the injection process and ensures the coordination of fluid flow and operation rhythm during the operation.

[0259] Therefore, by comprehensively considering the displacement of the flushing fluid, the displacement of the spacer fluid, and the preset duration, it can be ensured that each fluid is injected as needed during the operation, avoiding operation problems caused by insufficient or excessive fluid volume, thereby ensuring the operation effect and wellbore stability.

[0260] Optionally, the present application provides a possible implementation method, including:

[0261] The first step is to determine the volume of the flushing fluid according to the displacement of the flushing fluid and the preset duration.

[0262] In this step, for example, the volume of the flushing fluid can be determined according to the following formula.

[0263] V f = Q f * t

[0264] Among them, V f represents the volume of the flushing fluid, with the unit of m 3 ; Q f represents the displacement of the flushing fluid, with the unit of m 3 / min; t represents the preset duration, with the unit of min.

[0265] In the second step, determine the volume of the spacer fluid according to the displacement and preset duration of the spacer fluid.

[0266] In this step, for example, the volume of the spacer fluid can be determined according to the following formula.

[0267] V s =Q s *t

[0268] Among them, V s represents the volume of the spacer fluid, with the unit of m 3 ; Q s represents the displacement of the spacer fluid, with the unit of m 3 / min; t represents the preset duration, with the unit of min.

[0269] In the third step, determine the volume of the displacement fluid by adding the volume of the drill pipe and the volume of the liner.

[0270] Among them, the purpose of this step is to ensure that during the cementing operation, the displacement fluid can effectively replace the original fluid in the well and push the required flushing fluid and spacer fluid to the predetermined position in the well.

[0271] It can be understood that during the cementing process, the flushing fluid is used to clean the wellbore, and the spacer fluid is used to prevent the mixing of different fluids. By calculating the sum of the volume of the drill pipe and the volume of the liner, it can be ensured that the amount of the displacement fluid is sufficient, thus ensuring the smooth progress of the operation and avoiding affecting the operation effect or the balance of the well pressure due to insufficient fluid.

[0272] In this step, for example, the volume of the displacement fluid can be determined according to the following formula.

[0273] V d =V p +V t

[0274] Among them, V d represents the volume of the displacement fluid, with the unit of m 3 ; V p represents the volume of the drill pipe, with the unit of m 3 ; V t represents the volume of the liner, with the unit of m 3 .

[0275] S207. Determine the annular static liquid column pressure from the wellhead to the depth where each cementing fluid is located according to the liquid column height of each cementing fluid after entering the annulus and the density of each cementing fluid.

[0276] Among them, the annular static liquid column pressure refers to the static pressure generated by the liquid column formed by the cementing fluid in the wellbore.

[0277] The purpose of this step is to determine the annular static liquid column pressure from the wellhead to the depth where each cementing fluid is located during the cementing process.

[0278] It can be understood that, first of all, the liquid column height of each cementing fluid after entering the annulus represents the vertical distribution state of the fluid in the annulus area between the wellbore and the casing. The greater the liquid column height of the fluid, the wider the space it occupies in the annulus, and the greater the static liquid column pressure generated.

[0279] Secondly, the greater the density of the cementing fluid, the greater the mass contained in its unit volume, which means that at the same height, the fluid with a greater density will generate a higher static liquid column pressure.

[0280] Therefore, by combining the density of the cementing fluid and the liquid column height after entering the annulus, the annular static liquid column pressure can be accurately calculated.

[0281] In this step, for example, the following formula can be used to determine the annular static liquid column pressure from the wellhead to the depth where each cementing fluid is located.

[0282]

[0283] Among them, represents the annular static liquid column pressure from the wellhead to the depth where each cementing fluid is located at time t, with the unit of MPa; represents the sum of the products of the density and liquid column height from the wellhead to the depth where each cementing fluid i is located at time t; represents the liquid column height of each cementing fluid i after entering the annulus at time t, with the unit of m; represents the density of each cementing fluid i after completely entering the annulus at time t, with the unit of g / cm 3 .

[0284] If the cementing fluid is the flushing fluid, then is the product of the liquid column height of the flushing fluid after completely entering the annulus and the density of the flushing fluid, plus the product of the liquid column height of the drilling fluid in the annulus and the density of the drilling fluid.

[0285] If the cementing fluid is the spacer fluid, then is the product of the liquid column height of the flushing fluid after completely entering the annulus and the density of the flushing fluid, plus the product of the liquid column height of the drilling fluid in the annulus and the density of the drilling fluid, and plus the product of the liquid column height of the spacer fluid after completely entering the annulus and the density of the spacer fluid.

[0286] If the cementing fluid is the leading cement slurry, then It is the liquid column height after the displacement fluid completely enters the annulus multiplied by the density of the displacement fluid, plus the liquid column height of the drilling fluid in the annulus multiplied by the density of the drilling fluid, and, plus the liquid column height after the spacer fluid completely enters the annulus multiplied by the density of the spacer fluid, and finally, plus the liquid column height after the leading cement slurry completely enters the annulus multiplied by the density of the leading cement slurry.

[0287] If the cementing fluid is the tail cement slurry, then It is the liquid column height after the displacement fluid completely enters the annulus multiplied by the density of the displacement fluid, plus the liquid column height of the drilling fluid in the annulus multiplied by the density of the drilling fluid, and, plus the liquid column height after the spacer fluid completely enters the annulus multiplied by the density of the spacer fluid, and finally, plus the liquid column height after the leading cement slurry completely enters the annulus multiplied by the density of the leading cement slurry. In addition, plus the liquid column height after the tail cement slurry completely enters the annulus multiplied by the density of the tail cement slurry.

[0288] S208. Determine the annular friction pressure drop from the wellhead to the depth where each cementing fluid is located according to the displacement, wellbore diameter, liner diameter, and the liquid column height of each cementing fluid after it enters the annulus.

[0289] Among them, the annular friction pressure drop refers to the pressure loss generated by fluid friction when each cementing fluid flows in the annular area between the wellbore and the casing.

[0290] The purpose of this step is to calculate the annular friction pressure drop from the wellhead to the depth where each cementing fluid is located.

[0291] It can be understood that the displacement determines the flow velocity and flow rate of each cementing fluid in the annulus, affecting the flow velocity and friction force of the cementing fluid in the annulus; the wellbore diameter determines the cross-sectional size of the wellbore, affecting the friction degree when the cementing fluid flows; the liner diameter determines the space size of the annulus, affecting the distribution and flow of the fluid in the annulus; and the liquid column height of the cementing fluid after it enters the annulus represents the vertical distance occupied by the fluid in the annulus, reflecting the distribution state of the fluid in the annulus.

[0292] Therefore, by comprehensively considering the displacement, wellbore diameter, liner diameter, and the liquid column height of each cementing fluid after it enters the annulus, the annular friction pressure drop from the wellhead to the depth where the cementing fluid is located can be calculated, which helps to optimize the fluid injection plan for the cementing operation and ensure the smooth progress of the cementing operation.

[0293] In this step, for example, the annular friction pressure drop from the wellhead to the depth where each cementing fluid is located can be determined according to the following formula.

[0294]

[0295] Among them, represents the annular friction pressure drop from the wellhead to the depth where each cementing fluid is located at time t, with the unit of MPa; f represents the annular friction coefficient of each cementing fluid; H represents the liquid column height after each cementing fluid completely enters the annulus at time t, with the unit of m; D a represents the wellbore diameter, with the unit of meter (m); D c represents the liner diameter, with the unit of meter (m); v represents the flow velocity of each cementing fluid, with the unit of m / s; represents the density of each cementing fluid i after it completely enters the annulus at time t, with the unit of g / cm 3 .

[0296]

[0297] Among them, f represents the annular friction coefficient of each cementing fluid; Re represents the annular fluid Reynolds number of each cementing fluid.

[0298]

[0299] Among them, Re represents the annular fluid Reynolds number of each cementing fluid; D a represents the wellbore diameter, with the unit of meter (m); D c represents the liner diameter, with the unit of meter (m); v represents the flow velocity of each cementing fluid, with the unit of m / s; τ0 represents the yield stress, with the unit of pa; K represents the consistency coefficient; n represents the flow behavior index.

[0300]

[0301] Among them, v represents the flow velocity of each cementing fluid, with the unit of m / s; represents the displacement of each cementing fluid, with the unit of m 3 / min; A represents the annular cross-sectional area, with the unit of square inch, or m 2 .

[0302] S209. Determine the sum of the annular static liquid column pressure and the annular friction pressure drop from the wellhead to the depth where each cementing fluid is located as the annular pressure from the wellhead to the depth where each cementing fluid is located.

[0303] Among them, the annular pressure refers to the total pressure formed in the annulus during the cementing operation due to the static liquid column pressure of the cementing fluid and the friction pressure drop generated by the fluid flow.

[0304] It can be understood that during the cementing operation, the annular static liquid column pressure is the pressure generated by the density of the cementing fluid and the liquid column height at this depth, while the annular friction pressure drop is the pressure loss caused by the friction between the fluid and the wellbore wall during fluid flow.

[0305] To ensure the smooth progress of the cementing operation, it is necessary to determine the annulus pressure at each depth position based on the sum of the annular static liquid column pressure and the frictional pressure drop from the wellhead to the depth where each cementing fluid is located.

[0306] Therefore, by superimposing the annular static liquid column pressure from the wellhead to the depth where each cementing fluid is located and the annular frictional pressure drop, the actual total annular pressure from the wellhead to each depth can be accurately calculated, which helps to ensure that the annular pressure during cementing will neither be too low to cause formation fluid invasion (overflow risk) nor too high to fracture the formation (loss risk).

[0307] In this step, for example, the annulus pressure from the wellhead to the depth where each cementing fluid is located can be determined according to the following formula.

[0308]

[0309] Among them, represents the annulus pressure from the wellhead to the depth where each cementing fluid is located at time t, with the unit of MPa; represents the annular static liquid column pressure from the wellhead to the depth where each cementing fluid is located at time t, with the unit of MPa; represents the annular frictional pressure drop from the wellhead to the depth where each cementing fluid is located at time t, with the unit of MPa.

[0310] For example, assuming that the annular static liquid column pressure from the wellhead to the depth where the leading slurry of cement slurry is located is 3500 MPa and the annular frictional pressure drop is 4000 MPa, then based on the above information, the annulus pressure from the wellhead to the depth where the leading slurry of cement slurry is located can be determined to be 7500 MPa.

[0311] S210. Determine the equivalent density of pressure at different depths in the wellbore after each cementing fluid enters the annulus according to the density of each cementing fluid, the liquid column height after each cementing fluid enters the annulus, and the annulus pressure from the wellhead to the depth where each cementing fluid is located.

[0312] Among them, the purpose of this step is to determine the equivalent density of pressure generated by each cementing fluid at different depth positions in the wellbore after entering the annulus.

[0313] It can be understood that, first of all, in the cementing operation, due to the density difference and liquid column height of different cementing fluids, different pressure effects will be generated at each depth position in the wellbore.

[0314] Secondly, the annulus pressure from the wellhead to the depth where each cementing fluid is located reflects the total pressure exerted by the cementing fluid on the wellbore wall at that depth.

[0315] Therefore, by comprehensively considering the density of each cementing fluid, the liquid column height after entering the annulus, and the annulus pressure from the wellhead to the depth where each cementing fluid is located, the density corresponding to the actual pressure exerted by each fluid on the wellbore at different depth positions can be calculated, that is, the equivalent density of pressure.

[0316] In this step, for example, the equivalent density of pressure at different depths in the wellbore after each cementing fluid enters the annulus can be determined according to the following formula.

[0317]

[0318] Among them, represents the equivalent density of pressure at different depths in the wellbore after each cementing fluid enters the annulus at time t, with the unit of g / cm 3 ; represents the annulus pressure from the wellhead to the depth where each cementing fluid is located at time t, with the unit of MPa; represents the sum of the liquid column heights from the wellhead to the depth where each cementing fluid i is located at time t, with the unit of m; represents the liquid column height of each cementing fluid i after entering the annulus at time t, with the unit of m.

[0319] Among them, if the cementing fluid is the flushing fluid, then is the liquid column height after the flushing fluid completely enters the annulus, plus the liquid column height of the drilling fluid in the annulus.

[0320] If the cementing fluid is the spacer fluid, then is the liquid column height after the flushing fluid completely enters the annulus, plus the liquid column height of the drilling fluid in the annulus, and then plus the liquid column height after the spacer fluid completely enters the annulus;

[0321] If the cementing fluid is the leading cement slurry, then is the liquid column height after the flushing fluid completely enters the annulus, plus the liquid column height of the drilling fluid in the annulus, and then plus the liquid column height after the spacer fluid completely enters the annulus, and finally, the liquid column height after the leading cement slurry completely enters the annulus.

[0322] If the cementing fluid is the trailing cement slurry, then is the liquid column height after the flushing fluid completely enters the annulus, plus the liquid column height of the drilling fluid in the annulus, and then plus the liquid column height after the spacer fluid completely enters the annulus, and finally, the liquid column height after the leading cement slurry completely enters the annulus. In addition, the liquid column height after the trailing cement slurry completely enters the annulus is added.

[0323] S211. In the case where the equivalent density of pressure at different depths in the wellbore does not meet the preset conditions, adjust the injection plan of the cementing fluid until the equivalent density of pressure at different depths in the wellbore meets the preset conditions, and control the injection of each cementing fluid into the annulus according to the injection plan of the cementing fluid.

[0324] Among them, the explanation of step S211 is similar to that of step S104 above, and will not be elaborated here.

[0325] The liner cementing method provided by the embodiments of the present application first detects the equivalent density of pore pressure and the equivalent density of lost circulation pressure at different depths in the wellbore, and then determines the depths of the lost circulation risk layer and the overflow risk layer. According to these depths, combined with the casing shoe depth, the liner depth, the wellbore diameter, and the liner diameter, the volumes of the leading slurry and the tail slurry of the cement slurry are calculated, and the types and volumes of other cementing fluids (such as flushing fluid, spacer fluid, displacement fluid, etc.) are determined. Subsequently, according to the equivalent density of pore pressure and the equivalent density of lost circulation pressure, the densities of the leading slurry and the tail slurry of the cement slurry are determined, and according to the relationship between the density of the cement slurry and the density of the drilling fluid, the densities of the flushing fluid and the spacer fluid are adjusted. Then, the displacement rates of each cementing fluid are calculated, and further the volumes and the corresponding annular static liquid column pressures and frictional pressure drops are determined. Considering these factors comprehensively, the annular pressure from the wellhead to the depth where each cementing fluid is located is calculated, and then the equivalent density of pressure at each depth is determined. Finally, if the equivalent density of pressure does not meet the preset conditions, the injection scheme of the cementing fluid is adjusted to ensure that the expected downhole pressure conditions are achieved, and each cementing fluid is injected into the annulus according to the adjusted scheme. This method successfully addresses the problems brought about by the significant pressure differences between formations at different depths during the downhole cementing process by determining the injection scheme of the cementing fluid, effectively preventing possible phenomena such as fracturing the formation or overflow during the cementing process, thereby ensuring the safe and smooth progress of the cementing operation. In addition, this method also avoids potential risks such as wellbore rupture and formation collapse that may be caused by excessive formation depth, further improving the overall stability and reliability of the cementing operation.

[0326] Figure 4 is a schematic structural diagram of the liner cementing device provided by the present application, as Figure 4 shown, the liner cementing device 300 provided in this embodiment includes:

[0327] An acquisition module 301, configured to acquire the equivalent density of pore pressure and the equivalent density of lost circulation pressure at different depths in the wellbore, and determine the depth of the lost circulation risk layer and the depth of the overflow risk layer according to the equivalent density of pore pressure and the equivalent density of lost circulation pressure at different depths in the wellbore;

[0328] A determination module 302, configured to determine the injection scheme of the cementing fluid according to the depth of the lost circulation risk layer, the depth of the overflow risk layer, the equivalent density of pore pressure at the overflow risk layer, the equivalent density of lost circulation pressure at the lost circulation risk layer, and the equivalent density of lost circulation pressure at the overflow risk layer, where the injection scheme of the cementing fluid includes: the density, volume, and displacement rate of each cementing fluid;

[0329] The determining module 302 is further configured to determine the equivalent density of pressure at different depths in the wellbore after each cementing fluid enters the annulus according to the density, displacement of each cementing fluid, and the liquid column height after each cementing fluid enters the annulus.

[0330] The adjustment module 303 is configured to adjust the injection scheme of the cementing fluid until the equivalent density of pressure at different depths in the wellbore meets the preset conditions when the equivalent density of pressure at different depths in the wellbore does not meet the preset conditions.

[0331] The control module 304 is configured to control the injection of each cementing fluid into the annulus according to the injection scheme of the cementing fluid.

[0332] Optionally, the determining module 302 is further configured to determine the volume of the leading slurry of the cement slurry and the volume of the trailing slurry of the cement slurry according to the casing shoe depth, liner depth, wellbore diameter, liner diameter, depth of the lost circulation risk zone, and depth of the kick risk zone.

[0333] The determining module 302 is further configured to determine the density of the leading slurry of the cement slurry and the density of the trailing slurry of the cement slurry according to the equivalent density of pore pressure at the kick risk zone, the equivalent density of lost circulation pressure at the lost circulation risk zone, and the equivalent density of lost circulation pressure at the kick risk zone.

[0334] The determining module 302 is further configured to determine the density of the displacement fluid as the density of the drilling fluid, and determine the density of the flushing fluid and the density of the spacer fluid according to the density of the leading slurry of the cement slurry and the density of the drilling fluid.

[0335] The determining module 302 is further configured to determine the displacement of each cementing fluid according to the density of each cementing fluid, the wellbore diameter, and the liner diameter.

[0336] The determining module 302 is further configured to determine the volume of the flushing fluid, the volume of the spacer fluid, and the volume of the displacement fluid according to the displacement of the flushing fluid, the displacement of the spacer fluid, and a preset time duration.

[0337] Optionally, the determining module 302 is further configured to determine the liquid column height of the leading slurry of the cement slurry and the liquid column height of the trailing slurry of the cement slurry according to the casing shoe depth, the liner depth, the depth of the lost circulation risk zone, and the depth of the kick risk zone.

[0338] The determining module 302 is further configured to determine the volume of the leading slurry of the cement slurry according to the wellbore diameter, the liner diameter, and the liquid column height of the leading slurry of the cement slurry.

[0339] The determining module 302 is specifically configured to determine the volume of the cement slurry tail slurry according to the wellbore diameter, the liner diameter, and the liquid column height of the cement slurry tail slurry.

[0340] Optionally, the determining module 302 is further configured to subtract the casing shoe depth from the depth of the lost circulation risk layer to obtain a first liquid column height;

[0341] The determining module 302 is further configured to subtract the casing shoe depth from the depth of the overflow risk layer to obtain a second liquid column height;

[0342] The determining module 302 is specifically configured to determine the liquid column height of the cement slurry leading slurry according to the rule that the liquid column height of the cement slurry leading slurry is greater than the first liquid column height and less than the second liquid column height;

[0343] The determining module 302 is specifically configured to subtract the liquid column height of the cement slurry leading slurry from the result of subtracting the casing shoe depth from the liner depth to obtain the liquid column height of the cement slurry tail slurry.

[0344] Optionally, the determining module 302 is specifically configured to determine the density of the cement slurry leading slurry and the density of the cement slurry tail slurry according to the following rules:

[0345] The density of the cement slurry leading slurry is greater than the equivalent density of the pore pressure at the overflow risk layer, and the density of the cement slurry leading slurry is less than the equivalent density of the lost circulation pressure at the lost circulation pressure risk layer; the density of the cement slurry tail slurry is greater than the equivalent density of the pore pressure at the overflow risk layer, and the density of the cement slurry tail slurry is less than the equivalent density of the lost circulation pressure at the overflow risk layer, to determine the density of the cement slurry leading slurry and the density of the cement slurry tail slurry.

[0346] Optionally, the determining module 302 is specifically configured to determine the displacement of the flushing fluid according to the density of the flushing fluid, the wellbore diameter, and the liner diameter;

[0347] The determining module 302 is specifically configured to determine the displacement of the spacer fluid according to the density of the spacer fluid, the wellbore diameter, and the liner diameter;

[0348] The determining module 302 is specifically configured to determine the displacement of the cement slurry leading slurry according to the density of the cement slurry leading slurry, the wellbore diameter, and the liner diameter;

[0349] The determining module 302 is specifically configured to determine the displacement of the cement slurry tail slurry according to the density of the cement slurry tail slurry, the wellbore diameter, and the liner diameter;

[0350] The determining module 302 is specifically configured to determine the displacement of the displacement fluid as the displacement of the cement slurry tail slurry.

[0351] Optionally, the determining module 302 is specifically configured to determine the volume of the flushing fluid according to the displacement of the flushing fluid and a preset duration.

[0352] The determining module 302 is specifically configured to determine the volume of the spacer fluid according to the displacement of the spacer fluid and a preset duration.

[0353] The determining module 302 is specifically configured to determine the sum of the drill pipe volume and the liner volume as the volume of the displacement fluid.

[0354] Optionally, the determining module 302 is further configured to determine the annular static hydrostatic pressure from the wellhead to the depth where each cementing fluid is located according to the liquid column height of each cementing fluid after entering the annulus and the density of each cementing fluid.

[0355] The determining module 302 is further configured to determine the annular frictional pressure drop from the wellhead to the depth where each cementing fluid is located according to the displacement of each cementing fluid, the wellbore diameter, the liner diameter, and the liquid column height of each cementing fluid after entering the annulus.

[0356] The determining module 302 is further configured to determine the sum of the annular static hydrostatic pressure and the annular frictional pressure drop from the wellhead to the depth where each cementing fluid is located as the annular pressure from the wellhead to the depth where each cementing fluid is located.

[0357] The determining module 302 is specifically configured to determine the equivalent density of the pressure at different depths in the wellbore after each cementing fluid enters the annulus according to the density of each cementing fluid, the liquid column height of each cementing fluid after entering the annulus, and the annular pressure from the wellhead to the depth where each cementing fluid is located.

[0358] The liner cementing device 300 provided in this embodiment can execute the method provided in the above method embodiment, and its implementation principle and technical effect are similar, which will not be elaborated here in this embodiment.

[0359] Figure 5 This is a schematic structural diagram of the liner cementing equipment provided in the present application. As Figure 5 shown, the electronic device 400 provided in this embodiment includes at least one processor 401 and a memory 402. Optionally, the device 400 further includes a communication component 403. Among them, the processor 401, the memory 402, and the communication component 403 are connected through a bus 404.

[0360] In a specific implementation process, at least one processor 401 executes the computer execution instructions stored in the memory 402, so that at least one processor 401 executes the above method.

[0361] For the specific implementation process of the processor 401, reference may be made to the above method embodiments. Their implementation principles and technical effects are similar, and will not be elaborated here in this embodiment.

[0362] In the above embodiments, it should be understood that the processor may be a central processing unit (CPU for short), or other general-purpose processors, digital signal processors (DSP for short), application specific integrated circuits (ASIC for short), etc. The general-purpose processor may be a microprocessor or any conventional processor, etc. The steps of the method disclosed in combination with the invention can be directly embodied as being completed by the execution of the hardware processor, or by the combination of hardware and software modules in the processor.

[0363] The memory may include a high-speed random access memory (RAM), and may also include non-volatile memory (NVM), such as at least one disk memory.

[0364] The bus may be an Industry Standard Architecture (ISA) bus, a Peripheral Component Interconnect (PCI) bus, an Extended Industry Standard Architecture (EISA) bus, etc. The bus can be divided into an address bus, a data bus, a control bus, etc. For the convenience of representation, the buses in the drawings of this application are not limited to only one bus or one type of bus.

[0365] This application also provides a computer program product, including a computer program, which implements the above method when executed by a processor.

[0366] This application also provides a computer-readable storage medium, in which computer-executable instructions are stored. When the processor executes the computer-executable instructions, the above method is implemented.

[0367] The above-readable storage medium can be implemented by any type of volatile or non-volatile storage device or a combination thereof, such as static random access memory (SRAM), electrically erasable programmable read-only memory (EEPROM), erasable programmable read-only memory (EPROM), programmable read-only memory (PROM), read-only memory (ROM), magnetic memory, flash memory, a magnetic disk, or an optical disk. The readable storage medium can be any available medium accessible by a general-purpose or special-purpose computer.

[0368] An exemplary readable storage medium is coupled to the processor, enabling the processor to read information from and write information to the readable storage medium. Of course, the readable storage medium can also be an integral part of the processor. The processor and the readable storage medium can be located in an application specific integrated circuit (ASIC). Of course, the processor and the readable storage medium can also exist as discrete components in a device.

[0369] The division of units is only a logical function division. In actual implementation, there may be other division methods. For example, multiple units or components can be combined or integrated into another system, or some features can be ignored or not executed. Another point is that the couplings, direct couplings, or communication connections shown or discussed among each other can be indirect couplings or communication connections through some interfaces, devices, or units, and can be in electrical, mechanical, or other forms.

[0370] The units described as separate components may or may not be physically separated, and the components shown as units may or may not be physical units, that is, they can be located in one place or distributed to multiple network units. Some or all of the units can be selected according to actual needs to achieve the purpose of the solution of this embodiment.

[0371] In addition, in each embodiment of the present invention, the functional units can be integrated in a processing unit, or each unit can exist physically alone, or two or more units can be integrated in one unit.

[0372] If a function is implemented in the form of a software functional unit and sold or used as an independent product, it can be stored in a computer-readable storage medium. Based on this understanding, the technical solution of the present invention, in essence, or the part that contributes to the prior art or a part of this technical solution, can be embodied in the form of a software product. This computer software product is stored in a storage medium and includes several instructions for causing a computer device (which may be a personal computer, a server, or a network device, etc.) to execute all or part of the steps of the methods of various embodiments of the present invention. The aforementioned storage medium includes: USB flash drives, mobile hard disks, read-only memories (ROMs), random access memories (RAMs), magnetic disks, or optical discs, etc., various media that can store program codes.

[0373] Those of ordinary skill in the art can understand that all or part of the steps of implementing the above method embodiments can be completed by hardware related to program instructions. The aforementioned program can be stored in a computer-readable storage medium. When this program is executed, it executes the steps including the above method embodiments; and the aforementioned storage medium includes: ROMs, RAMs, magnetic disks, or optical discs, etc., various media that can store program codes.

[0374] Finally, it should be noted that: After considering the specification and practicing the invention disclosed herein, those skilled in the art will readily think of other implementation manners of the present invention. The present invention is intended to cover any variations, uses, or adaptive changes of the present invention. These variations, uses, or adaptive changes follow the general principles of the present invention and include the common general knowledge or conventional technical means in the technical field of the present invention that are not disclosed in the present invention. It is not limited to the exact structures described above and shown in the drawings, and various modifications and changes can be made without departing from its scope. The scope of the present invention is only limited by the appended claims.

Claims

1. A liner cementing method, characterized in that, Including: Obtaining the equivalent density of pore pressure and the equivalent density of lost circulation pressure at different depths in the wellbore, and determining the depth of the lost circulation risk layer and the depth of the overflow risk layer according to the equivalent density of pore pressure and the equivalent density of lost circulation pressure at different depths in the wellbore; Determining an injection plan for the cementing fluid according to the depth of the lost circulation risk layer, the depth of the overflow risk layer, the equivalent density of pore pressure at the overflow risk layer, the equivalent density of lost circulation pressure at the lost circulation risk layer, and the equivalent density of lost circulation pressure at the overflow risk layer, where the injection plan for the cementing fluid includes: the density, volume, and displacement of each cementing fluid; Determining the equivalent density of pressure at different depths in the wellbore after each cementing fluid enters the annulus according to the density and displacement of each cementing fluid and the liquid column height after each cementing fluid enters the annulus; In the case where the equivalent density of pressure at different depths in the wellbore does not meet the preset conditions, adjusting the injection plan for the cementing fluid until the equivalent density of pressure at different depths in the wellbore meets the preset conditions, and controlling the injection of each cementing fluid into the annulus according to the injection plan for the cementing fluid.

2. The method according to claim 1, characterized in that, The cementing fluid includes a flushing fluid, a spacer fluid, a leading cement slurry, a tail cement slurry, and a displacement fluid; The determining the injection plan for the cementing fluid according to the depth of the lost circulation risk layer, the depth of the overflow risk layer, the equivalent density of pore pressure at the overflow risk layer, the equivalent density of lost circulation pressure at the lost circulation risk layer, and the equivalent density of lost circulation pressure at the overflow risk layer includes: Determining the volume of the leading cement slurry and the volume of the tail cement slurry according to the casing shoe depth, liner depth, wellbore diameter, liner diameter, the depth of the lost circulation risk layer, and the depth of the overflow risk layer; Determining the density of the leading cement slurry and the density of the tail cement slurry according to the equivalent density of pore pressure at the overflow risk layer, the equivalent density of lost circulation pressure at the lost circulation risk layer, and the equivalent density of lost circulation pressure at the overflow risk layer; Determining the density of the displacement fluid as the density of the drilling fluid, and determining the density of the flushing fluid and the density of the spacer fluid according to the density of the leading cement slurry and the density of the drilling fluid; Determining the displacement of each cementing fluid according to the density of each cementing fluid, the wellbore diameter, and the liner diameter; Determining the volume of the flushing fluid, the volume of the spacer fluid, and the volume of the displacement fluid according to the displacement of the flushing fluid, the displacement of the spacer fluid, and a preset time period.

3. The method according to claim 2, wherein The determining the volume of the leading cement slurry and the volume of the tail cement slurry according to the casing shoe depth, liner depth, wellbore diameter, liner diameter, the depth of the lost circulation risk layer, and the depth of the overflow risk layer includes: Determining the liquid column height of the leading cement slurry and the liquid column height of the tail cement slurry according to the casing shoe depth, the liner depth, the depth of the lost circulation risk layer, and the depth of the overflow risk layer; Determining the volume of the leading cement slurry according to the wellbore diameter, the liner diameter, and the liquid column height of the leading cement slurry; Determine the volume of the tail slurry of the cement slurry according to the wellbore diameter, the liner diameter, and the liquid column height of the tail slurry of the cement slurry.

4. The method according to claim 3, characterized in that, Determining the liquid column height of the leading slurry of the cement slurry and the liquid column height of the tail slurry of the cement slurry according to the casing shoe depth, the liner depth, the depth of the lost circulation risk layer, and the depth of the overflow risk layer includes: Subtract the casing shoe depth from the depth of the lost circulation risk layer to obtain the first liquid column height; Subtract the casing shoe depth from the depth of the overflow risk layer to obtain the second liquid column height; Determine the liquid column height of the leading slurry of the cement slurry according to the rule that the liquid column height of the leading slurry of the cement slurry is greater than the first liquid column height and less than the second liquid column height; After subtracting the casing shoe depth from the liner depth, subtract the liquid column height of the leading slurry of the cement slurry to obtain the liquid column height of the tail slurry of the cement slurry.

5. The method according to claim 2, characterized in that, Determining the density of the leading slurry of the cement slurry and the density of the tail slurry of the cement slurry according to the equivalent density of the pore pressure at the overflow risk layer, the equivalent density of the lost circulation pressure at the lost circulation risk layer, and the equivalent density of the lost circulation pressure at the overflow risk layer includes: Determine the density of the leading slurry of the cement slurry and the density of the tail slurry of the cement slurry according to the following rules: The density of the leading slurry of the cement slurry is greater than the equivalent density of the pore pressure at the overflow risk layer, and the density of the leading slurry of the cement slurry is less than the equivalent density of the lost circulation pressure at the lost circulation pressure risk layer; the density of the tail slurry of the cement slurry is greater than the equivalent density of the pore pressure at the overflow risk layer, and the density of the tail slurry of the cement slurry is less than the equivalent density of the lost circulation pressure at the overflow risk layer, and determine the density of the leading slurry of the cement slurry and the density of the tail slurry of the cement slurry.

6. The method according to claim 2, wherein Determining the displacement of each cementing fluid according to the density of each cementing fluid, the wellbore diameter, and the liner diameter includes: Determine the displacement of the displacement fluid according to the density of the displacement fluid, the wellbore diameter, and the liner diameter; Determine the displacement of the spacer fluid according to the density of the spacer fluid, the wellbore diameter, and the liner diameter; Determine the displacement of the leading slurry of the cement slurry according to the density of the leading slurry of the cement slurry, the wellbore diameter, and the liner diameter; Determine the displacement of the tail slurry of the cement slurry according to the density of the tail slurry of the cement slurry, the wellbore diameter, and the liner diameter; Determine the displacement of the displacement fluid as the displacement of the tail slurry of the cement slurry.

7. The method according to claim 2, characterized in that, Determining the volume of the displacement fluid, the volume of the spacer fluid, and the volume of the displacement fluid according to the displacement of the displacement fluid, the displacement of the spacer fluid, and a preset time period includes: Determine the volume of the displacement fluid according to the displacement of the displacement fluid and the preset time period; Determine the volume of the spacer fluid according to the displacement of the spacer fluid and the preset time period; Determine the sum of the drill pipe volume and the liner volume as the volume of the displacement fluid.

8. The method according to any one of claims 2-7, characterized in that, Determining the equivalent density of the pressure at different depths in the wellbore after each cementing fluid enters the annulus according to the density, displacement, and liquid column height of each cementing fluid after it enters the annulus includes: Determine the annular static liquid column pressure from the wellhead to the depth where each cementing fluid is located according to the liquid column height of each cementing fluid after entering the annulus and the density of each cementing fluid; Determine the annular frictional pressure drop from the wellhead to the depth where each cementing fluid is located according to the displacement of each cementing fluid, the wellbore diameter, the liner diameter, and the liquid column height of each cementing fluid after entering the annulus; Determine the sum of the annular static liquid column pressure and the annular frictional pressure drop from the wellhead to the depth where each cementing fluid is located as the annular pressure from the wellhead to the depth where each cementing fluid is located; Determine the equivalent density of pressure at different depths downhole after each cementing fluid enters the annulus according to the density of each cementing fluid, the liquid column height of each cementing fluid after entering the annulus, and the annular pressure from the wellhead to the depth where each cementing fluid is located.

9. A liner cementing device, characterized in that, Comprising: A memory and a processor; The memory stores computer-executable instructions; The processor executes the computer-executable instructions stored in the memory, so that the processor executes the method according to any one of claims 1-8.

10. A computer-readable storage medium, characterized in that, Computer-executable instructions are stored in the computer-readable storage medium, and when the computer-executable instructions are executed by the processor, they are used to implement the method according to any one of claims 1-8.

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