Controlled pressure cementing method and system based on deep wellbore cement slurry system simulation

Abstract

The present invention provides a pressure-controlled cementing method and system based on the simulation of deep wellbore cement slurry system, the method comprising the following steps: simulating the hydration reaction of wellbore cement slurry according to the basic data of the operating well and the cementing data, calculating the bottom hole pressure in the cementing process in real time according to the simulation, adjusting the opening of the throttle manifold to control the wellhead back pressure, so that the formation pore pressure < bottom hole pressure < formation fracture pressure. The system comprises a computer-readable medium storing a preset program, which can implement the above method when executed. The method and system described in the present invention can calculate the bottom hole pressure in real time by simulating the physical or chemical reaction process of the cement slurry system during the cementing process, and control the wellhead back pressure by adjusting the throttle manifold, so that the bottom hole pressure is always maintained within the formation safety operation window, thereby preventing the occurrence of complex accidents such as well kick, gas channeling, and leakage.

Description

Technical Field

[0001] The present invention relates to the technical field of oil and gas well development, and in particular to a pressure-controlled cementing method and system based on deep wellbore cement slurry system simulation. Background Art

[0002] As the world's energy continues to be depleted, newly discovered oil and gas reservoirs around the world continue to develop in deep layers and deep waters. Deep and deep-water oil and gas reservoirs bring not only abundant oil and gas resources, but also increasingly complex geological conditions. During the cementing process of deep oil and gas wells, problems such as the narrow safety density window of complex oil and gas reservoirs will lead to frequent well kicks, well leakage, and gas channeling during the cementing process, which seriously threatens the integrity of the wellbore.

[0003] Traditional cementing technology usually uses high-density cement slurry to balance the formation pressure to prevent gas channeling. However, under the narrow safety density window, overly heavy cement slurry can easily fracture the formation and induce leakage accidents. There are complex physical and chemical reactions in the cement slurry system in the wellbore during the cementing process, and phenomena such as cement slurry hydration and weight loss can also induce cementing gas channeling accidents. In addition, the cementing process is complicated, including multiple working conditions such as circulating well washing, casing lowering, cement injection, and waiting for solidification, which leads to variable wellbore pressure during the cementing process, making it easier to induce well kicks, leakage, gas channeling and other accidents. Therefore, traditional cementing technology has been unable to meet the requirements of safe and efficient cementing in deep and complex formation conditions. Summary of the invention

[0004] In view of the problems existing in the prior art, the present invention proposes a pressure-controlled cementing method and system based on the simulation of deep wellbore cement slurry system. The bottom hole pressure can be calculated in real time by simulating the physical or chemical reaction process of the cement slurry system during the cementing process, and the wellhead back pressure can be controlled by adjusting the throttling manifold, so that the bottom hole pressure is always maintained within the safe operating window of the formation, thereby preventing the occurrence of complex accidents such as well kick, gas channeling, and leakage, and making up for the shortcomings of traditional cementing technology.

[0005] In order to achieve the above object, the technical solution adopted by the present invention is:

[0006] A controlled pressure cementing method based on deep wellbore cement slurry system simulation comprises the following steps: simulating the reaction of wellbore cement slurry according to basic data of operating wells and cementing data, calculating the bottom hole pressure in the cementing process in real time according to the simulation, and adjusting the opening of the throttle manifold to control the wellhead pressure, so that the formation pore pressure < bottom hole pressure < formation fracture pressure.

[0007] As a further optimization of the present invention, the following steps are also included: if it is a well washing operation, the dynamic flow process of the well washing fluid is simulated and the bottom hole pressure is calculated. Among them, p bis the bottom hole pressure; p a is the wellhead back pressure, ρ is the wellbore fluid density, h is the wellbore length, f is the annular friction coefficient, v is the annular drilling fluid velocity, d w is the borehole diameter, d co is the outer diameter of the casing.

[0008] As a further optimization of the present invention, the following steps are also included: if it is a casing operation, the wellbore pressure distribution during the casing lowering process is simulated, and the equivalent flow rate during the casing lowering process is calculated. in, is the annulus equivalent flow velocity; v c Casing running speed; K c is the viscosity coefficient of drilling fluid.

[0009] As a further optimization of the present invention, the following steps are also included: if it is a cementing operation, the flow process of the slurry column liquid level in the wellbore is simulated, and the bottom hole pressure is calculated Where n is the type of injected fluid.

[0010] As a further optimization of the present invention, the following steps are also included: if it is a wait-and-set operation, the cement slurry solidification process in the wellbore is simulated according to the cement slurry data, and the bottom hole pressure is calculated. Among them, h i is the length of the i-th cement paste; α i is the hydration degree of the i-th cement paste; α 500 It is the hydration degree of cement slurry when the strength of cement slurry reaches the preset strength.

[0011] As a further optimization of the present invention, if the bottom hole pressure is less than the formation pore pressure when the throttling manifold is opened to a preset minimum opening, the back pressure pump is turned on to increase the wellhead pressure, thereby making the bottom hole pressure greater than the formation pore pressure.

[0012] A pressure-controlled cementing system based on deep wellbore cement slurry system simulation, comprising a throttle manifold, a back-pressure pump connected to the throttle manifold, a processor electrically connected to the throttle manifold and the back-pressure pump, respectively, and a computer-readable medium connected to the processor, wherein the computer-readable medium stores a preset program, which, when executed by the processor, can implement the pressure-controlled cementing method based on deep wellbore cement slurry system simulation as described in any of the above items.

[0013] Compared with the prior art, the present invention has the following beneficial effects:

[0014] The controlled pressure cementing method based on deep wellbore cement slurry system simulation described in the present invention calculates the bottom hole pressure in real time by simulating the physical or chemical reaction process of the cement slurry system during the cementing process, and controls the wellhead back pressure by adjusting the throttling manifold, so that the bottom hole pressure is always maintained within the safe operation window of the formation, thereby preventing the occurrence of complex accidents such as well kick, gas channeling, and leakage, and making up for the shortcomings of traditional cementing technology.

[0015] The pressure-controlled cementing system based on deep wellbore cement slurry system simulation described in the present invention can automatically control the throttling manifold and the back-pressure pump according to the simulation and real-time calculation, thereby effectively ensuring the safety and reliability of the cementing process, preventing the occurrence of complex accidents such as well kicks, gas channeling, and leakage, and making up for the shortcomings of traditional cementing technology. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] In order to more clearly illustrate the examples of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0017] Figure 1 It is a schematic diagram of the well washing operation of the controlled pressure cementing system based on the simulation of the deep wellbore cement slurry system of the present invention;

[0018] Figure 2 It is a schematic diagram of casing lowering operation of a controlled pressure cementing system based on deep wellbore cement slurry system simulation of the present invention;

[0019] Figure 3 It is a schematic diagram of cementing operation of a controlled pressure cementing system based on deep wellbore cement slurry system simulation of the present invention;

[0020] Figure 4 It is a schematic diagram of the waiting setting operation of the controlled pressure cementing system based on the simulation of the deep wellbore cement slurry system of the present invention.

[0021] In the figure: 1, drilling rig; 2, rotating control head; 3, blowout preventer; 4, wellbore; 5, drilling fluid pump; 6, drilling fluid tank; 7, cement slurry pump; 8, cement tank; 9, back pressure pump; 10, throttling manifold; 11, processor; 12, flow meter; 13, gas-liquid separation tank; 14, mud pool; 15, drill pipe; 16, drill bit; 17, casing; 18, casing head; 19, cement slurry; 20, wellbore proppant; 21, branch wellbore; 22, computer readable medium. DETAILED DESCRIPTION

[0022] The present invention is described in detail below by way of exemplary embodiments. However, it should be understood that elements, structures, and features in one embodiment may also be beneficially combined in other embodiments without further description.

[0023] In the description of the present invention, it should be noted that the directions or positional relationships indicated by the terms "inside", "outside", "upper", "lower", "front", "rear", etc. are based on the positional relationships shown in the drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific direction, be constructed and operated in a specific direction, and therefore cannot be understood as limiting the present invention. In addition, the terms "first", "second", and "third" are used for descriptive purposes only, and cannot be understood as indicating or implying relative importance.

[0024] refer to Figure 1-2 The present invention proposes a pressure-controlled cementing method based on deep wellbore cement slurry system simulation, comprising the following steps: simulating the reaction of wellbore cement slurry according to basic data of the operating well and cementing data, calculating the bottom hole pressure in the cementing process in real time according to the simulation, and adjusting the opening of the throttle manifold to control the wellhead pressure, so that the formation pore pressure < bottom hole pressure < formation fracture pressure.

[0025] The controlled pressure cementing method based on deep wellbore cement slurry system simulation described in the present invention calculates the bottom hole pressure in real time by simulating the physical or chemical reaction process of the cement slurry system during the cementing process, and controls the wellhead back pressure by adjusting the throttling manifold, so that the bottom hole pressure is always maintained within the safe operation window of the formation, thereby preventing the occurrence of complex accidents such as well kick, gas channeling, and leakage, and making up for the shortcomings of traditional cementing technology.

[0026] The controlled pressure cementing method based on deep wellbore cement slurry system simulation in this embodiment specifically includes the following steps:

[0027] Determine the current job status;

[0028] S1. If it is a well-washing operation, the dynamic flow process of the well-washing fluid in the wellbore is simulated, and the bottom hole pressure is determined by the following formula:

[0029]

[0030] Where:

[0031] p b is the bottom hole pressure, Pa;

[0032] p a is the wellhead back pressure, Pa;

[0033] ρ is the wellbore fluid density, kg / m 3 ;

[0034] h is the wellbore length, m;

[0035] f is the annulus module coefficient;

[0036] v is the annular drilling fluid velocity, m / s;

[0037] d w is the borehole diameter, m

[0038] d co is the outer diameter of the casing, m.

[0039] The bottom hole pressure is calculated by formula (1) and compared with the formation pore pressure and formation fracture pressure. If the bottom hole pressure is lower than the formation pore pressure, the choke manifold opening is reduced to increase the wellhead back pressure by:

[0040] Δp=p p -p b (2)

[0041] If the bottom hole pressure is greater than the formation fracture pressure, increase the opening of the choke manifold to make the wellhead back pressure reach the bottom hole, and the reduction is:

[0042] Δp=p b -p f (3)

[0043] In the formula, p p is the formation pore pressure, p f is the formation fracture pressure.

[0044] S2. If it is a casing operation, simulate the wellbore pressure distribution under the action of casing pressure and calculate the equivalent flow rate when casing is lowered:

[0045]

[0046] Where:

[0047] is the annulus equivalent flow velocity, m / s;

[0048] v c Casing running speed, m / s;

[0049] K c is the viscosity coefficient of drilling fluid, dimensionless.

[0050] Then, in combination with formula (1), the bottom hole pressure during casing lowering is obtained in real time according to the annular equivalent flow rate, and the comparison of the bottom hole pressure with the formation pore pressure and the formation fracture pressure in step S1 and the corresponding operations are repeated.

[0051] S3. If it is a cementing operation, the dynamic flow process of various liquids in the well is simulated. The temporal and spatial distribution of various types of fluids such as cement slurry, spacer fluid, flushing fluid, etc. are considered in the simulation, and the real-time bottom hole pressure is calculated by the following formula:

[0052]

[0053] Where:

[0054] n is the type of injected fluid.

[0055] Then, the comparison of the bottom hole pressure with the formation pore pressure and the formation fracture pressure in step S1 and the corresponding operations are repeated.

[0056] S4. If it is a wait-and-set operation, it is necessary to simulate the cement slurry hydration and solidification process in the wellbore, consider the cement slurry hydration weight loss phenomenon, and determine the real-time bottom hole pressure by the following formula:

[0057]

[0058] Where:

[0059] h i is the length of the ith cement paste, m;

[0060] α i is the hydration degree of the i-th cement slurry;

[0061] α 500 It is the hydration degree of the cement slurry when the strength of the cement slurry reaches the set strength. In this embodiment, it is set to the hydration degree of the cement slurry at 239Pa.

[0062] Then, the comparison of the bottom hole pressure with the formation pore pressure and the formation fracture pressure in step S1 and the corresponding operations are repeated.

[0063] In this way, the bottom hole pressure in the entire cementing process is simulated in real time, and the wellhead back pressure is controlled by controlling the throttling manifold and back pressure pump, so as to effectively control the bottom hole pressure within a safe range, preventing the occurrence of complex accidents such as well kick, gas channeling, and leakage during the cementing process. At the same time, the simulated bottom hole pressure can be compared with the tested pressure in real time, effectively judging the bottom hole situation and further ensuring the safety of construction.

[0064] It should be noted that, in this embodiment, the basic data of the operating well includes wellbore trajectory, wellbore structure, three-pressure profile of the formation, slurry column fluid parameters, formation temperature gradient, etc.

[0065] In addition, reference Figure 1-4The present invention also proposes a pressure-controlled cementing system based on deep wellbore cement slurry system simulation, including a throttle manifold 10, a back-pressure pump 9 connected to the throttle manifold 10, a processor 11 electrically connected to the throttle manifold 10 and the back-pressure pump 9, respectively, and a computer-readable medium 22 connected to the processor 11, wherein a preset program is stored in the computer-readable medium 22, and when the preset program is executed by the processor, the pressure-controlled cementing method based on deep wellbore cement slurry system simulation as described above can be implemented.

[0066] refer to Figure 1-4 , which is the operation status of the four stages of well washing, casing running, cementing and waiting for setting in this embodiment:

[0067] like Figure 1 As shown, in the well washing operation, the drilling fluid pump 5 injects the well washing fluid to wash the cuttings in the wellbore. At this time, the processor 11 adjusts the opening of the throttle manifold 10 according to the simulation in the computer readable medium 11, the bottom hole pressure calculated according to formula (1), and the comparison result between the bottom hole pressure and the formation pore pressure and the formation fracture pressure, so as to control the wellhead back pressure;

[0068] like Figure 2 As shown, during the casing operation, the casing is slowly lowered into the wellbore, which will cause agitated pressure. The processor 11 calculates the equivalent flow rate according to the wellbore pressure distribution simulated in the computer-readable medium 22 according to formula (4), and calculates the bottom hole pressure according to the equivalent flow rate. The calculated bottom hole pressure is compared with the formation pore pressure and the formation fracture pressure to adjust the opening of the throttle manifold 10 or the back pressure pump 9, thereby adjusting the wellhead back pressure;

[0069] like Figure 3 As shown, in the cementing operation, cement slurry, spacer fluid and flushing fluid are required for cementing, which are injected into the wellbore through the cement slurry pump 7. The processor 11 calculates the bottom hole pressure according to the simulation in the computer readable medium 11 and the formula (5), and adjusts the opening of the choke manifold 10 by comparing the calculated bottom hole pressure with the formation pore pressure and the formation fracture pressure, thereby adjusting the wellhead back pressure.

[0070] like Figure 4 As shown, in the waiting setting operation, when the cement slurry column is injected to the set position, the cement slurry pump 7 stops, and the processor 11 calculates the bottom hole pressure by formula (5) based on the simulation in the computer readable medium 22 and taking into account the hydration formula of the cement slurry. The calculated bottom hole pressure is compared with the formation pore pressure and the formation fracture pressure to adjust the opening of the throttling manifold 10 or the back pressure pump 9, thereby adjusting the wellhead back pressure.

[0071] The above description is only a preferred embodiment of the present invention and does not limit the present invention in other forms. Any technician familiar with the profession may use the technical content disclosed above to change or modify it into an equivalent embodiment with equivalent changes and apply it to other fields. However, any simple modification, equivalent change and modification made to the above embodiment based on the technical essence of the present invention without departing from the content of the technical solution of the present invention still falls within the protection scope of the technical solution of the present invention.

Claims

1. A pressure controlled cementing method based on deep wellbore cement slurry system simulation, characterized in that: The method comprises the following steps: simulating the reaction of the wellbore cement slurry according to the basic data of the operating well and the cementing data, calculating the bottom hole pressure in the cementing process in real time according to the simulation, and adjusting the opening of the throttle manifold to control the wellhead pressure, so that the formation pore pressure < bottom hole pressure < formation fracture pressure; If it is a well-washing operation, simulate the dynamic flow process of the well-washing fluid and calculate the bottom hole pressure Among them, p b is the bottom hole pressure; p a is the wellhead back pressure, ρ is the wellbore fluid density, h is the wellbore length, f is the annular friction coefficient, v is the annular drilling fluid velocity, d w is the borehole diameter, d co is the outer diameter of the casing; If it is a casing operation, simulate the wellbore pressure distribution during the casing lowering process and calculate the equivalent flow rate during the casing lowering process in, is the annulus equivalent flow velocity; v c Casing running speed; K c is the viscosity coefficient of drilling fluid; If it is a cementing operation, the flow process of the slurry column liquid surface in the wellbore is simulated and the bottom hole pressure is calculated Where n is the type of injected fluid; If it is a wait-and-set operation, the cement slurry solidification process in the wellbore is simulated according to the cement slurry data, and the bottom hole pressure is calculated. Among them, h i is the length of the i-th cement paste; α i is the hydration degree of the i-th cement paste; α 500 It is the hydration degree of cement slurry when the strength of cement slurry reaches the preset strength.

2. The controlled pressure cementing method based on deep wellbore cement slurry system simulation according to claim 1, characterized in that: The method also includes the following steps: if the bottom hole pressure is still lower than the formation pore pressure when the throttling manifold is opened to the preset minimum opening, the back pressure pump is started to increase the wellhead pressure, thereby making the bottom hole pressure higher than the formation pore pressure.

3. A pressure controlled cementing system based on deep wellbore cement slurry system simulation, characterized in that: It includes a throttle manifold, a back-pressure pump connected to the throttle manifold, a processor electrically connected to the throttle manifold and the back-pressure pump, respectively, and a computer-readable medium connected to the processor, wherein a preset program is stored in the computer-readable medium, and when the preset program is executed by the processor, the pressure-controlled cementing method based on deep wellbore cement slurry system simulation as described in any one of claims 1-2 can be implemented.

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