Horizontal well cementing method and application thereof

Abstract

The invention discloses a horizontal well cementing method and application thereof. The method comprises the steps that a casing string is tripped into a horizontal well, and the distance between the tail end of the casing string and the well bottom is preset; the preset distance is larger than the sum of the telescopic length after the casing string is heated to the target temperature and the length of a well cementation operation reserved open hole pocket; drilling fluid is pumped into the casing string for circulating well washing operation; a first rubber plug is put into the casing string in sequence, and a first preset amount of cement paste is pumped into the casing string; a second rubber plug is put in, and a second preset amount of non-cementitious substance is pumped in; a third rubber plug is put in, displacement liquid is pumped into the third rubber plug for slurry replacement operation till the third rubber plug reaches the float collar to be collided and pressed, so that after well cementation is completed, the cement slurry fills the well cementation annulus outside the free toe end section well cementation annulus, and the non-cementation substance fills the free toe end section well cementation annulus; wherein the free toe end section well cementation annulus is a well cementation annulus between the well bottom and the preset distance above the float shoe. Space can be provided for stretching of the casing string, and an emptying channel is provided for circulation of hot fluid in the casing string.

Description

Technical Field

[0001] The present invention relates to the technical field of oil and gas drilling, and in particular to a horizontal well cementing method and application thereof. Background Art

[0002] In-situ conversion refers to the use of horizontal well electric heating light-weighting technology to continuously heat the organic-rich shale layer (source rock) buried at a depth of 300 to 3000m, so that various types of organic matter undergo light-weighting conversion to achieve oil and gas development. Ultra-high temperature downhole heating is an important way to achieve underground in-situ conversion, and it is also a practical technology for achieving medium- and low-maturity source rock oil and gas development; according to research, the temperature for light-weighting conversion of medium- and low-maturity source rock oil and gas organic matter is generally around 300 to 350°C, and in order to ensure continuous heating development in the development area, the wellbore temperature of the downhole heating well needs to exceed 500°C or even higher for a long time, and the heating time is generally more than 2 years.

[0003] Well completion is the final step in the drilling and completion process, including drilling into the oil layer, selection of completion methods, cementing, and perforating operations. Figure 1 As shown, in order to allow fluids such as oil, gas, and water 11 to flow smoothly into the wellbore 12, be produced to the ground 13, and facilitate subsequent well repair operations, and ensure long-term stable and high production of the oil well, casing cementing is generally required for cementing and completion. Figure 1 As shown, the annulus between the casing 16 lowered into the wellbore and the formation 17 is filled with cementing cement 15, and the contact surfaces between the cement and the casing, and the cement and the formation have good bonding properties in the well section close to the bottom of the well 14, so as to achieve the purpose of cementing.

[0004] In the prior art, when developing medium- and low-maturity source rock oil and gas using in-situ conversion technology, conventional casing cementing and completion methods are generally used for cementing horizontal wells. Summary of the invention

[0005] The supercritical hot fluid in the horizontal wellbore needs an emptying channel, and the excessive thermal expansion and contraction of the completion string also requires a certain amount of moving space; in the prior art, after the casing cementing is completed, the annulus between the casing and the formation is filled with cementing cement, so that the hot fluid lacks an emptying channel, and a special perforating operation needs to be set up to establish the connection between the hot fluid in the wellbore and the formation after heating. At the same time, the use of the existing casing cementing method also limits the thermal expansion and contraction of the completion string, which is easy to cause the casing string to be lifted at the wellhead or the casing string to deform, causing the seal between the heating device and the casing string to fail, thereby destroying the integrity of the wellbore and causing the possibility of complex fluid media (such as hydrogen sulfide) leaking to the ground, thereby causing safety accidents; therefore, it is very necessary to study a cementing method to solve or partially solve the problem that the toe casing of the horizontal well lacks a communication channel with the formation and the toe casing cannot be freely expanded and contracted due to the existing cementing method in the process of oil and gas development using in-situ conversion technology.

[0006] In view of the above problems, the present invention is proposed to provide a horizontal well cementing method and application thereof that overcomes the above problems or at least partially solves the above problems.

[0007] The horizontal well cementing method provided by the embodiment of the present invention comprises:

[0008] The casing string is lowered into the horizontal well, and the end of the casing string is set at a preset distance from the bottom of the well, wherein the casing string includes: a casing string, a float collar, a casing section and a float shoe connected in sequence from top to bottom; the preset distance is greater than the sum of the elongation length of the casing string after being heated to the target temperature and the length of the open hole pocket reserved for cementing operation;

[0009] Pump drilling fluid into the casing string to perform circulating well washing operations;

[0010] A first rubber plug is put into the casing string, and a first preset amount of cement slurry is pumped in; after the cement slurry is pumped in, a second rubber plug is put into the casing string, and a second preset amount of non-cementing material is pumped in; after the non-cementing material is pumped in, a third rubber plug is put into the casing, and displacement fluid is pumped in to perform slurry displacement operations, until the third rubber plug reaches the float collar and hits the pressure, and the first rubber plug and the second rubber plug rupture under the action of pressure, so that the cementing annulus inside the casing string and between the casing string and the formation or the outer casing is connected, and then the cement slurry fills the cementing annulus outside the cementing annulus of the free toe end section, and the non-cementing material fills the cementing annulus of the free toe end section; wherein the cementing annulus of the free toe end section is the cementing annulus between the bottom of the well and the preset distance above the float shoe; the third rubber plug can rupture under the preset pressure to establish communication between the inside of the casing string and the formation.

[0011] In an optional embodiment, the telescopic length of the casing string after being heated to the target temperature is determined based on: the temperature difference increased when the casing string is heated to the target temperature, the length of the effective deformation section of the casing string and the linear elongation coefficient of the casing.

[0012] In an optional embodiment, when the length of the horizontal section of the casing string is less than or equal to the effective deformation section threshold of the casing string, when determining the telescopic length of the casing string after the casing string is heated to the target temperature, the effective deformation section length of the casing string used is the length of the horizontal section of the casing string;

[0013] When the length of the horizontal section of the casing string is greater than the effective deformation section threshold of the casing string, when determining the telescopic length of the casing string after being heated to the target temperature, the effective deformation section length of the casing string used is the effective deformation section threshold; the effective deformation section threshold is determined based on the strength of the cement used in the cementing process.

[0014] In an optional embodiment, the non-cementitious material includes: clean water, seawater, a liquid to which a substance for preventing casing corrosion or a substance for delaying casing corrosion is added, and a liquid mixture containing cementing cement having a bonding strength within a preset range; the preset range of the bonding strength is that the compressive strength of the cement stone after 24 to 48 hours is less than 5 MPa.

[0015] In an optional embodiment, the free toe end section cementing annulus is the cementing annulus between the bottom of the well and the position of 2 to 3 casings above the floating shoe.

[0016] In an optional embodiment, the horizontal well cementing method provided by the embodiment of the present invention, before pumping non-cementing material into the casing string, also includes: determining the second preset amount based on the preset length of the free toe end section cementing annulus and the operable output of the field operation equipment.

[0017] In an optional embodiment, the second preset amount is determined based on a preset length of the cementing annulus of the free toe end section and an output amount operable by the field operation equipment; including: based on the preset length of the cementing annulus of the free toe end section, the preset amount of non-cemented material is calculated in combination with the following formula;

[0018]

[0019] Wherein, P is the calculated preset amount of non-cemented material; K is the elongation length of the casing string after being heated to the target temperature; P 1 is the average expansion coefficient; D b Dc is the diameter of the drill bit; Dc is the diameter of the casing; ci is the inner diameter of the casing; c 1is the length between the float shoe and the float collar; C is the open hole pocket length reserved for cementing operations; N is the length between the float shoe of the casing string and the top of the cementing annulus of the free toe end section in the preset length of the cementing annulus of the free toe end section;

[0020] If the calculated preset amount of non-cementitious material is less than the operable output of the field operation equipment, the operable output of the field operation equipment is used as the second preset amount; accordingly, the actual length of the cementing annulus of the free toe section is determined by the second preset amount pumped in;

[0021] If the calculated preset amount of non-cementitious material is greater than the operable output of the on-site operation equipment, the calculated preset amount is used as the second preset amount.

[0022] In an optional embodiment, before the casing string is lowered into a preset position in the wellbore, the horizontal well cementing method provided by the embodiment of the present invention further includes: determining a target well depth of the horizontal well, and drilling the target formation to the target well depth of the horizontal well using drilling equipment and a drilling tool assembly according to the drilling design; the target well depth of the horizontal well is the depth of the horizontal well section that enters the target oil and gas layer and has a well inclination of more than 85 degrees;

[0023] Wellbore cleaning operations are carried out after drilling the target well depth.

[0024] In an optional embodiment, the wellbore cleaning operation includes: short-distance drilling operation, 1 to 3 drill string runs to clear the well, circulating drilling fluid in the original drill string, and injecting a certain amount of cleaning fluid to clean the wellbore wall.

[0025] In an optional embodiment, the step of pumping drilling fluid into the casing string to perform a circulating well washing operation includes:

[0026] Adjust drilling fluid properties to preset requirements;

[0027] Inject drilling fluid into the casing string and fill the inner hole of the casing string to keep the wellbore pressure and formation pressure in a preset equilibrium state;

[0028] Increase the drilling fluid displacement from small to large, so that the drilling fluid is injected from the casing string and discharged from the annulus formed between the casing string and the formation or the outer casing, and continue for a preset time to realize the circulation of the drilling fluid.

[0029] In an optional embodiment, the first rubber plug, the second rubber plug and the third rubber plug are self-locking rubber plugs with rupture disks.

[0030] Based on the same inventive concept, an embodiment of the present invention provides an application of the above-mentioned horizontal well cementing method in the field of oil and gas drilling technology.

[0031] The beneficial effects of the above technical solution provided by the embodiment of the present invention include at least:

[0032] The horizontal well cementing method provided by the embodiment of the present invention makes the end of the casing string a preset distance from the bottom of the well when the casing string is lowered into the horizontal well, wherein the preset distance is greater than the sum of the elongation length of the casing string after being heated to the target temperature and the length of the open hole pocket reserved for the cementing operation; and when the cementing operation is performed, the cementing annulus in the free toe section is filled with non-cemented materials, so as to provide corresponding expansion and contraction space for the thermal elongation of the casing string generated by ultra-high temperature when developing medium and low maturity source rock oil and gas using in-situ conversion technology, so as to reduce the lifting and deformation of the casing string at the wellhead. Moreover, during cementing, the inserted third rubber plug can rupture under preset conditions to establish communication between the inside of the casing string and the formation, so that the critical thermal fluid generated during the ultra-high temperature heating process can be discharged to the formation, which reduces the possibility that the critical thermal fluid generated will form a high temperature and high pressure state in the casing, push the sealing device between the casing string and the heating device to move, and make the seal between the casing string and the heating device fail, thereby destroying the integrity of the wellbore and causing the possibility of complex fluid media (such as hydrogen sulfide) to leak to the ground, thereby improving the safety of the operation, while reducing the pressure requirements of the sealing device and reducing the operating cost.

[0033] Other features and advantages of the present invention will be described in the following description, and partly become apparent from the description, or understood by practicing the present invention. The purpose and other advantages of the present invention can be realized and obtained by the structures particularly pointed out in the written description, claims, and drawings.

[0034] The technical solution of the present invention is further described in detail below through the accompanying drawings and embodiments. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] The accompanying drawings are used to provide a further understanding of the present invention and constitute a part of the specification. Together with the embodiments of the present invention, they are used to explain the present invention and do not constitute a limitation of the present invention. In the accompanying drawings:

[0036] Figure 1 It is a schematic diagram of casing cementing in the prior art;

[0037] Figure 2 A schematic diagram of heating a horizontal well section when developing medium- and low-maturity source rock oil using in-situ conversion technology in the prior art;

[0038] Figure 3 A schematic diagram of a process of a horizontal well cementing method according to an embodiment of the present invention;

[0039] Figure 4 Schematic diagram of the positional relationship of the casing string and the casing string when it is lowered into a horizontal well in an embodiment of the present invention;

[0040] Figure 5 A schematic diagram of the length of a horizontal section in a horizontal well developed for in-situ conversion of electric heating light materials in an embodiment of the present invention;

[0041] Figure 6 Schematic diagram of the segmented structure of a horizontal well in an embodiment of the present invention;

[0042] Figure 7 It is a schematic diagram of the structure of a horizontal well after cementing is completed in an embodiment of the present invention. DETAILED DESCRIPTION

[0043] The exemplary embodiments of the present disclosure will be described in more detail below with reference to the accompanying drawings. Although the exemplary embodiments of the present disclosure are shown in the accompanying drawings, it should be understood that the present disclosure can be implemented in various forms and should not be limited by the embodiments set forth herein. On the contrary, these embodiments are provided to enable a more thorough understanding of the present disclosure and to fully convey the scope of the present disclosure to those skilled in the art.

[0044] Reference Figure 2 As shown, when the in-situ conversion technology is used to develop medium- and low-maturity source rock oil and gas, the wellbore of the horizontal well 21 needs to be heated by an ultra-high temperature heating device 22, so that the initial wellbore residual fluid 23 is converted into a high-temperature and high-pressure state, and even forms a hot fluid in a high-temperature and high-pressure supercritical state. However, since the cementing method for horizontal wells in the prior art is generally casing cementing completion, the high-quality cement ring 15 in the casing string and the formation or the upper casing annulus makes the hot fluid lack a channel for emptying to the formation 17, and thus the casing string 24 structure is too high, increasing the operating cost; at the same time, after ultra-high temperature heating, the thermal expansion and contraction of the overheated completion casing string also requires a certain amount of moving space, and the high-quality cementing quality after the casing cementing completion limits the thermal expansion and contraction of the completion casing string 16.

[0045] In order to solve the problems in the prior art of the existing cementing method in the process of oil and gas development using in-situ conversion technology, such as the lack of communication channel between the toe casing of the horizontal well and the inability of the toe casing to freely expand and contract, the embodiment of the present invention provides a horizontal well cementing method and its application. It should be noted that in the embodiment of the present invention, the direction close to the bottom of the well is called down, and the direction close to the wellhead is called up; and the non-cemented material in the embodiment of the present invention specifically refers to a material with a compressive strength of less than 2Mpa after 24 hours.

[0046] The horizontal well cementing method provided by the embodiment of the present invention has a flow chart referring to Figure 1 As shown, the following steps are included:

[0047] Step S101: lowering a casing string into a horizontal well, and making the end of the casing string a preset distance from the bottom of the well, the casing string comprising: a casing string, a float collar, a casing section and a float shoe connected in sequence from top to bottom; the preset distance is greater than the sum of the telescopic length of the casing string after being heated to the target temperature and the length of the open hole pocket reserved for cementing operation;

[0048] Step S102: Pumping drilling fluid into the casing string to perform circulating well washing operations;

[0049] Step S103: a first rubber plug is put into the casing string, and a first preset amount of cement slurry is pumped into the casing string; after the cement slurry is pumped into the casing string, a second rubber plug is put into the casing string, and a second preset amount of non-cementing material is pumped into the casing string; after the non-cementing material is pumped into the casing string, a third rubber plug is put into the casing, and displacement fluid is pumped into the casing string for displacement operation, until the third rubber plug reaches the floating collar and is pressed, and the first rubber plug and the second rubber plug are broken under the action of pressure, so that the cementing annulus inside the casing string and between the casing string and the formation or the outer casing is connected, and then the cement slurry fills the cementing annulus outside the cementing annulus of the free toe end section, and the non-cementing material fills the cementing annulus of the free toe end section; wherein, the cementing annulus of the free toe end section is the cementing annulus between the bottom of the well and the preset distance above the float shoe; the third rubber plug can be broken under the preset pressure to establish communication between the inside of the casing string and the formation.

[0050] The horizontal well cementing method provided by the embodiment of the present invention makes the end of the casing string a preset distance from the bottom of the well when the casing string is lowered into the horizontal well, wherein the preset distance is greater than the sum of the elongated length of the casing string after being heated to the target temperature and the length of the open hole pocket reserved for the cementing operation; and when the cementing operation is performed, the cementing annulus in the free toe section is filled with non-cemented materials, that is, after the cementing is completed, the end of the casing string is still in a state where it can be extended toward the bottom of the well, thereby providing corresponding expansion and contraction space for the thermal elongation of the casing string generated by ultra-high temperature when developing medium and low maturity source rock oil and gas using in-situ conversion technology, so as to reduce the elongation of the casing string toward the wellhead, resulting in the lifting and deformation of the casing string at the wellhead.

[0051] Moreover, when cementing, the inserted third rubber plug can be broken under preset conditions to establish communication between the inside of the casing string and the formation, so that the critical thermal fluid generated during the ultra-high temperature heating process can be discharged to the formation, which reduces the possibility that the critical thermal fluid generated will form a high temperature and high pressure state in the casing, push the sealing device between the casing string and the heating device to move, and make the seal between the casing string and the heating device fail, thereby destroying the integrity of the wellbore and causing the possibility of complex fluid media (such as hydrogen sulfide) to leak to the ground, thereby improving the safety of the operation, while reducing the pressure requirements for the sealing device and reducing the operating cost.

[0052] Specifically, refer to Figure 4As shown, the casing string 4 includes "floating shoe 41 + casing section 42 + floating collar 43 + casing string 44" from bottom to top; wherein, the length of the casing section 42 can be selected as the length of 1 to 2 casings, and generally the length of a single casing is about 10 meters, that is, the length of the casing section 42 can be selected as 10 to 20 meters; the casing string 44 includes a casing or casing combination of corresponding heat-resistant and corrosion-resistant steel grades selected according to the fluid or produced fluid contained in the formation lowered (whether it contains hydrogen sulfide, hydrogen, carbon dioxide, the temperature of the produced fluid, etc.); the floating shoe 41 is connected to the end of the casing string, and plays the role of casing guide shoe and back pressure valve. The floating collar 43 is connected to the casing section 42 20 to 30 meters away from the end of the casing string, and plays the role of cementing collision pressure, support ring and back pressure valve. Optionally, the floating shoe 41 and the floating collar 43 are used in horizontal wells for in-situ conversion and development of medium and low-mature shale oil, and have the ability to withstand temperatures above 350°C.

[0053] Furthermore, the preset distance between the end of the casing string and the bottom of the well is specifically Figure 4 The length M in the middle, that is, after the casing string 44 is lowered into the horizontal well, the floating shoe 41 at its bottom (lower part) is M meters away from the bottom of the drilling well 45. Among them, in this embodiment, the preset distance between the end of the casing string and the bottom of the well is greater than the sum of the elongation length of the casing string after it is heated to the target temperature and the length of the open hole pocket reserved for cementing operations. Among them, the open hole pocket length C reserved for cementing operations is generally 0.5m to 10m, which is determined according to the cleaning condition of the horizontal well drilling wellbore. The better the cleaning degree, the smaller the C value, otherwise the larger it is. Compared with conventional cementing, which only reserves a C-meter open hole pocket length to reserve space for sand deposition on the well wall; the preset distance in the embodiment of the present invention also includes: the elongation length after the casing string is heated to the target temperature, so as to reserve a safe space for the expansion and contraction of the casing string in subsequent operations, and the value of the preset distance M can be selected according to actual needs, and the embodiment of the present invention does not make specific limitations.

[0054] In one embodiment, when determining the preset distance, the telescopic length of the casing string after being heated to the target temperature can be determined based on the temperature difference increased when the casing string is heated to the target temperature, the length of the effective deformation section of the casing string and the linear elongation coefficient of the casing.

[0055] Specifically, the telescopic length of the casing string after being heated to the target temperature is calculated based on the product of the temperature difference when the casing string is heated to the target temperature in subsequent working conditions, the length of the effective deformation section of the casing string, and the linear elongation coefficient of the casing; the calculation formula is as follows:

[0056] K=m 1 ×ΔT×P

[0057] Where K is the telescopic length of the casing string after it is heated to the target temperature, in meters; m 1is the length of the effective deformation section of the casing string, in meters; P is the linear elongation coefficient of the casing, in meters per degree Celsius; ΔT is the temperature change when the casing is heated to the target temperature, in degrees Celsius.

[0058] In actual applications, the temperature difference of the casing string in subsequent working conditions is greater than 200°C, up to 600°C; the inventors of this application found in their research that the length of the effective deformation section of the casing string is less than or equal to the length of the horizontal section of the casing string, and the length of the effective deformation section of the casing string is determined according to the strength of the cement in the horizontal section. The greater the strength, the smaller the threshold value m of the effective deformation section of the casing string, and the value of m is generally between 200 and 400 meters. Therefore, in actual applications, when the horizontal section of the casing string is greater than the threshold value m of the effective deformation section of the casing string, the length of the effective deformation section of the casing string is m meters, and when the horizontal section of the casing string is less than the threshold value m of the effective deformation section of the casing string, the length of the effective deformation section of the casing string is equal to the length of the horizontal section of the casing string.

[0059] That is, in one embodiment, when the horizontal section length of the casing string is less than or equal to the effective deformation section threshold m of the casing string, the effective deformation section length m of the casing string used when determining the telescopic length of the casing string after heating to the target temperature is 1 is the length of the horizontal section of the casing string;

[0060] When the length of the horizontal section of the casing string is greater than the effective deformation section threshold m of the casing string, the effective deformation section length m of the casing string used when determining the telescopic length of the casing string after heating to the target temperature is 1 is the effective deformation segment threshold, wherein the effective deformation segment threshold is determined based on the strength of the cement used in the cementing process.

[0061] In one embodiment, when cementing is performed in this embodiment, the non-cementing substances used may include: clean water, seawater, liquid to which substances that prevent casing string corrosion or substances that delay casing string corrosion are added, and a liquid mixture containing cementing cement with a bonding strength within a preset range; the preset range of bonding strength refers to the compressive strength of cement stone after 24 to 48 hours is less than 5MPa. Among them, the substances added to prevent casing string corrosion or substances that delay casing string corrosion may be: such as fatty amines, aromatic amines, imidazolines, quaternary ammonium salts, chromates, nitrites, phosphates, etc.

[0062] In one embodiment, before step S101: lowering the casing string into a preset position in the wellbore, the method further includes: determining a target depth of the horizontal well, and drilling the target formation to the target depth of the horizontal well using drilling equipment and a drilling tool assembly according to the drilling design; the target depth of the horizontal well is the depth of the horizontal well section that enters the target oil and gas layer and has a well inclination of more than 85 degrees;

[0063] Wellbore cleaning operations are carried out after drilling the target well depth.

[0064] Reference Figure 5 As shown, it is a schematic diagram of a horizontal well, in which the horizontal well section 31 of the horizontal well is a hole with a single size and a certain length, specifically starting from the depth point A where the target oil and gas layer is entered and the well inclination (well inclination is the angle between the wellbore axis and the plumb bob direction) exceeds 85 degrees, to the final drilling depth point B, which is also located in the target oil and gas layer and the well inclination exceeds 85 degrees; the length L of the horizontal well section 31 is the difference between the well depths of point B and point A, and L is generally greater than or equal to 200 meters, usually between 400 and 1500 meters.

[0065] In one embodiment, when a horizontal well is used for oil and gas development using in-situ conversion technology, determining a target well depth of the horizontal well includes:

[0066] Determine the length of the effective heating horizontal well section of the target well, wherein the length of the effective heating horizontal well section can be determined based on the needs of the oil and gas reservoir to be developed, the power required for heating to the target temperature, the ground power supply conditions, etc.;

[0067] The additional length of the horizontal well section is determined based on the change in thermal elongation of the heating device that needs to be lowered into the horizontal well section when the target well is heated to the target temperature during in-situ conversion development, the engineering error required during the installation of the heating device, and the preset distance between the end of the casing string and the bottom of the well;

[0068] The target depth of the horizontal well is determined based on the length of the effective heated horizontal well section and the additional length.

[0069] Reference Figure 5 As shown, when using the electric heating lightweight in-situ conversion technology for oil and gas development, the determination of the length L of the horizontal well section includes: L=l+k. l is the length of the effective heating horizontal well section required for the electric heating lightweight in-situ conversion, which is generally greater than or equal to 200 meters, usually between 400 and 1500 meters, and its effective heating horizontal well section is usually located in the middle of the horizontal well section, leaving a certain distance near point A and point B; k is the additional length required to consider the thermal elongation change of the heating device in the electric heating lightweight in-situ conversion technology, the engineering error required for setting up the heating device in the effective heating area during drilling and completion, and the preset distance between the end of the casing string and the bottom of the well. k is generally between 10 and 100 meters, and the larger the effective heating horizontal well section l, the larger k. Specifically, refer to Figure 5As shown, the additional length is divided into two parts, namely, the additional length section near position A and the additional length section near point B. The additional length section near position A is mainly required for the additional length near point A required for the installation of the heating device set in the effective heating area during the drilling and completion process, and the additional length section near position B is required for the additional length to take into account the thermal elongation change of the heating device in the electric heating lightweight in-situ conversion technology, the engineering error required for the installation of the heating device near point B set in the effective heating area during the drilling and completion process, and the preset distance between the end of the casing string and the bottom of the well.

[0070] After the casing string is lowered into the designated position of the wellbore, the purpose of performing the wellbore cleaning operation is mainly to remove the remaining drill cuttings and other contaminants in the wellbore, improve the smoothness of the wellbore wall, provide a relatively clean and regular wellbore environment for subsequent casing and cementing operations, and ensure the safety of the operation. In one embodiment, the wellbore cleaning operation includes: short-distance drilling string operation, 1 to 3 drilling string operations, circulating drilling fluid in the original drill string, and injecting a certain amount of cleaning fluid to clean the wellbore wall.

[0071] Specifically, the short-distance drill string operation is to pull out several column drill pipes (1 column drill pipe is 3 to 4 drill pipes, each drill pipe is about 9 meters long), and then lower them to the bottom of the well. It can detect whether there are abnormalities such as wellbore stability / wellbore pressure, effectively remove rock cuttings or sediments at the bottom of the well, keep the bottom of the well clean, and reduce the risk of drill bit sticking.

[0072] The well cleaning operation involves running the drill string down 1 to 3 times to remove obstacles, sediments and other impurities in the wellbore, keep the wellbore clean, and at the same time test the wellbore integrity and confirm that the wellbore is unobstructed, providing good wellbore conditions for subsequent operations.

[0073] The original drill string circulating drilling fluid mainly refers to the continuous circulation of drilling fluid at a certain depth from the bottom of the well or at a specific formation location to remove cuttings, sediments or other impurities accumulated in the wellbore, to improve the wellbore environment, and to provide complete and unobstructed wellbore conditions for subsequent operations.

[0074] Injecting a certain amount of cleaning fluid to improve the surface finish and wettability of the well wall means injecting a cleaning fluid with certain properties, and changing the surface finish of the well wall and even the surface wettability of the rock through circulation, thereby providing good wellbore conditions for subsequent cementing operations and improving the bonding performance of cement slurry and formation.

[0075] After the casing string is lowered into the well, the annulus inside and outside the casing string is still filled with drilling fluid. At the same time, there is still sand settling in the wellbore and blocks falling off the well wall during the casing string lowering process, which requires circulating drilling fluid for cleaning. In one embodiment, in step S102, drilling fluid is pumped into the casing string for circulating well washing operations, which specifically includes:

[0076] First, adjust the drilling fluid properties to the preset requirements to control the viscosity, cutter, water loss, and mud cake friction of the drilling fluid; the preset requirements are specified in the drilling engineering design;

[0077] Secondly, drilling fluid is injected into the casing string to fill the inner hole of the casing string, so as to keep the wellbore pressure and the formation pressure in a preset equilibrium state, wherein the preset equilibrium state can be specifically an approximate equilibrium state;

[0078] Finally, increase the drilling fluid displacement from small to large so that the drilling fluid is injected from the casing string and discharged from the annulus formed between the casing string and the formation or the outer casing for a preset time to realize the circulation of the drilling fluid, thereby removing the cuttings, sediment or other impurities accumulated in the wellbore after casing lowering, so as to improve the wellbore environment and provide complete and unobstructed wellbore conditions for subsequent cementing operations.

[0079] After the drilling fluid circulation and well washing are completed, cementing operation can be started. Specifically, during the process of cementing the free toe end of the horizontal well in step S103, if Figure 6 and Figure 7 As shown, the cementing annulus 5 of the target horizontal well can be divided into a horizontal section cementing annulus 51 and a non-horizontal section cementing annulus 52 .

[0080] Among them, the cementing annulus 5 of the horizontal well is the annulus between the casing string 4 and the formation 6 or the inner diameter of the upper-level casing 46, the horizontal section cementing annulus 51 is the annulus between the casing and the wellbore between the depth points A and B where the well inclination exceeds 85 degrees, and the non-horizontal section cementing annulus 52 is the horizontal well cementing annulus except the horizontal section cementing annulus 51.

[0081] The horizontal section cementing annulus 51 can be further divided into a free toe section cementing annulus 511 and an effective horizontal section cementing annulus 512 , and the effective horizontal section cementing annulus 512 and the non-horizontal section cementing annulus 52 constitute the cementing annulus except the free toe section cementing annulus 511 .

[0082] The inventors of the present application discovered in their research that when designing the free toe section cementing annulus 511, if the designed length is long, the section of the casing string at the end that lacks cement ring support will be long after cementing is completed, which will lead to a decrease in the stability of the casing string and shorten the effective heating section of the horizontal well, reducing the economic benefits of oil and gas development; and if the designed length of the free toe section cementing annulus is short, the second preset amount of non-cementing material to be pumped is small, and the operability of the on-site operation equipment is poor. Therefore, optionally, the free toe section cementing annulus can be the cementing annulus between the bottom of the well and the position of 2 to 3 casing pipes above the float shoe, that is, the free toe section cementing annulus 51 starts from the position of 2 to 3 casing pipes above the float shoe 43 of the casing string and ends at the bottom of the well 45, such as Figure 6 The length of Q shown in is specifically equal to the preset distance M from the end of the casing string to the bottom of the well + the length of 2 to 3 casings.

[0083] In one embodiment, before pumping non-cementitious materials into the casing string in step S103, the cementing method provided by the embodiment of the present invention further includes: determining the second preset amount based on a preset length of the cementing annulus of the free toe section and an operable output of the field operation equipment.

[0084] Specifically, the second preset amount is determined based on the preset length of the cementing annulus of the free toe end section and the operable output of the field operation equipment; including: based on the preset length of the cementing annulus of the free toe end section, the preset amount of non-cemented material is calculated in combination with the following formula;

[0085]

[0086] Wherein, P is the calculated preset amount of non-cemented material; K is the elongation length of the casing string after being heated to the target temperature; P 1 is the average expansion coefficient; D b is the drill bit diameter; Dc is the casing diameter; Dci is the casing inner diameter; c 1 is the length between the float shoe and the float collar; C is the length of the open hole pocket reserved for cementing operations; N is the length between the float shoe of the casing string and the top of the cementing annulus of the free toe end section in the preset length of the cementing annulus of the free toe end section; where, the drill bit diameter D b Specifically: the diameter of the drill bit used in horizontal well drilling; when calculating, the unit of P is cubic meters; K, Dc, Dci, D b The units of C, c1 are all meters; 1 is the average expansion coefficient, generally between 1.2 and 1.5, P 1 The value of can be selected according to empirical parameters, or can be obtained by measuring the wellbore diameter by inserting a wellbore diameter measuring instrument, which is not limited in the embodiment of the present invention;

[0087] If the calculated preset amount of non-cementitious material is less than the operable output of the on-site operation equipment, the operable output of the on-site operation equipment is used as the second preset amount; accordingly, the actual length of the cementing annulus of the free toe section is determined by the second preset amount pumped in;

[0088] If the calculated preset amount of non-cementitious material is greater than the operable output of the on-site operation equipment, the calculated preset amount is used as the second preset amount.

[0089] Among them, the operational output of general on-site operation equipment is at least 1 cubic meter, usually between 1.5 and 3 cubic meters.

[0090] Optionally, the first rubber plug, the second rubber plug and the third rubber plug used in the horizontal well cementing method provided in the embodiment of the present invention are specifically self-locking rubber plugs with rupture disks or rupture membranes.

[0091] Further, in order to realize the cementing operation of the three sections of the free toe section cementing annulus 511, the effective horizontal section cementing annulus 512, and the non-horizontal section cementing annulus 52, refer to Figure 7 As shown, the specific process of step S103 is as follows: first, a first self-locking rubber plug 7 with a rupture disk or a rupture membrane is put in, and a first preset amount of cementing cement slurry is pumped in. Then, a second self-locking rubber plug 8 with a rupture disk or a rupture membrane is put in, and after a second preset amount of non-cementitious material is pumped in, a third self-locking rubber plug 9 with a rupture disk or a rupture membrane is put in and displacement fluid is pumped in. Among them, the first self-locking rubber plug with a rupture disk or a rupture membrane reaches the floating collar in place, and the rupture disk or the rupture membrane ruptures under pressure to communicate with the cementing annulus, and cement slurry enters the cementing annulus, and the second self-locking rubber plug 8 with a rupture disk or a rupture membrane is continuously put in. During the process of pumping in non-cementing materials, all cement slurry is replaced into the cementing annulus, and the second self-locking rubber plug 8 with a rupture disk or a rupture membrane reaches the floating collar in place, and the rupture disk or the rupture membrane ruptures under pressure to communicate with the cementing annulus, and non-cementing materials enter the cementing annulus at the bottom of the pipe shoe and the free toe end section; continue to replace, the third self-locking rubber plug 9 with a rupture disk or a rupture membrane reaches the floating collar in place and impacts; after the third self-locking impact with a rupture disk or a rupture membrane is completed, the pressure is released and the wellhead is observed to return, and solidification is waited to complete cementing.

[0092] Reference Figure 7 As shown, after cementing is completed, the effective horizontal cementing annulus and the non-horizontal cementing annulus (i.e., the cementing annulus except the free toe end section) are filled with cement stone 15, which can achieve the sealing effect of the corresponding layer on oil, gas, and water; the free toe end cementing annulus is filled with non-cementing material 10, so that the toe end casing is in a freely retractable state, providing a movable space for the thermal expansion and contraction of the casing string after ultra-high temperature heating. Among them, the temperature resistance grade of the cement stone can be selected according to the wellbore temperature field during the subsequent oil and gas production operation. For details, please refer to the existing technology and will not be repeated here.

[0093] Then, in the subsequent operation stage, such as in the horizontal wells for the in-situ development of low- and medium-mature shale oil with electric heating and lightweighting, the liquid residue is heated after the wellbore is started to heat, forming an ultra-high temperature and high pressure environment in the casing string. The third rubber plug can automatically open the rupture disk or rupture membrane under the action of pressure, establish communication with the formation, and provide an emptying channel for the flow of hot fluid in the casing string to the ground.

[0094] Based on the same inventive concept, an embodiment of the present invention also provides an application of the above-mentioned horizontal well cementing method in the field of oil and gas drilling technology.

[0095] It should be noted that the horizontal well cementing method provided in the embodiment of the present invention, when applied to the field of oil and gas drilling technology, can be used not only in horizontal wells for in-situ development of low- and medium-maturity shale oil with electric heating and lightweighting, but can also be used in large-scale volume fracturing transformation of long-section horizontal wells of shale oil and gas when bridge plug perforation is used for completion, etc. The present invention does not make any specific limitations on it.

[0096] The cementing method and application thereof provided in an embodiment of the present invention include: determining a target well depth of a horizontal well, drilling a target formation to the target well depth of the horizontal well using drilling equipment and a drilling tool combination according to a drilling design; secondly, performing a wellbore cleaning operation; subsequently, assembling a casing string and lowering it to a depth a certain distance from the bottom of the well; then pumping in drilling fluid for circulation and well washing; finally, selecting cement slurry columns of different temperature resistance grades according to the requirements of the subsequent wellbore temperature field to complete the cementing operation. The cementing method sets a safe well section that allows the casing to be extended and retracted, and after the cementing is completed, the toe end pipe string is in a freely retractable state, which can meet the need for corresponding retractable space for the thermal elongation generated by ultra-high temperature during oil and gas development using an electrically heated lightweight in-situ conversion technology, and the high-temperature and high-pressure thermal fluid generated during the heating process can be discharged into the formation through a high-temperature resistant float shoe and a float collar.

[0097] It should be understood that the specific order or hierarchy of steps in the disclosed process is an example of an exemplary method. Based on design preferences, it should be understood that the specific order or hierarchy of steps in the process can be rearranged without departing from the scope of protection of the present disclosure. The attached method claims present the elements of the various steps in an exemplary order and are not intended to be limited to the specific order or hierarchy described.

[0098] In the above detailed description, various features are grouped together in a single embodiment to simplify the disclosure. This method of disclosure should not be interpreted as reflecting an intention that the embodiments of the claimed subject matter require more features than are clearly stated in each claim. On the contrary, as reflected in the appended claims, the invention is in a state of having less than all the features of the disclosed individual embodiments. Therefore, the appended claims are hereby expressly incorporated into the detailed description, with each claim standing on its own as a separate preferred embodiment of the invention.

[0099] The above description includes examples of one or more embodiments. Of course, it is impossible to describe all possible combinations of components or methods for the purpose of describing the above embodiments, but it should be recognized by those skilled in the art that the various embodiments may be further combined and arranged. Therefore, the embodiments described herein are intended to cover all such changes, modifications and variations that fall within the scope of protection of the appended claims. In addition, with respect to the term "comprising" used in the specification or claims, the word is covered in a manner similar to the term "including", just as "including," is explained as a transitional word in the claims. In addition, any term "or" used in the specification of the claims is intended to mean "non-exclusive or".

Claims

1. A horizontal well cementing method, characterized in that: include: The casing string is lowered into the horizontal well, and the end of the casing string is set at a preset distance from the bottom of the well, wherein the casing string includes: a casing string, a float collar, a casing section and a float shoe connected in sequence from top to bottom; the preset distance is greater than the sum of the elongation length of the casing string after being heated to the target temperature and the length of the open hole pocket reserved for cementing operation; Pump drilling fluid into the casing string to perform circulating well washing operations; A first rubber plug is put into the casing string, and a first preset amount of cement slurry is pumped in; after the cement slurry is pumped in, a second rubber plug is put into the casing string, and a second preset amount of non-cementing material is pumped in; after the non-cementing material is pumped in, a third rubber plug is put into the casing, and displacement fluid is pumped in to perform slurry displacement operations, until the third rubber plug reaches the float collar and hits the pressure, and the first rubber plug and the second rubber plug rupture under the action of pressure, so that the cementing annulus inside the casing string and between the casing string and the formation or the outer casing is connected, and then the cement slurry fills the cementing annulus outside the cementing annulus of the free toe end section, and the non-cementing material fills the cementing annulus of the free toe end section; wherein the cementing annulus of the free toe end section is the cementing annulus between the bottom of the well and the preset distance above the float shoe; the third rubber plug can rupture under the preset pressure to establish communication between the inside of the casing string and the formation.

2. The horizontal well cementing method according to claim 1, characterized in that: The telescopic length of the casing string after being heated to the target temperature is determined based on: the temperature difference increased when the casing string is heated to the target temperature, the length of the effective deformation section of the casing string and the linear elongation coefficient of the casing.

3. The horizontal well cementing method according to claim 2, characterized in that: When the length of the horizontal section of the casing string is less than or equal to the effective deformation section threshold of the casing string, when determining the telescopic length of the casing string after the casing string is heated to the target temperature, the effective deformation section length of the casing string used is the length of the horizontal section of the casing string; When the length of the horizontal section of the casing string is greater than the effective deformation section threshold of the casing string, when determining the telescopic length of the casing string after being heated to the target temperature, the effective deformation section length of the casing string used is the effective deformation section threshold; the effective deformation section threshold is determined based on the strength of the cement used in the cementing process.

4. The horizontal well cementing method according to claim 1, characterized in that: The non-cementitious substances include: clean water, seawater, liquid with added substances for preventing casing corrosion or substances for delaying casing corrosion, and a liquid mixture containing cementing cement with a bonding strength within a preset range; the preset range of the bonding strength is that the compressive strength of the cement stone after 24 to 48 hours is less than 5MPa.

5. The horizontal well cementing method according to claim 1, characterized in that: The free toe end section cementing annulus is the cementing annulus between the well bottom and the position of 2 to 3 casings above the floating shoe.

6. The horizontal well cementing method according to claim 1, characterized in that: Before pumping the non-cemented material into the casing string, the method further includes: determining the second preset amount based on a preset length of the cementing annulus of the free toe section and an operable output of the on-site operation equipment.

7. The horizontal well cementing method according to claim 6, characterized in that: Determining the second preset amount based on the preset length of the cementing annulus of the free toe end section and the operable output of the field operation equipment; including: based on the preset length of the cementing annulus of the free toe end section, combining the following formula to calculate the preset amount of non-cemented material; Wherein, P is the calculated preset amount of non-cemented material; K is the elongation length of the casing string after heating to the target temperature; P1 is the average expansion coefficient; D b Dc is the diameter of the drill bit; Dc is the diameter of the casing; ci is the inner diameter of the casing; c1 is the length between the float shoe and the float collar; C is the length of the open hole pocket reserved for cementing operations; N is the length between the float shoe of the casing string and the top of the cementing annulus of the free toe end section in the preset length of the cementing annulus of the free toe end section; If the calculated preset amount of non-cementitious material is less than the operable output of the field operation equipment, the operable output of the field operation equipment is used as the second preset amount; accordingly, the actual length of the cementing annulus of the free toe section is determined by the second preset amount pumped in; If the calculated preset amount of non-cementitious material is greater than the operable output of the on-site operation equipment, the calculated preset amount is used as the second preset amount.

8. The horizontal well cementing method according to claim 1, characterized in that: Before lowering the casing string into the preset position in the wellbore, the method also includes: determining the target depth of the horizontal well, and drilling the target formation to the target depth of the horizontal well using drilling equipment and drilling tool assembly according to the drilling design; the target depth of the horizontal well is the depth of the horizontal well section that enters the target oil and gas layer and has a well inclination of more than 85 degrees; Wellbore cleaning operations are carried out after drilling the target well depth.

9. The horizontal well cementing method according to claim 8, characterized in that: The implementation of wellbore cleaning operations includes: short-distance drilling string operation, 1 to 3 times of drilling string operation, circulation of drilling fluid in the original drill string, and injection of a certain amount of cleaning fluid for wellbore wall cleaning.

10. The horizontal well cementing method according to claim 1, characterized in that: The step of pumping drilling fluid into the casing string to perform circulating well washing operation includes: Adjust drilling fluid properties to preset requirements; Inject drilling fluid into the casing string and fill the inner hole of the casing string to keep the wellbore pressure and formation pressure in a preset equilibrium state; Increase the drilling fluid displacement from small to large, so that the drilling fluid is injected from the casing string and discharged from the annulus formed between the casing string and the formation or the outer casing, and continue for a preset time to realize the circulation of the drilling fluid.

11. The horizontal well cementing method according to any one of claims 1 to 10, characterized in that: The first rubber plug, the second rubber plug and the third rubber plug are self-locking rubber plugs with rupture disks or rupture membranes.

12. Application of the horizontal well cementing method as claimed in any one of claims 1 to 10 in the field of oil and gas drilling technology.

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