A device and method for measuring shear bond strength of high-temperature and high-pressure cementing interface

Abstract

The present invention discloses a device and method for measuring the shear bond strength of a high-temperature and high-pressure cementing interface, and belongs to the field of oil and gas well cementing. The device includes a kettle body, an oil storage tank, a hydraulic pump, an electronic control system, a display, a support frame and a base. The kettle body includes a top cover, an upper kettle, a lower kettle, a bottom cover, a simulated casing, a simulated formation, a positioning steel cylinder, a piston cylinder, an inner piston, an outer piston and a floating support plate. The method includes: pouring cement slurry into the annular space between the simulated casing and the simulated formation; curing the cement slurry at a constant temperature and pressure; slowly increasing the pressure in the piston cavity, and moving the inner piston downward until the simulated casing is separated from the cement ring; continuing to increase the pressure in the piston cavity, and the outer piston moves downward under the push of the inner piston until the cement ring is separated from the simulated formation. The test process of the present invention is controllable, and the test results are consistent with the downhole environment, providing an important technical means for optimizing cement slurry performance and cementing process parameters, and further improving the cementing quality of oil and gas wells.

Description

Technical Field

[0001] The present invention belongs to the field of oil and gas well cementing, and particularly relates to a device and method for curing an interface shear bond strength test piece in a high-temperature and high-pressure environment and measuring the shear bond strength of a cementing interface. Background Art

[0002] Cementing is a key link connecting oil and gas well drilling and subsequent completion, testing, and oil / gas production. The quality of cementing not only affects whether subsequent operations of a well can be carried out smoothly, but also affects the progress, safety and benefits of oil and gas field exploration and development.

[0003] The primary objectives of cementing are, firstly, to secure, support, and protect the casing with the cement sheath, preventing secondary accidents such as axial slippage, radial expansion / contraction, and corrosion from formation water during subsequent production, thereby ensuring the life of the well and meeting the needs of long-term oil and gas field development. Secondly, through good bonding between the cement sheath, the formation, and the casing, the outer strata of the casing can be isolated and annular flow can be prevented. During subsequent drilling, fracturing, and other production processes, the interface bond between the cement sheath, the formation, and the casing can be easily damaged due to temperature and pressure fluctuations within the casing, leading to interlayer isolation failure, leakage of formation fluids from downhole into the wellhead annulus, and abnormal wellhead annulus pressure. Therefore, testing, evaluating, and controlling the quality of the interface bond between the cement sheath, the formation, and the casing is particularly important.

[0004] There are three commonly used evaluation indicators for cementing interface bonding quality: 1) Interface shear bond strength, which refers to the ability of the interface between the casing and cement sheath (referred to as the first interface) or the interface between the cement sheath and the formation (referred to as the second interface) to resist slippage when subjected to axial shear force; 2) Interface hydraulic bond strength, which refers to the ability of the interface between the cement stone, casing and formation to resist water penetration and channeling after the cement stone is bonded to the casing and formation; 3) Interface adhesion strength, which refers to the ability of the interface to resist the casing from separating from the cement stone or the cement stone from the formation when the formation confining pressure and casing internal pressure change and the first and second cementing interfaces are subjected to vertical tension and compression.

[0005] Currently, the most commonly used measurement is shear bond strength. This is accomplished by pouring cement slurry into a steel cylinder mold. Once the slurry solidifies, it bonds to the steel cylinder. A compressive strength tester is then used to press a cement cylinder downward from the cylinder. The force required to break the interfacial bond between the cylinder and the steel cylinder is measured, and the force is divided by the area of ​​the interface to obtain the shear bond strength of the interface downhole. If a simulated rock core is placed in the cement slurry, the pressure required to dislodge the core from the cement stone is measured in the same manner to calculate the shear bond strength of the two interfaces downhole.

[0006] The "In-situ Testing Device and Method for Cement Stone Bond Strength under Simulated High-Temperature and High-Pressure Downhole Conditions" (CN110470596A) and "An Experimental Device and Method for Testing Cement Bond Strength of Cementing" (CN115931543A) test the bond strength of the cement sheath interface under high temperature and high pressure, avoiding the risk of structural or strength changes when transferring the cured samples to indoor conditions of normal temperature and pressure. The "Specimen Preparation Device for Cementing Interface Bond Strength Testing" (CN214251753U) tests the shear bond strength of the cement sheath interface under normal pressure or with pressure-holding and setting conditions by applying annular pressure to form a virtual mud on the core surface, similar to actual downhole conditions. However, these devices are unable to simultaneously measure the shear bond strength of both the primary and secondary interfaces, nor can they explore the effects of changes in casing internal pressure and formation pressure on interface bond strength.

[0007] Some researchers have also measured the shear bond strength of both the primary and secondary interfaces simultaneously, and simulated the formation and flushing of drilling fluid cakes under high temperature and high pressure (Xu Bihua et al. A New Method for Testing the Bond Strength of Cement Sheaths in Oil Wells under High Temperature and High Pressure [J]. Natural Gas Industry, 2016, Vol. 36(11): 65-69). However, in essence, the method still involves curing under high temperature and high pressure and testing the shear bond strength at room temperature and pressure, which cannot accurately reflect the shear bond strength of the primary and secondary interfaces. The "Cement Bond Strength Test Device" (CN105422080A) cannot simulate changes in formation pressure and casing internal pressure, and cannot reflect the interface shear bond strength under actual working conditions.

[0008] It can be seen that the conventional method can only measure the shear bond strength of the first or second cementing interface separately. At the same time, there is also the problem that the cement stone is cured under high temperature and high pressure and the shear bond strength is tested at room temperature and pressure. The huge temperature and pressure difference affects the measurement results. Moreover, it is impossible to test the shear bond strength on the first and second cementing interfaces when the formation pressure and casing internal pressure change as needed. Summary of the Invention

[0009] The purpose of the present invention is to provide a device for measuring the shear bond strength of the cementing interface at high temperature and high pressure. The device has a reliable principle and is easy to operate. By curing the test piece in a high temperature and high pressure environment and measuring the shear bond strength of the first and second cementing interfaces, the curing and testing can be integrated, thereby exploring the influence of formation pressure changes and casing internal pressure changes on the shear bond strength of the first and second cementing interfaces. The device has broad market application prospects.

[0010] Another object of the present invention is to provide a method for measuring the shear bond strength of the high-temperature and high-pressure cementing interface using the above-mentioned device. The test process is controllable and the test results are more consistent with the downhole environment. It provides an important technical means for studying the influencing factors of the shear bond strength of the cementing interface, optimizing cement slurry performance and cementing process parameters, and further improving the cementing quality of oil and gas wells.

[0011] In order to achieve the above technical objectives, the present invention adopts the following technical solutions.

[0012] A high-temperature and high-pressure cementing interface shear bond strength measuring device mainly consists of a top cover, an upper kettle, a lower kettle, a bottom cover, a simulated formation, a simulated casing, a positioning steel cylinder, a floating support plate, a piston cylinder, an inner piston, an outer piston, a pressure regulator, a hydraulic pump, a liquid inlet pressure pipeline with a valve, a gas pipeline, an overflow pipeline with a condensate tank and a back pressure valve, a heating and insulation sleeve, a support frame, an electronic control system, a display and a base.

[0013] The top cover is connected to the upper kettle by bolts. The top cover is provided with two through holes, which are respectively connected to the liquid inlet pressure pipeline and the gas pipeline with valves.

[0014] The upper kettle is a hollow, thick-walled cylindrical kettle with a smooth inner wall; a plurality of through holes are provided on the side, which are respectively connected to the liquid inlet pressure pipeline, gas pipeline and overflow pipeline; the bottom is a circular flange, which is connected to the lower kettle by bolts.

[0015] The lower kettle is a hollow, thick-walled cylindrical kettle body with a smooth inner wall. It has a corresponding circular flange on the top and is connected to the upper kettle by bolts. There are three sizes of inner diameters in the lower kettle: the upper inner diameter is the largest, and the step formed is provided with a positioning block to support the positioning steel cylinder; the middle inner diameter is the second largest, and the floating support plate can slide up and down on its inner wall; the lower inner diameter is the smallest, and the step formed is used to support the floating support plate. The side is connected to the liquid pressure pipeline and gas pipeline / overflow pipeline with valves.

[0016] The bottom cover is connected to the lower kettle through bolts, and a sealing ring is used to achieve sealing between the two.

[0017] The simulated stratum is a real stratum cylinder cut from the outcrop rock of the underground stratum or a simulated stratum cylinder made of concrete-like materials, which is fixed in the positioning steel cylinder by resin or cement. The upper and lower end surfaces of the simulated stratum are properly polished and smooth, and its lower end surface cooperates with the annular sealing plate to form a seal.

[0018] The simulation sleeve is a thick-walled metal cylinder with an exhaust hole and a corresponding sealing plug on the upper end face. Liquid is introduced into the inner cavity of the simulation sleeve to exhaust the air. After the exhaust is completed, the sealing plug is tightened to form the inner cavity of the simulation sleeve; two notches are symmetrically arranged on the lower end face, corresponding to the screws in the positioning groove in the center of the floating support plate, so as to realize the circumferential fixation of the simulation sleeve.

[0019] The positioning steel cylinder is a hollow thick-walled metal cylinder with a convex edge at the lower end. The convex edge sits on the positioning block set at the largest part of the inner diameter of the lower kettle to achieve positioning of itself and the simulated formation. The side of the convex edge and the side of the body are provided with circumferential sealing rings, which are sealed with the upper inner wall of the lower kettle and the lower inner wall of the upper kettle respectively.

[0020] The simulated casing, simulated formation and positioning steel cylinder constitute a test piece.

[0021] The floating support plate is provided with a circumferential sealing ring groove and a sealing ring on the side, which cooperates with the inner wall of the lower kettle to achieve sealing and forms the lower chamber of the lower kettle with the bottom cover. There is a boss on the upper part of the floating support plate, whose outer diameter is larger than the inner diameter of the positioning steel cylinder, and a groove for fixing the simulation casing is provided on its upper end face, and positioning grooves for annular sealing gaskets are provided at the positions corresponding to the positioning steel cylinder and the simulation formation. By filling the sealing ring and the annular sealing gasket, under the top action of the pressure in the lower chamber of the lower kettle, they cooperate with the lower end face of the simulation casing, the positioning steel cylinder and the simulation formation to form a seal and form the upper chamber of the lower kettle. The upper chamber of the lower kettle is pressurized, exhausted and overflowed through the corresponding liquid inlet pressure pipeline, gas pipeline / overflow pipeline; a gas channel is provided in the boss, and the pressure of the upper chamber of the lower kettle is transmitted to the simulation casing through the channel.

[0022] The piston cylinder is a thick-walled metal cylinder fixed on the top cover. It cooperates with the inner piston with a sealing ring to form a piston cavity. The piston cavity is exhausted and pressurized through the liquid inlet and pressure-pressurizing pipelines and gas pipelines on the top cover, thereby pushing the inner and outer pistons downward to simulate the shear bonding strength of the first and second interfaces of cementing.

[0023] The inner piston is a two-stage solid metal cylinder with a larger upper part and a smaller lower part. A circumferential sealing ring is provided on the outer side of the upper cylinder, which cooperates with the inner wall of the piston cylinder to form a seal and straighten the coaxiality; the diameter of the lower cylinder is 2-3mm smaller than the outer diameter of the simulated casing to ensure that the inner piston will not touch the cement ring when pressing down the simulated casing.

[0024] The outer piston is a thick-walled metal cylinder that is larger at the top and smaller at the bottom. The inner diameter of the upper cylinder matches the outer diameter of the piston cylinder, and a sealing ring is used between the two to achieve sealing and coaxial alignment. The outer diameter of the lower cylinder is 1.5-2 mm smaller than the outer diameter of the cement ring, and the inner diameter is 1.5-2 mm larger than the inner diameter of the cement ring. After the inner piston presses down the simulated casing, destroys the simulated cementing interface, and continues to descend a certain distance, the outer piston moves downward under the push of the inner piston, thereby pressing down the cement ring to test the shear bond strength of the simulated cementing interface.

[0025] The pressure regulator can control the pressure of each chamber automatically or manually.

[0026] The liquid inlet pressure pipelines are used to pressurize the liquid inlet to each cavity, and are all high-pressure pipelines to increase the pressure level of the device.

[0027] The overflow pipeline with the condensation tank and the back pressure valve is used to discharge the corresponding volume of liquid when the piston cylinder is pressurized, the inner / outer piston moves downward, the simulated casing / cement ring moves downward, and the volume of the upper kettle outer cavity and the lower kettle upper cavity increases, so as to maintain the stability of the pressure in the upper kettle outer cavity and the lower kettle upper cavity to prevent their changes from affecting the accuracy of the test results.

[0028] The condensation tank, after being connected to the tap water source, is used to cool the high-temperature and high-pressure fluid discharged from the kettle body to prevent the high-temperature fluid from damaging the downstream back pressure valve.

[0029] The back pressure valve is used to adjust the back pressure of the overflow liquid from the kettle during the test, ensuring the pressure stability of the upper kettle outer cavity and the lower kettle upper cavity, and preventing pressure fluctuations from affecting the test results.

[0030] The hydraulic pump is a high-pressure pump, which is connected to the liquid inlet pressure pipeline to pressurize and relieve pressure in each chamber.

[0031] The electronic control system sets, controls and displays the temperature and pressure of the outer cavity of the upper kettle, the inner cavity of the piston, the upper cavity of the lower kettle and the lower cavity of the lower kettle.

[0032] The kettle body is supported by a supporting frame fixed to the base, and the outer wall is covered with a heating and heat-insulating jacket.

[0033] The support frame is constructed of square steel, aluminum profiles and other similar materials, and is fixed to the base of the device to fix and support the kettle body and corresponding pipelines to prevent them from becoming unstable or shifting during installation and testing.

[0034] The base is made of steel plate or similar materials and is used to install the support frame. The bottom is provided with movable and positionable universal wheels to facilitate the movement and positioning of the device.

[0035] The method for measuring the shear bond strength of the high-temperature and high-pressure cementing interface using the above device comprises the following steps in sequence:

[0036] (1) Pressurize the lower chamber of the lower kettle to form an effective seal between the boss of the floating support plate and the lower end surface of the specimen, remove the top cover of the upper kettle, and slowly pour the prepared cement slurry into the annular space between the simulated casing and the simulated formation;

[0037] (2) Fill the inner cavity of the simulated casing with liquid and exhaust the air, then tighten the plug of the exhaust hole of the simulated casing and connect the upper kettle with the top cover;

[0038] (3) Liquid is introduced into and exhausted from the outer cavity of the upper kettle and the inner cavity of the piston, and the pressure of the outer cavity of the upper kettle, i.e., the formation confining pressure, is set. Pressure is applied to the upper cavity of the lower kettle and the inner cavity of the simulated casing, i.e., the casing internal pressure, and the kettle body is heated. When the temperature reaches the set target, the cement slurry is cured at a constant temperature and pressure;

[0039] (4) After the cement slurry is cured to the set age, the pressure in the lower chamber of the lower kettle is reduced to a level lower than the pressure in the upper chamber of the lower kettle. The floating support plate is separated from the lower end surface of the specimen and moves downward until it rests on the last step in the lower kettle. The valve of the liquid inlet pressure pipeline in the lower chamber of the lower kettle is closed.

[0040] (5) Open the overflow pipeline valves of the upper kettle outer chamber and the lower kettle upper chamber, slowly increase the pressure in the piston cavity, and the inner piston moves downward to press the simulated casing until the simulated casing is separated from the cement ring; continue to increase the pressure in the piston cavity, and the outer piston moves downward under the push of the inner piston to press the cement ring until the cement ring is separated from the simulated formation;

[0041] (6) Calculate the shear bond strength of the first and second interfaces of the simulated cementing:

[0042] Cementing-interface shear bond strength ;

[0043] Shear bond strength of cementing interface ;

[0044] in is the cementing-interface shear bond strength, kPa;

[0045] is the shear bond strength of the cementing interface, kPa;

[0046] is the pressure of the upper chamber of the lower kettle, kPa;

[0047] The maximum force simulating the moment when the casing is separated from the cement sheath, kN;

[0048] is the maximum force at the moment when the cement sheath separates from the simulated formation, kN;

[0049] To simulate the contact area between casing and cement sheath, ;

[0050] is the contact area between the cement sheath and the simulated formation, .

[0051] Furthermore, by changing the pressure of the upper kettle outer chamber and the pressure of the lower kettle upper chamber, the shear bonding strength of the first and second cementing interfaces under different formation confining pressures and casing internal pressures was tested.

[0052] Compared with the prior art, the present invention has the following beneficial effects:

[0053] 1) Curing and testing the shear bond strength of the first and second interfaces of the simulated cementing under high temperature and high pressure avoids the problem of conventional methods that require curing under high temperature and high pressure and then testing the shear bond strength of the interface under normal pressure after cooling and depressurizing;

[0054] 2) Using a hydraulic pump to adjust the pressure inside the simulated casing, the shear bond strength was tested under different radial pressure differences between the inside and outside of the simulated casing, thereby studying the effect of pressure changes inside the simulated casing on the interface shear bond strength;

[0055] 3) By replacing simulated casings with different outer diameters and matching floating support plates, the shear bond strength corresponding to cement sheaths of different thicknesses was obtained, thereby studying the effect of cement sheath thickness on the interfacial shear bond strength;

[0056] 4) It can significantly reduce the complexity of experimental operations and greatly reduce the development cost and experimental cost of the device. BRIEF DESCRIPTION OF THE DRAWINGS

[0057] Figure 1 This is a cross-sectional view of the high-temperature and high-pressure cementing interface shear bond strength measurement device.

[0058] Figure 2 A schematic diagram of the overall structure of the device.

[0059] In the figure: 1—gas pipeline; 2—top cover; 3—sealing ring; 4—gas pipeline; 5—valve; 6—valve; 7—condensate tank; 8—back pressure valve; 9—overflow pipeline; 10—upper kettle; 11—upper kettle outer cavity; 12—piston cylinder; 13—piston inner cavity; 14—inner piston; 15—outer piston; 16—simulated casing inner cavity; 17—connecting bolt; 18—lower kettle; 19—support frame; 20—pressure gauge; 21—valve; 22—pressure regulator; 23—liquid inlet pressure pipeline; 24—plug; 25—simulated casing; 26—simulated formation; 27—positioning steel cylinder; 28—liquid inlet pressure pipeline; 29—lower kettle upper cavity; 30—floating support plate; 31—lower kettle lower cavity; 32—bottom cover; 33—oil storage tank; 34—hydraulic pump; 35—electronic control system; 36—display; 37—base. DETAILED DESCRIPTION

[0060] The present invention is further described below with reference to the accompanying drawings and examples to facilitate understanding of the present invention by those skilled in the art. However, it should be understood that the described embodiments are only a portion of the embodiments of this application, not all of them. For those skilled in the art, all other embodiments obtained without creative work are also protected.

[0061] A high-temperature and high-pressure cementing interface shear bond strength measuring device includes a kettle body, an oil storage tank 33, a hydraulic pump 34, an electronic control system 35, a display 36, a support frame 19 and a base 37. The kettle body is supported by the support frame 19 fixed to the base 37. The kettle body is connected to the oil storage tank 33, the hydraulic pump 34, the electronic control system 35 and the display 36 in sequence. A heating and insulation sleeve is provided on the outer wall of the kettle body to connect to the temperature control system. The kettle body includes a top cover 2, an upper kettle 10, a lower kettle 18, a bottom cover 32, a simulated casing 25, a simulated formation 26, a positioning steel cylinder 27, a piston cylinder 12, an inner piston 14, an outer piston 15 and a floating support plate 30.

[0062] The top cover 2 is connected to the upper kettle 10 by bolts, the bottom cover 32 is connected to the lower kettle 18 by bolts, the upper kettle and the lower kettle are flange-connected by connecting bolts 17, and a test piece is placed in the upper kettle. The test piece is composed of a simulated casing 25, a simulated formation 26 and a positioning steel cylinder 27 from the inside to the outside. An annular space is formed between the simulated casing and the simulated formation. The simulated formation is fixed in the positioning steel cylinder by resin or cement, and a seal is achieved between the positioning steel cylinder and the inner wall of the upper kettle; the piston cylinder 12 is placed above the test piece, and the test piece is placed in the upper kettle. Below the component is a floating support plate 30; the lower kettle has three sizes of inner diameters: the upper inner diameter is the largest, and the step formed is provided with a positioning block to support the positioning steel cylinder 27; the middle inner diameter is the second largest, and the floating support plate 30 can slide up and down on its inner wall; the lower inner diameter is the smallest, and the step formed is used to support the floating support plate; the piston cylinder 12 is a thick-walled metal cylinder fixed to the top cover, and the piston cylinder forms a piston cavity 13 through the inner piston 14, and the piston cavity is connected to the liquid inlet pressure pipeline through the two through holes in the top cover. 23 and gas pipeline 1, the outer piston 15 is formed outside the piston cylinder body through the outer chamber 11 of the upper kettle, and the upper kettle outer chamber is provided with a liquid inlet pressure pipeline 28, a gas pipeline 4 and an overflow pipeline 9; the inner piston is a double-stage cylinder with a larger upper portion and a smaller lower portion, the upper cylinder cooperates with the inner wall of the piston cylinder to form a seal, and the diameter of the lower cylinder is smaller than the outer diameter of the simulation casing; the outer piston is a thick-walled cylinder with a larger upper portion and a smaller lower portion, the upper cylinder cooperates with the outer wall of the piston cylinder to achieve a seal, the outer diameter of the lower cylinder is smaller than the outer diameter of the cement ring, and the inner diameter is larger than the outer diameter of the water ring The inner diameter of the mud ring; the floating support plate 30 is sealed by cooperating with the inner wall of the lower kettle through the circumferential sealing ring on the side, and forms a lower kettle lower cavity 31 with the bottom cover 32. There is a boss on the top of the floating support plate, and the outer diameter of the boss is larger than the inner diameter of the positioning steel cylinder. When the boss is in contact with the lower end face of the specimen, the lower kettle upper cavity 29 is formed. The lower kettle upper cavity 29 and the lower kettle lower cavity 31 are both provided with a liquid inlet pressure pipeline and an overflow pipeline, and a gas channel is provided in the boss, through which the pressure of the lower kettle upper cavity is transmitted to the inner cavity 16 of the simulation casing.

[0063] Furthermore, a groove for fixing the simulated casing is provided in the center of the boss of the floating support plate, and a positioning groove for an annular sealing gasket is provided corresponding to the position of the positioning steel cylinder and the simulated formation. By filling the sealing ring and the annular sealing gasket, a seal is formed with the lower end face of the specimen under the upward action of the pressure in the lower chamber of the lower kettle.

[0064] Furthermore, the upper end surface of the simulation sleeve is provided with an exhaust hole and a corresponding sealing plug 24, and the exhaust hole is used to exhaust the liquid in the simulation sleeve. The sealing plug is tightened to form the inner cavity 16 of the simulation sleeve, and the lower end surface is circumferentially fixed by the groove in the center of the floating support plate boss.

[0065] Furthermore, the lower end of the positioning steel cylinder has a convex edge, and a positioning block is provided at a position corresponding to the convex edge on the inner wall of the lower kettle to further fix the positioning steel cylinder.

[0066] Furthermore, the piston cavity is exhausted and pressurized through the liquid pressure pipeline and gas pipeline at the top cover, pushing the inner piston and outer piston downward to test the shear bonding strength of the first and second cementing interfaces respectively.

[0067] Furthermore, the inner piston has a circumferential sealing ring on the outer side of the upper cylinder, which cooperates with the inner wall of the piston cylinder to form a seal and straighten the coaxiality. The diameter of the lower cylinder is 2-3 mm smaller than the outer diameter of the simulated casing, ensuring that the inner piston will not touch the cement ring when pressing down the simulated casing, thereby testing the shear bonding strength of the cementing interface.

[0068] Furthermore, the inner diameter of the upper cylinder of the outer piston matches the outer diameter of the piston cylinder, and the two are sealed and coaxially aligned through a sealing ring. The outer diameter of the lower cylinder is 1.5-2 mm smaller than the outer diameter of the cement ring, and the inner diameter is 1.5-2 mm larger than the inner diameter of the cement ring. After the inner piston presses down the simulated casing and destroys the first cementing interface, it continues to descend a certain distance. Under the push of the inner piston, the outer piston moves downward and presses the cement ring to test the shear bonding strength of the second cementing interface.

[0069] Furthermore, a pressure gauge 20, a valve 21 and a pressure regulator 22 are provided on the liquid inlet pressure pipeline 23, and the pressure regulator controls the pressure of each chamber.

[0070] Furthermore, the overflow pipeline 9 is provided with a valve 6, a condensation tank 7 and a back pressure valve 8. The valve is used to isolate or connect the condensation tank and the back pressure valve at the rear end. The overflowed hot oil is discharged after being cooled in the condensation tank to prevent high-temperature liquid from entering and damaging the back pressure valve.

[0071] The method for measuring the shear bond strength of the high-temperature and high-pressure cementing interface using the above-mentioned device comprises the following steps in sequence:

[0072] Prepare and fix the simulated stratum 26: Take a thick glass plate, apply a layer of butter on the surface, place the positioning steel cylinder on it, put the prepared simulated stratum ring into the steel cylinder, and pour cement slurry into the annulus between the simulated stratum and the inner wall of the steel cylinder, and wait for it to solidify and harden.

[0073] Install the positioning steel cylinder 27 and the simulated casing 25: place the floating support plate 30 on the last step of the lower kettle 18; start the hydraulic pump to fill and exhaust the lower cavity of the lower kettle, pressurize the lower cavity of the lower kettle, push the floating support plate upward, place the positioning steel cylinder 27 with the simulated stratum on the floating support plate, and place the simulated casing 25 with a sealing ring in the central groove of the floating support plate.

[0074] Pour cement slurry and connect the upper kettle 10 and the lower kettle 18: Prepare cement slurry as required, slowly pour it into the annulus between the simulated casing and the simulated formation to achieve the connection and sealing of the upper kettle and the lower kettle, and tighten the bolts 17.

[0075] Apply initial pressure to the lower chamber 31 of the lower kettle: start the corresponding pressure regulator to ensure that the floating support plate 30 can always support the cement slurry and the simulated casing.

[0076] Liquid inlet and exhaust: Liquid is introduced and exhaust is conducted into the upper chamber 29 of the lower kettle through the exhaust hole of the simulation sleeve. After exhaust is completed, the plug of the exhaust hole is tightened to seal the inner chamber 16 of the simulation sleeve. After installing the top cover, liquid is introduced and exhaust is conducted into the inner chamber 13 of the piston and the outer chamber 11 of the upper kettle.

[0077] Apply initial pressure to the outer cavity 11 of the upper kettle, the inner cavity 13 of the piston, the upper cavity 29 of the lower kettle and the inner cavity 16 of the simulated casing: turn on the hydraulic pump to apply pressure to each cavity. The pressure in the outer cavity of the upper kettle is slightly higher than the pressure in the upper cavity of the lower kettle and the inner cavity of the simulated casing to prevent the simulated casing from moving upward.

[0078] Cement slurry waiting for setting: Heat the kettle body, and when the temperature reaches the set target, maintain the cement slurry at constant temperature and pressure until the set age.

[0079] Measure the initial bond strength of the simulated cementing interface: reduce the pressure in the outer chamber of the upper kettle to the pressure in the upper chamber of the lower kettle; reduce the pressure in the lower chamber of the lower kettle to a level 0.5 MPa lower than the pressure in the upper chamber of the lower kettle. The floating support plate detaches from the lower end surface of the specimen and moves downward until it rests on the step in the lower kettle. Close the valve of the liquid inlet pressure pipeline in the lower chamber of the lower kettle and open the valve of the overflow pipeline. Slowly increase the pressure in the piston cavity until the simulated casing moves downward and the pressure in the piston cavity drops flashing, thereby obtaining the pressure difference that drives the simulated casing to move. Calculate the initial shear bond strength of the cementing interface when there is no pressure difference inside and outside the simulated casing.

[0080] Measure the bonding strength of the simulated cementing interface when the pressure changes in the casing: slowly and synchronously increase or decrease the pressure in the outer cavity of the upper kettle and the upper cavity of the lower kettle to the set target pressure to ensure that the upper and lower pressure differences of the casing are basically balanced, and then gradually open the back pressure valve until it drips, completing the setting of the back pressure valve target pressure; gradually increase the pressure in the piston cavity until the simulated casing is pushed down again and the pressure in the piston cavity drops suddenly. At this time, the pressure difference between the inner cavity of the piston and the outer cavity of the upper kettle is the upper and lower pressure difference required to overcome the interface shear bonding strength caused by the radial pressure difference of the simulated casing. Based on this, the shear bonding strength caused by the radial pressure difference can be calculated; repeat this step to obtain the interface shear bonding strength under more simulated casing radial pressure differences until the inner piston contacts the outer piston, the outer piston starts to press down the cement ring, and the pressure rises suddenly.

[0081] Measure the initial bond strength of the simulated cementing interface: After the outer piston contacts the cement sheath, continue to increase the pressure in the piston cavity while simultaneously pushing the inner and outer pistons downward, simultaneously pressing down on the simulated casing and cement sheath. Measure the upper and lower pressure differentials required to destroy the simulated interface, and calculate the corresponding shear bond strength of the interface. Gradually reduce the target pressures of the upper kettle outer cavity, the lower kettle upper cavity, and the corresponding overflow line backpressure valve. Starting from the initial curing pressure of the cement sheath, first measure the shear bond strength of the interface at zero radial pressure differential. Then gradually increase the target pressures of the upper kettle outer cavity, the lower kettle upper cavity, and the corresponding overflow line backpressure valve to measure the shear bond strength of the interface at different radial pressure differentials.

Claims

1. A high-temperature and high-pressure cementing interface shear bond strength measuring device, comprising a kettle, an oil storage tank, a hydraulic pump, an electronic control system, a display, a support frame, and a base. The kettle is supported by a support frame fixed to the base, and the kettle is sequentially connected to the oil storage tank, the hydraulic pump, the electronic control system, and the display. A heating and insulation jacket is provided on the outer wall of the kettle body and connected to the temperature control system. The device is characterized in that: The kettle body includes a top cover, an upper kettle, a lower kettle, a bottom cover, a simulated casing, a simulated formation, a positioning steel cylinder, a piston cylinder, an inner piston, an outer piston and a floating support plate, the top cover is connected to the upper kettle by bolts, the bottom cover is connected to the lower kettle by bolts, the upper kettle and the lower kettle are connected by flanges, a test piece is placed in the upper kettle, the test piece is composed of a simulated casing, a simulated formation and a positioning steel cylinder from the inside to the outside, an annular space is formed between the simulated casing and the simulated formation, the simulated formation is fixed in the positioning steel cylinder by resin or cement, and a seal is achieved between the positioning steel cylinder and the inner wall of the upper kettle; the piston cylinder is above the test piece, and the floating support plate is below the test piece; there are three sizes of inner diameters in the lower kettle: the upper inner diameter is the largest, and the step formed is provided with a positioning block to support the positioning steel cylinder, the middle inner diameter is the second largest, and the floating support plate can slide up and down on its inner wall, and the lower inner diameter is the smallest, and the step formed is used to support the floating support plate; the piston cylinder is a thick-walled metal cylinder fixed to the top cover, and a piston inner cavity is formed in the piston cylinder by the inner piston, and the movable The inner cavity of the plug is connected to the liquid inlet pressure pipeline and the gas pipeline through the two through holes of the top cover respectively. The outer cavity of the upper kettle is formed by the outer piston outside the piston cylinder body. The liquid inlet pressure pipeline, the gas pipeline and the overflow pipeline are set in the upper kettle outer cavity; the inner piston is a double-stage cylinder with a larger upper portion and a smaller lower portion. The upper cylinder cooperates with the inner wall of the piston cylinder to form a seal, and the diameter of the lower cylinder is smaller than the outer diameter of the simulation sleeve; the outer piston is a thick-walled cylinder with a larger upper portion and a smaller lower portion. The upper cylinder cooperates with the outer wall of the piston cylinder to achieve a seal, and the outer diameter of the lower cylinder is smaller than The outer diameter and inner diameter of the cement ring are larger than the inner diameter of the cement ring; the floating support plate cooperates with the inner wall of the lower kettle through the circumferential sealing ring on the side to achieve sealing, and forms the lower chamber of the lower kettle with the bottom cover. There is a boss on the top of the floating support plate, and the outer diameter of the boss is larger than the inner diameter of the positioning steel cylinder. When the boss is in contact with the lower end face of the specimen, the upper chamber of the lower kettle is formed. The upper chamber of the lower kettle and the lower chamber of the lower kettle are both provided with liquid inlet pressure pipelines and overflow pipelines. A gas channel is provided in the boss, and the pressure of the upper chamber of the lower kettle is transmitted to the inner chamber of the simulated casing through the channel.

2. The high-temperature and high-pressure cementing interface shear bond strength measuring device according to claim 1, characterized in that: A groove for fixing the simulated casing is provided in the center of the boss of the floating support plate, and a positioning groove for an annular sealing gasket is provided corresponding to the position of the positioning steel cylinder and the simulated formation. By filling the sealing ring and the annular sealing gasket, a seal is formed with the lower end surface of the specimen under the upward action of the pressure in the lower chamber of the lower kettle.

3. The high-temperature and high-pressure cementing interface shear bond strength measuring device according to claim 1, characterized in that: The upper end face of the simulation sleeve is provided with an exhaust hole and a corresponding sealing plug. The exhaust hole is used to exhaust the liquid in the simulation sleeve. The sealing plug is tightened to form the inner cavity of the simulation sleeve. The lower end face is circumferentially fixed by the groove in the center of the floating support plate boss.

4. The high-temperature and high-pressure cementing interface shear bond strength measuring device according to claim 1, characterized in that: The lower end of the positioning steel cylinder has a convex edge, and a positioning block is arranged at a position corresponding to the convex edge on the inner wall of the lower kettle to further fix the positioning steel cylinder.

5. The high-temperature and high-pressure cementing interface shear bond strength measuring device according to claim 1, characterized in that: The inner piston has a circumferential sealing ring on the outer side of the upper cylinder, which cooperates with the inner wall of the piston cylinder to form a seal and straighten the coaxiality. The diameter of the lower cylinder is 2-3 mm smaller than the outer diameter of the simulation sleeve.

6. The high-temperature and high-pressure cementing interface shear bond strength measuring device according to claim 1, characterized in that: The inner diameter of the upper cylinder of the outer piston matches the outer diameter of the piston cylinder, and the two are sealed and coaxially aligned through a sealing ring. The outer diameter of the lower cylinder is 1.5-2mm smaller than that of the cement ring, and the inner diameter is 1.5-2mm larger than that of the cement ring.

7. The high-temperature and high-pressure cementing interface shear bond strength measuring device according to claim 1, characterized in that: A pressure gauge, a valve and a pressure regulator are arranged on the liquid inlet pressure pipeline.

8. The high-temperature and high-pressure cementing interface shear bond strength measuring device according to claim 1, characterized in that: The overflow pipeline is provided with a valve, a condensation tank and a back pressure valve.

9. A method for measuring the shear bond strength of a high-temperature and high-pressure cementing interface using the device of claim 1, comprising the following steps: (1) Pressurize the lower chamber of the lower kettle to form an effective seal between the boss of the floating support plate and the lower end surface of the specimen, remove the top cover of the upper kettle, and slowly pour the prepared cement slurry into the annular space between the simulated casing and the simulated formation; (2) Fill the inner cavity of the simulated casing with liquid and exhaust the air, then tighten the plug of the exhaust hole of the simulated casing and connect the upper kettle with the top cover; (3) Liquid is introduced into and exhausted from the outer cavity of the upper kettle and the inner cavity of the piston, and the pressure of the outer cavity of the upper kettle, i.e., the formation confining pressure, is set. Pressure is applied to the upper cavity of the lower kettle and the inner cavity of the simulated casing, i.e., the casing internal pressure, and the kettle body is heated. When the temperature reaches the set target, the cement slurry is cured at a constant temperature and pressure; (4) After the cement slurry is cured to the set age, the pressure in the lower chamber of the lower kettle is reduced to a level lower than the pressure in the upper chamber of the lower kettle. The floating support plate is separated from the lower end surface of the specimen and moves downward until it rests on the last step in the lower kettle. The valve of the liquid inlet pressure pipeline in the lower chamber of the lower kettle is closed. (5) Open the overflow pipeline valves of the upper kettle outer chamber and the lower kettle upper chamber, slowly increase the pressure in the piston cavity, and move the inner piston downward to press the simulated casing until the simulated casing is separated from the cement ring; Continue to increase the pressure in the piston cavity, and the outer piston moves downward under the push of the inner piston to press the cement ring until the cement ring is separated from the simulated formation; (6) Calculate the shear bond strength of the first and second interfaces of the simulated cementing.

10. The method according to claim 9, wherein The shear bond strength of the first and second interfaces of the simulated cementing is calculated in step (6) as follows: Cementing-interface shear bond strength ; Shear bond strength of cementing interface ; in is the cementing-interface shear bond strength, kPa; is the shear bond strength of the cementing interface, kPa; is the pressure of the upper chamber of the lower kettle, kPa; The maximum force simulating the moment when the casing is separated from the cement sheath, kN; is the maximum force at the moment when the cement sheath separates from the simulated formation, kN; To simulate the contact area between casing and cement sheath, ; is the contact area between the cement sheath and the simulated formation, .

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