Device and method for testing the bond strength between casing and cementing cement by rotational torque

Abstract

The application relates to a device and a method for testing the bonding strength between a casing and well cement by using rotary torque, and belongs to the technical field of drilling material detection. The device comprises a test sample, a slip, a joint and a load applying device. Power is generated by a power device of a rotary dynamic torque tester to form rotary output, which drives a wellbore simulation casing to rotate. The wellbore simulation casing and a cement sheath fixed on a cementing cylinder are relatively displaced to form rotary torque. A torsion meter reads and records the torsion value when the cementing interface is damaged in real time, and the maximum value of the torsion value is taken as an index for representing the cementing strength. The device disclosed by the application is simple and convenient to operate, simple in structure, low in cost and reusable, and can be widely applied to the measurement and evaluation of the cementing performance of casings and well cement of different wellbore sizes.

Description

Technical Field

[0001] This invention relates to the field of drilling material testing technology, specifically to an apparatus and method for testing the bond strength between casing and cementing cement using rotational torque. Background Technology

[0002] In deepwater drilling operations, the quality of shallow subsea cementing has a significant impact on the safety of deepwater oil and gas wells. If the bonding strength and other properties between the casing and cement in shallow cementing do not meet requirements, it can lead to wellhead subsidence, well integrity failure, wellbore abandonment, blowouts, formation fluid leakage, oil spills, and a series of other risks. The Deepwater Horizon blowout in the Gulf of Mexico, USA, occurred because the cement sheath failed to effectively seal the gap between the casing and the formation, allowing wellbore fluids and oil and gas to escape through this gap to the wellhead. This caused a pressure imbalance in the wellbore, ultimately leading to an uncontrolled blowout and losses amounting to $68 billion.

[0003] Currently, experiments on the bond strength between the well casing and cement-based components in shallow cementing are mostly conducted using pull-out methods. For example, the Chinese invention patent application No. 202110829370.6, "A Verification Device for the Bearing Capacity of Offshore Pile-Shoe Platform Pile Foundation and Preloading Method", uses an upper ring fitted on the preloaded pile to apply a vertical load to the preloaded pile for pull-out.

[0004] However, in actual engineering, shallow cemented wells are located in the deep sea. Besides the vertical pull-out load, the wellbore and cement-based components also bear rotational torque caused by the movement of deep seawater, resulting in a tendency for rotation between the wellbore and the cement-based components. Therefore, the bond strength between the wellbore and the cement-based components (usually forming a cement sheath) in shallow cemented wells in the deep sea is not only related to the pull-out force, but also significantly influenced by the rotational torque between the wellbore and the cement sheath. Furthermore, due to variations in stress distribution within the cement slurry bonded cylinder under different wellbore sizes in actual engineering, the bond strength of the cement slurry varies. Currently, there is a lack of methods to test the bond strength between the wellbore and the cement sheath for wellbore sizes with rotational torque. Existing publicly available pull-out simulation casing tests for cementing effects require constraining the cement sheath to prevent displacement along with the casing. This increases the confining pressure of the cement sheath on the casing, indirectly increasing the friction between the cement sheath and the casing. This results in measured strengths that are higher than the actual bond strength between the cement sheath and the casing, affecting test accuracy. Summary of the Invention

[0005] To address the aforementioned problems, the present invention aims to provide an apparatus and method for testing the bond strength between casing and cementing cement using rotational torque. This addresses the lack of relevant research due to neglecting the rotational torque between the wellbore and the cement slurry bonding cylinder, as well as the lack of a method for testing the bond strength between wellbore and cement sheath of different sizes using rotational torque.

[0006] To achieve the above objectives, the present invention adopts the following technical solution:

[0007] In a first aspect, the present invention discloses an apparatus for testing the bond strength between casing and cementing cement using rotational torque, comprising a test sample, slips, a joint, and a load application device. The test sample includes a simulated well casing and a cement slurry bonding cylinder. The cement slurry bonding cylinder is fitted over the outside of the simulated well casing. The annular space between the cement slurry bonding cylinder and the simulated well casing is used to form a cement ring. The outer wall of the simulated well casing and the inner wall of the cement ring are bonded together. One end of the simulated well casing extends out of the cement slurry bonding cylinder and is exposed to form a joint end. The outer wall of one end of the cement slurry bonding cylinder, which is in the opposite direction to the joint end of the simulated well casing, is fixed to form a fixed end. The load application device includes a rotational dynamic torque tester and a torque meter. The rotational dynamic torque tester is equipped with a power device to generate a rotational output. The rotational output shaft of the rotational dynamic torque tester is connected to one end of the joint via the torque meter. The other end of the joint is connected to the joint end of the simulated well casing via slips.

[0008] Preferably, the slip includes several slip bodies, and multiple adjacent slip bodies are connected in a ring by hinge pins; when the test sample needs to be replaced, the number of slip bodies of the slip increases or decreases according to the diameter of the well casing.

[0009] Preferably, the test chamber is also included, which is a temperature-controlled chamber, including an open chamber body and a lid; a temperature control device is installed inside the chamber body; the test sample is placed inside the test chamber, and the fixed end of the cement slurry bonding cylinder is fixed to the bottom or inner wall of the test chamber; the annular space between the outer wall of the cement slurry bonding cylinder and the inner wall of the test chamber is filled with experimental soil.

[0010] Preferably, the cement slurry bonding cylinder includes a bonding cylinder body, a bonding cylinder base, and a bonding cylinder top cover; the bonding cylinder base is used to seal the bottom of the bonding cylinder body when cement slurry is injected into the bonding cylinder; the bonding cylinder top cover is used to seal the top of the bonding cylinder body filled with cement slurry.

[0011] Preferably, the fixed end of the cement slurry bonding cylinder is fixed to the bottom or inner wall of the test chamber by fasteners; the fasteners are fixing rings composed of two half-rings, which are fixed to the bottom or inner wall of the test chamber by bolts, and the two half-rings form a fixing ring by locking the bonding cylinder body or the bonding cylinder base of the cement slurry bonding cylinder.

[0012] Preferably, the rotary dynamic torque tester includes a power device, a torque power meter, a torque sensor, and a torque display instrument. The power device is connected to the torque sensor via a coupling, and the torque sensor is connected to a torque meter via a coupling. The power device is a rotary motor. The power device is equipped with a torque power meter for controlling power output. The torque sensor is equipped with a torque display instrument for displaying the torque sensed by the torque sensor.

[0013] Preferably, the load application device further includes a control console and a test frame, with the torque power meter and the torque display meter mounted on the control console, and the power device and the torque sensor mounted on the test frame.

[0014] Preferably, the test sample is vertically arranged inside the test chamber to simulate a vertical well.

[0015] Preferably, the test sample is arranged horizontally or at an angle inside the test chamber to simulate a horizontal well or an inclined well.

[0016] Secondly, the present invention also discloses a method for testing the bond strength between casing and cementing cement using rotational torque, employing the aforementioned apparatus for testing the bond strength between casing and cementing cement using rotational torque, including...

[0017] Step 1: Install the cement grouting cylinder in the test chamber, and place test soil around the cement grouting cylinder to make a well of the required size for the cement grouting cylinder. Compact the static soil layer until it is dense, and control the temperature of the test soil through the temperature control equipment of the test chamber.

[0018] Step 2: Insert the simulated well casing into the cement slurry bonding cylinder, and inject the prepared cement slurry into the annular space between the cement slurry bonding cylinder and the simulated well casing. Wait for the cement slurry to solidify and form until the cement ring reaches the design strength.

[0019] Step 3: Start the load application equipment. The power equipment of the rotating dynamic torque tester generates power to form a rotational output, which in turn drives the torque meter, joint and well casing simulation casing to rotate.

[0020] The relative displacement between the well casing and the cement ring fixed in the cement slurry binder creates a rotational torque, simulating the rotational torque that causes the well casing and cement ring to rotate due to the deep sea motion.

[0021] Uniformly rotating the wellbore simulates the casing, increasing the torque between the rotating wellbore simulated casing and the cement sheath;

[0022] As the rotational torque continues to increase, the simulated casing of the wellbore rotates, and the morphology of the cemented surface failure is observed until any cemented interface between the simulated casing of the wellbore and the cement sheath is destroyed. The torque meter reads and records the torque value when the cemented interface is destroyed in real time, thus completing the torque test between the simulated casing of the wellbore and the cement sheath, and using the maximum torque value as an indicator of the cemented strength.

[0023] Step 4: Change the size of the test sample and repeat steps 1 to 3 to test and evaluate the bond strength between the simulated well casing with different diameters and the cement slurry bonded casing.

[0024] The present invention has the following advantages due to the adoption of the above technical solutions:

[0025] (I) This invention discloses a device for testing the bond strength between casing and cementing slurry using rotational torque. The load-applying device generates power through a power unit configured with a rotational dynamic torque tester, forming a rotational output. The rotational output shaft of the rotational dynamic torque tester is connected to one end of a connector via a torque meter, and the other end of the connector is connected to the connector end of a simulated well casing via a slip. When the power unit configured with the dynamic torque tester generates a rotational output, it sequentially drives the torque meter, connector, and simulated well casing to rotate. The simulated well casing and the cement ring fixed inside the cement slurry-bonded cylinder undergo relative displacement, generating a rotational torque. This simulates the rotational torque applied to the well casing by deep-sea water movement, causing a rotational tendency between the well casing and the cement slurry-bonded cylinder. The rotational torque can supplement pull-out test studies and is an important part of the bonding strength test between the well casing and the cement slurry-bonded cylinder in shallow cementing.

[0026] (II) This invention discloses a device for testing the bond strength between casing and cementing cement using rotational torque. The joint end of the simulated casing is connected to the joint via slips. Each slip comprises several slip bodies, and the slips are classified as three-piece, four-piece, or multi-piece slips based on the number of slip bodies. When the test sample needs to be replaced, the number of slip bodies increases or decreases according to the diameter of the simulated casing. Therefore, this invention can simulate cement bonding strength testing and evaluation experiments under different wellbore sizes. Based on the experimental results, cement slurry optimization can be performed for different drilling processes (first, second, and third drilling stages, etc.). When the diameter of the simulated casing is changed, the device disclosed in this invention can simulate the bonding performance of different cement slurries under different wellbore sizes and soil conditions, thereby studying the bonding performance of cement slurry under different wellbore diameters in different soil environments and drilling stages, as well as its compatibility with the formation soil.

[0027] (III) This invention discloses an apparatus and method for testing the bond strength between casing and cementing slurry using rotational torque. By simulating the rotation of the casing in the wellbore, a relative displacement occurs between the simulated casing and the cement sheath, generating a rotational torque. This simulates the rotational torque exerted on the wellbore by deep-sea motion, causing a rotational tendency between the wellbore and the cement slurry bonded casing. Furthermore, by changing the size of the simulated casing, the bond strength between the simulated casing and the cement sheath can be tested and evaluated for wellbore diameters of different sizes. The experimental results can provide a data basis for optimizing cement slurry at different drilling stages. The apparatus disclosed in this invention is simple and convenient to operate, has a simple structure, low cost, and is reusable. It can be widely used for measuring and evaluating the slurry bonding performance of casing and cementing slurry of different wellbore sizes.

[0028] (IV) This invention discloses an apparatus and method for testing the bond strength between casing and cementing cement using rotational torque. It innovatively employs the ratio of rotational torque to diameter at different diameters to obtain the tangential force, which characterizes the bonding strength. Correspondingly, the upper lifting mechanism of the testing device is replaced with a rotating mechanism, changing the previous reliance solely on the lifting force to characterize the cement-casing bond strength. The magnitude of this force characterizes the bond strength between the outer wall of the pipe and the cement slurry bonding cylinder. The advantage of this invention is that it eliminates the influence of frictional resistance at the contact surface caused by gravity and confining pressure on the accurate acquisition of the bonding strength. Attached Figure Description

[0029] Figure 1 This is a schematic diagram of the device for testing the bond strength between casing and cementing cement in a simulated vertical well, as disclosed in Embodiment 1 of the present invention.

[0030] Figure 2 This is a schematic diagram of the structure of the kava disclosed in Embodiment 1 of the present invention;

[0031] Figure 3This is a schematic diagram of the horizontally mounted rotating dynamic torque tester disclosed in Embodiment 1 of the present invention;

[0032] Figure 4 This is a schematic diagram of the device for testing the bond strength between casing and cementing cement in a simulated horizontal or inclined well, as disclosed in Embodiment 1 of the present invention.

[0033] Explanation of reference numerals in the attached drawings: 1-Test sample, 11-Simulated casing of wellbore, 12-Cement grouting cylinder; 2-Slipper; 3-Joint; 4-Load application equipment, 41-Rotating dynamic torque tester, 42-Torque meter, 43-Control console, 44-Test frame; 5-Test chamber. Detailed Implementation

[0034] Exemplary embodiments of the invention will now be described in more detail with reference to the accompanying drawings. While exemplary embodiments of the invention are shown in the drawings, it should be understood that the invention can be implemented in various forms and should not be limited to the embodiments set forth herein. Rather, these embodiments are provided to enable a more thorough understanding of the invention and to fully convey the scope of the invention to those skilled in the art.

[0035] This invention discloses an apparatus and method for testing the bond strength between casing and cementing cement using rotational torque. A relative displacement occurs between the simulated casing 11 and the cement sheath fixed within a cement slurry bonding cylinder 12, generating rotational torque. This simulates the rotational torque exerted on the wellbore by deep-sea motion, causing a rotational tendency between the wellbore and the cement sheath. Simultaneously, the morphology of the bonding surface failure is observed until any bonding interface between the simulated casing 11 and the cement sheath fails. A torque meter 42 reads and records the torque value at the point of bonding interface failure in real time, thus completing the test of the bond strength between the simulated casing 11 and the cement sheath. Torque was tested, and the maximum torque value was used as an indicator of the bonding strength. The size of the test sample 1 was changed, and the number of slips of the slip 2 was increased or decreased according to the diameter of the well casing 11. This enabled the testing and evaluation of the bonding strength between the well casing and the cement sheath for different well casing diameters. This achieved the rational selection of cement slurry and drilling fluid in cementing processes with different well diameters, resulting in a higher compatibility between the formation and cement. This solved the problem in the existing technology that the bonding strength between the casing and the cement sheath in shallow cementing experiments with different well diameters could not be tested.

[0036] Example 1

[0037] Example 1 provides a device for testing the bond strength between casing and cementing cement using rotational torque. Its structure is described in detail below with reference to the accompanying drawings.

[0038] refer to Figure 1 and Figure 4The device for testing the bond strength between casing and cementing cement using rotational torque includes a test sample 1, slips 2, a joint 3, and a load application device 4.

[0039] Test sample 1 includes a well casing 11 and a cement grout-bonded casing 12.

[0040] The cement grout bonding cylinder 12 is fitted onto the outside of the well casing simulation casing 11. The annular space between the cement grout bonding cylinder 12 and the well casing simulation casing 11 is used to form a cement ring. The outer wall of the well casing simulation casing 11 and the inner wall of the cement ring are bonded together as one unit. One end of the well casing simulation casing 11 extends out of the cement grout bonding cylinder 12 and is exposed to the outside to form a joint end. The outer wall of one end of the cement grout bonding cylinder 12, which is in the opposite direction to the joint end of the well casing simulation casing 11, is fixed to form a fixed end.

[0041] The load application device 4 includes a rotary dynamic torque tester 41 and a torque meter 42. The rotary dynamic torque tester 41 is equipped with a power device to generate a rotary output. The rotary output shaft of the rotary dynamic torque tester 41 is connected to one end of the connector 3 through the torque meter 42. The other end of the connector 3 is connected to the connector end of the well casing simulation casing 11 through a slip 2.

[0042] Slippers are tools used during drilling operations to hold and suspend the drill string and casing string during tripping in and out of the well. (Reference) Figure 2 The 2-piece clapper consists of several clapper bodies, and multiple adjacent clapper bodies are connected in a ring by hinge pins. The 2-piece clapper is divided into three-piece, four-piece or multi-piece clappers according to the number of clapper bodies. Among them, multi-piece clappers refer to clappers with more than four clapper bodies.

[0043] When the test sample needs to be replaced, the number of slips in slip 2 is selected according to the change in the diameter of the well casing 11.

[0044] Furthermore, the device for testing the bond strength between the casing and cementing cement using rotational torque also includes a test chamber 5.

[0045] Test sample 1 is placed inside test chamber 5, and the fixed end of cement grout bonding cylinder 12 is fixed to the bottom or inner wall of test chamber 5. The annular space between the outer wall of cement grout bonding cylinder 12 and the inner wall of test chamber 5 is filled with test soil.

[0046] Specifically, test chamber 5 is a temperature-controlled chamber, including an open chamber body and a lid; the chamber body is equipped with temperature control equipment. Due to the addition of the temperature control system, the effect of different temperatures on the bond strength between cement and the sleeve can be simulated, and it can be used to evaluate the temperature resistance performance of the cement slurry system.

[0047] Specifically, the cement slurry bonding cylinder 12 includes a bonding cylinder body, a bonding cylinder base, and a bonding cylinder top cover; the bonding cylinder base is used to seal the bottom of the bonding cylinder body when cement slurry is injected into the bonding cylinder; the bonding cylinder top cover is used to seal the top of the bonding cylinder body filled with cement slurry.

[0048] To prevent the cement ring from rotating along with the well casing 11 when the simulated casing 11 rotates with the cement ring fixed inside the cement slurry bonding cylinder 12, the fixed end of the cement slurry bonding cylinder 12 is fixed to the bottom or inner wall of the test chamber 5 by fasteners 13.

[0049] To prevent the bond strength between the simulated well casing 11 and the cement ring inside the cement slurry bonding cylinder 12 from being greater than the bond strength between the inner wall of the cement slurry bonding cylinder 12 and the cement ring, one specific embodiment is to roughen the inner surfaces of the bonding cylinder body and the bonding cylinder base to enhance the bond strength between the inner wall of the cement slurry bonding cylinder 12 and the cement ring, ensuring that the bond strength between the simulated well casing 11 and the cement ring inside the cement slurry bonding cylinder 12 is less than the bond strength between the inner wall of the cement slurry bonding cylinder 12 and the cement ring.

[0050] Specifically, fastener 13 is a fixing ring consisting of two semi-rings. The two semi-rings are fixed to the bottom or inner wall of the test chamber 5 by bolts, and the two semi-rings form a fixing ring by fastening the cement grout bonding cylinder body or the bonding cylinder base of the cement grout bonding cylinder 12. Such fasteners 13 are common on the market and will not be described in detail here.

[0051] Since vertical wells, horizontal wells, and inclined wells exist in actual engineering projects, the device disclosed in this invention can be adjusted to simulate vertical wells, horizontal wells, and inclined wells. Specifically, refer to... Figure 1 The test sample was vertically positioned inside test chamber 5 to simulate a vertical well. (Reference) Figure 4 The test samples are placed horizontally or at an angle inside the test chamber 5 to simulate horizontal or inclined wells. In one specific implementation, the test chamber 5 can be placed either vertically or horizontally. When placed horizontally, the well casing 11 and connector 3 are both placed horizontally, which can simulate the bonding strength between the well casing and the cement slurry bonding cylinder of a horizontal well.

[0052] Specifically, the rotary dynamic torque tester 41 includes a power unit, a torque power meter, a torque sensor, and a torque display. The power unit is connected to the torque sensor via a coupling, and the torque sensor is connected to the torque meter 42 via a coupling. Figure 3 As shown.

[0053] The power equipment is a rotary electric motor;

[0054] The power equipment is equipped with a torque power meter, which is used to control the power output by controlling the power meter.

[0055] The torque sensor is equipped with a torque display to show the torque sensed by the torque sensor.

[0056] More specifically, the rotary dynamic torque tester 41 is a small rotary dynamic torque tester, and its operating environment is as follows: ambient temperature not exceeding 40℃, altitude not exceeding 2500m. When the ambient temperature is 20℃, the relative humidity is not greater than 85%. The installation of the rotary dynamic torque tester 41 is as follows... Figure 3 As shown.

[0057] More specifically, the load application device 4 also includes a control console 43 and a test frame 44.

[0058] The torque power meter and torque display are mounted on the control console 43, while the power equipment and torque sensor are mounted on the test rack 44.

[0059] Specifically, the torque meter 42 includes a locking drill chuck and a digital force gauge, which are connected via a data cable. More specifically, the torque meter 42 is a high-precision torque meter.

[0060] Specifically, connector 3 is located at the top of the well casing 11, and the top of connector 3 has a quick connector for docking with torque meter 42.

[0061] The working principle of the device disclosed in this invention is as follows:

[0062] The load application device 4 is started, and the power device of the rotating dynamic torque tester 41 generates power to form a rotation output, which in turn drives the torque meter 42, the joint 3 and the well casing 11 to rotate.

[0063] The relative displacement between the well casing 11 and the cement ring fixed in the cement slurry bonding cylinder 12 creates a rotational torque, simulating the rotational torque that causes the well casing and cement ring to rotate due to the deep sea motion applied to the well casing.

[0064] The well casing 11 is rotated at a constant speed to increase the torque between the rotating well casing 11 and the cement sheath.

[0065] As the rotational torque continues to increase, the simulated casing 11 in the wellbore rotates;

[0066] Simultaneously observe the morphology of the bonded surface failure until any bonded interface between the simulated casing 11 and the cement sheath is damaged. Torque meter 42 reads and records the torque value when the bonded interface is damaged in real time, thus completing the torque test between the simulated casing 11 and the cement sheath. The maximum torque value is used as an indicator to characterize the bond strength.

[0067] Example 2

[0068] Example 2 provides a method for testing the bond strength between casing and cementing using rotational torque, employing the apparatus for testing the bond strength between casing and cementing using rotational torque provided in Example 1. The method includes the following steps:

[0069] Step 1: Install the cement grouting cylinder 12 inside the test chamber 5, and place experimental soil around the cement grouting cylinder 12 to make a well of the required size for the cement grouting cylinder 12. Compact the static soil layer until it is dense, and control the temperature of the experimental soil through the temperature control equipment of the test chamber 5.

[0070] Step 2: Insert the well casing 11 into the cement slurry bonding cylinder 12, and inject the prepared cement slurry into the annular space between the cement slurry bonding cylinder 12 and the well casing 11. Wait for the cement slurry to solidify and form until the cement ring reaches the design strength.

[0071] Step 3: Start the load application device 4, and generate power through the power device of the rotating dynamic torque tester 41 to form a rotation output, which in turn drives the torque meter 42, the connector 3 and the well casing 11 to rotate.

[0072] The relative displacement between the well casing 11 and the cement ring fixed in the cement slurry bonding cylinder 12 creates a rotational torque, simulating the rotational torque that causes the well casing and cement ring to rotate due to the deep sea motion applied to the well casing.

[0073] The well casing 11 is rotated at a constant speed to increase the torque between the rotating well casing 11 and the cement sheath.

[0074] As the rotational torque continues to increase, the simulated casing 11 rotates, and the morphology of the cemented surface failure is observed until any cemented interface between the simulated casing 11 and the cement sheath is destroyed. The torque meter 42 reads and records the torque value when the cemented interface is destroyed in real time, thus completing the torque test between the simulated casing 11 and the cement sheath, and using the maximum torque value as an indicator of the cemented strength.

[0075] Step 4: Change the size of test sample 1. The number of slips 2 is increased or decreased according to the diameter of the well casing 11. Repeat steps 1 to 3 to test and evaluate the bonding strength between the well casing 11 with different diameters and the cement slurry bonded casing.

[0076] The invention will be further explained below with reference to the cement grout, casing and formation bonding strength test experiments of different specifications:

[0077] This experiment used three types of cement—425#, 525#, and offshore cementing grade G—to test the cement bonding strength.

[0078] For the purpose of establishing a baseline and comparison, all three types of cement were pure cement, without any additives. Following the above procedures, after different setting times, the following phenomena were observed:

[0079] I. Condensation Time

[0080] During the experiment, it was found that before the setting time of 2 hours, all the sleeves rotated from the cement grouting cylinder. After 4 hours, the sleeves in the low-grade cement rotated, while the sleeves in the medium-grade cement and G-grade cement, along with the cement grouting cylinder, rotated in the soil, and the torque decreased. After 6 hours, all three grades of cement rotated in the soil, with both the sleeves and the cement grouting cylinder rotating, and the torque decreased.

[0081] II. Lateral friction

[0082] The change in the bonding strength between the water-proof conduit and the cement can be reflected in the change in the lateral friction force. The average lateral friction force between the cement grout-bonded cylinder and the steel pipe pile and the soil can be measured experimentally. That is, the change in the lateral friction force reflects the change in the bonding strength.

[0083] III. Bond Strength Analysis Between Cement Grout and Waterproof Conduit

[0084] The 2-inch 425 cement sleeve reaches its bonding strength after 5 hours of setting, with a frictional force of 0.039 MPa per unit area; the 3-inch 425 cement sleeve reaches its bonding strength after 5 hours of setting, with a frictional force of 0.036 MPa per unit area.

[0085] The 2-inch 525 cement sleeve reaches its bonding strength after 5 hours of setting, with a frictional force of 0.042 MPa per unit area; the 3-inch 525 cement sleeve reaches its bonding strength after 5 hours of setting, with a frictional force of 0.041 MPa per unit area.

[0086] Grade G cement 2-inch sleeves reach their bonding strength after 4 hours of setting, with a frictional force of 0.041 MPa per unit area; Grade G cement 3-inch sleeves reach their bonding strength after 4 hours of setting, with a frictional force of 0.033 MPa per unit area.

[0087] The above experiments demonstrate that Grade G cement bonds faster and stronger in the formation, and is a better match for the experimental formation.

[0088] IV. Analysis of the bond strength between cement grout and seabed soil

[0089] The 2-inch 425 cement sleeve reaches its bonding strength after 13 hours of curing, at which point the frictional force per unit area is 0.055 MPa. As the curing time increases to 24 hours, the frictional force per unit area becomes 0.062 MPa.

[0090] The 3-inch 425 cement sleeve reaches its bonding strength after 13 hours of curing, at which point the frictional force per unit area is 0.052 MPa. As the curing time increases to 24 hours, the frictional force per unit area is 0.059 MPa.

[0091] The 2-inch 525 cement sleeve reaches its bonding strength after 13 hours of curing, at which point the frictional force per unit area is 0.056 MPa. As the curing time increases to 24 hours, the frictional force per unit area is 0.071 MPa.

[0092] The 3-inch sleeve made of 525 cement reaches its bonding strength after 13 hours of curing, at which point the frictional force per unit area is 0.06 MPa. As the curing time increases to 24 hours, the frictional force per unit area is 0.075 MPa.

[0093] The G-grade cement 2-inch sleeve reaches its bonding strength after 10 hours of curing, at which point the frictional force per unit area is 0.078 MPa. As the curing time increases to 24 hours, the frictional force per unit area is 0.01 MPa.

[0094] Grade G cement 3in sleeve reaches its bonding strength after 10 hours of curing, at which point the frictional force per unit area is 0.071MPa. As the curing time increases to 24 hours, the frictional force per unit area is 0.011MPa.

[0095] Before the cementing process has been completed for 6 hours, the steel pipe pile rotates in the cement grouting cylinder. Therefore, it is only necessary to provide the change in the bonding strength between the cement grout and the seabed soil after 6 hours.

[0096] This experimental testing method allows for the selection of high-performance drilling fluids and cement slurries for different wellbore diameters, based on experimental results, effectively improving cementing quality and reducing risks.

[0097] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A device for testing the bond strength between casing and cementing cement using rotational torque, characterized in that, It includes test sample (1), slip (2), joint (3), load application equipment (4) and test chamber (5). The test sample (1) includes a well casing simulation sleeve (11) and a cement slurry bonding cylinder (12). The cement slurry bonding cylinder (12) is fitted on the outside of the well casing simulation sleeve (11). The annular space between the cement slurry bonding cylinder (12) and the well casing simulation sleeve (11) is used to form a cement ring. The outer wall of the well casing simulation sleeve (11) and the inner wall of the cement ring are bonded together. One end of the well casing simulation sleeve (11) extends out of the cement slurry bonding cylinder (12) and is exposed to the outside to form a joint end. The outer wall of one end of the cement slurry bonding cylinder (12) is fixed in the opposite direction to the joint end of the well casing simulation sleeve (11) to form a fixed end. The load application device (4) includes a rotary dynamic torque tester (41) and a torque meter (42). The rotary dynamic torque tester (41) includes a power device, a torque power meter, a torque sensor, and a torque display. The power device is connected to the torque sensor via a coupling, and the torque sensor is connected to a torque meter (42) via a coupling. The power device is a rotary motor. The power device is equipped with a torque power meter for controlling power output. The torque sensor is equipped with a torque display for displaying the torque sensed by the torque sensor. The rotating dynamic torque tester (41) is equipped with a power device to generate a rotating output. The rotating output shaft of the rotating dynamic torque tester (41) is connected to one end of the connector (3) through a torque meter (42). The other end of the connector (3) is connected to the connector end of the well casing simulation (11) through a slip (2). The slip (2) includes several slip bodies, and multiple adjacent slip bodies are connected in a ring by hinge pins. When the test sample needs to be replaced, the number of slip bodies of the slip (2) increases or decreases according to the diameter of the well casing simulation (11). The test chamber (5) is a temperature-controlled chamber, including an open chamber body and a lid; a temperature control device is installed inside the chamber body; the test sample (1) is placed inside the test chamber (5), and the fixed end of the cement slurry bonding cylinder (12) is fixed to the bottom or inner wall of the test chamber (5); the annular space between the outer wall of the cement slurry bonding cylinder (12) and the inner wall of the test chamber (5) is filled with experimental soil; The cement slurry bonding cylinder (12) includes a bonding cylinder body, a bonding cylinder base, and a bonding cylinder top cover; the bonding cylinder base is used to seal the bottom of the bonding cylinder body when cement slurry is injected into the bonding cylinder; the bonding cylinder top cover is used to seal the top of the bonding cylinder body filled with cement slurry; wherein, the fixed end of the cement slurry bonding cylinder (12) is fixed to the bottom or inner wall of the test chamber (5) by fasteners (13); the fasteners (13) are fixing rings composed of two half rings, the two half rings are fixed to the bottom or inner wall of the test chamber (5) by bolts, and the two half rings form a fixing ring by locking the bonding cylinder body or the bonding cylinder base of the cement slurry bonding cylinder (12).

2. The apparatus for testing the bond strength between casing and cementing cement using rotational torque according to claim 1, characterized in that, The load application device (4) also includes a control console (43) and a test frame (44). The torque power meter and the torque display are mounted on the control console (43), and the power device and the torque sensor are mounted on the test frame (44).

3. The apparatus for testing the bond strength between casing and cementing cement using rotational torque according to claim 1, characterized in that, The test sample is vertically placed inside the test chamber (5) to simulate a vertical well.

4. The apparatus for testing the bond strength between casing and cementing cement using rotational torque according to claim 1, characterized in that, The test sample is set horizontally or at an angle inside the test chamber (5) to simulate a horizontal well or an inclined well.

5. A method for testing the bond strength between casing and cementing cement using rotational torque, employing the apparatus for testing the bond strength between casing and cementing cement using rotational torque as described in any one of claims 1 to 4, characterized in that, include Step 1: Install cement grouting cylinder (12) in test chamber (5), place test soil around cement grouting cylinder (12), make wellbore of the required size for cement grouting cylinder (12), compact the static soil layer to compact, and control the temperature of test soil through the temperature control equipment of test chamber (5). Step 2: Insert the well casing simulation pipe (11) into the cement slurry bonding cylinder (12), and inject the prepared cement slurry into the annular space between the cement slurry bonding cylinder (12) and the well casing simulation pipe (11), and wait for the cement slurry to solidify and form until the cement ring reaches the design strength. Step 3: Start the load application device (4), and generate power through the power device of the rotating dynamic torque tester (41) to form a rotation output, which in turn drives the torque meter (42), the joint (3) and the well casing (11) to rotate. The well casing (11) and the cement ring fixed in the cement slurry cementing cylinder (12) undergo relative displacement to form a rotational torque, simulating the rotational torque that causes the well casing and cement ring to rotate due to the deep sea water movement applied to the well casing. The well casing (11) is rotated at a constant speed to increase the torque between the rotating well casing (11) and the cement sheath; As the rotational torque continues to increase, the well casing (11) rotates, and the shape of the bonded surface is observed until any bonded interface between the well casing (11) and the cement sheath is destroyed. The torque meter (42) reads and records the torque value when the bonded interface is destroyed in real time, and completes the torque test between the well casing (11) and the cement sheath. The maximum value of the torque value is used as an indicator to characterize the bond strength. Step 4: Change the size of the test sample (1) and repeat steps one to three to achieve the test and evaluation of the bonding strength between the simulated casing and the cement slurry bonded casing with different diameters of the simulated casing (11).

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