An instrument for measuring micro-annulus of cement ring

Abstract

An instrument for measuring micro-annulus of cement ring of cementing well relates to the technical field of cementing well in oil and gas fields, and comprises a curing kettle, a temperature and pressure regulating system, a cement mold and a micro-annulus measuring device; the temperature and pressure regulating system is used to regulate the temperature and pressure in the curing kettle; the cement mold is located in the curing kettle, and the cement mold comprises two casings, and an annular space with a bottom end closed is provided between the two casings; the micro-annulus measuring device comprises a probe and a probe displacement measuring device, the probe comprises a rod body and a seat body connected to one end of the rod body, the seat body is located in the annular space and is arranged close to the pipe wall of one of the casings, and the other end of the rod body moves out from an opening arranged on the casing close to the seat body along the radial direction of the annular space, and the probe displacement measuring device is used to measure the radial displacement of the rod body in the annular space during the cement slurry curing process. The measuring instrument of the present application can measure the radial contraction of cement slurry during the simulated curing process, which corresponds to the actual working conditions downhole.

Description

Technical Field

[0001] The present application relates to the technical field of oil and gas field cementing, and in particular to an instrument for measuring micro-annulus of cement ring of cementing. Background Art

[0002] Solving the problem of preventing cement slurry from channeling in oil and gas fields is the key to improving cementing quality and protecting oil and gas formations.

[0003] During the cementing process, cement slurry hydration is divided into two stages: gelling stage and hardening stage.

[0004] During the gelation stage, the cement slurry loses weight continuously. When the effective liquid column pressure after the cement slurry loses weight is less than the formation fluid pressure, the formation fluid will flow into the cement slurry in the well. The main means to prevent crossflow in this stage are to improve the slurry column structure with a pressure stability coefficient, use a cement slurry system with strong anti-crossflow ability, and use a cement crossflow meter for simulation evaluation.

[0005] During the hardening stage, the volume of cement generally shrinks, causing micro-annulus gaps to appear at the first interface between casing and cement and the second interface between cement and formation, destroying the sealing integrity, leading to interlayer crossflow and even wellhead annulus pressure, which poses a serious safety hazard to production. An effective way to prevent micro-annulus gaps in cement rings is to add the right type and amount of cement expansion agent to the cement slurry.

[0006] The hydration reaction of cement is a very complex physical and chemical reaction. Some cement slurries expand axially but shrink radially; some cement slurries expand in outer diameter and inner diameter, i.e., micro-annulus occurs at the first interface; some cement slurries expand in outer diameter and shrink in inner diameter, and there is no micro-annulus at both interfaces. Cementing engineering pursues a cement slurry formula with no micro-annulus at the first interface and the second interface under downhole temperature and pressure conditions and with micro-expansion.

[0007] At present, the expansion instruments used to evaluate the expansion capacity of cement slurry are mainly divided into three categories: "low temperature open ring method", "volume expansion method" and "axial displacement method". They evaluate the expansion capacity of cement from different dimensions, but all have the disadvantages of poor correspondence with the actual working conditions downhole and inability to evaluate the "micro-annular space gap" which is the most essential feature of sealing under high temperature and high pressure. Summary of the invention

[0008] An embodiment of the present application provides an instrument for measuring micro-annulus of cement ring of cementing, comprising a curing kettle, a temperature and pressure regulating system, a cement mold and a micro-annulus measuring device; the temperature and pressure regulating system is used to regulate the temperature and pressure in the curing kettle; the cement mold is located in the curing kettle, the cement mold comprises two casings, an annular space with a bottom end closed is provided between the two casings, the annular space is used to carry out the curing process of cement slurry therein; the micro-annulus measuring device comprises a probe and a probe displacement measuring device, the probe comprises a rod body and a seat body connected to one end of the rod body, the seat body is located in the annular space and is arranged close to the pipe wall of one of the casings, and the other end of the rod body moves out from an opening provided on the casing close to the seat body along the radial direction of the annular space; the probe displacement measuring device is used to measure the displacement of the rod body in the radial direction of the annular space during the curing process of cement slurry.

[0009] Beneficial effects:

[0010] The instrument for measuring the micro-annulus of cement ring in the embodiment of the present application measures the radial displacement of the cement ring after the cement slurry solidifies, that is, the radial contraction of the cement ring, which is also the "micro-annulus gap" (i.e., micro-annulus) value between the cement ring and the inner casing or the outer casing. Compared with the existing cement expansion capacity evaluation method, the radial displacement of the cement ring measured in the embodiment of the present application can evaluate the "micro-annulus gap" with the most essential sealing characteristics, which corresponds to the actual working conditions downhole, and the evaluation of the expansion and contraction capacity of cement slurry is more accurate.

[0011] In addition, the instrument for measuring the micro-annulus of the cement ring of the embodiment of the present application can continuously measure the radial displacement of the cement ring, and the change process of the inner and outer diameters of the cement ring can be known.

[0012] The instrument for measuring the micro-annulus of cement ring of the embodiment of the present application can simulate the curing process of cement slurry under actual downhole working conditions by adjusting the temperature and pressure in the curing kettle. The measured radial displacement of the cement ring can better evaluate the expansion performance of the cement slurry under actual downhole working conditions. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] The accompanying drawings are used to provide further understanding of the technical solution of the present application and constitute a part of the specification. Together with the embodiments of the present application, they are used to explain the technical solution of the present application and do not constitute a limitation on the technical solution of the present application.

[0014] Figure 1 A schematic diagram of the structure of an instrument for measuring micro-annulus of cement ring in one embodiment of the present application;

[0015] Figure 2 This is a schematic diagram of the structure in which a displacement measuring device is installed on a curing kettle in one embodiment of the present application;

[0016] Figure 3 This is a schematic diagram of the structure in which a probe is installed on a cement mold in one embodiment of the present application;

[0017] Figure 4 for Figure 3 A schematic diagram of the installation structure of the second probe and the second elastic limiting device;

[0018] Figure 5 This is a schematic diagram of the cross-sectional structure of a cement mold according to an embodiment of the present application;

[0019] Figure 6 for Figure 5 A schematic diagram of the cross-sectional structure of the outer sleeve of the cement mold deforming during the expansion process of the cement ring;

[0020] The accompanying drawings are marked as follows: 1. cement mold, 11. annular space, 12. outer sleeve, 13. inner sleeve, 14. base, 15. isolation sleeve, 16. lifting part, 17. annular protrusion, 201. hollow body, 202. core assembly, 203. zero adjustment spring, 204. induction assembly, 205. zero adjustment nut, 21. second probe displacement measuring device, 22. second probe, 221. rod body of second probe, 222. seat body of second probe, 23. first probe displacement measuring device, 24. first probe, 2 41. Rod body of the first probe, 242. Seat body of the first probe, 25. Reference displacement measuring device, 31. Second bushing, 32. Second clamping cap, 33. Second elastic member, 41. First connecting seat, 42. Second connecting seat, 43. Spring, 44. Nut, 45. Connecting rod, 5. Curing kettle, 51. Kettle wall, 6. Temperature measuring device, 71. Liquid inlet pipeline, 72. Liquid discharge pipeline, 81. Air inlet pipeline, 82. Constant pressure valve, 83. Pressure pump, 84. Air source, 9. Heating device, 10. Monitoring device. DETAILED DESCRIPTION

[0021] The technical solution of the present application is further described below in conjunction with the accompanying drawings and through specific implementation methods. It should be understood that the specific embodiments described herein are only used to explain the present application, rather than to limit the present application.

[0022] like Figure 1 As shown, an embodiment of the present application provides an instrument for measuring micro-annulus of cement ring of cementing, including a curing kettle 5, a temperature and pressure regulating system, a cement mold 1 and a micro-annulus measuring device.

[0023] The temperature and pressure regulating system is used to regulate the temperature and pressure in the curing kettle 5, so that the measuring instrument can meet the requirements of measuring the micro-annulus of cement ring under high temperature and high pressure conditions.

[0024] The cement mold 1 is located in the curing kettle 5. The cement mold 1 includes two sleeves, namely an inner sleeve 13 and an outer sleeve 12. An annular space 11 with a closed bottom is provided between the inner sleeve 13 and the outer sleeve 12. The annular space 11 is used for the cement slurry curing process. The annular space 11 may have the same width as the cementing annular gap, for example, 20 mm.

[0025] After the cement slurry loses fluidity after hydration to final setting, lattice contraction (the cement ring contracts) or lattice expansion (the cement ring expands). If lattice contraction occurs, the cement ring formed by solidification will break away from the tube wall of the inner casing 13 or / and the outer casing 12, thereby forming a first interface micro-annulus or / and a second interface micro-annulus. If lattice expansion occurs, the inner annular surface or / and the outer annular surface of the cement ring formed by solidification will be bonded to the tube wall of the inner casing 13 or / and the outer casing 12, and no micro-annular gap will be generated at the two interfaces. If lattice expansion occurs, it is generally necessary to measure the expansion amount of the outer annular surface of the cement ring (i.e., the expansion amount of the outer diameter of the cement ring). Therefore, in order to enable the device for measuring the micro-annular gap of the cement ring of this embodiment to measure the first interface micro-annular gap or / and the second interface micro-annular gap, it can also measure the expansion amount of the outer annular surface of the cement ring, optionally, the outer casing 12 of the cement mold is configured to be able to expand and deform, so that its diameter becomes larger under the action of the cement ring expansion force. However, it is understandable that, when measuring the first interface micro-annular gap and / or the second interface micro-annular gap, there is no requirement on whether the outer sleeve 12 can undergo the above-mentioned expansion deformation, that is, the outer sleeve 12 can be set to be unable to deform like the inner sleeve 13, or the outer sleeve 12 can also be set to be able to undergo the above-mentioned expansion deformation.

[0026] In the following embodiments, the outer sleeve 12 is configured to be expandable and deformable so that its diameter increases under the expansion force of the cement sheath.

[0027] The micro-annulus measurement device includes a probe and a probe displacement measurement device. The probe includes a rod body and a seat body connected to one end of the rod body. The seat body is located in the annular space 11 and is arranged close to the wall of one of the casings. The other end of the rod body moves out from an opening arranged on the casing close to the seat body along the radial direction of the annular space 11. The seat body is used to be fixed inside the cement ring during the process of cement slurry solidifying into a cement ring. The seat body can drive the rod body to move along the radial direction of the annular space 11 during the contraction or expansion of the cement ring. The probe displacement measurement device is used to measure the displacement of the rod body in the radial direction of the annular space 11 during the solidification of cement slurry. The displacement is the micro-annulus value or micro-expansion value of the cement ring of the cementing well.

[0028] In this embodiment, the temperature and pressure in the curing kettle 5 are adjusted by the temperature and pressure regulating system, so as to simulate the curing process of cement slurry under actual downhole working conditions. The measured radial displacement of the cement ring can better evaluate the expansion performance of the cement slurry under actual downhole working conditions.

[0029] The temperature and pressure regulating system may include a liquid supply system, a gas supply system and a heating device 9. The liquid supply system includes a liquid inlet pipeline 71 and a liquid discharge pipeline 72 connected to the inside of the curing kettle 5, which are respectively used to transport and discharge liquid (such as water) into and out of the curing kettle 5. The heating device 9 is used to heat the liquid in the curing kettle 5 so that the curing kettle 5 can reach the required temperature. The heating device 9 can be arranged outside or inside the curing kettle 5. The gas supply system is used to transport gas (such as nitrogen) into the curing kettle 5 so that the inside of the curing kettle 5 can reach the required pressure. The temperature in the curing kettle 5 can be adjusted by the heating device 9, and the pressure in the curing kettle 5 can be adjusted by the gas supply system.

[0030] The gas supply system may include a gas source (which may be a nitrogen source) 84, an air intake pipeline 81 and a pressure pump 83. One end of the air intake pipeline 81 is connected to the gas source 84, and the other end is connected to the inside of the curing kettle 5. The pressure pump 83 is arranged on the air intake pipeline 81. The pressure pump 83 is used to pressurize the gas from the gas source 84 and then transport it to the curing kettle 5 through the air intake pipeline 81. A constant pressure valve 82, a pressure gauge, etc. may also be arranged on the air intake pipeline 81. The constant pressure valve 82 can ensure that the pressure of the gas entering the curing kettle 5 is constant. The pressure pump 83 may be a pneumatic pump, which uses compressed air to drive the pneumatic pump to pressurize the nitrogen from the high-pressure nitrogen bottle to a preset pressure value. In this embodiment, the curing kettle 5 is pressurized by gas pressurization. During the entire test process, even if there is a slight leakage, the pressure decay is very small. The pressure pump 83 is almost never started again to replenish the system pressure during the test, thus avoiding unnecessary vibrations and ensuring accurate measurement of each displacement measuring device. In addition, the pressure pump 83 is a pneumatic pump, which can also prevent the influence of excessive vibrations during the pressure loading process on the displacement measurement results.

[0031] The instrument for measuring cement micro-annulus of this embodiment may further include a temperature measuring device 6 and a monitoring device 10. The temperature measuring device 6 is used to measure the temperature in the curing kettle 5 and can send the measured data to the monitoring device 10. The temperature measuring device 6 may be a thermocouple. The monitoring device 10 monitors the temperature in the curing kettle 5 and can control the heating temperature of the heating device 9. The monitoring device 10 may also monitor the measurement results of each displacement measuring device.

[0032] During the measurement of cement micro-annulus, the curing kettle 5 is in a closed state, the cement mold 1 is in the high-temperature liquid in the curing kettle 5, and the gas above the liquid surface ensures the pressure in the curing kettle 5, so that the cement slurry in the cement mold 1 is in a high-temperature and high-pressure environment of the actual underground working conditions. To meet this test environment, for example, Figure 1 and Figure 2 As shown, the probe displacement measuring device includes a hollow body 201, a core assembly 202 and a sensing assembly 204; the hollow body 201 is open at one end and closed at the other end, and the open end of the hollow body 201 is fixed on the curing kettle 5 and communicated with the inside of the curing kettle 5; the core assembly 202 is slidably arranged inside the hollow body 201, and one end of the core assembly 202 extends out of the open end of the hollow body 201, and is arranged to abut or hard connect with the other end of the rod body of the probe, so that it can move under the push or pull of the rod body of the probe; the sensing assembly 204 is arranged outside the hollow body 201, and is used to detect the displacement of the core assembly 202. Among them, the open end of the hollow body 201 is sealed and connected to the kettle wall 51 of the curing kettle 5 to prevent the liquid in the kettle from leaking. During the measurement process, the interior of the hollow body 201 of the probe displacement measuring device is connected to the interior of the curing kettle 5. The interior of the hollow body 201 and the interior of the curing kettle 5 are in the same high temperature and high pressure state. The temperature and pressure state of the core assembly 202 as a whole is consistent, which will not affect the movement of the core assembly 202 and can avoid affecting the measurement results. Therefore, the probe displacement measuring device of this embodiment can continuously measure the radial displacement of the rod body of the probe under high temperature and high pressure.

[0033] The probe displacement measuring device can be installed on the side wall of the curing kettle 5. In order to make the rod of the probe pre-installed in the cement mold 1 correspond to the position of the measuring end of the probe displacement measuring device (i.e., one end of the core assembly 202) after the cement mold 1 enters the curing kettle 5, the cement mold 1 is provided with a first limiting portion, and the curing kettle 5 is provided with a second limiting portion. The first limiting portion and the second limiting portion cooperate to enable the cement mold 1 to reach a predetermined position when it is sent into the curing kettle 5. Exemplarily, a track is provided on the inner wall of the curing kettle 5, and a slide groove for slidingly cooperating with the track is provided on the cement mold 1. The cement mold 1 can slide into the kettle along the track on the kettle wall, so that the end of the rod of the probe contacts the measuring end of the probe displacement measuring device.

[0034] The core assembly 202 may include a measuring rod and an iron core connected to one end of the measuring rod, and the other end of the measuring rod extends from the open end of the hollow body 201 and is configured to abut against the other end of the rod body of the probe (for example, it may be in close contact with the magnetic attraction) or hard-connected. The other end of the measuring rod is hard-connected to the other end of the rod body of the probe, and during the expansion or contraction of the cement, the probe will drive the iron core to move through the measuring rod, and then the sensing assembly 204 measures the displacement of the probe. The other end of the measuring rod is hard-connected to the other end of the rod body of the probe, such as a threaded connection, a connection with a connector, etc., so that the radial displacement of the rod body of the probe can be completely transmitted to the core assembly 202, the measurement is more accurate, and small changes in displacement can also be measured.

[0035] The induction component 204 may be an electromagnetic induction component 204, which can output an electrical signal according to the change of the magnetic field when the iron core moves, that is, convert the displacement of the iron core into an electrical signal for output. The induction component 204 may include a coil frame and a primary coil and a secondary coil arranged on the coil frame, and its induction principle is the same as that of a differential transformer.

[0036] The probe displacement measuring device may further include a zero adjustment spring 203 and a zero adjustment nut 205. The coil frame of the induction component 204 is sleeved on the hollow body 201. One end of the zero adjustment spring 203 is limited to a convex ring provided on the outer wall of the hollow body 201, and the other end abuts against one end of the induction component 204. The zero adjustment nut 205 is threadedly connected to the hollow body 201 and limits the other end of the induction component 204. The position of the induction component 204 can be adjusted by rotating the zero adjustment nut 205 to achieve the purpose of zero adjustment.

[0037] The micro-annulus measurement device is used to measure the radial contraction displacement or expansion displacement of the cement ring after the cement slurry solidifies. The micro-annulus measurement device can be set to two sets, namely a first micro-annulus measurement device and a second micro-annulus measurement device. The first micro-annulus measurement device can be used to measure the micro-annulus between the cement ring and the inner casing 13 (i.e., the first interface) after the cement slurry solidifies, and the second micro-annulus measurement device can be used to measure the micro-annulus between the cement ring and the outer casing 12 (i.e., the second interface) after the cement slurry solidifies. The measurement principles of the two sets of micro-annulus measurement devices can be the same, and the two sets of micro-annulus measurement devices measure independently. It is also possible to set only one set of micro-annulus measurement devices to measure the micro-annulus between the cement ring and the inner casing 13 or between the cement ring and the outer casing 12 as needed.

[0038] like Figure 3As shown, in an exemplary embodiment, two sets of the micro-annular gap measuring devices are provided, the first micro-annular gap measuring device includes a first probe 24 and a first probe displacement measuring device 23, the first probe 24 includes a rod body 241 and a seat body 242 connected to one end of the rod body 241, the seat body 242 of the first probe is located in the annular space 11 and is arranged close to the pipe wall of the inner sleeve 13, the other end of the rod body 241 of the first probe is movably passed through the opening provided on the inner sleeve 13 along the radial direction of the annular space 11, and extends to the outside of the outer sleeve 12. Among them, the other end of the rod body 241 of the first probe passes through the first opening of the inner sleeve, the second opening of the inner sleeve, and the first opening of the outer sleeve in sequence. Alternatively, the other end of the rod body 241 of the first probe is movably passed through the first opening of the inner sleeve provided on the inner sleeve 13 along the radial direction of the annular space 11, and is located in the inner sleeve 13. The seat 242 of the first probe is used to be fixed inside the cement ring during the process of cement slurry solidifying into a cement ring. The seat 242 of the first probe can drive the rod 241 of the first probe to move radially along the annular space 11 during the process of cement ring contraction. The first probe displacement measuring device 23 is used to measure the displacement of the rod 241 of the first probe in the radial direction of the annular space 11. The first probe displacement measuring device 23 can measure the radial displacement of the other end of the rod 241 of the first probe. For example, the measuring head of the first probe displacement measuring device 23 is connected or abutted to the other end of the rod 241 of the first probe. The radial movement of the rod 241 of the first probe can drive or push the measuring head of the first probe displacement measuring device 23 to move, and then the radial displacement of the rod 241 of the first probe can be measured. The first probe displacement measuring device 23 can use a displacement measuring device that can measure linear displacement, such as a differential transformer.

[0039] The other end of the rod body 241 of the first probe extends to the outside of the outer sleeve 12. In order to prevent the rod body 241 of the first probe from being solidified with the cement slurry in the annular space 11, the cement mold 1 also includes an isolation sleeve 15. The two ends of the isolation sleeve 15 are respectively arranged in the isolation sleeve 15 installation holes set on the inner sleeve 13 and the outer sleeve 12, and the rod body 241 of the first probe moves through the isolation sleeve 15. Among them, one end of the isolation sleeve 15 is arranged in the first opening of the outer sleeve, and the other end can be arranged in the first opening of the inner sleeve or the second opening of the inner sleeve. During the installation process, the isolation sleeve 15 can be first inserted into the isolation sleeve 15 installation holes set on the inner sleeve 13 and the outer sleeve 12, and then the rod body 241 of the first probe can be inserted into place from the isolation sleeve 15, and then the seat body 242 of the first probe is threadedly connected to one end of the rod body 241. When the other end of the isolation sleeve 15 is arranged in the second opening of the inner sleeve, a first bushing can be arranged in the first opening of the inner sleeve. The first bushing can protrude from the first opening of the inner sleeve to play a certain supporting and guiding role for the rod body 241 of the first probe.

[0040] The second micro-annular gap measuring device includes a second probe 22 and a second probe displacement measuring device 21. The second probe includes a rod body 221 and a seat body 222 connected to one end of the rod body. The seat body 222 of the second probe is located in the annular space 11 and is arranged close to the wall of the outer sleeve 12. The other end of the rod body 221 of the second probe moves out from the second opening of the outer sleeve arranged on the outer sleeve 12 along the radial direction of the annular space 11. The seat body 222 of the second probe is used to be solidified inside the cement ring during the process of cement slurry solidifying into a cement ring. The seat body 222 of the second probe can drive the rod body 221 of the second probe to move along the radial direction of the annular space 11 during the contraction or expansion of the cement ring. Since the outer sleeve 12 can expand and deform, the cement ring can push the outer sleeve 12 and drive the rod body 221 of the second probe to move along the radial direction of the annular space 11 during the expansion of the outer diameter of the cement ring. When the outer diameter of the cement ring shrinks, the cement ring drives the second probe 22 to move synchronously in the opposite direction along the radial direction of the annular space 11, and a micro-annular gap appears between the outer diameter of the cement ring and the outer sleeve 12, i.e., the second interface. The second probe displacement measuring device 21 is used to measure the displacement of the rod body 221 of the second probe in the radial direction of the annular space 11. The second probe displacement measuring device 21 can measure the radial displacement of the other end of the rod body 221 of the second probe, for example, the measuring head of the second probe displacement measuring device 21 is connected or abutted to the other end of the rod body 221 of the second probe, and the radial movement of the rod body 221 of the second probe can drive or push the measuring head of the second probe displacement measuring device 21 to move, and then the radial displacement of the rod body 221 of the second probe can be measured. The second probe displacement measuring device 21 can use a displacement measuring device that can measure linear displacement, such as a differential transformer.

[0041] The two probes of the two sets of micro-annular gap measuring devices, namely the first probe 24 and the second probe 22, can be installed at the same or different heights on the cement mold.

[0042] like Figure 1As shown, in order to reduce the measurement error caused by system factors, the micro-annulus measurement device can also include a reference displacement measurement device 25 for measuring the reference displacement. The reference displacement measurement device 25 is used to measure the measurement value generated by the system factors, that is, the reference displacement. The structure and product specifications of the reference displacement measurement device 25 and its setting method on the curing kettle 5 are the same as those of the first probe displacement measurement device 23 and the second probe displacement measurement device 21. The difference is that the reference displacement measurement device 25 measures the displacement generated by the system factors, which is used to eliminate the measurement system error caused by the change of ambient temperature and electromagnetic environment during the experiment. Its measuring head can be inserted into the curing kettle 5 without abutting or hard connection with the probe. During the measurement process, after the temperature and pressure of the cement slurry in the curing kettle 5 rise to the designed experimental value and remain constant for two hours, the three displacement measurement devices are all adjusted to zero to eliminate the error of the displacement measurement device's measuring rod lengthening caused by the high temperature and high pressure in the kettle body. Subsequently, the measurement values ​​of the first probe displacement measurement device 23 and the second probe displacement measurement device 21 are subtracted from the measurement values ​​of the reference displacement measurement device 25, which is the true change result of the inner and outer diameters of the cement ring.

[0043] like Figure 3 and Figure 4 As shown, both sets of micro-annular gap measuring devices may also include an elastic limiting device, wherein the elastic limiting device includes an elastic member, and the elastic member is used to make the seat of the probe contact the pipe wall of the corresponding casing under the action of its elastic force. The elastic limiting device is set to make the seat of the probe contact the corresponding casing or other components. In this way, during each cement slurry solidification simulation measurement process, the position of the seat of the probe in the radial direction is fixed, which can reduce the measurement error caused by its non-fixed position. Exemplarily, the first micro-annular gap measuring device also includes a first elastic limiting device, which is used to make the seat 242 of the first probe contact the pipe wall of the inner casing 13 under the action of its elastic force; the second micro-annular gap measuring device also includes a second elastic limiting device, which is used to make the seat 222 of the second probe contact the pipe wall of the outer casing 12 under the action of its elastic force. The structures of the first elastic limiting device and the second elastic limiting device can be the same.

[0044] like Figure 4As shown, the second elastic limiting device includes a second bushing 31 and a second elastic member 33, the second elastic member 33 can be a spring, the second bushing 31 is arranged in the second opening of the outer sleeve arranged on the outer sleeve 12, the portion of the second bushing 31 protruding from the second opening of the outer sleeve (i.e. the portion of the second bushing 31 protruding from the outside of the outer sleeve 12) is sleeved with the spring, the spring is in a compressed state, one end of which is fixed on the outer sleeve 12 or the second bushing 31, and the other end is fixed on the rod body 221 of the second probe. In this embodiment, the second elastic limiting device uses the elastic force of its spring to tighten the rod body 221 of the second probe, so that the seat body 222 of the second probe can be close to the tube wall of the outer sleeve 12 or the second bushing 31.

[0045] To facilitate the installation of the second elastic limiting device, the second elastic limiting device also includes a second clamping cap 32, which can be threadedly connected to the other end of the rod body 221 of the second probe, and one end of the spring can abut against the outer wall of the outer sleeve 12, and the other end abuts against the inside of the second clamping cap 32. The gap between the end face of the second clamping cap 32 and the outer wall of the outer sleeve 12 must be no less than the maximum radial shrinkage of the cement. During the installation process, the second bushing 31 can be first installed in the second opening of the outer sleeve, and the inner wall of the second bushing 31 is coated with sealing grease. The rod body 221 of the second probe is passed through the second bushing 31 to the outside of the outer sleeve 12, and then the spring is put on the second bushing 31, and then the second clamping cap 32 is threadedly connected to the other end of the rod body 221 of the second probe. After the installation is completed, the second clamping cap 32 is manually pressed, which should be flexible, and the clamping and ejection are not restricted.

[0046] like Figure 3 As shown, the first elastic limiting device can be installed at the first opening of the outer sleeve, and its setting method is similar to the second elastic limiting device. In the embodiment of the first elastic limiting device, the isolation sleeve 15 can be similar to the second bushing 31 of the second elastic limiting device. Exemplarily, one end of the isolation sleeve 15 protrudes from the outside of the outer sleeve 12, and the portion of the isolation sleeve 15 protruding from the outside of the outer sleeve 12 is sleeved with a spring, one end of the spring is fixed to the rod body 241 of the first probe, and the other end is fixed to the isolation sleeve 15 or the outer sleeve 12. The spring is in a compressed state and makes the seat body 242 of the first probe contact the wall of the inner sleeve 13. Similarly, to facilitate the installation of the first elastic limiting device, the first elastic limiting device also includes a first clamping cap, which can be threadedly connected to the other end of the rod body 241 of the first probe, one end of the spring can contact the first clamping cap, and the other end can contact the outer wall of the outer sleeve 12. Other settings and installation methods of the first elastic limiting device are the same as those of the second elastic limiting device, and will not be repeated.

[0047] In this embodiment, cement slurry is solidified in the annular space 11 of the cement mold 1, simulating the solidification process of cement slurry for underground cementing. After solidification, cement slurry becomes cement, which solidifies in the annular space 11, i.e., a cement ring. As the cement hardening stage proceeds, the volume of the cement ring solidified by the cement slurry will expand or contract, thereby generating a certain radial contraction or expansion. The radial contraction or expansion of the cement ring has a great influence on the evaluation of the anti-channeling performance of the cement slurry.

[0048] In this embodiment, a probe is pre-set in the annular space 11 of the cement mold 1. As the cement slurry solidifies, the seat of the probe is fixed to the inside of the cement ring. The contraction force or expansion force of the cement ring during the contraction or expansion process drives the rod of the probe to move in the radial direction of the cement ring, and the displacement of the rod of the probe in the radial direction of the cement ring is measured by the probe displacement measuring device, so that the contraction or expansion of the cement ring in the radial direction can be measured. The radial contraction is also the size of the micro-annular gap between the cement ring and the casing, which corresponds to the actual working conditions downhole, and the evaluation of the expansion capacity of the cement slurry is more accurate. In addition, the device for measuring the cement micro-annular gap in the embodiment of the present application can continuously measure the radial displacement of the rod of the probe, so that the change process of the radial contraction or expansion of the cement ring can be known. In this embodiment, the seat of the probe is set close to the casing wall, and the measured radial contraction of the cement ring is closer to the actual micro-annular gap value between the cement and the casing.

[0049] like Figure 3 , Figure 5 and Figure 6 As shown, in this embodiment, the cement mold further includes a base 14, an inner sleeve 13 and an outer sleeve 12 are arranged on the base 14 to form the annular space 11, and the outer sleeve 12 is arranged to be expandable and deformable so that its diameter becomes larger under the action of the cement ring expansion force; during the expansion of the cement ring, the cement ring can push the outer sleeve 12 and drive the rod body of the probe to move radially along the annular space 11. Regarding the structure of the outer sleeve 12, exemplarily, the outer sleeve 12 can include two or more arc-shaped plates, and the two or more arc-shaped plates surround the outer sleeve 12, and the adjacent two arc-shaped plates are sealed and connected by a connecting assembly; under the action of the cement ring expansion force, the adjacent two arc-shaped plates can generate relative displacement to increase the diameter of the outer sleeve 12.

[0050] For example, the number of the arc-shaped plates can be set to two, each arc-shaped plate has a semicircular structure, and the connection component is arranged at the junction of the two arc-shaped plates. One or more connection components can be arranged between two adjacent arc-shaped plates.

[0051] In this embodiment, the inner sleeve 13 and the outer sleeve 12 can both be made of metal materials, such as stainless steel. The connecting assembly tightly connects the two adjacent arc-shaped plates together when the cement slurry has not yet solidified to generate expansion force, and when the cement slurry solidifies to generate expansion force, the two adjacent arc-shaped plates can be relatively displaced to increase the diameter of the outer sleeve 12, that is, the outer sleeve 12 expands and deforms.

[0052] Exemplarily, the connecting assembly includes a first connecting seat 41, a second connecting seat 42, a connecting rod 45 and a spring 43. The first connecting seat 41 and the second connecting seat 42 are respectively arranged on two adjacent arc-shaped plates. One end of the connecting rod 45 is fixed on the first connecting seat 41, and the other end is movable through a rod hole arranged on the second connecting seat 42. The spring 43 is sleeved on the connecting rod 45 and uses its own elastic force to make the connecting parts of the two adjacent arc-shaped plates close together.

[0053] The first connection seat 41 and the second connection seat 42 can be arranged opposite to each other. When the first connection seat 41 and the second connection seat 42 are close together, the butt joints of the two adjacent arc-shaped plates are close together, and the two adjacent arc-shaped plates are in a sealed state. The butt joints (i.e., the joints) of the two adjacent arc-shaped plates can be overlapped, and the two can be sealed by setting sealing strips or other sealing parts, applying sealing grease, etc., to prevent the cement slurry from leaking before solidification.

[0054] To facilitate installation and disassembly of the connection assembly, the other end of the connection rod 45 is threadedly connected with a nut 44, and the spring 43 is in a compressed state, with one end abutting against the nut 44 and the other end abutting against the second connection seat 42. One end of the connection rod 45 can be threadedly connected to the first connection seat 41, and the end can be fastened with another nut.

[0055] In this embodiment, after the cement slurry (initially flowable) is injected into the annular space 11 of the cement mold, the cement slurry begins to solidify. Figure 5 As shown, when the cement slurry has not yet solidified and generated expansion force, the elastic force of the spring 43 of the connecting assembly makes the butt joints of the two adjacent arc-shaped plates close together, and each of the two adjacent arc-shaped plates is closely connected. Figure 6 As shown, as the cement slurry solidifies, after the cement slurry loses fluidity after hydration to final setting, lattice expansion occurs, and the expansion force generated by solidification overcomes the elastic force of the spring 43 of the connecting assembly, and a relative displacement occurs between the two adjacent arc-shaped plates, and the outer sleeve 12 expands and deforms, and its diameter becomes larger, but there will be no leakage (the cement slurry has solidified). If lattice contraction occurs, the cement ring formed by solidification will separate from the inner wall of the outer sleeve 12, resulting in a micro-annular gap.

[0056] An annular protrusion 17 is provided on the top surface of the base 14, the bottom end of the outer sleeve 12 is placed on the top surface of the base 14, and the inner wall of the outer sleeve 12 is set close to the outer wall of the annular protrusion 17; the bottom end of the inner sleeve 13 is fixedly connected to the top surface of the base 14, and the outer wall of the inner sleeve 13 is set close to the inner wall of the annular protrusion 17. During the installation of the cement mold, sealing grease can be applied to the bottom of the inner sleeve 13 and the outer sleeve 12, as well as the inner and outer walls of the annular protrusion 17 to ensure that the bottom of the annular space 11 will not leak cement slurry. Among them, the annular protrusion 17 can play a positioning role, which is convenient for positioning the installation position of the outer sleeve 12 and the inner sleeve 13 on the base 14, and the outer sleeve 12 and the inner sleeve 13 can be easily coaxially arranged. In addition, the annular protrusion 17 can also play a limiting role. When the cement slurry solidifies and shrinks, the outer sleeve 12 can be limited to move inward, and the inner sleeve 13 can be limited to move outward. In this way, the size of the micro-annular gaps at the two interfaces caused by cement shrinkage will not be affected, and the measurement result will be more accurate when measuring the micro-annular gaps at the two interfaces of cement. In addition, the annular protrusion 17 can limit the movement of the outer sleeve 12 and the inner sleeve 13 when the cement solidifies and shrinks, and when the cement solidifies and expands, the outer sleeve 12 will not be limited to move outward. The outer sleeve 12 can be expanded and deformed by the expansion force of the cement ring (that is, the diameter becomes larger), which will not affect the measurement of the cement ring expansion.

[0057] A hoisting portion 16 is provided on the top surface of the base 14, and the hoisting portion 16 is located in the inner sleeve 13 and is used to connect a hoisting device to hoist the mold when placing the mold. The hoisting portion 16 can be a fixed seat, on which a detachable lifting ear assembly is installed to connect with the hoisting device.

[0058] In the cement slurry solidification simulation test, the cement mold 1 of this embodiment can be placed in the curing kettle 5 after injecting cement slurry into the annular space 11. By adjusting the temperature and pressure state in the curing kettle 5, the high temperature and high pressure environment of cement slurry solidification in the well can be simulated, and the measurement result is closer to the actual situation.

[0059] The outer sleeve 12 of the cement mold of this embodiment is a split structure. After the cement slurry solidification simulation test, the solidified cement ring can be easily taken out and the cement mold can be reused.

[0060] The measuring instrument of the present application can realize the solidification simulation of cement slurry and the continuous measurement of the inner and outer diameters of cement ring. It is simple to operate, highly repeatable, and well matched with downhole working conditions. It is suitable for the design of expansion cement slurry to prevent micro-annular gap channeling in oil and gas well cementing and the development and research of cement expansion materials.

[0061] In the description of the embodiments of the present application, unless otherwise clearly specified and limited, the terms "connection", "fixed connection", "installation", and "assembly" should be understood in a broad sense. For example, it can be a fixed connection, a detachable connection, or an integral connection; the terms "installation", "connection", and "fixed connection" can be a direct connection, an indirect connection through an intermediate medium, or a connection between two components. For ordinary technicians in this field, the specific meanings of the above terms in the embodiments of the present application can be understood according to specific circumstances.

Claims

1. An instrument for measuring micro-annulus of cement ring, characterized in that: It includes a curing kettle, a temperature and pressure regulating system, a cement mold and a micro-annular gap measuring device; The temperature and pressure regulating system is used to regulate the temperature and pressure in the curing kettle; The cement mold is located in the curing kettle, and the cement mold includes two sleeves, and an annular space with a closed bottom is provided between the two sleeves, and the annular space is used for performing a cement slurry curing process therein; The micro-annular gap measuring device comprises a probe and a probe displacement measuring device, wherein the probe comprises a rod body and a seat body connected to one end of the rod body, wherein the seat body is located in the annular space and is arranged close to the pipe wall of one of the casings, and the other end of the rod body is movable and passes through an opening arranged on the casing close to the seat body along the radial direction of the annular space; The probe displacement measuring device is used to measure the displacement of the rod body in the radial direction of the annular space during the cement slurry solidification process; The micro-annular gap measuring device also includes an elastic limiting device, which includes an elastic member, and the elastic member is used to make the seat of the probe contact the pipe wall of the casing under the action of its elastic force.

2. The instrument for measuring micro-annulus of cement ring of well cementing as claimed in claim 1, characterized in that: The probe displacement measuring device comprises a hollow body, an iron core component and a sensing component; One end of the hollow body is open and the other end is closed, and the open end of the hollow body is fixed on the curing kettle and communicated with the interior of the curing kettle; The core assembly is slidably disposed inside the hollow body, one end of the core assembly extends out of the opening end of the hollow body and is arranged to abut or be rigidly connected with the other end of the rod body of the probe; The sensing component is arranged outside the hollow body and is used to detect the displacement of the core component.

3. The instrument for measuring micro-annulus of cement ring of well cementing as claimed in claim 1, characterized in that: It also includes a reference displacement measuring device for measuring a reference displacement, and the reference displacement measuring device and the probe displacement measuring device have the same product specifications.

4. The instrument for measuring micro-annulus of cement ring of well cementing as claimed in claim 1, characterized in that: The temperature and pressure regulating system includes a liquid supply system, a gas supply system and a heating device; The liquid supply system is used to transport liquid into the curing kettle, and the heating device is used to heat the liquid in the curing kettle; The air supply system comprises an air source, an air intake pipeline and a pressure pump. One end of the air intake pipeline is connected to the air source, and the other end is connected to the interior of the curing kettle. The pressure pump is arranged on the air intake pipeline.

5. The instrument for measuring micro-annulus of cement ring of well cementing as claimed in claim 1, characterized in that: The elastic limiting device also includes a bushing, the elastic member is a spring, the bushing is arranged in the opening set on the sleeve, the part of the bushing protruding from the opening is sleeved with the spring, the spring is in a compressed state, one end of which is fixed to the sleeve or the bushing, and the other end is fixed to the rod body of the probe.

6. The instrument for measuring micro-annulus of cement ring of well cementing as claimed in claim 1, characterized in that: It comprises two sets of micro-annular gap measuring devices, namely a first micro-annular gap measuring device and a second micro-annular gap measuring device; The two sleeves are respectively an inner sleeve and an outer sleeve; The seat body of the probe of the first micro-annular gap measuring device is arranged close to the tube wall of the inner casing, and the seat body of the probe of the second micro-annular gap measuring device is arranged close to the tube wall of the outer casing.

7. The instrument for measuring micro-annulus of cement ring of well cementing as claimed in claim 6, characterized in that: The other end of the rod body of the probe of the first micro-annular gap measuring device moves out of the opening provided on the inner sleeve along the radial direction of the annular space and extends to the outside of the outer sleeve; The cement mold also includes an isolation sleeve, the two ends of which are respectively arranged in isolation sleeve mounting holes provided on the inner sleeve and the outer sleeve, and the rod body of the probe of the first micro-annular gap measuring device movably passes through the isolation sleeve.

8. The instrument for measuring micro-annulus of cement ring of well cementing as claimed in claim 1, characterized in that: The two casings are respectively an inner casing and an outer casing, and the outer casing is configured to be expandable and deformable so that its diameter increases under the action of the cement sheath expansion force; During the expansion of the cement ring, the cement ring can push the outer sleeve and drive the rod body to move along the radial direction of the annular space.

9. The instrument for measuring micro-annulus of cement ring of well cementing as claimed in claim 8, characterized in that: The outer sleeve includes more than two arc-shaped plates, which surround the outer sleeve. Two adjacent arc-shaped plates are sealed and connected by a connecting component. Under the action of the expansion force of the cement ring, relative displacement can occur between the two adjacent arc-shaped plates to increase the diameter of the outer sleeve.

Images