Device and method for in-situ testing of healing capacity of cement capable of self-healing when encountering air

Abstract

The invention discloses an in-situ testing device and method for the healing capacity of gas-encountering self-healing cement, a model system unit is provided with a first space, a second space and a third space, the second space surrounds the periphery of the first space, the third space surrounds the periphery of the second space, and the second space is used for injecting cement paste. The gas injection unit is used for injecting a gas medium into the second space. The alternating stress loading unit is used for providing internal pressure loading for the first space and providing alternating load loading. The servo loading unit is used for providing top pressure loading for the second space and providing annular pressure loading for the third space. The failure detection unit is used for obtaining the flow of the dry gas flowing out of the second space. The control unit is used for controlling the temperature inside the first space and outside the third space. The device disclosed by the invention can simulate an underground high-temperature and high-pressure test environment, and can continuously carry out an artificial fracture prefabricating and healing performance evaluation process, so that the in-situ test of the healing capability of the self-healing cement is realized.

Description

Technical Field

[0001] This invention relates to the field of wellbore integrity control, and more particularly to an in-situ testing device and method for the healing ability of gas-contaminated self-healing cement. Background Technology

[0002] Cementing is a crucial step in oil and gas development, with cement sheaths playing a vital role in casing support, formation fluid isolation, and wellbore safety. However, cement stone is a brittle material. Under the high temperature, high pressure, and complex stress variations of the downhole environment, the cement sheath is susceptible to stress impact and deformation, leading to micro-annular gaps or micro-cracks. This results in the failure of the cement sheath's sealing integrity, ultimately causing interlayer flow and annular pressure issues. Common methods used in cementing to address these problems include toughened cement slurries and self-healing cement slurries. Toughened cement slurries primarily improve the mechanical properties and deformation capacity of the cement stone to prevent damage, but once damaged, they cannot self-repair and are difficult to remedy. Self-healing cement, on the other hand, can restore the cement sheath's sealing integrity through self-diagnosis and repair technology after cement stone damage, making it an important means of addressing cement sheath sealing integrity failure in the cementing industry.

[0003] After years of development, research on self-healing cement has made significant progress. However, many shortcomings remain in the evaluation of its healing performance, and a unified evaluation device and method have not yet been established. A review of relevant literature and patents reveals that existing methods for evaluating the healing performance of self-healing cement mainly include the conductivity method, acoustic wave method, permeability method, and CT scan method. All of these methods involve first artificially creating cracks in the cement stone, then curing it for a certain period under specific conditions, and finally testing its conductivity, acoustic transit time, permeability, and pore volume. These parameters are then compared with those of the cement stone before the cracks were created to evaluate the healing performance of the self-healing cement.

[0004] Currently, the main methods for artificially creating cracks include the pull-out method, the temperature degradation method, and the expansion-contraction method. The pull-out method involves pre-inserting thin steel columns, crack-forming plates, high-strength carbon fibers, etc., into the cement slurry. After the cement slurry initially sets, these components are pulled out, forming cracks or through-holes. The temperature degradation method involves pre-inserting temperature-degradable plastics into the cement slurry. After the cement slurry initially sets, the temperature is increased to cause the temperature-degradable plastics to degrade, forming cracks. The expansion-contraction method involves expanding the tubing under internal pressure before the cement slurry initially sets, and then releasing the internal pressure after the cement slurry initially sets, causing the tubing to contract and forming micro-annular gaps.

[0005] Existing technologies for evaluating the healing performance of self-healing cement utilize methods such as thin steel columns, fracture-creating plates, high-strength carbon fibers, temperature-degradable plastics, and expansion-shrinkage slotted steel pipes to address the standardization, dimensional control, and operability issues of artificially pre-fabricated fractures. However, all of these methods suffer from varying degrees of poor operability, poor repeatability, and insufficient control. Furthermore, the temperature and pressure conditions applicable to these existing technologies are difficult to simulate the high-temperature and high-pressure testing environment in wells. Additionally, the discontinuity between the artificially pre-fabricated fractures and the healing performance evaluation process makes in-situ testing of the healing capacity of self-healing cement difficult. Summary of the Invention

[0006] This invention provides an in-situ testing device and method for the healing ability of self-healing cement upon contact with air, which enables in-situ testing of the healing ability of self-healing cement upon contact with air under high temperature and high pressure conditions.

[0007] This invention provides an in-situ testing device for the healing ability of gas-insensitive self-healing cement, comprising a model system unit, a gas injection unit, an alternating stress loading unit, a servo loading unit, a failure detection unit, and a control unit. The model system unit has a first space, a second space, and a third space. The second space surrounds the outer periphery of the first space, and the third space surrounds the outer periphery of the second space. The second space is used for injecting cement slurry. The gas injection unit is used to inject a gaseous medium into the second space. The alternating stress loading unit is used to provide internal pressure loading and alternating load loading to the first space. The servo loading unit is used to provide top pressure loading to the second space and ring pressure loading to the third space. The failure detection unit is used to acquire the flow rate of dry gas leaking from the second space. The control unit is used to control the temperature inside the first space and outside the third space.

[0008] In some embodiments, the model system unit includes a cylinder, a perforated steel pipe, a rubber cylinder, and a sleeve. The cylinder is vertically arranged. The perforated steel pipe is coaxially fitted inside the cylinder. The rubber cylinder is coaxially fitted inside the perforated steel pipe and fits snugly against the perforated steel pipe; the upper and lower parts of the gap between the rubber cylinder and the cylinder are sealed, forming a third space. The sleeve is coaxially fitted inside the rubber cylinder; the upper and lower parts of the gap between the sleeve and the rubber cylinder are sealed, forming a second space; the upper and lower parts of the sleeve are sealed, forming a first space.

[0009] In some embodiments, the in-situ testing device for the healing ability of gas-contaminated self-healing cement further includes an upper tapered sleeve and a lower tapered sleeve. The upper tapered sleeve is coaxially fitted inside the cylinder, with an inner diameter equal to that of the rubber cylinder. The outer peripheral wall of the upper tapered sleeve has an upper outer tapered surface that gradually tapers from top to bottom and an upper boss positioned above the upper outer tapered surface. The upper outer tapered surface is sealed to the upper inner tapered surface of the rubber cylinder, and a sealing ring is used to seal the upper boss with the cylinder. The lower tapered sleeve is coaxially fitted inside the cylinder, with an inner diameter equal to that of the rubber cylinder. The outer peripheral wall of the lower tapered sleeve has a lower outer tapered surface that gradually tapers from bottom to top and a lower boss positioned below the lower outer tapered surface. The lower outer tapered surface is sealed to the lower inner tapered surface of the rubber cylinder, and a sealing ring is used to seal the lower boss with the cylinder.

[0010] In some embodiments, the in-situ testing device for the healing ability of gas-contaminated self-healing cement further includes an upper ring, a lower ring, an upper sealing plug, a lower sealing plug, and a gasket. The upper ring is fitted between the sleeve and the upper tapered sleeve. The lower ring is fitted between the sleeve and the lower tapered sleeve. The upper sealing plug has a ring-shaped structure, fitted between the sleeve and the upper tapered sleeve, and positioned above the upper ring. Sealing rings are used to seal the upper sealing plug with the sleeve and between the upper sealing plug and the upper tapered sleeve. The lower sealing plug has a ring-shaped structure, fitted between the sleeve and the lower tapered sleeve, and positioned below the lower ring. Sealing rings are used to seal the lower sealing plug with the sleeve and between the lower sealing plug and the lower tapered sleeve. The gasket is fitted between the sleeve and the lower tapered sleeve, and positioned above the lower ring.

[0011] In some embodiments, the in-situ testing device for the healing ability of gas-contaminated self-healing cement further includes an upper cylinder cover and a lower cylinder cover. The upper cylinder cover is located at the top of the cylinder, and a sealing ring is used to seal the upper cylinder cover and the sleeve. The lower cylinder cover is located at the bottom of the cylinder, and a sealing ring is used to seal the lower cylinder cover and the sleeve.

[0012] An embodiment of the present invention provides a method for in-situ testing the healing ability of self-healing cement upon exposure to air using the above-described in-situ testing device, comprising the following steps:

[0013] Grouting and curing: The prepared air-insensitive self-healing cement grout is injected into the second space. The curing temperature T1, curing internal pressure P1, curing top pressure P2, and curing ring pressure P3 are set, and curing is carried out according to the curing time t1 to obtain a cement ring.

[0014] Cement ring integrity verification: Set the top pressure drop to zero. Inject a gas detection medium into the bottom of the second space. Observe the real-time flow rate Q1 of the dry gas flowing out of the second space. Verify the integrity of the cement ring based on Q1.

[0015] Creating an artificial crack: Apply an alternating load to the first space to cause the interface between the sleeve separating the first and second spaces and the cement ring in the second space to detach, thus creating an artificial crack. Observe the real-time flow rate Q2 of the dry gas flowing out of the second space. Verify the success of creating the artificial crack based on Q2.

[0016] Quantifying artificial cracks: Obtaining the initial artificial crack scale F1.

[0017] Adjusting the artificial fracture: Adjust the artificial fracture according to F1 to obtain the adjusted artificial fracture scale F. n until F n Achieving the ideal experimental scale F m .

[0018] Self-healing capability evaluation: Gas healing medium was injected into the bottom of the second space. Healing curing time t2. The final artificial crack scale F2 was obtained. Based on F2 and F... n Evaluate the healing ability of self-healing cement upon contact with air.

[0019] In some embodiments, verifying the integrity of the cement ring based on Q1 includes: if Q1 is zero, the cement ring integrity is good; if Q1 is not zero, the cement ring integrity is poor, and the above steps are repeated until Q1 is zero.

[0020] In some embodiments, verifying the success of artificially created cracks based on Q2 includes: determining whether Q2 is consistently zero during the internal pressure rise phase of the alternating load. If Q2 is not consistently zero during the internal pressure rise phase of the alternating load, the above steps are repeated until Q2 is consistently zero during the internal pressure rise phase of the alternating load. It also involves determining whether Q2 is not zero during the internal pressure fall phase of the alternating load. If Q2 is not zero during the internal pressure fall phase of the alternating load, the artificially created crack is considered successful. If Q2 is zero during the internal pressure fall phase of the alternating load, the artificially created crack is considered unsuccessful, and the alternating pressure amplitude and the number of alternating load cycles are adjusted until Q2 is not zero during the internal pressure fall phase of the alternating load.

[0021] After verifying the successful creation of the artificial crack, the internal pressure was adjusted to the lower limit of the alternating load, P5.

[0022] In some embodiments, obtaining the initial artificial fracture scale F1 includes: continuously observing the change in the flow rate of dry gas flowing out of the second space, and recording the flow rate of dry gas flowing out of the second space as Q3 after the flow rate stabilizes. The artificial fracture scale is calculated using formula (1) to obtain the initial artificial fracture scale F1.

[0023] Formula (1):

[0024]

[0025] In the formula, Q is the steady flow rate of dry gas exiting from the second space, in meters. 3 / s. P—Gas injection pressure, Pa. L—Axial length of cement ring, m. D1—Inner diameter of cement ring, m. E1—Dynamic viscosity of gas medium, Pa·s. F—Dimension of artificial fracture, m.

[0026] In some embodiments, the artificially created fracture is adjusted according to F1 to obtain the adjusted artificially created fracture scale F. n until F n Achieving the ideal experimental scale F m This includes: comparing F1 with the limiting healing scale F of the self-healing agent product under test. g Compare and determine if F1 is less than F. g If F1 is greater than F g If the internal pressure is increased, the artificial fracture size is calculated using formula (1) to obtain the adjusted artificial fracture size F. n If F n Still greater than F g Then continue to increase the internal pressure until F n Less than F g If F1 is less than F g Then determine whether F1 reaches the ideal experimental scale F. m If F1 is less than F m If the lower limit of alternating load is lowered or the number of alternating load cycles is increased, the artificial crack size is calculated using formula (1) to obtain the adjusted artificial crack size F. n If F n Still less than F m If so, continue to lower the lower limit of the alternating load or increase the number of alternating load cycles until F... n Reaching F m If F1 is greater than F m If the internal pressure is increased, the artificial fracture size is calculated using formula (1) to obtain the adjusted artificial fracture size F. n If F n Still greater than F m Then continue to increase the internal pressure until F n Reaching F m .

[0027] In some embodiments, obtaining the final artificial crack scale F2 after the healing and maintenance time t2 includes: observing the change in the flow rate of the dry gas flowing out of the second space, and after the flow rate of the dry gas flowing out of the second space stabilizes, recording the flow rate of the dry gas flowing out of the second space as Q4 at this time, calculating the artificial crack scale according to formula (1), and obtaining the final artificial crack scale F2 after the healing and maintenance time t2.

[0028] According to F2 and F n The evaluation of the healing ability of self-healing cement upon exposure to air includes: using formula (2) to evaluate the healing ability of self-healing cement upon exposure to air.

[0029] Formula (2):

[0030]

[0031] In the formula, η represents the self-healing ability of air-sensitive cement stone, in percentage terms. F n —After adjustment, it approaches the ideal experimental scale F m The artificial fracture size, in meters. F2—the final artificial fracture size after healing and curing time t2, in meters.

[0032] An in-situ testing device for the healing ability of self-healing cement upon contact with air, according to an embodiment of the present invention, includes a model system unit, a gas injection unit, an alternating stress loading unit, a servo loading unit, a failure detection unit, and a control unit. The model system unit has a first space, a second space, and a third space. The second space surrounds the outer periphery of the first space, and the third space surrounds the outer periphery of the second space. The second space is used for injecting cement slurry. The gas injection unit is used to inject a gaseous medium into the second space. The alternating stress loading unit is used to provide internal pressure loading and alternating load loading to the first space. The servo loading unit is used to provide top pressure loading to the second space and annular pressure loading to the third space. The failure detection unit is used to obtain the flow rate of dry gas leaking out of the second space. The control unit is used to control the temperature inside the first space and outside the third space. In the device of the present invention, the model system unit, gas injection unit, alternating stress loading unit, servo loading unit, failure detection unit, and control unit cooperate with each other to simulate the high-temperature and high-pressure testing environment downhole, and also enable continuous artificial pre-fabrication of fractures and the evaluation process of healing performance, realizing in-situ testing of the healing ability of self-healing cement. Attached Figure Description

[0033] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0034] Figure 1 This is a schematic diagram of the in-situ testing device for the healing ability of self-healing cement upon contact with air, provided in an embodiment of the present invention.

[0035] Figure 2 for Figure 1 Enlarged schematic diagram of the unit part of the model system;

[0036] Figure 3 for Figure 1 An enlarged schematic diagram of part A in the middle;

[0037] Figure 4 for Figure 1 Enlarged schematic diagram of part B in the middle;

[0038] Figure 5 This is a test curve for in-situ crack creation of a certain self-healing cement upon exposure to air. Detailed Implementation

[0039] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention.

[0040] See Figure 1 The present invention provides an in-situ testing device for the self-healing ability of gas-contaminated cement, comprising a model system unit S1, a gas injection unit S2, an alternating stress loading unit S3, a servo loading unit S4, a cooling circulation unit S5, a failure detection unit S6, and a data acquisition and control unit S7.

[0041] See Figure 2 Model system unit S1 is used for curing the cement ring and creating artificial cracks. Model system unit S1 has a first space 25, a second space 26, and a third space 27. The second space 26 surrounds the outer periphery of the first space 25, and the third space 27 surrounds the outer periphery of the second space 26. The first space 25 is used to apply internal pressure, alternating loads, and alternating temperatures. The second space 26 is used to inject cement grout, apply top pressure, and provide a channel for crack detection. The third space 27 is used to apply ring pressure.

[0042] The model system unit S1 includes a sleeve 1, a rubber cylinder 2, a perforated steel pipe 3, a cylinder 4, an outer heating sleeve 5, an upper tapered sleeve 6, a lower tapered sleeve 7, an upper sealing plug 8, a lower sealing plug 9, an upper ring 10, a lower ring 11, a gasket 12, an electric heating tube 13, a heating protection tube 14, a cooling circulation tube 15, an internal temperature sensor 16, connecting valves 17-20, bolts 21, an upper cylinder cover 22, a lower cylinder cover 23, and an external temperature sensor 24.

[0043] See Figure 3-4 The cylinder 4 is vertically arranged. Ring pressure loading port 31 and ring pressure unloading port 32 are provided on both sides of the cylinder 4. The ring pressure loading port 31 is located above the ring pressure unloading port 32.

[0044] The upper cylinder cover 22 is located on the upper part of the cylinder 4. The upper cylinder cover 22 is threadedly connected to the cylinder 4 by bolts 21. The upper cylinder cover 22 has an internal pressure loading port 28, an electric heating tube insertion port 29, and two centrally symmetrically distributed upper connecting valve insertion ports 30. Each of the two upper connecting valve insertion ports 30 has a connecting valve 17-18 with a central through hole. The upper cylinder cover 22 and the sleeve 1 are sealed with an O-ring.

[0045] The lower cylinder cover 23 is located at the lower part of the cylinder 4. The lower cylinder cover 23 is threadedly connected to the cylinder 4 by bolts 21. The lower cylinder cover 23 has an internal pressure unloading port 33, a coolant inlet 34, a coolant outlet 35, and two centrally symmetrically distributed lower connecting valve insertion ports 36. Each of the two lower connecting valve insertion ports 36 has a connecting valve 19-20 with a central through hole. The lower cylinder cover 23 is sealed to the sleeve 1 by a sealing ring. The sealing ring is an O-ring.

[0046] The perforated steel pipe 3 is coaxially fitted inside the cylinder 4 to accommodate the rubber cylinder 2, preventing deformation of the rubber cylinder 2 and transmitting ring pressure. Both ends of the perforated steel pipe 3 have tapered surfaces on their inner sides.

[0047] The rubber cylinder 2 is coaxially fitted inside the perforated steel pipe 3 and is in close contact with the perforated steel pipe 3. The upper and lower parts of the gap between the rubber cylinder 2 and the cylinder body 4 are sealed, forming a third space 27. Both the inner and outer sides of both ends of the rubber cylinder 2 are provided with conical surfaces. The outer conical surfaces at both ends of the rubber cylinder 2 correspond to the inner conical surfaces at both ends of the perforated steel pipe 3 and are in close contact with each other.

[0048] The sleeve 1 is coaxially fitted inside the rubber cylinder 2. The upper and lower parts of the gap between the sleeve 1 and the rubber cylinder 2 are sealed to form a second space 26, and the upper and lower parts of the sleeve 1 are sealed to form a first space 25.

[0049] The upper tapered sleeve 6 is coaxially fitted inside the cylinder 4. The inner circumferential wall of the upper tapered sleeve 6 is a smooth arc surface. The inner diameter of the upper tapered sleeve 6 is equal to the inner diameter of the rubber cylinder 2. The outer circumferential wall of the upper tapered sleeve 6 has an upper outer tapered surface that gradually tapers from top to bottom and an upper boss located above the upper outer tapered surface. The upper outer tapered surface corresponds to the upper inner tapered surface of the rubber cylinder 2, and the upper outer tapered surface is sealed to the upper inner tapered surface of the rubber cylinder 2. A sealing ring is used to seal between the upper boss and the cylinder 4. The sealing ring is an O-ring. It should be noted that the solidified surface of the cement slurry after hydration should not be lower than the lower end face of the upper tapered sleeve 6. A sealing ring is used to seal between the upper tapered sleeve 6 and the upper cylinder cover 22.

[0050] The lower tapered sleeve 7 is coaxially fitted inside the cylinder 4. The inner circumferential wall of the lower tapered sleeve 7 is a smooth arc surface. The inner diameter of the lower tapered sleeve 7 is equal to the inner diameter of the rubber cylinder 2. The outer circumferential wall of the lower tapered sleeve 7 has a lower outer tapered surface that gradually tapers from bottom to top and a lower boss located below the lower outer tapered surface. The lower outer tapered surface corresponds to the lower inner tapered surface of the rubber cylinder 2, and the lower outer tapered surface is sealed to the lower inner tapered surface of the rubber cylinder 2. A sealing ring is used to seal between the lower boss and the cylinder 4. The sealing ring is an O-ring. A sealing ring is also used to seal between the lower tapered sleeve 7 and the upper cylinder cover 22.

[0051] The aforementioned upper tapered sleeve 6 and lower tapered sleeve 7 are used to solve the problem of the rubber sleeve 2 being cut and damaged under ring pressure due to the drop in the solidification surface and the unevenness of the solidification surface after the cement slurry hydrates during in-situ jointing and in-situ testing.

[0052] The upper ring 10 is specifically a aligning ring. The upper ring 10 is fitted between the sleeve 1 and the upper tapered sleeve 6, centered the sleeve 1. The upper ring 10 has a through hole, which is directly opposite the upper connecting valve insertion port 30 and is interconnected with it.

[0053] The lower ring 11 is specifically a vent ring. The lower ring 11 is fitted between the sleeve 1 and the lower tapered sleeve 7, with the sleeve 1 centered. Sealing rings are used between the lower ring 11 and the sleeve 1, and between the lower ring 11 and the lower tapered sleeve 7. These sealing rings are O-rings. The lower ring 11 has a through hole, directly opposite the lower connecting valve insertion port 36, and they are interconnected.

[0054] The upper sealing plug 8 has a ring-shaped structure. It is fitted between the sleeve 1 and the upper tapered sleeve 6, and positioned above the upper ring 10. Sealing rings are used between the upper sealing plug 8 and the sleeve 1, and between the upper sealing plug 8 and the upper tapered sleeve 6. These sealing rings are O-rings. The upper sealing plug 8 has a through hole, directly opposite the upper connecting valve insertion port 30, and they are interconnected. The upper sealing plug 8 is threadedly connected to the connecting valve 17-18, which passes through the upper connecting valve insertion port 30.

[0055] The lower sealing plug 9 has a ring-shaped structure. It is fitted between the sleeve 1 and the lower tapered sleeve 7, and positioned below the lower ring 11. Sealing rings are used between the lower sealing plug 9 and the sleeve 1, and between the lower sealing plug 9 and the lower tapered sleeve 7. These sealing rings are O-rings. The lower sealing plug 9 has a through hole, directly opposite the lower connecting valve insertion port 36, and they are interconnected. The lower sealing plug 9 is threadedly connected to the connecting valve 19-20, which passes through the lower connecting valve insertion port 36.

[0056] The gasket 12 is placed between the sleeve 1 and the lower tapered sleeve 7 and positioned above the lower ring 11 to prevent cement slurry from settling.

[0057] The external heating jacket 5 is placed outside the cylinder 4 to provide external heating for the model system unit S1, simulating the external temperature environment of the downhole cement sheath.

[0058] One end of the heating protection tube 14 is open. The heating protection tube 14 is coaxially inserted into the sleeve 1, and the open end of the heating protection tube 14 is connected to the upper cylinder cover 22 for the insertion of the power supply heating tube 13, thus isolating the electric heating tube 13 from the high-pressure environment inside the sleeve 1. The heating protection tube 14 and the upper cylinder cover 22 are connected by bolts or threads. An O-ring seal is used between the heating protection tube 14 and the upper cylinder cover 22.

[0059] The electric heating tube 13 is inserted into the heating protection tube 14 through the electric heating tube insertion port 29 to provide internal heating for the model system unit S1 and simulate the internal temperature environment of the downhole cement sheath.

[0060] The cooling circulation pipe 15 is inserted into the sleeve 1 and connected to the coolant inlet 34 and coolant outlet 35. It is used to connect the cooling circulation unit S5 and provide cooling for the model system unit S1. The cooling circulation pipe 15 is integrally formed with the lower cylinder cover 23.

[0061] An internal temperature sensor 16 is installed inside the sleeve 1 to measure the internal temperature of the model system unit S1 in real time. The internal temperature sensor 16 is integrally formed with the upper cylinder cover 22.

[0062] An external temperature sensor 24 is installed on the external heating jacket 5 to measure the external temperature of the model system unit S1 in real time.

[0063] See Figure 1The gas injection unit S2 is used to inject a gas healing medium or a gas detection medium into the second space 26 of the model system unit S1. The gas injection unit S2 is connected to the second space 26 via a first pipeline 43 and a connecting valve 20. A switch valve 65 is installed on the first pipeline 43. The second space 26 is connected to a tenth pipeline 62 via a connecting valve 19. A switch valve 74 is installed on the tenth pipeline 62. The gas injection unit S2 includes a first gas cylinder 37, a second gas cylinder 38, a first gas cylinder pressure dividing valve 39, a second gas cylinder pressure dividing valve 40, an inlet gas flow meter 41, and a pressure sensor 42 for the first pipeline 43. The first gas cylinder 37 is used to store the gas detection medium. The second gas cylinder 38 is used to store the gas healing medium. The first gas cylinder pressure dividing valve 39 is installed on the first gas cylinder 37 and is used to adjust the output pressure of the first gas cylinder 37. The second gas cylinder pressure dividing valve 40 is installed on the second gas cylinder 38 and is used to adjust the output pressure of the second gas cylinder 38. The first gas cylinder 37 is connected to the inlet gas flow meter 41 via a first branch line 76, and a switch valve 64 is installed on the first branch line 76. The second gas cylinder 38 is connected to the inlet gas flow meter 41 via a second branch line 77, and a switch valve 63 is installed on the second branch line 77. A pressure sensor 42 is installed on the first line 43, located between the inlet gas flow meter 41 and the model system unit S1, and is used to record the inlet gas pressure.

[0064] See Figure 1 The alternating stress loading unit S3 is used to provide internal pressure loading for simulating the internal pressure environment of the downhole casing 1 in the first space 25 of the model system unit S1, and to provide alternating load loading for creating artificial fractures. The alternating stress loading unit S3 is connected to the first space 25 through the second pipeline 46 and the internal pressure loading port 28. The second pipeline 46 is equipped with a switch valve 66. The first space 25 is connected to the ninth pipeline 61 through the internal pressure unloading port 33. The ninth pipeline 61 is equipped with a switch valve 73. The alternating stress loading unit S3 includes an internal pressure loading pump 44 and a pressure sensor 45 for the second pipeline 46. The pressure sensor 45 for the second pipeline 46 is located on the second pipeline 46, between the internal pressure loading pump 44 and the model system unit S1, and is used to record the pressure in the first space 25.

[0065] See Figure 1The servo loading unit S4 provides top pressure loading to the second space 26 of the model system unit S1 to simulate the pressure of the downhole cement slurry column, and provides annular pressure loading to the third space 27 of the model system unit S1 to simulate the confining pressure environment of the downhole cement sheath. The servo loading unit S4 is connected to the second space 26 via a third pipeline 51 and a connecting valve 17, with a switch valve 67 installed on the third pipeline 51. The servo loading unit S4 is connected to the third space 27 via a fourth pipeline 52 and annular pressure loading port 31, with a switch valve 68 installed on the fourth pipeline 52. The third space 27 is connected to an eighth pipeline 60 via annular pressure unloading port 32, with a switch valve 72 installed on the eighth pipeline 60. The servo loading unit S4 includes a top pressure loading pump 47, an annular pressure loading pump 48, a pressure sensor 49 on the third pipeline 51, and a pressure sensor 50 on the fourth pipeline 52. Pressure sensor 49 is installed on the third pipeline 51, between the top pressure loading pump 47 and the model system unit S1, and is used to record the pressure in the second space 26. Pressure sensor 50 is installed on the fourth pipeline 52, between the ring pressure loading pump 48 and the model system unit S1, and is used to record the pressure in the third space 27.

[0066] See Figure 1 The failure detection unit S6 is used to acquire the flow rate of the dry gas flowing out of the second space 26 of the model system unit S1, in order to detect whether the artificial crack created by the model system unit S1 is successful, assess the size of the artificial crack, and evaluate the healing effect of the gas-induced self-healing cement. The failure detection unit S6 is connected to the second space 26 via a seventh pipeline 59 and a connecting valve 18. A switch valve 71 is installed on the seventh pipeline 59. The failure detection unit S6 includes an outlet gas flow meter 56, a drying tank 57, and a buffer bottle 58. The buffer bottle 58 is used for preliminary gas-liquid separation of the flowing gas-liquid mixture. The drying tank 57 is used to store desiccant and further dry the gas-liquid mixture after preliminary gas-liquid separation to protect the outlet gas flow meter 56. The outlet gas flow meter 56 is used to record the outlet gas flow rate.

[0067] See Figure 1 The cooling circulation unit S5 is used to inject and circulate liquid cooling medium into the first space 25 of the model system unit S1, and to provide heat dissipation for the liquid cooling medium. The cooling circulation unit S5 is connected to the cooling circulation pipe 15 through the fifth pipe 54, the sixth pipe 55, the coolant inlet 34, and the coolant outlet 35. The fifth pipe 54 and the sixth pipe 55 are respectively equipped with switch valves 69 and 70. The cooling circulation unit S5 includes a low-temperature bath 53.

[0068] The data acquisition and control unit S7 is used to acquire and control the temperature, pressure, and gas flow rate of the model system unit S1, gas injection unit S2, alternating stress loading unit S3, servo loading unit S4, cooling circulation unit S5, and failure detection unit S6 in real time, and to process and analyze the experimental data. The data acquisition and control unit S7 is electrically connected to the model system unit S1, gas injection unit S2, alternating stress loading unit S3, servo loading unit S4, cooling circulation unit S5, and failure detection unit S6. The data acquisition and control unit S7 includes a data acquisition module, a temperature and pressure control module, and an image processing module. The data acquisition module is used to acquire real-time temperature, pressure, and gas flow rate data from the model system unit S1, gas injection unit S2, alternating stress loading unit S3, servo loading unit S4, cooling circulation unit S5, and failure detection unit S6. The image processing module is used to generate real-time temperature, pressure, and gas flow rate monitoring curves from the acquired data. The temperature and pressure control module is used to adjust the temperature, pressure, loading method, and loading speed of the model system unit S1, alternating stress loading unit S3, servo loading unit S4, and cooling circulation unit S5.

[0069] The aforementioned cooling circulation unit S5 and data acquisition and control unit S7 together form a control unit, which can control the temperature inside the first space 25 and outside the third space 27.

[0070] An embodiment of the present invention provides a method for in-situ testing the healing ability of self-healing cement upon exposure to air using the above-described in-situ testing device, comprising the following steps:

[0071] (1) Assembly and connection of equipment: Assemble the in-situ testing device for the healing ability of self-healing cement in the presence of air.

[0072] In the above steps, refer to Figure 2 Assemble the model system unit S1, and refer to Figure 1 Connect the model system unit S1 to the gas injection unit S2, the alternating stress loading unit S3, the servo loading unit S4, the cooling circulation unit S5, the failure detection unit S6, and the data acquisition and control unit S7.

[0073] (2) Grouting and curing: The prepared self-healing cement grout is injected into the second space 26. The curing temperature T1, curing internal pressure P1, curing top pressure P2, and curing ring pressure P3 are set, and curing is carried out according to the curing time t1 to obtain a cement ring.

[0074] In the above steps, according to the proportions of each material in the formula of the self-healing cement slurry system to be tested, the self-healing cement slurry to be evaluated is prepared according to the method specified in "5 Preparation of Cement Slurry" of GB / T19139-2012 "Test Methods for Oil Well Cement". When the prepared self-healing cement slurry is injected into the second space 26, the slurry level is made flush with the bottom of the upper ring 10. Using the temperature and pressure control module of the data acquisition and control unit S7, the curing temperature T1, curing internal pressure P1, curing top pressure P2, and curing ring pressure P3 are set.

[0075] (3) Cement ring integrity verification: Set the top pressure drop to zero. Inject gas detection medium into the bottom of the second space 26. Observe the real-time dry gas flow rate Q1 flowing out of the second space 26. Verify the integrity of the cement ring based on Q1.

[0076] In the above steps, the internal pressure and ring pressure of the model system unit S1 are kept constant. The top pressure of the model system unit S1 is gradually unloaded by the top pressure loading pump 47 until the top pressure drops to zero, creating conditions for gas channeling detection. Gas detection medium is injected into the bottom of the second space 26 through the gas injection unit S2, and the gas injection pressure is P4. The real-time dry gas flow rate flowing out of the second space 26 is the real-time gas flow rate of the outlet gas flow meter 56 in the failure detection unit S6. The integrity of the cement ring is verified according to Q1, including: if Q1 is zero, it means that the cement ring is intact. If Q1 is not zero, it means that there is a defect in the cement ring after curing, that is, the integrity of the cement ring is not good. Repeat steps (1)-(3) until Q1 is zero to ensure that the integrity of the cement ring is good.

[0077] (4) Creating an artificial crack: Apply an alternating load to the first space 25 to cause the interface between the sleeve 1 separating the first space 25 and the second space 26 and the cement ring in the second space 26 to detach, forming an artificial crack—a micro-annular gap. Observe the real-time flow rate Q2 of the dry gas flowing out of the second space 26. Verify whether the micro-annular gap was successfully created based on Q2.

[0078] In the above steps, the gas injection pressure P4 of the gas injection unit S2 is kept constant, and an alternating load is applied to the first space 25 through the alternating stress loading unit S3. The real-time dry gas flow rate Q2 flowing out from the second space 26 is the real-time gas flow rate of the outlet gas flow meter 56 in the failure detection unit S6. The micro-annular gap is verified according to Q2 to determine whether Q2 is always zero during the internal pressure rise phase of the alternating load. If Q2 is always zero during the internal pressure rise phase of the alternating load, it indicates that no radial microcracks have been generated. If Q2 is not always zero during the internal pressure rise phase of the alternating load, it indicates that radial microcracks have been generated (the number and size of radial microcracks are uncontrollable), and steps (1)-(4) are repeated until Q2 is always zero during the internal pressure rise phase of the alternating load. And it is determined whether Q2 is not zero during the internal pressure fall phase of the alternating load. If Q2 is not zero during the internal pressure fall phase of the alternating load, it indicates that the micro-annular gap has been successfully manufactured. If Q2 is zero during the internal pressure decrease phase of the alternating load, it indicates that the micro-annulus fabrication was unsuccessful. Adjust the alternating pressure amplitude and the number of alternating load cycles until Q2 is not zero during the internal pressure decrease phase of the alternating load. It should be noted that the upper limit of the alternating load P6 should not cause tensile failure of the cement ring, thereby generating radial microcracks.

[0079] After verifying the successful fabrication of the micro-annular gap, the internal pressure of the model system unit S1 was adjusted to the lower limit of the alternating load P5.

[0080] (5) Quantify artificial cracks: Obtain the initial artificial crack scale F1.

[0081] In the above steps, obtaining the initial artificial fracture scale F1 includes: continuously observing the change in the flow rate of the dry gas flowing out of the second space 26, and recording the flow rate of the dry gas flowing out of the second space 26 as Q3 after the flow rate stabilizes. The change in the flow rate of the dry gas flowing out of the second space 26 is the change in the gas flow rate of the outlet gas flow meter 56 in the failure detection unit S6. Based on the fracture permeability formula and Darcy's formula, according to the stable gas flow rate Q3 of the outlet gas flow meter 56 in the failure detection unit S6 when the internal pressure of the model system unit S1 is the lower limit of the alternating load P5, the gas injection pressure P4 during the application of the alternating load, the axial length L of the cement ring, the inner diameter D1 of the cement ring, and the dynamic viscosity E1 of the gas medium, the artificial fracture scale is calculated using formula (1) to obtain the initial artificial fracture scale F1.

[0082] Formula (1):

[0083]

[0084] In the formula, Q—the stable gas flow rate of the outlet gas flow meter 56 in the failure detection unit S6, in m 3 / s. P—Gas injection pressure, Pa. L—Axial length of cement ring, m. D1—Inner diameter of cement ring, m. E1—Dynamic viscosity of gas medium, Pa·s. F—Dimension of artificial fracture, m.

[0085] In the above calculation process, P = P4, Q = Q3, and the calculated F is F1.

[0086] (6) Adjusting artificial cracks: Adjust the artificial cracks according to F1 to obtain the adjusted artificial crack scale F. n until F n Achieving the ideal experimental scale F m .

[0087] In the above steps, the artificial fracture is adjusted according to F1 to obtain the adjusted artificial fracture scale F. n until F n Achieving the ideal experimental scale F m This includes: comparing F1 with the limiting healing scale F of the self-healing agent product under test. g Compare and determine if F1 is less than F. g If F1 > F g This indicates that the initial size of the man-made crack is too large and does not meet the requirements for the self-healing cement healing ability test. By appropriately increasing the internal pressure through the internal pressure loading pump 44, the expansion deformation of the sleeve 1 is increased, thereby reducing the size of the micro-annular gap. The man-made crack size is calculated using formula (1). Based on formula (1), the adjusted man-made crack size F is obtained. n If F n Still greater than F g Then continue to increase the internal pressure until F n <F g If F1 < F g Then determine whether F1 is approximately equal to the ideal experimental scale F. m If F1 < F m Then, by appropriately reducing the lower limit of alternating load P5 or increasing the number of alternating load cycles through the internal pressure loading pump 44, the shrinkage deformation of the sleeve 1 or the irreversible plastic deformation of the cement stone is increased, thereby increasing the size of the micro-annular gap. The artificial crack size is calculated using formula (1). Based on formula (1), the adjusted artificial crack size F is obtained. n If F n Still less than F m If so, continue to lower the lower limit of alternating load P5 or increase the number of alternating load cycles until F... n ≈F m If F1 > F mThen, by appropriately increasing the internal pressure value through the internal pressure loading pump 44, the expansion deformation of the casing 1 is increased, thereby reducing the size of the micro-annular gap. The artificial crack size is calculated using formula (1). Based on formula (1), the adjusted artificial crack size F is obtained. n If F n Still greater than F m Then continue to increase the internal pressure value until F n ≈F m To obtain the artificial cracks required for the experiment.

[0088] (7) Self-healing capability evaluation: Gas healing medium was injected into the bottom of the second space 26. Healing curing time t2. The final artificial crack size F2 after obtaining the healing curing time t2. Based on F2 and F... n Evaluate the healing ability of self-healing cement upon contact with air.

[0089] In the above steps, gas healing medium is injected into the bottom of the second space 26 through gas injection unit S2. The gas injection pressure is consistent with the gas injection pressure P4 in steps (3) and (4) to ensure the stability of the micro-annular gap size. The final artificial crack size F2 after the healing and curing time t2 is obtained, including: observing the change in the flow rate of dry gas flowing out of the second space 26 during the healing and curing period. After the flow rate of dry gas flowing out of the second space 26 stabilizes, the flow rate of dry gas flowing out of the second space 26 at this time is recorded as Q4. The artificial crack size is calculated according to formula (1) to obtain the final artificial crack size F2 after the healing and curing time t2. In the above calculation process, P = P4, Q = Q4, and the calculated F is F2. Based on F2 and F n The evaluation of the healing ability of self-healing cement upon exposure to air includes: using formula (2) to evaluate the healing ability of self-healing cement upon exposure to air.

[0090] Formula (2):

[0091]

[0092] In the formula, η represents the self-healing ability of air-sensitive cement stone, in percentage terms. F n —After adjustment, it approaches the ideal experimental scale F m The artificial fracture size, in meters. F2—the final artificial fracture size after healing and curing time t2, in meters.

[0093] The basic principle of the above method is as follows: Considering that cement stone itself is an elastic-plastic material, under alternating stress, cement stone will undergo irreversible plastic deformation, and with the increase of alternating load amplitude and alternating load cycle number, the irreversible plastic deformation of cement stone will continuously increase; for the casing-cement ring interface, due to the significant difference in elastic mechanical parameters between the casing and cement stone, under the same stress change conditions, the casing and cement stone will produce different deformations. When the stress change reaches a certain level, deformation incoordination will occur at the casing-cement ring interface, thus generating micro-annular gaps; a large number of literature and studies have shown that micro-annular gaps are generally generated at the casing-cement ring interface, with the characteristics of single location and unique number, which can solve the problems of traditional manual joint creation methods. The problem of the large randomness in the number and spatial distribution of cracks can be addressed. Based on the crack permeability formula and Darcy's formula, the micro-annular gap size can be quantified based on parameters such as gas flow rate, gas injection pressure, and cement ring geometry. Utilizing the expansion and contraction characteristics of the casing under alternating loads, and the characteristic that irreversible plastic deformation of cement stone accumulates under alternating loads, the micro-annular gap size can be controlled by reasonably controlling the alternating load amplitude, the number of alternating load cycles, and the internal pressure. Since the micro-annular gap is manufactured by applying alternating loads, the ring pressure and temperature conditions remain unchanged, thus enabling in-situ crack creation. After successfully creating a micro-annular gap of ideal size, the gas detection medium can be directly replaced with a gas healing medium for healing testing and evaluation.

[0094] The above method creates artificial fractures through alternating loads, and controls the size of these fractures by varying the amplitude of the alternating load, the number of alternating load cycles, and the internal pressure. The size of the artificial fractures is quantified by measuring the outlet gas flow rate and using the fracture permeability formula and Darcy's formula. The change in the size of the artificial fractures is used as an indicator to evaluate the self-healing ability of the gas-contaminated cement stone.

[0095] The existing solutions have the following problems: The solution disclosed in patent CN104502419A produces large-scale fractures, exceeding the healing capacity limits of some self-healing agents, and the fracture-creating tool is difficult to remove and prone to breakage. Furthermore, it is only applicable to room temperature and atmospheric pressure environments and cannot simulate the high-temperature and high-pressure environment downhole. The solution disclosed in patent CN218067762U also suffers from difficulty in removing the fracture-creating tool, especially when the fracture plate thickness is very small, leading to breakage. Additionally, acoustic measurement is easily affected by the oil-phase healing medium, limiting its application. The solution disclosed in patent CN11356754A remains complex and difficult in actual operation and cannot simulate the high-temperature and high-pressure environment downhole. The solution disclosed in patent CN215525800U is difficult to standardize due to factors such as the incomplete degradation of temperature-degradable plastics, and the temperature-degradable plastics themselves limit the curing temperature of the cement slurry, resulting in limited application conditions and an inability to simulate the high-temperature and high-pressure environment downhole. The solution disclosed in patent CN206540910U relies solely on the expansion and contraction characteristics of the slotted steel pipe, making it difficult to control the size of the micro-annular gap and thus failing to achieve standardization of artificial micro-cracks / annular gaps.

[0096] Compared to existing technologies, this invention solves the problems of large randomness in the number and spatial distribution of cracks and uncontrollable scale in traditional artificial crack-making methods, as detailed below:

[0097] Cement stone is an elasto-plastic material. Under alternating stress, it undergoes irreversible plastic deformation, and this deformation increases with the amplitude of the alternating pressure and the number of alternating load cycles. At the casing-cement ring interface, due to significant differences in the elastic mechanical parameters of the casing and cement stone, they will exhibit different deformations under the same stress changes. When the stress change reaches a certain level, deformation incoordination occurs at the casing-cement ring interface, leading to the formation of micro-annular gaps. Numerous studies and literature indicate that these micro-annular gaps are predominantly located at the casing-cement ring interface, exhibiting a unique location and quantity.

[0098] Therefore, this invention uses alternating loads to create micro-annular gaps. Based on the crack permeability formula and Darcy's formula, and using parameters such as gas flow rate, gas injection pressure, and cement ring geometry, the micro-annular gap size is quantified. Furthermore, by utilizing the expansion and contraction characteristics of the casing under alternating loads and the characteristic that irreversible plastic deformation of cement stone accumulates under alternating loads, the micro-annular gap size is controlled by reasonably controlling the amplitude of the alternating load, the number of alternating load cycles, and the internal pressure. This solves the problems of large randomness in the number and spatial distribution of cracks and uncontrollable size in traditional artificial crack-making methods.

[0099] Compared to existing technologies, this invention solves the problem of in-situ testing of the healing ability of self-healing cement in the presence of air under high temperature and high pressure, as detailed below:

[0100] An in-situ testing device for the healing ability of self-healing cement upon contact with air is provided. In terms of device function, it is equipped with a model system unit S1, a gas injection unit S2, an alternating stress loading unit S3, a servo loading unit S4, a cooling circulation unit S5, a failure detection unit S6, and a data acquisition and control unit S7. The model system unit S1 includes an external heating jacket 5 and an electric heating tube 13, which can simulate the external temperature of the downhole cement sheath and the internal temperature environment of the downhole casing, respectively. The gas injection unit S2 includes a first gas cylinder 37, a second gas cylinder 38, and an inlet gas flow meter 41, which can inject gas detection medium or gas healing medium into the model system unit S1, providing gas source and power for gas channeling detection and healing maintenance. The alternating stress loading unit S3 includes an internal pressure loading pump 44, which can provide internal pressure loading and alternating load loading for the model system unit S1, used to simulate the internal pressure of the downhole casing and the pressure changes within the downhole casing, respectively. The servo loading unit S4 includes a top pressure loading pump 47 and annular pressure loading pump 48, which can provide top pressure and annular pressure loading for the model system unit S1, used to simulate the cement slurry column pressure and the external confining pressure of the downhole cement sheath, respectively. The cooling circulation unit S... The built-in cryogenic bath 53 can inject and circulate liquid cooling medium into the model system unit S1 and provide heat dissipation for the liquid cooling medium to simulate the temperature environment changes of the downhole cement sheath; the failure detection unit S6 has a built-in outlet gas flow meter 56, a drying tank 57, and a buffer bottle 58, which can monitor the outlet gas flow in real time to determine whether the artificial fracture is successfully created, assess the size of the artificial fracture, and evaluate the self-healing cement healing ability in the presence of gas; the data acquisition and control unit S7 has a built-in temperature and pressure control module to control the temperature and pressure of the model system unit S1, as well as the loading mode and loading speed of the alternating stress loading unit S3 and the servo loading unit S4; the units are integrated through circuits and connected by pipelines, enabling the device to simulate the high temperature and high pressure environment downhole, create artificial fractures and detect gas channeling, and has good intelligence and operability.

[0101] Furthermore, in terms of device structure, a tapered sleeve structure is designed within the model system unit S1. Because the cement slurry contains air bubbles and exhibits some shrinkage after solidification, the actual solidified surface of the hydrated cement slurry is often lower than the initial slurry surface and uneven, resulting in cavities not filled by the cement slurry. During the creation of artificial cracks, healing curing, and healing capacity testing, the top pressure needs to be completely released. This makes the rubber cylinder 2 easily squeezed into the cavity under external confining pressure, causing shear failure and leading to seal failure. Therefore, a tapered sleeve structure is introduced, placing the cement solidified surface above the bottom of the tapered sleeve to protect the rubber cylinder 2 from shearing, and forming an end-face seal with the rubber cylinder 2 through the tapered surface design. This tapered sleeve structure avoids secondary processing of the cement ring, ensuring the continuity of the process from artificially creating cracks to evaluating healing performance, and achieving the purpose of in-situ testing.

[0102] In summary, the present invention has the following advantages:

[0103] (1) The present invention uses artificial micro-annular gaps to prefabricate cracks, which has the advantages of single location and unique quantity. By adjusting the amplitude of alternating load, the number of alternating load cycles, and the magnitude of internal pressure, the crack size is controlled, crack standardization is achieved, and the influence of crack quantity, size, spatial distribution and other factors on the test results is reduced.

[0104] (2) By combining the model system unit S1, gas injection unit S2, alternating stress loading unit S3, servo loading unit S4, cooling circulation unit S5, failure detection unit S6 and data acquisition and control unit S7, this invention has the ability to simulate the high temperature and high pressure environment downhole, create artificial fractures and detect gas channeling, which is more in line with the actual working conditions on site. Moreover, each unit is integrated through circuits, which has good intelligence and operability.

[0105] (3) By introducing a tapered sleeve structure, this invention avoids the secondary processing of the cement ring, ensures the continuity of the process from artificially creating cracks to evaluating healing performance, and achieves the purpose of in-situ testing.

[0106] (4) The principle of creating artificial cracks in this invention is the same as the principle of micro-annular gaps in downhole cement sheaths. Furthermore, the process and environment of in-situ testing are similar to the process and environment of self-healing cement in downholes when exposed to air, which is more in line with the actual working conditions on site, and the test results are more meaningful for engineering guidance.

[0107] (5) This invention uses the gas flow test method, based on the crack permeability formula and Darcy's formula, to calculate the crack size. The change in crack size reflects the healing ability, thus realizing a quantitative evaluation of the healing ability of gas-inducing self-healing cement. The principle is scientific and the data error is small.

[0108] The following detailed description is provided with reference to specific embodiments:

[0109] Using the in-situ testing device for the healing ability of self-healing cement upon exposure to air provided by this invention, an in-situ crack was created on a certain self-healing cement upon exposure to air to obtain the artificial crack required for the test. The specific steps are as follows:

[0110] Step 1, Equipment assembly and connection: Refer to Figure 2 Assemble the model system unit S1, and refer to Figure 1 Connect the model system unit S1 to the gas injection unit S2, the alternating stress loading unit S3, the servo loading unit S4, the cooling circulation unit S5, the failure detection unit S6, and the data acquisition and control unit S7.

[0111] Step 2, Grouting and Curing: Based on the proportions of each material in the formula of the self-healing cement slurry system to be tested, prepare the self-healing cement slurry to be evaluated according to the method specified in "5 Preparation of Cement Slurry" of GB / T19139-2012 "Test Methods for Cement in Oil Wells". Inject the prepared self-healing cement slurry into the second space 26, making the slurry level flush with the bottom of the upper ring 10. Using the temperature and pressure control module of the data acquisition and control unit S7, set the curing temperature to 80℃, the internal curing pressure to 20MPa, the top curing pressure to 3MPa, and the ring curing pressure to 3MPa, and cure for 48 hours to obtain the cement ring.

[0112] Step 3, Cement Ring Integrity Verification: Maintain the internal pressure and ring pressure of model system unit S1 unchanged. First, gradually unload the top pressure of model system unit S1 using top pressure loading pump 47 until the top pressure drops to 0 MPa, creating conditions for gas channeling detection. Then, inject gas detection medium into the bottom of the second space 26 through gas injection unit S2 at a gas injection pressure of 2.5 MPa. Observe the real-time gas flow rate Q1 of the outlet gas flow meter 56 in failure detection unit S6. Figure 5 As shown, Q1 is 0 ml / min, indicating that the cement ring has good integrity.

[0113] Step 4, creating artificial cracks: Maintaining the gas injection pressure of gas injection unit S2 at a constant 2.5 MPa, apply an alternating load to the first space 25 through alternating stress loading unit S3. The alternating load range is 2–24 MPa, causing the interface between the sleeve 1 and the cement ring to detach under alternating stress, forming a micro-annular gap. Observe the real-time gas flow rate Q2 of the outlet gas flow meter 56. Figure 5As shown, during the internal pressure rise phase of the alternating load, Q2 remained at 0 ml / min, indicating that no radial microcracks were generated. During the internal pressure decrease phase of the alternating load, Q2 reached 4 ml / min in the second alternating load cycle, indicating that the micro-annulus was successfully created. Furthermore, as the number of alternating load cycles increased, Q2 gradually increased from 4 ml / min to 10 ml / min, indicating that the micro-annulus size increased with the number of alternating load cycles. The internal pressure of the model system unit S1 was adjusted to the lower limit of the alternating load, 2 MPa.

[0114] Step 5, quantify the artificial gap: Continuously observe the gas flow rate change of the outlet gas flow meter 56. After the gas flow rate of the outlet gas flow meter 56 stabilizes, record the gas flow rate of the outlet gas flow meter 56 at this time as Q3. For example... Figure 5 As shown, Q3 is 35 ml / min and the stable time is more than 5 hours, indicating that the size of the micro-annulus is stable. Based on the crack permeability formula and Darcy's formula, according to the stable gas flow rate Q3 of the outlet gas flow meter 56 is 35 ml / min, the gas injection pressure P4 is 2.5 MPa, the axial length L of the cement ring is 570 mm, the inner diameter D1 of the cement ring is 88.9 mm, and the dynamic viscosity E1 of the gas detection medium is 0.0181 mPa·s, the artificial crack size is calculated using formula (1), and the initial artificial crack size F1 is 72 μm.

[0115] Formula (1):

[0116]

[0117] In the formula, Q—the stable gas flow rate of the outlet gas flow meter 56 in the failure detection unit S6, in m 3 / s. P—Gas injection pressure, Pa. L—Axial length of cement ring, m. D1—Inner diameter of cement ring, m. E1—Dynamic viscosity of gas medium, Pa·s. F—Dimension of artificial fracture, m.

[0118] Step 6, Adjusting for Artificial Cracks: Compare F1 with the ultimate healing scale Fg of the self-healing agent product under test. According to the product's specifications, the ultimate healing scale Fg of the self-healing agent product is... g For 100um, F1 < F g This indicates that the initial artificial crack size meets the requirements for testing the healing ability of the self-healing cement. Due to the ideal test size F... m 55um, F1 > F mAt 71.2h of the test, the internal pressure was increased by 1MPa by the internal pressure loading pump 44, which increased the expansion deformation of the sleeve 1 and thus reduced the size of the micro-annular gap. The gas flow rate of the outlet gas flow meter 56 was observed. At 72h of the test, the gas flow rate of the outlet gas flow meter 56 was stable. The gas flow rate of the outlet gas flow meter 56 at this time was recorded as Q3. The adjusted Q3 was 15ml / min. The artificial crack size was calculated according to formula (1) to obtain the adjusted artificial crack size F. n Approximately 54.2 μm, F n ≈F m They obtained the artificial cracks required for the experiment.

[0119] After obtaining the artificially created cracks required for the experiment, an in-situ test was conducted on a certain gas-sensitive self-healing cement. The specific steps are as follows:

[0120] Step 7, Self-healing ability evaluation: At 72h of the test time, gaseous healing medium-methane was injected into the bottom of the second space 26 through gas injection unit S2 at a gas injection pressure of 2.5MPa. After the injection of gaseous healing medium-methane, the real-time gas flow rate Q2 of the outlet gas flow meter 56 was stable in the initial stage, indicating that the size of the micro-annular gap was stable at this time. The healing curing time was 12h. The change of gas flow rate of the outlet gas flow meter 56 was observed during the healing curing period. After the gas flow rate of the outlet gas flow meter 56 stabilized, the gas flow rate of the outlet gas flow meter 56 at this time was recorded as Q4. After 12h of healing curing time, Q4 was 5ml / min. According to formula (1), the artificial crack size was calculated, and the final artificial crack size F2 after 12h of healing curing time was obtained as 37.6μm. The healing ability η of the gas-contaminated self-healing cement after 12h of healing curing time was evaluated using formula (2) and found to be 30.6%.

[0121] Formula (2):

[0122]

[0123] In the formula, η represents the self-healing ability of air-sensitive cement stone, in percentage terms. F n —After adjustment, it approaches the ideal experimental scale F m The artificial fracture size, in meters. F2—the final artificial fracture size after healing and curing time t2, in meters.

[0124] In the accompanying drawings of this embodiment, the same or similar reference numerals correspond to the same or similar components. In the description of this invention, it should be understood that if terms such as "upper," "lower," "left," and "right" indicate the orientation or positional relationship based on the orientation or positional relationship shown in the drawings, they are only for the convenience of describing this invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, the terms used to describe positional relationships in the drawings are only for illustrative purposes and should not be construed as limiting this invention. For those skilled in the art, the specific meaning of the above terms can be understood according to the specific circumstances.

[0125] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. An in-situ testing device for the healing ability of self-healing cement upon contact with air, characterized in that, include: The model system unit has a first space, a second space and a third space. The second space surrounds the outer periphery of the first space, and the third space surrounds the outer periphery of the second space. The second space is used for injecting cement grout. A gas injection unit is used to inject a gaseous medium into the second space; An alternating stress loading unit is used to provide internal pressure loading and alternating load loading to the first space; A servo loading unit is used to provide top pressure loading to the second space and ring pressure loading to the third space; A failure detection unit is used to obtain the flow rate of dry gas flowing out of the second space; A control unit is used to control the temperature inside the first space and outside the third space.

2. The in-situ testing device for the healing ability of self-healing cement upon contact with air as described in claim 1, characterized in that, The model system unit includes: The cylindrical body is installed vertically. A perforated steel pipe is coaxially fitted inside the cylinder. A rubber cylinder is coaxially fitted inside the perforated steel pipe and fits against the perforated steel pipe. The upper and lower parts of the gap between the rubber cylinder and the cylinder body are sealed, forming the third space. A sleeve is coaxially fitted inside the rubber cylinder. The upper and lower parts of the gap between the sleeve and the rubber cylinder are sealed to form the second space, and the upper and lower parts of the sleeve are sealed to form the first space.

3. The in-situ testing device for the healing ability of self-healing cement upon contact with air as described in claim 2, characterized in that, Also includes: An upper tapered sleeve is coaxially fitted inside the cylinder. The inner diameter of the upper tapered sleeve is equal to the inner diameter of the rubber cylinder. The outer peripheral wall of the upper tapered sleeve has an upper outer tapered surface that gradually tapers from top to bottom and an upper boss located above the upper outer tapered surface. The upper outer tapered surface is sealed to the upper inner tapered surface of the rubber cylinder, and a sealing ring is used to seal the upper boss and the cylinder. A lower tapered sleeve is coaxially fitted inside the cylinder. The inner diameter of the lower tapered sleeve is equal to the inner diameter of the rubber cylinder. The outer peripheral wall of the lower tapered sleeve has a lower outer tapered surface that gradually tapers from bottom to top and a lower boss located below the lower outer tapered surface. The lower outer tapered surface is sealed to the lower inner tapered surface of the rubber cylinder, and the lower boss is sealed to the cylinder with a sealing ring.

4. The in-situ testing device for the healing ability of self-healing cement upon contact with air as described in claim 3, characterized in that, Also includes: The upper ring is fitted between the sleeve and the upper tapered sleeve; The lower ring is fitted between the sleeve and the lower tapered sleeve; The upper sealing plug has a ring-shaped structure. The upper sealing plug is sleeved between the sleeve and the upper tapered sleeve and is positioned above the upper ring. The upper sealing plug and the sleeve, as well as the upper sealing plug and the upper tapered sleeve, are sealed with sealing rings. The lower sealing plug has a ring-shaped structure. The lower sealing plug is sleeved between the sleeve and the lower tapered sleeve and is located below the lower ring. The lower sealing plug and the sleeve, as well as the lower sealing plug and the lower tapered sleeve, are sealed with sealing rings. A gasket is fitted between the sleeve and the lower tapered sleeve, and positioned above the lower ring; An upper cylinder cover is located on the upper part of the cylinder, and a sealing ring is used to seal the upper cylinder cover and the sleeve. The lower cylinder cover is located at the lower part of the cylinder, and a sealing ring is used to seal the lower cylinder cover and the sleeve.

5. A method for in-situ testing the healing ability of self-healing cement upon exposure to air using the in-situ testing device for the healing ability of self-healing cement according to any one of claims 1-4, characterized in that, Includes the following steps: Grouting and curing: Inject the prepared air-insensitive self-healing cement grout into the second space; Set the curing temperature T1, curing internal pressure P1, curing top pressure P2, and curing ring pressure P3, and carry out curing according to the curing time t1 to obtain a cement ring; Cement ring integrity verification: Set the top pressure drop to zero; Inject gas detection medium into the bottom of the second space; Observe the real-time flow rate Q1 of the dry gas flowing out of the second space; verify the integrity of the cement ring based on Q1. Creating artificial cracks: Applying alternating loads to the first space causes the interface between the sleeve separating the first space and the second space and the cement ring in the second space to detach, thus creating artificial cracks; Observe the real-time flow rate Q2 of the dry gas escaping from the second space; verify whether the artificial fracture was successfully created based on Q2. Quantifying artificial cracks: Obtaining the initial artificial crack scale F1; Adjusting the artificial fracture: Adjust the artificial fracture according to F1 to obtain the adjusted artificial fracture scale F. n until F n Achieving the ideal experimental scale F m ; Self-healing capability evaluation: Injecting gaseous healing medium into the bottom of the second space; healing curing time t2; obtaining the final artificial crack size F2; based on F2 and F... n Evaluate the healing ability of self-healing cement upon contact with air.

6. The in-situ testing method for the healing ability of self-healing cement upon contact with air as described in claim 5, characterized in that, To verify the integrity of the cement ring, Q1 is used as follows: If Q1 is zero, the cement ring integrity is good. If Q1 is not zero, the cement ring integrity is poor. Repeat the above steps until Q1 is zero.

7. The in-situ testing method for the healing ability of self-healing cement upon contact with air as described in claim 5, characterized in that, Verifying the success of artificially created cracks based on Q2 includes: determining whether Q2 remains zero during the internal pressure rise phase of the alternating load; if Q2 does not remain zero during the internal pressure rise phase of the alternating load, repeating the above steps until Q2 remains zero during the internal pressure rise phase of the alternating load; and determining whether Q2 is not zero during the internal pressure fall phase of the alternating load; if Q2 is not zero during the internal pressure fall phase of the alternating load, it indicates that the artificial crack was successfully created; if Q2 is zero during the internal pressure fall phase of the alternating load, it indicates that the artificial crack was unsuccessfully created, and adjusting the alternating pressure amplitude and the number of alternating load cycles until Q2 is not zero during the internal pressure fall phase of the alternating load. After verifying the successful creation of the artificial crack, the internal pressure was adjusted to the lower limit of the alternating load, P5.

8. The in-situ testing method for the healing ability of self-healing cement upon contact with air as described in claim 7, characterized in that, To obtain the initial artificial fracture scale F1, the following steps are taken: continuously observe the change in the flow rate of the dry gas flowing out of the second space, and after the flow rate of the dry gas flowing out of the second space stabilizes, record the flow rate of the dry gas flowing out of the second space as Q3; calculate the artificial fracture scale using formula (1) to obtain the initial artificial fracture scale F1. Formula (1): In the formula, Q is the steady flow rate of dry gas exiting from the second space, in meters. 3 / s; P—Gas injection pressure, Pa; L—Axial length of cement ring, m; D1—Inner diameter of cement ring, m; E1—Dynamic viscosity of gas medium, Pa·s; F—Dimension of man-made crack, m.

9. The method as described in claim 8, characterized in that, Based on F1, adjust the artificial fracture to obtain the adjusted artificial fracture scale F. n until F n Achieving the ideal experimental scale F m This includes: comparing F1 with the limiting healing scale F of the self-healing agent product under test. g Compare and determine if F1 is less than F. g If F1 is greater than F g If the internal pressure is increased, the artificial fracture size is calculated using formula (1) to obtain the adjusted artificial fracture size F. n If F n Still greater than F g Then continue to increase the internal pressure until F n Less than F g If F1 is less than F g Then determine whether F1 reaches the ideal experimental scale F. m If F1 is less than F m If the lower limit of alternating load is lowered or the number of alternating load cycles is increased, the artificial crack size is calculated using formula (1) to obtain the adjusted artificial crack size F. n If F n Still less than F m If so, continue to lower the lower limit of the alternating load or increase the number of alternating load cycles until F... n Reaching F m If F1 is greater than F m If the internal pressure is increased, the artificial fracture size is calculated using formula (1) to obtain the adjusted artificial fracture size F. n If F n Still greater than F m Then continue to increase the internal pressure until F n Reaching F m .

10. The method as described in claim 8, characterized in that, The final artificial crack scale F2 after the healing and maintenance time t2 is obtained includes: observing the change in the flow rate of the dry gas flowing out of the second space, and recording the flow rate of the dry gas flowing out of the second space as Q4 after the flow rate of the dry gas flowing out of the second space stabilizes. The artificial crack scale is calculated according to formula (1) to obtain the final artificial crack scale F2 after the healing and maintenance time t2. According to F2 and F n The evaluation of the healing ability of self-healing cement upon exposure to air includes: using formula (2) to evaluate the healing ability of self-healing cement upon exposure to air. Formula (2): In the formula, η—the self-healing ability of air-contaminated cement stone, %; F n —After adjustment, it approaches the ideal experimental scale F m F2—the final artificial crack size after healing and curing time t2, in meters.

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