A high-temperature and high-pressure formation fluid containing large-pore fracture plugging simulation device and method

Abstract

The present application relates to a kind of high temperature high pressure formation fluid containing large hole fracture plugging simulation device, including nitrogen bottle, liquid storage tank, simulation wellbore, heating insulation cover, back pressure valve and hole fracture isolation plate, there is inner cylinder in upper kettle body, there is simulation leakage layer in inner cylinder, upper kettle body and lower kettle body are connected by flange, hole fracture isolation plate is set between upper kettle body and lower kettle body, back pressure valve is set at the place close to hole fracture isolation plate of lower kettle body, heating insulation cover is set on the outer wall of upper kettle body and lower kettle body.The simulation method for high temperature high pressure formation fluid containing large hole fracture plugging using the above device, including: plugging slurry is discharged or passed through formation fluid and then enters simulation leakage layer;The plugging effect of conventional drilling fluid on small hole fracture leakage layer is judged by the pressure difference of upper kettle body and lower kettle body;The breakthrough pressure of sealing zone is obtained by the pressure difference between upper kettle body and lower kettle body after sealing zone is formed by solidified cementation type plugging slurry.The present application is in line with actual downhole, easy and fast to operate, provides platform and means for the plugging research of formation fluid containing large hole fracture leakage layer.

Description

Technical Field

[0001] This invention belongs to the field of oil and gas well engineering technology, specifically relating to a high-temperature, high-pressure simulation experimental device and method for plugging large pores and fissures containing formation fluids. Background Technology

[0002] As oil exploration and development deepens, more and more complex formations are encountered in deep and ultra-deep wells, leading to increasingly prominent issues of frequent and substantial drilling fluid loss. This severely impacts drilling safety, limits drilling speed, and depletes drilling fluid materials. Furthermore, once drilling fluid leaks into the reservoir, it causes serious damage, significantly affecting oil and gas production and development efficiency. For example, the severe losses caused by large fractures in igneous rocks and large fractures in carbonate formations at Sinopec Northwest Oilfield Company have seriously affected its development efficiency. Conventional plugging simulation experimental devices and methods are mostly developed for small-pore fractures to evaluate the ability of conventional plugging materials to remain, bridge, fill, and ultimately seal leaking formations in small-pore fractures. For example, the "Intelligent High-Temperature and High-Pressure Dynamic Leakage Evaluation Test Instrument" (CN1731176A) uses drilling fluid and completion fluid with added leakage plugging agent in a mud tank to conduct leakage plugging experiments on steel ball leak beds, artificial fracture plates, and formation cores under simulated formation temperature, pressure, and flow rate conditions. This evaluates the leakage plugging effect of the plugging materials in the drilling fluid and completion fluid. The "High-Temperature and High-Pressure Leakage Formation Simulation and Plugging Test Device" (CN102518432A) simulates the leakage plugging process of drilling fluid under different operating conditions for conventional leakage, tests relevant parameters, determines the plugging effect, and evaluates the plugging performance of the plugging agent and drilling fluid. The "High-Temperature and High-Pressure Drilling Fluid Leakage Dynamic..." test instrument is also available. The "Evaluation Instrument" (CN102562040A) is used to simulate the leakage and plugging process of complex fractures. Its fracture module mainly consists of an upper column, a lower column, and a heating plate. A rubber gasket is placed between the upper and lower columns with grooves to form a fracture. It features high automation, complete functions, a wide variety of fracture module types and large size, and real-time monitoring of drilling fluid filtration loss. It overcomes the shortcomings of conventional plugging devices, such as small size, single fracture type, inability to simulate complex fracture-vuggy leakage and fracture wall filtration loss, and inability to evaluate the location and permeability of the plugging layer. The "High Temperature and High Pressure Circulating Drilling Fluid Simulation Plugging Experimental Device" (CN215985935U) can simulate the process of plugging drilling fluid sealing fractures in the leaking layer.

[0003] The methods and devices described above all work by simulating the retention, bridging, filling, and forming a sealing band in the pores and fissures of the leaking layer, thereby sealing the leaking layer. Conventional plugging materials, due to their small size, are difficult to retain, bridge, and fill in large pores and fissures, and are not suitable for simulating the sealing process of large pores and fissures containing formation fluids.

[0004] Curing-bonded sealing grouts effectively seal large-pore leaks by curing and bonding within the grout to form a high-strength solidified body. However, their sealing mechanism differs from that of conventional sealing materials, which rely on retention, bridging, and filling. Furthermore, the system may not contain bridging materials such as fibers or particles. Therefore, conventional sealing simulation devices, which are currently used to evaluate the sealing effectiveness of conventional sealing materials for small pores, are insufficient to assess the sealing capability of these curing-bonded sealing grouts for large-pore leaks. Summary of the Invention

[0005] The purpose of this invention is to provide a high-temperature and high-pressure simulation device for plugging large-pore fractures in formation fluids. This device closely matches the actual downhole conditions, has a simple and reliable structure, and is easy and quick to operate, providing a platform and means for the research on plugging of large-pore fractures in formation fluids.

[0006] Another objective of this invention is to provide a simulation method for sealing large-pore fractures containing formation fluid under high temperature and high pressure using the above-mentioned device. By more realistically simulating the sealing process of large-pore fractures containing formation fluid under dynamic conditions, the sealing effect of solidified cementitious sealing slurry can be quantitatively evaluated.

[0007] To achieve the above technical objectives, the present invention adopts the following technical solution.

[0008] This invention addresses the problem of large-pore leaks that are difficult to effectively seal with conventional sealing materials and grouts. It transforms the bridging and filling of pores and cracks by conventional sealing materials into the filling, curing, and bonding of large-pore leaks containing formation fluids by grout.

[0009] Considering the presence of formation fluids in large pores and fissures, the plugging slurry must displace these fluids before entering the leaking layer. The slurry may be contaminated or damaged by formation fluids as it advances through the large pores and fissures. The density difference between the slurry and the formation fluids may affect the distribution of the slurry within the large pores and fissures, thus impacting the sealing effect. Therefore, the evaluation of the sealing effect in this invention has shifted from the conventional methods of evaluating the type, particle size, and dosage of plugging materials, the amount of leakage before effective sealing, the thickness of the sealing layer, and the breakdown pressure of the sealing layer, to assessing the slurry's resistance to water intrusion, its retention capacity, its filling efficiency, the strength of the slurry after curing, the thickness of the sealing zone, and its pressure-bearing capacity.

[0010] A high-temperature, high-pressure, formation fluid-containing large-pore fracture plugging simulation device mainly consists of a simulated wellbore, a pressurization system, a heating system, and a data testing and acquisition system.

[0011] The simulated wellbore includes a lid, an upper body, and a lower body. The lid has an inlet and an outlet. The simulated wellbore is connected to a pressurization system through the inlet. The upper body has a cylindrical inner cylinder at its center. The upper and lower bodies are connected by a flange. An isolation plate with perforations is installed between the upper and lower bodies to achieve mechanical isolation and support the inner cylinder in the upper body. The bottom of the lower body is connected to a base. Heating and insulation sleeves and temperature sensors are installed on the outer walls of the upper and lower bodies.

[0012] The inner cylinder contains fine sand / particles and spheres / stones of varying sizes to simulate leaky layers with different pore sizes. The larger spheres / stones are directly piled up to simulate large-pore leaky layers, while the smaller fine sand / particles are more likely to leak through the intermediate isolation plate, requiring spheres / stones for support underneath. Simulated formation fluid is then used to submerge the leaky layer, simulating leaky layers with different pore sizes and containing formation fluid.

[0013] The simulated wellbore is fixed on a rotating support. The simulated wellbore's tilt angle is adjusted by rotation to simulate the states of vertical wells, highly deviated wells, and horizontal wells.

[0014] The upper vessel is a high-pressure chamber, pressurized by a nitrogen cylinder, providing the plugging slurry with the power to displace formation fluids in the large-pore fracture leak layer, to advance within the large-pore fracture leak layer, and to test the breakdown pressure of the sealing strip after the plugging slurry has solidified and cemented.

[0015] The lower vessel is a low-pressure chamber filled with formation fluid, simulating a karst cave filled with formation fluid, and receiving the plugging slurry that passes through the large pore leak layer and the intermediate isolation plate.

[0016] The lower vessel is equipped with a back pressure valve near the middle isolation slit plate, which can adjust the pressure relief value. It is closed before the experiment to ensure that the lower and upper vessels are filled with formation fluid. When the plugging slurry passes through the leak layer and the isolation slit plate and enters the lower vessel, it discharges liquid and relieves pressure. The amount of plugging slurry injected is controlled according to the volume of formation fluid discharged.

[0017] The pressurization system includes a nitrogen cylinder, a pressure gauge, a pressure pipeline, a storage tank, and an inlet pipeline. The nitrogen cylinder provides pressure to the storage tank through the pressure pipeline, squeezing the plugging slurry into the simulated leaking layer. The amount squeezed in is controlled by simulating the discharge of formation fluid at the back pressure valve. When the simulated wellbore is completely filled with liquid, the discharge volume of the back pressure valve is the amount of plugging slurry or displacement fluid squeezed in. For solidified cemented plugging slurry without bridging materials, the discharge pressure of the back pressure valve is increased after the injection is completed to pressurize the entire simulated wellbore, simulating the high-pressure environment of the plugging slurry downhole to a certain extent.

[0018] The heating system includes a temperature sensor and a heating insulation jacket, used to measure, display and control the temperature inside the simulated wellbore, simulate the high-temperature environment of the plugging slurry in the downhole leak layer, and accelerate the solidification process of the plugging slurry.

[0019] The data testing and acquisition system includes pressure sensors installed on the upper and lower reactor bodies and a back pressure valve discharge volume measuring instrument. For bridge-type plugging slurry, the plugging effect of the slurry on the simulated leak layer can be judged based on the increase and stability of the upper chamber pressure during injection. At the same time, the cumulative leakage at different times can be obtained by using the discharge volume of the back pressure valve, thereby enabling detailed and quantitative analysis of the approximate process of the sealing zone formation.

[0020] The lid, upper body, inner cylinder, lower body, and intermediate isolation plate are all made of high-temperature resistant stainless steel.

[0021] The lid and upper body of the vessel are connected by threads and flanges, and the upper and lower bodies are connected by threads and flanges. The intermediate isolation plate is seated at the lower end of the upper body or the upper end of the lower body by threads or steps.

[0022] The simulation method for plugging large-pore fractures containing formation fluids using the above-mentioned device includes the following steps:

[0023] (1) Close the back pressure valve to fill the annular space between the upper vessel and the inner cylinder and the lower vessel with formation fluid. Pile a set number of stones / spheres, particles / fine sand or their combinations into the inner cylinder from bottom to top to form a simulated leak layer. Pour formation fluid into the inner cylinder until it submerges the simulated leak layer.

[0024] (2) Open the heating insulation jacket and heat it to the set temperature value. Squeeze the plugging slurry in the storage tank through the nitrogen cylinder into the inner cylinder. After the plugging slurry is discharged or passes through the formation fluid, it enters the simulated leak layer. The plugging slurry forms a sealing band in the simulated leak layer. Adjust the back pressure valve to the set pressure value. When the plugging slurry passes through the simulated leak layer and the perforated isolation plate and enters the lower vessel, the back pressure valve discharges liquid and releases pressure to the outside.

[0025] (3) For bridge-type plugging of small hole gap leakage layer, the volume of liquid discharged from back pressure valve is measured according to the increase and stability of pressure in the upper vessel during the injection period, and the cumulative leakage at different times is obtained to judge the plugging effect of plugging slurry on simulated leakage layer.

[0026] (4) For cemented plugging of large-pore-seam leaks, the simulated wellbore is heated and kept warm for a period of time. After the plugging slurry has solidified and cemented, the upper vessel is pressurized directly until the back pressure valve of the lower vessel discharges the liquid and releases the pressure. This indicates that the sealing strip has been broken through. The pressure difference between the upper and lower vessels is the pressure-bearing capacity of the sealing strip.

[0027] (5) Turn off the power supply of the heating and insulation jacket to cool down the simulated well. When the temperature of the simulated well drops below 45°C, depressurize the upper and lower vessels through the exhaust valve and the drain port respectively.

[0028] (6) The sealing strip is pushed out from the inner cylinder to obtain its shear bonding strength. A 50mm section is cut from the top surface of the sealing strip to test its compressive strength. The sealing strip is subjected to CT scanning to observe the internal structure of the simulated leak layer after being sealed by the sealing grout.

[0029] Compared with existing technologies, the present invention has the following advantages:

[0030] (1) By accumulating fine sand / particles / spheres / stones or combinations thereof of different sizes in the inner cylinder, leakage layers with different pore sizes can be simulated. It can be used for bridging simulation experiments of conventional drilling fluid for small pores, as well as for simulating leakage plugging experiments of solidified cemented plugging slurry for large pore leakage layers. In addition, it can also simulate large caverns common in fractured leakage layers by filling the lower cavity with simulated formation fluid.

[0031] (2) It fully considers that the large-pore fracture contains formation fluids and that the plugging slurry may be diluted and damaged by the formation fluids when it is advanced in the fracture, which may affect the pressure bearing capacity of the sealing strip after the plugging slurry is solidified. It is more in line with the actual situation of plugging large-pore fracture leakage layers downhole.

[0032] (3) By measuring the volume of liquid discharged through the back pressure valve, it is possible to detect the instantaneous and cumulative leakage of conventional drilling fluid when bridging and plugging small-hole fractured leakage layers, and to control the amount of solidified cemented plugging slurry squeezed into large-hole fractured leakage layers.

[0033] (4) The effect of conventional drilling fluid on small hole and fracture leakage layer can be judged by detecting the pressure difference between the upper and lower vessels during the plugging process. The breakdown pressure of the sealing zone can also be obtained by the pressure difference between the upper and lower vessels after the solidified cemented plugging slurry forms a sealing zone.

[0034] (5) The solidified cementitious plugging grout forms a sealing band in the large-pore fracture leakage layer. Its shear cement strength and compressive strength can be measured by a compressive strength tester, and its internal structure can be observed by CT scan. This allows for a better study of the plugging mechanism of the large-pore fracture leakage layer containing formation fluid, laying the foundation for selecting the best plugging grout suitable for the large-pore fracture leakage layer containing formation fluid and improving the plugging efficiency of the large-pore fracture leakage layer. Attached Figure Description

[0035] Figure 1 This is a schematic diagram of a high-temperature, high-pressure, water-containing large-pore leak-sealing simulation experimental device.

[0036] Figure 2 This is a schematic diagram of a perforated partition plate (perforated plate).

[0037] Figure 3 This is a schematic diagram of a perforated slotted partition plate (slotted plate).

[0038] In the diagram: 1. Nitrogen cylinder; 2, 9. Pressure gauges; 3. Sealing plate; 4. Storage tank; 5. Agitator; 6, 16. Drain port; 7. Inlet valve; 8. Rotating support; 10. Heating and insulation jacket; 11. Upper vessel body; 12. Perforated partition plate; 13. Flange; 14. Lower vessel body; 15. Back pressure valve; 17, 21. Fixed flange; 18. Formation fluid; 19. Nut; 20. Inner cylinder; 22. Vessel cover; 23. Exhaust valve. Implementation

[0039] In order to provide a clearer understanding of the technical features, objectives and beneficial effects of the present invention, the technical solution of the present invention will now be described in detail below, but it should not be construed as limiting the scope of implementation of the present invention.

[0040] See Figure 1 , Figure 2 , Figure 3 .

[0041] A high-temperature, high-pressure, formation fluid-containing large-pore leak sealing simulation device includes a nitrogen cylinder 1, a liquid storage tank 4, a simulated wellbore, a heating and insulation jacket 10, a back pressure valve 15, a perforated isolation plate 12, and a flange 13.

[0042] The simulated wellbore includes a lid 22, an upper vessel body 11, and a lower vessel body 14. The lid is equipped with an inlet and an exhaust valve. The upper vessel body has a cylindrical inner cylinder 20 at its center, with a simulated leak layer inside. The nitrogen cylinder 1 and the storage tank 4 are connected to the inner cylinder through the inlet. The storage tank is equipped with a sealing plate 3 and a stirrer 5. Pressure gauges 2 and 9 are installed on the nitrogen cylinder and the inner cylinder. The upper and lower vessels are connected by a flange 13 and a nut 19. A perforated isolation plate 12 is installed between the upper and lower vessels. This isolation plate is located in the middle of the flange to achieve mechanical isolation between the upper and lower vessels and to support the inner cylinder located in the upper vessel body. A back pressure valve 15 is installed on the lower vessel body near the perforated isolation plate. The storage tank and the lower vessel body are equipped with drain ports 6 and 16. Heating and insulation sleeves 10 are installed on the outer walls of the upper and lower vessels.

[0043] The simulated leak layer refers to a leak layer with different pore sizes and containing formation fluid, which is simulated by accumulating fine sand / particles, spheres / stones or combinations thereof of different sizes in the inner cylinder and flooding it with formation fluid.

[0044] The simulated wellbore is fixed to the rotating support 8 by fixed flanges 17 and 21. Its tilt angle can be adjusted by rotation to simulate the state of vertical wells, highly deviated wells and horizontal wells.

[0045] The inner cylinder of the upper vessel is a high-pressure chamber, which is pressurized by a nitrogen cylinder to provide the power for the plugging slurry to propel through the simulated leak layer.

[0046] The lower vessel is a low-pressure cavity that simulates a cave filled with formation fluid and receives the plugging slurry that passes through the simulated leak layer and the perforated isolation plate.

[0047] The perforated slit isolation plate is an isolation plate with different depths and widths, with holes or slits to simulate large pores, allowing fluids, fine sand, and particles to enter the lower vessel from the upper vessel.

[0048] The storage tank is equipped with a stirrer, which simulates the flow process when the formation fluid or plugging slurry is introduced.

[0049] The formation fluid is water, brine, drilling fluid, crude oil, or a mixture thereof.

[0050] The sealing slurry is a bridge-type sealing slurry containing sealing material for small-pore leaks, a curing and bonding type sealing slurry without sealing material for large-pore leaks, or a combination thereof.

[0051] The nitrogen cylinder has a maximum pressure of 30 MPa, the liquid storage tank has a volume of 5 L-10 L, the pressure gauge has a range of 0-30 MPa, the maximum temperature limit of the heating insulation jacket is 300 °C, the heating rate is 1 °C / s, and the back pressure valve can be selected according to the experimental requirements. Generally, a PVC back pressure valve can be used within the range of 0-3 MPa, and a stainless steel back pressure valve can be used when the experimental pressure is greater than 3 MPa. In this embodiment, a stainless steel back pressure valve is used.

[0052] The leakage of large pores and fractures in the front section of the formation is simulated by filling the inner cylinder with fine sand / particles and spheres / rocks of different sizes. Intermediate isolation plates of different depths and widths simulate large pores and fractures. The holes in the intermediate isolation plates should be controlled within a circle with a diameter of 50 mm, and the overall fracture length is 1 m.

[0053] The experiment was conducted using a high-temperature, high-pressure, water-containing, large-pore crack sealing simulation device. The specific process is as follows:

[0054] Inject formation fluid 18 into the lower vessel 14 and seal it with flange 13 by thread. Pile fine sand / particles and spheres / stones of different sizes into the inner cylinder 20. Connect the inner cylinder and the intermediate isolation plate 12 by thread. Connect the upper vessel 11 and flange by thread. Seal the vessel cover 22. Open the heating insulation jacket 10 and set the heating temperature.

[0055] The leak is plugged by pressurizing the sealing slurry in the nitrogen cylinder 1 and the storage tank 4 according to the set pressure. The sealing slurry is stirred by the mixer 5. The inlet valve 7 is closed, and the sealing slurry in the storage tank is replaced with the replacement liquid. The pressurization pipeline is opened and the replacement liquid is injected according to the set pressure for replacement. The pressure of the lower vessel back pressure valve 15 is set, and the pressure rise of the upper vessel pressure gauge 9 and the leakage amount and leakage rate of the lower vessel back pressure valve 15 are observed and recorded to determine the sealing effect when the sealing slurry has not solidified.

[0056] After the plugging grout has cured and bonded, the upper vessel 11 is pressurized directly through the pressurization pipeline to test the pressure-bearing capacity of the sealing strip and evaluate the plugging grout's ability to seal the leakage layer in large pores.

[0057] After the sealing grout has cured and the temperature is below 45°C, open the exhaust valve 23 to release the gas and drain the liquid in the upper and lower reactor bodies through the drain port 16. Disassemble the upper and lower reactor bodies, cut a 50mm sealing layer from the top of the sand layer downwards, and test its strength on a compressive strength tester or its breakdown pressure on a high temperature and high pressure filter tester.

[0058] After the sealing grout has cured, a CT scan will be performed to observe the internal structure of the leakage layer after the sealing grout has cured and bonded.

[0059] Those skilled in the art should understand that these embodiments are for illustrative purposes only and should not be construed as limiting the scope of the invention. Further modifications to the invention without departing from its principles should also be considered within the scope of protection of the invention.

Claims

1. A high-temperature, high-pressure, formation fluid-containing large-pore fracture plugging simulation device, comprising a nitrogen cylinder, a liquid storage tank, a simulated wellbore, a heating and insulation jacket, a back pressure valve, a perforated isolation plate, and a flange, characterized in that, The simulated wellbore includes a lid, an upper body, and a lower body. The lid is equipped with an inlet and an exhaust valve. The upper body contains a cylindrical inner cylinder at its center, which contains a simulated leak layer. This simulated leak layer is created by accumulating fine sand, stones, or combinations thereof of different sizes within the inner cylinder and then flooding it with formation fluid, simulating leak layers with different pore sizes and containing formation fluid. The nitrogen cylinder and storage tank are connected to the inner cylinder via inlets. The upper and lower bodies are connected by flanges, and a perforated slit is provided between them. A perforated and slotted isolation plate is located in the middle of the flange to achieve mechanical isolation between the upper and lower vessel bodies and to support the inner cylinder located in the upper vessel body. The perforated and slotted isolation plate is an isolation plate with different depths and widths, with holes or slots, to simulate large pores and allow fluids and fine sand to enter the lower vessel body from the upper vessel body. A back pressure valve is installed in the lower vessel body near the perforated and slotted isolation plate, and the lower vessel body is provided with a drain port. Heating and heat preservation sleeves are installed on the outer walls of the upper and lower vessel bodies. The inner cylinder in the upper vessel body is a high-pressure chamber, and the lower vessel body is a low-pressure chamber.

2. The high-temperature, high-pressure, formation fluid-containing macroporous fracture plugging simulation device as described in claim 1, characterized in that, The simulated wellbore is fixed on a rotating support, and its tilt angle can be adjusted by rotation to simulate the state of vertical wells, highly deviated wells, and horizontal wells.

3. The high-temperature, high-pressure, formation fluid-containing macroporous fracture plugging simulation device as described in claim 1, characterized in that, The inner cylinder of the upper vessel is a high-pressure chamber, which means that the grout is pressurized by a nitrogen cylinder to provide the power for the plugging slurry to propel through the simulated leak layer.

4. The high-temperature, high-pressure, formation fluid-containing macroporous fracture plugging simulation device as described in claim 1, characterized in that, The lower vessel is a low-pressure cavity, which is a simulated cave filled with formation fluid, used to receive the plugging slurry that passes through the simulated leak layer and the perforated isolation plate.

5. The high-temperature, high-pressure, formation fluid-containing macroporous fracture plugging simulation device as described in claim 1, characterized in that, The storage tank is equipped with a stirrer, which simulates the flow process when the formation fluid or plugging slurry is introduced.

6. A simulation method for plugging large-pore fractures containing formation fluid under high temperature and high pressure using the apparatus described in claims 1, 2, 3, 4, or 5, comprising the following steps in sequence: (1) Close the back pressure valve to fill the annular space between the upper vessel and the inner cylinder and the lower vessel with formation fluid, and inject formation fluid until the simulated leak layer of the inner cylinder is submerged; (2) Open the heating insulation jacket to the set temperature value, squeeze the plugging slurry in the storage tank through the nitrogen cylinder into the inner cylinder, the plugging slurry is discharged or passes through the formation fluid and enters the simulated leak layer, the plugging slurry forms a sealing band in the simulated leak layer, adjust the back pressure valve to the set pressure value, and when the plugging slurry enters the lower vessel, the back pressure valve discharges liquid and releases pressure to the outside. (3) For bridge-type plugging of small hole gap leakage layer, measure the volume of liquid discharged from back pressure valve, obtain the cumulative leakage at different times, and judge the plugging effect of plugging slurry on simulated leakage layer; (4) For cement-type plugging of large pores and cracks, wait for a period of time for the plugging slurry to solidify and bond. Then, pressurize the upper vessel directly until the back pressure valve of the lower vessel discharges the liquid and releases the pressure. This indicates that the sealing strip has been broken through. The pressure difference between the upper and lower vessels is the pressure-bearing capacity of the sealing strip. (5) Close the heating and insulation jacket. When the temperature of the simulated wellbore drops below 45°C, depressurize the upper and lower vessels through the exhaust valve and the drain port respectively. (6) The sealing strip is pushed out from the inner cylinder to obtain its shear bonding strength and compressive strength. The sealing strip is then subjected to CT scanning to observe the internal structure of the simulated leak layer after it is sealed by the plugging grout.

7. The method as described in claim 6, characterized in that, The formation fluid is water, brine, drilling fluid, crude oil, or a mixture thereof.

8. The method as described in claim 6, characterized in that, The sealing slurry is a bridge-type sealing slurry containing sealing material for small-pore leaks, a curing and bonding type sealing slurry without sealing material for large-pore leaks, or a combination thereof.

Images