Well cementation cement sheath seepage corrosion and mechanical property evaluation device and method

Abstract

The invention discloses a well cementation cement sheath seepage corrosion and mechanical property evaluation device and method, and belongs to the field of oil and gas well cementation material corrosion evaluation. The device comprises an acidic corrosive gas injection system, a formation water injection system, a high-pressure oil injection system, a control system and a corrosion and test system, the corrosion and test system comprises a main body, an upper cover and a base, and the main body sequentially comprises a metal cylinder, a simulated formation, a simulated sleeve and a center rod from outside to inside; a cement sheath maintenance-corrosion space is formed between the simulated stratum and the simulated casing, a temperature control device is arranged in an annulus formed between the simulated casing and the center rod, and the center rod is provided with a plurality of displacement meters at different positions and angles to measure deformation displacement of a simulated casing-cement sheath combination. The method for evaluating seepage corrosion and mechanical properties of the well cementation cement sheath by using the device is simple and convenient to operate, realizes three functions of cement sheath maintenance, acid medium corrosion and cement sheath mechanical integrity evaluation at high temperature and high pressure, and has a wide application prospect.

Description

Technical Field

[0001] The invention belongs to the technical field of corrosion evaluation of cementing materials for oil and gas wells, and specifically relates to a device and method for realizing high-temperature and high-pressure maintenance of cement rings, seepage corrosion of cement rings and cement ring-formation interfaces, and mechanical integrity evaluation. Background Art

[0002] In cementing engineering, cement sheath, as a key part of the wellbore, plays the role of supporting casing and achieving interlayer isolation, ensuring the safe and efficient exploitation of oil and gas resources. However, compared with the metal casing and formation of the wellbore, the mechanical properties of cement sheath are the weakest, and it is very easy to become a weak link in the failure of the wellbore sealing integrity. At the same time, the cement sheath is also facing the high temperature and high pressure at the bottom of the well and the erosion environment of the formation fluid. Especially in high-H2S / CO2 oil and gas wells and CO2 storage wells, the neutralization reaction of acidic H2S and CO2 with alkaline cement sheath will change the chemical-microstructure of cement stone, destroy the cement sheath body and the cementing quality of cement sheath-formation interface, and cause the interlayer isolation of cement sheath to fail. Therefore, it is urgent to accurately grasp the mechanical properties and porosity and permeability evolution of cement stone in high-temperature and high-pressure-corrosive media, and provide means and support for the evaluation of the corrosion resistance of cement stone and the design of corrosion-resistant cement slurry in high-acid medium oil and gas wells and CO2 storage wells.

[0003] In recent years, scholars at home and abroad have focused on the corrosion of acidic media on cement stone by establishing corrosion methods. "Dynamic corrosion device for high temperature and high pressure corrosion medium migration" (CN109520878A) uses a rotating device to flip the corrosion kettle to simulate the flow and replacement of the corrosive medium on the surface of the cement stone, but the device cannot reflect the comprehensive process of corrosion between the corrosive medium and the cement stone, which needs to undergo seepage and then react; "A high temperature and high pressure seepage corrosion simulation experimental device and method" (CN118362491A) simulates the seepage corrosion process of high temperature and high pressure cement stone in the well through the seepage and corrosion reaction of the corrosive medium in the vertical direction of the cement stone, and can maintain the cement stone sample under the seepage corrosion condition; "Seepage corrosion device and seepage corrosion method for cementing cement stone two interfaces" (CN118029947A) realizes the simulation of gas and liquid two-phase corrosion process at the same time, and simulates the corrosion of cement stone by high pressure and multiple corrosion modes at the bottom of the well by applying confining pressure to the artificial well wall and adjusting the gas and liquid corrosive medium. Furthermore, considering that the cement stone is formed into a ring shape (also called cement ring) at the bottom of the well, which may affect the corrosion evaluation results, "A cement ring / plug corrosion integrity test device and method under high temperature and high pressure carbon dioxide" (CN118190766A) focuses on simulating the corrosion maintenance of the sealing cement ring / cement plug by injecting formation CO2 after the CCUS well is sealed, injecting liquid at the upper end of the cement plug to observe the bubble situation, and monitoring the sealing of the cement ring and cement plug; "A full-scale cement ring corrosion test device and method simulating the actual working conditions downhole" (CN114878448A) injects cement slurry between two metal pipes to form a cement ring, and then injects high-pressure corrosive medium into the end face of the cement ring to carry out unidirectional dynamic corrosion maintenance of the full-size cement ring. After the corrosion is completed, cement stone cores are drilled from the cement ring to test performance indicators such as compressive strength, porosity and corrosion depth.

[0004] Existing corrosion equipment focuses on the corrosion maintenance of cement sheaths in high temperature and high pressure corrosive media. The cement sheath is disassembled only after cooling and depressurization, and its mechanical properties are evaluated using other equipment. The cement sheath is a multi-component, porous and brittle material, and the cooling and depressurization process may cause microstructure-performance changes; in addition, the cement sheath and the metal casing have different material properties and significant differences in thermal expansion coefficients, which will also cause the cooling and depressurization process to damage the structure and performance of the cement sheath.

[0005] With the development of CO2 geological storage and oil recovery technologies, higher challenges have been brought to the corrosion equipment and evaluation technology of cement sheath. The existing equipment has a single function and cannot accurately evaluate the corrosion condition of cement sheath under bottom hole conditions and the influence of corrosion on the mechanical integrity of cement sheath. Summary of the invention

[0006] The purpose of the present invention is to provide a cementing cement ring seepage corrosion and mechanical property evaluation device, which can simultaneously realize three functions of cementing cement ring maintenance under high temperature and high pressure, corrosion of the cement ring body and the formation-cement ring interface by H2S / CO2 acidic medium, and evaluation of the mechanical integrity of the cement ring after corrosion, and has broad market application prospects.

[0007] Another object of the present invention is to provide a method for evaluating the seepage corrosion and mechanical properties of cement ring using the above-mentioned device. The method has reliable principles and is easy to operate. It solves the problem that the existing corrosion equipment cannot fully reflect the seepage corrosion of the cement ring body in the formation and the formation-cement ring interface, and directly evaluates the mechanical integrity of the cement ring after corrosion under high temperature and high pressure.

[0008] In order to achieve the above technical objectives, the present invention adopts the following technical solutions.

[0009] The cement ring seepage corrosion and mechanical property evaluation device comprises an acid corrosion gas injection system, a formation water injection system, a high pressure oil injection system, a control system and a corrosion and testing system.

[0010] The acidic corrosive gas injection system includes a gas cylinder, a control valve, a gas booster pump and a check valve, the gas booster pump is connected to the control system, the formation water injection system includes a liquid storage tank, a liquid booster pump and a check valve, the liquid booster pump is connected to the control system, the outlet ends of the acidic corrosive gas injection system and the formation water injection system are respectively provided with check valves, and are converged into a high-pressure pipeline, which is connected to the corrosion and testing system.

[0011] The high-pressure oil injection system includes an oil storage tank, a high-pressure oil pump and a check valve. The high-pressure oil pump is connected to a control system. The outlet end of the high-pressure oil injection system is equipped with a check valve and connected to a corrosion and testing system.

[0012] The corrosion and testing system includes a main body, an upper cover and a base. The main body is composed of a metal tube, a simulated formation, a simulated casing and a center rod from the outside to the inside. The center rod is located at the center of the base and is connected to the upper cover by a nut. The metal tube and the simulated formation are sealed after epoxy resin is cured. A cement ring curing-corrosion space is formed between the simulated formation and the simulated casing. A temperature control device is arranged in the annulus formed between the simulated casing and the center rod. The temperature control device is connected to the control system to adjust the temperature in the corrosion and testing system.

[0013] The base is provided with injection ports and oil inlets at corresponding positions of the simulated formation and the simulated annulus between the casing and the center rod, the injection ports are respectively connected to the formation water injection system and the acidic corrosive gas injection system, and the oil inlet is connected to the high-pressure oil injection system.

[0014] The upper cover is provided with a discharge port and an oil outlet at corresponding positions of the simulated formation and the simulated annulus between the casing and the center rod, and both the discharge port and the oil outlet are connected to the back pressure valve through a high-pressure pipeline.

[0015] The simulated casing is used to simulate the casing of cementing operation, and plays the role of supporting the well wall and preventing oil and gas leakage.

[0016] The central rod is provided with a plurality of (not less than 3) displacement meters at different positions and angles, and the stress-strain of the material is calculated by measuring the deformation displacement of the simulated casing-cement ring assembly when subjected to stress.

[0017] The acidic corrosive gas injection system and the formation water injection system provide the corrosion and testing system with acidic corrosive gas and formation water through the injection ports.

[0018] The high-pressure oil injection system injects high-temperature resistant oil into the corrosion and testing system through the oil inlet to control the pressure of the annulus between the simulated casing and the center rod, thereby achieving pressure control during high-temperature and high-pressure maintenance of the cement ring and mechanical property testing.

[0019] The control system is used to control the temperature and pressure conditions during the cementing cement ring maintenance and corrosion process, and is used for pressure control during the mechanical property test process.

[0020] The corrosion and testing system is used for curing and corroding cement sheaths under high temperature and high pressure, and evaluating the mechanical properties of the corroded cement sheaths.

[0021] The simulated formation can be processed by preferably selecting outcrop rock samples according to actual formation data or using artificial rock samples close to actual formation parameters.

[0022] The method for evaluating the seepage corrosion and mechanical properties of cement sheath by using the above device comprises the following steps in sequence: (1) Use epoxy resin to fix the simulated formation in the metal cylinder. After the epoxy resin is cured to form an effective seal, the center rod, simulated casing, and metal cylinder containing the simulated formation are installed on the base respectively; (2) Inject cement slurry into the space between the simulated formation and the simulated casing, install the cover and tighten it with a nut; (3) Open the high-pressure oil injection system to inject high-temperature resistant oil into the annulus between the simulated casing and the center rod, open the formation water injection system to inject formation water into the simulated formation, and close the back pressure valve when liquid flows out of the oil outlet and the discharge port; set the back pressure valve pressure, raise the temperature control device to the required temperature through the control system, start curing the cement ring, and form a simulated casing-cement ring combination; (4) After the maintenance is completed, open the acid corrosive gas injection system to introduce acid corrosive gas H2S / CO2 into the corrosion and testing system for corrosion testing; (5) After the corrosion is completed, the control system and the high-pressure oil injection system are used to inject pressure into the annulus between the simulated casing and the center rod at a certain rate, so as to form a pressure difference between the simulated casing-cement sheath assembly and the simulated formation. The radial displacement meter is used to record the deformation displacement of the simulated casing-cement sheath assembly under the pressure difference, collect data and draw stress-strain curves to analyze the mechanical properties of the cement sheath. (6) After the experiment, cool down and reduce the pressure, unscrew the nut, open the top cover, take out the cement ring, test the corrosion of the cement ring and simulate the formation-cement ring interface (including microstructure, corrosion depth, etc.), and analyze the corrosion law of the cement ring in the H2S / CO2 corrosion environment.

[0023] Furthermore, according to the needs of experimental simulation conditions, maintenance and corrosion can also be carried out simultaneously.

[0024] Compared with the prior art, the present invention has the following beneficial effects: (1) It can simultaneously realize the three functions of cement ring maintenance under high temperature and high pressure, corrosion of cement ring body and simulated formation-cement ring interface by H2S / CO2 acidic medium, and evaluation of mechanical integrity of cement ring after corrosion. Traditional devices have single functions, and different equipment must be used to complete the above operations, which is not only cumbersome to operate, but also easy to introduce human errors. The present invention completes multiple operations in the same device, significantly improves experimental efficiency, reduces equipment footprint, and reduces cost investment; (2) The problem that the existing corrosion device cannot directly evaluate the mechanical integrity of the cement sheath after corrosion under high temperature and high pressure is solved. The present invention sets a displacement meter in the device and applies pressure in combination with a control system. It can directly measure the stress deformation displacement of the cement sheath under high temperature and high pressure environment, collect stress-strain data, and more accurately evaluate the mechanical properties of the cement sheath. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 This is a schematic diagram of the structure of the cement ring seepage corrosion and mechanical properties evaluation device.

[0026] Figure 2 Schematic diagram of the corrosion and testing system structure.

[0027] In the figure: 100-acid corrosive gas injection system: 110-gas cylinder, 120-control valve, 130-gas booster pump, 140-check valve; 200-formation water injection system: 210-liquid storage tank, 220-liquid booster pump, 230-check valve; 300-high-pressure oil injection system: 310-oil storage tank, 320-high-pressure oil pump, 330-check valve; 400-control system; 500-corrosion and testing system System: 501-center rod, 502-nut, 503-back pressure valve, 504-back pressure valve, 505-metal cylinder, 506-simulated formation, 507-cement ring maintenance-corrosion space, 508-simulated casing, 509-annulus, 510-temperature control device, 511-oil outlet, 512-oil inlet, 513-injection port, 514-discharge port, 515-base, 516-upper cover, 517-radial displacement meter. DETAILED DESCRIPTION

[0028] The technical solution of the present invention is clearly and completely described below in conjunction with the embodiments and drawings.

[0029] See also Figure 1 , Figure 2 .

[0030] The cement ring seepage corrosion and mechanical property evaluation device comprises an acidic corrosive gas injection system 100, a formation water injection system 200, a high-pressure oil injection system 300, a control system 400 and a corrosion and testing system 500.

[0031] The acidic corrosive gas injection system 100 includes a gas cylinder 110, a control valve 120, a gas booster pump 130 and a check valve 140. The formation water injection system 200 includes a liquid storage tank 210, a liquid booster pump 220 and a check valve 230. The gas booster pump and the liquid booster pump are respectively connected to a control system 400. The outlet ends of the acidic corrosive gas injection system and the formation water injection system are respectively equipped with check valves and converge into a high-pressure pipeline, which is connected to a corrosion and testing system 500.

[0032] The high-pressure oil injection system 300 includes an oil storage tank 310, a high-pressure oil pump 320 and a check valve 330. The high-pressure oil pump is connected to a control system 400. The outlet end of the high-pressure oil injection system is equipped with a check valve and connected to a corrosion and testing system 500.

[0033] The corrosion and testing system 500 includes a main body, an upper cover 516 and a base 515. The main body is composed of a metal cylinder 505, a simulated formation 506, a simulated casing 508 and a center rod 501 from the outside to the inside. The center rod is located at the center of the base and is connected to the upper cover by a nut 502. The metal cylinder and the simulated formation are effectively sealed after epoxy resin is cured. A cement ring curing-corrosion space 507 is formed between the simulated formation and the simulated casing. An annulus 509 is formed between the simulated casing and the center rod, i.e., an annulus between the simulated casing and the center rod. A temperature control device 510 is arranged in the annulus. The temperature control device is connected to the control system 400; the base 515 is provided with an injection port 513 and an oil inlet 512 at corresponding positions of the simulated formation and the annulus between the simulated casing and the center rod, respectively, the injection ports are connected to the formation water injection system and the acid corrosion gas injection system, and the oil inlet is connected to the high-pressure oil injection system; the upper cover 516 is provided with a discharge port 514 and an oil outlet 511 at corresponding positions of the simulated formation and the annulus between the simulated casing and the center rod, respectively, the discharge port and the oil outlet are connected to the back pressure valves 503 and 504 through high-pressure pipelines; the center rod 501 is provided with a plurality of radial displacement meters 517 at different positions and angles.

[0034] The cementing cement ring seepage corrosion and mechanical property evaluation device can realize cementing cement ring maintenance under high temperature and high pressure, cement ring body and formation-cement ring interface seepage corrosion and mechanical integrity evaluation, and specifically includes the following steps: Step 1: Install the metal cylinder on the base, inject resin to fill the gap between the metal cylinder and the simulated formation, prepare H2S / CO2 gas cylinders, connect all high-pressure pipelines, and select outcrop rocks or artificial cores with corresponding porosity and permeability according to the simulated formation under experiment; Step 2: After the resin solidifies, prepare cement slurry according to GB / T 19139-2012, inject the cement slurry into the space formed between the simulated formation and the simulated casing, and tighten the upper cover with a nut to ensure that the device is sealed completely; Step 3: Open the high-pressure oil injection system to inject crude oil into the annulus between the simulated casing and the center rod, open the formation water injection system to inject formation water into the simulated formation, close the back pressure valve and the check valve when crude oil and formation water flow out of the oil outlet and the discharge port, raise the temperature control device to the required temperature through the control system, and maintain and form the cement ring; Step 4: Open the control valve and the check valve to introduce H2S / CO2 corrosive gas into the corrosion and testing system to perform corrosion testing; Step 5: After the corrosion is completed, the control system applies pressure to the annulus between the simulated casing and the center rod, and the cement ring expands toward the simulated formation. The displacement of the cement ring under pressure is recorded by a displacement meter, and the strain of the cement ring is calculated. Combined with known parameters such as the elastic modulus of the material, the stress on the material is indirectly calculated based on the measured displacement and strain data, and a stress-strain diagram is drawn; Step 6: After the experiment, open the upper cover and take out the cement ring. By observing and testing the corrosion of the cement ring, the corrosion condition of the cement ring under H2S / CO2 corrosion is obtained, and the corrosion law of the cement ring is analyzed.

[0035] Obviously, the above embodiments of the present invention are merely examples for clearly illustrating the present invention, and are not limitations on the implementation methods of the present invention. For ordinary technicians in the relevant field, other different forms of changes or modifications can be made on the basis of the above description. It is impossible to list all the implementation methods here. All obvious changes or modifications derived from the technical solution of the present invention are still within the protection scope of the present invention.

Claims

1. A cement ring seepage corrosion and mechanical property evaluation device, comprising an acidic corrosive gas injection system (100), a formation water injection system (200), a high-pressure oil injection system (300), a control system (400) and a corrosion and testing system (500), characterized in that: The acidic corrosive gas injection system (100) comprises a gas cylinder (110), a gas booster pump (130) and a check valve; the formation water injection system (200) comprises a liquid storage tank (210), a liquid booster pump (220) and a check valve; the gas booster pump and the liquid booster pump are respectively connected to a control system (400); the outlet ends of the acidic corrosive gas injection system and the formation water injection system are respectively connected to a corrosion and testing system (500); the high-pressure oil injection system (300) comprises an oil storage tank (310), a high-pressure oil pump (320) and a check valve; the high-pressure oil pump is connected to the control system (400); the outlet end of the high-pressure oil injection system is connected to the corrosion and testing system (500); the corrosion and testing system (500) comprises a main body, an upper cover (516) and a base (515); the main body comprises, from outside to inside, a metal cylinder (505), a simulated formation (506), a simulated casing (508) and a center rod (501); the center rod is located on the base The metal cylinder and the simulated formation are located at the center position and connected with the upper cover through a nut. The metal cylinder and the simulated formation are effectively sealed after being cured with epoxy resin. A cement ring curing-corrosion space (507) is formed between the simulated formation and the simulated casing. An annulus (509) is formed between the simulated casing and the center rod, i.e., an annulus between the simulated casing and the center rod. A temperature control device (510) is arranged in the annulus, and the temperature control device is connected to the control system (400). The base is provided with an injection port (513) and an oil inlet (512) at corresponding positions of the simulated formation and the annulus between the simulated casing and the center rod, respectively. The injection ports are connected to the formation water injection system and the acid corrosion gas injection system, respectively, and the oil inlet is connected to the high-pressure oil injection system. The upper cover is provided with a discharge port (514) and an oil outlet (511) at corresponding positions of the simulated formation and the annulus between the simulated casing and the center rod, respectively. The discharge port and the oil outlet are connected to the back pressure valve through a high-pressure pipeline. The center rod is provided with a plurality of radial displacement meters (517) at different positions and angles.

2. The cement sheath seepage corrosion and mechanical performance evaluation device according to claim 1, characterized in that: The acidic corrosive gas injection system and the formation water injection system provide the corrosion and testing system with acidic corrosive gas and formation water through the injection ports.

3. The cement sheath seepage corrosion and mechanical performance evaluation device according to claim 1, characterized in that: The high-pressure oil injection system injects high-temperature resistant oil into the corrosion and testing system through the oil inlet to control the pressure of the annulus between the simulated casing and the center rod, thereby achieving pressure control during high-temperature and high-pressure maintenance of the cement ring and mechanical property testing.

4. The cement sheath seepage corrosion and mechanical performance evaluation device according to claim 1, characterized in that: The control system is used to control the temperature and pressure conditions during the cementing cement ring maintenance and corrosion process, and is used for pressure control during the mechanical property test process.

5. The cement sheath seepage corrosion and mechanical performance evaluation device according to claim 1, characterized in that: The corrosion and testing system is used for curing and corroding cement sheaths under high temperature and high pressure, and evaluating the mechanical properties of the corroded cement sheaths.

6. The cement sheath seepage corrosion and mechanical performance evaluation device according to claim 1, characterized in that: The simulated formation is preferably processed from outcrop rock samples according to actual formation data or uses artificial rock samples close to actual formation parameters.

7. A method for evaluating the seepage corrosion and mechanical properties of cement sheath using the device of claim 1, 2, 3, 4, 5 or 6, comprising the following steps in sequence: (1) Use epoxy resin to fix the simulated formation in the metal cylinder. After the epoxy resin is cured to form an effective seal, the center rod, simulated casing, and metal cylinder containing the simulated formation are installed on the base respectively; (2) Inject cement slurry into the space between the simulated formation and the simulated casing, install the upper cover and tighten it with a nut; (3) Open the high-pressure oil injection system to inject high-temperature resistant oil into the annulus between the simulated casing and the center rod, open the formation water injection system to inject formation water into the simulated formation, and close the back pressure valve when liquid flows out of the oil outlet and the discharge port; set the back pressure valve pressure, raise the temperature control device to the required temperature through the control system, start curing the cement ring, and form a simulated casing-cement ring combination; (4) After the maintenance is completed, open the acid corrosive gas injection system to introduce acid corrosive gas H2S / CO2 into the corrosion and testing system for corrosion testing; (5) After the corrosion is completed, the control system and the high-pressure oil injection system are used to inject pressure into the annulus between the simulated casing and the center rod at a certain rate, so as to form a pressure difference between the simulated casing-cement sheath assembly and the simulated formation. The radial displacement meter is used to record the deformation displacement of the simulated casing-cement sheath assembly under the pressure difference, collect data and draw stress-strain curves to analyze the mechanical properties of the cement sheath. (6) Cool down and reduce pressure, unscrew the nut, open the upper cover and remove the cement ring, test the cement ring, simulate the corrosion of the formation-cement ring interface, and analyze the corrosion law of the cement ring in the H2S / CO2 corrosion environment.

8. The method according to claim 7, characterized in that According to the needs of experimental simulation conditions, maintenance and corrosion can be carried out simultaneously.

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