Visual preparation method and system of sandstone containing weak layers based on EICP technology

Abstract

The present invention discloses a method and system for visually preparing sandstone containing weak layers based on EICP technology. This method belongs to the field of carbon sequestration technology and solves the problem of high difficulty in obtaining sandstone samples from target strata in carbon sequestration research. The method specifically comprises: filling quartz sand inside a core holder to form a sand sample; increasing the axial pressure and confining pressure of the core holder; mixing a prepared urease solution and a cementing solution to obtain a mixed solution; using a double-cylinder displacement pump to drive the mixed solution into the core holder to cement the sand sample; and finally using formation water to displace the mixed solution in the sand sample to obtain saturated carbonate-cemented sandstone containing weak layers. In the present invention, the influence of formation stress on the sample cementation process is simulated by increasing the axial pressure and confining pressure of the core holder, which is more consistent with the natural sandstone sampling process. A large amount of carbonate sandstone containing weak layers can be quickly obtained in a short period of time, saving the economic and time costs of obtaining research samples.

Description

Technical Field

[0001] The present invention relates to the field of carbon sequestration technology, and in particular to a method and system for visually preparing sandstone containing weak layers based on EICP technology. Background Art

[0002] The massive extraction and use of fuel and energy resources has resulted in excessive CO2 emissions, dramatically increasing atmospheric CO2 concentrations and contributing to increasingly serious environmental problems such as global warming and the greenhouse effect. Carbon capture and storage (CCS) can achieve decarbonization and carbon neutrality without changing the current energy and industrial architecture. It is an effective means of stabilizing atmospheric greenhouse gas concentrations and mitigating global warming. CO2 geological storage involves compressing captured CO2 and injecting it into deep formations, isolating it from the atmosphere for long periods of time and reducing direct CO2 emissions into the atmosphere.

[0003] Current submarine carbon storage projects target a significant portion of target reservoirs primarily composed of carbonate-cemented sandstones. Carbonate-cemented sandstones are weak and have a loose structure, making field sampling both costly and difficult to obtain. Furthermore, deep reservoir sandstone cements are heterogeneous, prone to the formation of weak interlayers. Therefore, a system and method for visually preparing carbonate-cemented sandstone containing weak interlayers under in situ stress is urgently needed. Summary of the Invention

[0004] In response to the shortcomings of the existing technology, the present invention provides a method and system for visually preparing sandstone containing weak layers based on EICP technology, which solves the problem of difficulty in obtaining sandstone samples from target strata in carbon sequestration research.

[0005] In the first aspect, in order to achieve the above-mentioned purpose, the technical solution adopted by the present invention is:

[0006] A visualization preparation method for sandstone containing weak layers based on EICP technology includes the following steps:

[0007] S1: Prepare quartz sand and fill the core holder with the quartz sand to form a sand sample;

[0008] S2: Use axial pressure pump and confining pressure pump to increase the axial pressure and confining pressure of the core holder;

[0009] S3: Scan the sand sample in the core holder using a CT scanning system, and use the scan result as the initial state;

[0010] S4: preparing a urease solution and a cementing solution; and mixing the urease solution and the cementing solution to obtain a mixed solution;

[0011] S5: The mixed solution is placed in a piston container and driven into the core holder using a double-cylinder displacement pump to cement the sand sample; the temperature of the sand sample is increased using a zoned temperature controller in the core holder;

[0012] S6: After the sand sample is cemented, the mixed solution in the core holder is driven into the liquid storage tank;

[0013] S7: Scan the cemented sand sample using a CT scanning system and calculate the carbonate cement content in the sand sample;

[0014] S8: Repeat S5 to S7 until the carbonate cement content in the sand sample reaches the target value, and then enter S9;

[0015] S9: Formation water is prepared according to the target formation, and the mixed solution in the sand sample is displaced by the formation water to obtain saturated carbonate-cemented sandstone containing a weak layer.

[0016] In this scheme, an axial pressure pump and a confining pressure pump are used to increase the axial pressure and confining pressure in the core holder to simulate the influence of formation stress on the cementation process of the sand sample, and to truly simulate the formation conditions of natural sandstone. The zoned temperature controller of the core holder is used to control the formation temperature of the sand sample. A large amount of carbonate sandstone containing weak layers can be quickly obtained in a short period of time, saving the economic and time costs of obtaining research samples.

[0017] Furthermore, in S2, the axial pressure pump and the confining pressure pump gradually increase the axial pressure and confining pressure of the core holder by 0.2 MPa per stage to the target pressure value; and then maintain it for 24 hours.

[0018] In this scheme, the stress state in the formation is relatively complex, usually a superposition of stresses and strains in multiple directions; the method of applying axial pressure and confining pressure step by step can fully superimpose the two stresses, more realistically simulate the complex stress state in the formation, and thus better reflect the actual situation in the formation.

[0019] Furthermore, S4 includes:

[0020] S401: preparing a urease solution and adjusting the activity of the urease solution to 20 kU; storing the urease solution at 4°C;

[0021] S402: Mixing calcium chloride solution, urea solution, and skimmed milk powder solution in a volume ratio of 0.67:1:1 to obtain a cementing solution; and storing the cementing solution at 4° C.;

[0022] S403: mixing the prepared urease solution and the cementing solution in a volume ratio of 1:4 to obtain a mixed solution; and storing the mixed solution in an environment of 4°C.

[0023] In this scheme, the urease solution can catalyze the hydrolysis of urea to produce carbonic acid, and the carbonic acid reacts with the calcium chloride solution to generate calcium carbonate precipitate to fill the pores of the sand sample and achieve cementation.

[0024] Furthermore, S5 includes:

[0025] S501: Connect the dual-cylinder displacement pump and the piston container, and then connect the piston container to the liquid inlet of the core holder;

[0026] S502: Filling the mixed solution into the piston container;

[0027] S503: A dual-cylinder displacement pump injects water into the piston container. The water pushes the piston to move. During the movement of the piston, the mixed solution is injected into the core holder to cement the sand sample. The injection volume of the mixed solution should be no less than 1 times the pore volume.

[0028] S504: Control the first temperature zone of the core holder to heat up to 25-30°C by using a zone temperature controller; control the second temperature zone of the core holder to heat up to 10°C by using a zone temperature controller; control the third temperature zone of the core holder to heat up to 25-30°C by using a zone temperature controller; and let it stand for 6 hours after the temperature stabilizes.

[0029] Furthermore, S6 includes:

[0030] S601: Connect the double-cylinder displacement pump to the fluid inlet of the core holder;

[0031] S602: A double-cylinder displacement pump is used to inject gas into the core holder, and the gas drives the mixed solution in the core holder into the liquid storage tank.

[0032] Furthermore, the target value of the carbonate cement content in S8 is 11% to 14%.

[0033] Furthermore, S9 includes:

[0034] S901: Connect the dual-cylinder displacement pump and the piston container, and connect the piston container to the liquid inlet of the core holder;

[0035] S902: adding formation water prepared according to the target formation into the piston container;

[0036] S903: Use a double-cylinder displacement pump to inject the formation water in the piston container into the core holder to displace the mixed solution in the core holder to obtain saturated carbonate-cemented sandstone containing weak layers; the displacement volume of the formation water should be no less than 10 times the pore volume.

[0037] In this scheme, a double-cylinder displacement pump is used to displace formation water prepared according to the target formation into the sandstone, simulating carbonate-cemented sandstone with weak layers and properties similar to those of the target formation sandstone, thereby achieving rapid preparation of sandstone samples in the target formation.

[0038] In the second aspect, the present invention is based on the visual preparation method of sandstone containing weak layers based on EICP technology provided in the first aspect, and provides a visual preparation system of sandstone containing weak layers based on EICP technology, including a dual-cylinder displacement pump, a piston container, a core clamp, a CT scanning system, a pressurizing component and a zoned temperature controller; the dual-cylinder displacement pump is connected to the piston container through a pipeline; the piston container is connected to the liquid inlet of the core clamp through a grouting pipe, and the liquid outlet of the core clamp is connected to the liquid storage tank through a discharge pipe; the pressurizing component is connected to the core clamp; the zoned temperature controller is installed on the outside of the core clamp, and can adjust the temperature of different areas in the core clamp; the core clamp is arranged in the CT scanning system.

[0039] In this scheme, a visualization preparation system for carbonate-cemented sandstone containing weak layers under in-situ stress is constructed by using devices such as a dual-cylinder displacement pump, a core clamp, a pressurizing assembly, a CT scanning system, and a zoned temperature controller. This system realizes the zoned cementation of carbonate under high stress conditions, enables quantitative control of the carbonate cement content, and visualizes the entire preparation process, which has broad application prospects.

[0040] Furthermore, the pressurizing assembly includes an axial pressure pump and a confining pressure pump. The axial pressure pump is connected to the axial pressure interface of the core holder through a pipeline; the confining pressure pump is connected to the confining pressure interface of the core holder through a pipeline.

[0041] Furthermore, a drain valve is provided on the drain pipe.

[0042] The beneficial effects of the present invention are:

[0043] The present invention provides a visualization method for preparing sandstone containing weak layers based on EICP technology. The temperature of sand sample cementation is controlled by a zoned temperature controller of a core holder. The axial pressure and confining pressure provided by an axial pressure pump and a confining pressure pump are used to simulate layer stress, thereby simulating the natural conditions for the formation of sandstone in the target formation. This makes the properties of the prepared sand sample more consistent with the sandstone mined from the target formation. A dual-cylinder displacement pump is used to drive the mixed solution into the sand sample for cementation. After each cementation, a CT scanning system is used to detect the carbonate cement content in different areas of the sand sample, thereby realizing visualization of the preparation process. Formation water is driven into the sand sample to obtain carbonate sandstone containing weak layers. A large number of representative carbonate sandstone containing weak layers can be prepared in a short period of time, saving costs. BRIEF DESCRIPTION OF THE DRAWINGS

[0044] Figure 1This is a structural schematic diagram of a visualization preparation system for sandstone containing weak layers based on EICP technology of the present invention.

[0045] Reference numerals:

[0046] 1. Axial pressure pump; 2. Dual-cylinder displacement pump; 3. Piston container; 5. CT scanning system; 6. Zone temperature controller; 7. First temperature zone; 8. Second temperature zone; 9. Third temperature zone; 10. Sand sample; 11. Core holder; 12. Liquid storage tank; 13. Confining pressure pump; 14. Drain valve; DETAILED DESCRIPTION

[0047] The present invention will be further described below with reference to the accompanying drawings and specific embodiments. Specific embodiments of the present invention are described below to facilitate understanding of the present invention by those skilled in the art. However, it should be understood that the present invention is not limited to the scope of the specific embodiments. For those skilled in the art, as long as various changes are within the spirit and scope of the present invention as defined and determined by the appended claims, these changes are obvious, and all inventions and creations utilizing the concepts of the present invention are protected.

[0048] Example 1

[0049] like Figure 1 As shown, this embodiment provides a visual preparation method for sandstone containing weak layers based on EICP technology. The method simulates the natural conditions for the formation of sandstone in the target formation and can quickly prepare carbonate cemented sandstone containing weak layers with properties similar to those of sandstone mined in the target formation. The method specifically includes the following steps:

[0050] S1: Quartz sand is screened according to the target particle size, washed with ultrapure water, and then dried in an oven at 105°C for 24 hours;

[0051] The dried quartz sand is filled into the core holder 11 in three times to form a sand sample 10; the sand sample 10 is a cylinder with a diameter of 25 mm and a height of 50 mm; before filling, the required quartz sand mass can be estimated based on the quartz sand density and the volume of the sand sample 10 after filling. The quartz sand density can be calculated as 1.60 g / cm3.

[0052] S2: The axial pressure and confining pressure of the core holder 11 are gradually increased by 0.2 MPa per step using the axial pressure pump 1 and the confining pressure pump 13 to simulate the complex stress state in the formation; until the axial pressure and confining pressure reach the target pressure value, and then maintained for 24 hours; the target pressure value is 14-16 MPa.

[0053] S3: Scan the sand sample 10 in the core holder 11 using the CT scanning system 5, and use the scanning result as the initial state.

[0054] S4: preparing a urease solution and a cementing solution; and mixing the urease solution and the cementing solution to obtain a mixed solution; specifically comprising:

[0055] S401: preparing a urease solution and adjusting the activity of the urease solution to 20 kU; storing the urease solution at 4°C;

[0056] S402: Mixing calcium chloride solution, urea solution, and skimmed milk powder solution in a volume ratio of 0.67:1:1 to obtain a cementing solution; and storing the cementing solution at 4° C.;

[0057] S403: mixing the prepared urease solution and the cementing solution in a volume ratio of 1:4 to obtain a mixed solution; and storing the mixed solution in an environment of 4°C.

[0058] S5: The mixed solution is loaded into the piston container 3, and the mixed solution is driven into the core holder 11 by the double-cylinder displacement pump 2 to cement the sand sample 10; and the temperature of the sand sample 10 is increased by the zone temperature controller 6 of the core holder 11. Specifically, the steps include:

[0059] S501: Connect the dual-cylinder displacement pump 2 and the piston container 3, and then connect the piston container 3 to the liquid inlet of the core holder 11;

[0060] S502: The mixed solution is loaded into the piston container 3;

[0061] S503: The dual-cylinder displacement pump 2 injects water into the piston container 3. The water pushes the piston to move. During the movement of the piston, the mixed solution is injected into the core holder 11 to cement the sand sample 10. The injection rate of the mixed solution is 2 ml / min, and the injection volume of the mixed solution is 1.1 times the pore volume.

[0062] S504: Control the first temperature zone 7 of the core holder 11 to heat up to 25-30°C through the zone temperature controller 6; control the second temperature zone 8 of the core holder 11 to heat up to 10°C through the zone temperature controller 6; control the third temperature zone 9 of the core holder 11 to heat up to 25-30°C through the zone temperature controller 6; and let it stand for 6 hours after the temperature stabilizes.

[0063] S6: After the sand sample 10 is cemented, the mixed solution in the core holder 11 is driven into the liquid storage tank 12; specifically, the steps include:

[0064] S601: Connect the dual-cylinder displacement pump 2 to the liquid inlet of the core holder 11;

[0065] S602 : using the double-cylinder displacement pump 2 to inject gas into the core holder 11 , and the gas drives the mixed solution in the core holder 11 into the liquid storage tank 12 .

[0066] S7: Scanning the cemented sand sample 10 using the CT scanning system 5 and calculating the carbonate cement content in the sand sample 10;

[0067] The CT scanning system 5 may adopt the Sanying nanoVoxel-4000 series high-penetration CT system.

[0068] S8: Repeat S5 to S7 until the carbonate cement content in the sand sample 10 reaches the target value, and then proceed to S9; the target value of the carbonate cement content is 11% to 14%.

[0069] S9: Formation water is prepared according to the target formation, and the mixed solution in the sand sample 10 is displaced by the formation water to obtain saturated carbonate-cemented sandstone containing a weak layer; specifically, the following steps are included:

[0070] S901: Connect the dual-cylinder displacement pump 2 and the piston container 3, and connect the piston container 3 to the liquid inlet of the core holder 11;

[0071] S902: Adding formation water prepared according to the target formation into the piston container 3;

[0072] S903: Use the double-cylinder displacement pump 2 to inject the formation water in the piston container 3 into the core holder 11, displace the mixed solution in the core holder 11, and obtain saturated carbonate-cemented sandstone containing a weak layer; the displacement volume of the formation water should be no less than 10 times the pore volume.

[0073] In this embodiment, the axial pressure pump 1 and the confining pressure pump 13 are used to increase the axial pressure and confining pressure in the core holder 11 to simulate the influence of formation stress on the cementation process of the sand sample 10, and truly simulate the formation conditions of natural sandstone; the zone temperature controller 6 of the core holder 11 is used to control the formation temperature of the sand sample 10; a large amount of carbonate sandstone containing weak layers can be quickly obtained in a short time, saving the economic cost and time cost of obtaining research samples.

[0074] Example 2

[0075] like Figure 1 As shown, this embodiment provides a visual preparation system for sandstone containing weak layers based on the EICP technology based on the visual preparation method for sandstone containing weak layers provided in Example 1. The preparation system can realize carbonate zoning cementation under high stress conditions and quantitative control of carbonate cement content; the system specifically includes:

[0076] Dual-cylinder displacement pump 2, piston container 3, core holder 11, CT scanning system 5, pressurizing assembly, liquid storage tank 12 and zone temperature controller 6;

[0077] Among them, the pressure control range of the dual-cylinder displacement pump 2 is 0-30 MPa, and the minimum control flow rate is 0.001 ml / min; the dual-cylinder displacement pump 2 is connected to the piston container 3 through a pipeline; the piston container 3 is connected to the liquid inlet of the core clamp 11 through a grouting pipe, and the liquid outlet of the core clamp 11 is connected to the liquid storage tank 12 through a discharge pipe; the pressurizing assembly is connected to the core clamp 11; the zone temperature controller 6 is installed on the outside of the core clamp 11 and can adjust the temperature of different areas in the core clamp 11; the core clamp 11 is set in the CT scanning system 5.

[0078] The pressurizing assembly includes an axial pressure pump 1 and a confining pressure pump 13. The pressure control range of the axial pressure pump 1 and the confining pressure pump 13 is 0-50 MPa, and the minimum control pressure is 0.01 MPa; the axial pressure pump 1 is connected to the axial pressure interface of the core holder 11 through a pipeline; the confining pressure pump 13 is connected to the confining pressure interface of the core holder 11 through a pipeline.

[0079] A discharge valve 14 is provided on the discharge pipe.

[0080] Those skilled in the art will appreciate that the embodiments herein are intended to help readers understand the principles of the present invention, and it should be understood that the scope of protection of the present invention is not limited to such specific descriptions and embodiments. Those skilled in the art can make various other specific variations and combinations based on the technical teachings disclosed in the present invention without departing from the essence of the present invention, and such variations and combinations are still within the scope of protection of the invention.

Claims

1. A visualization preparation method for sandstone containing weak layers based on EICP technology, characterized in that: The following steps are involved: S1: Prepare quartz sand and fill the core holder (11) with the quartz sand to form a sand sample (10); S2: using the axial pressure pump (1) and the confining pressure pump (13) to increase the axial pressure and confining pressure of the core holder (11); the axial pressure pump (1) and the confining pressure pump (13) gradually increase the axial pressure and confining pressure of the core holder (11) by 0.2 MPa per stage to the target pressure value; and then maintain it for 24 hours; S3: Scan the sand sample (10) in the core holder (11) using a CT scanning system (5), and use the scanning result as the initial state; S4: preparing a urease solution and a cementing solution; and mixing the urease solution and the cementing solution to obtain a mixed solution; S5: The mixed solution is placed in a piston container (3), and the mixed solution is driven into the core holder (11) by a double-cylinder displacement pump (2) to cement the sand sample (10); and the temperature of the sand sample (10) is increased by a zoned temperature controller (6) of the core holder (11); S6: After the sand sample (10) is cemented, the mixed solution in the core holder (11) is driven into the liquid storage tank (12); S7: Scan the cemented sand sample (10) using a CT scanning system (5) and calculate the carbonate cement content in the sand sample (10); S8: Repeat S5 to S7 until the carbonate cement content in the sand sample (10) reaches the target value, and then enter S9; S9: Formation water is prepared according to the target formation, and the mixed solution in the sand sample (10) is displaced by the formation water to obtain saturated carbonate cemented sandstone containing a weak layer; An axial pressure pump (1) and a confining pressure pump (13) are used to increase the axial pressure and confining pressure in the core holder (11) to simulate the influence of formation stress on the cementation process of the sand sample, thereby truly simulating the formation conditions of natural sandstone; a zone temperature controller (6) of the core holder (11) is used to control the formation temperature of the sand sample; a large amount of carbonate sandstone containing weak layers can be quickly obtained in a short time, saving the economic cost and time cost of obtaining research samples; The S4 includes: S401: Prepare a urease solution and adjust the activity of the urease solution to 20 kU; store the urease solution at 4°C; the urease solution can catalyze the hydrolysis of urea to produce carbonate ions, which react with the calcium chloride solution to form calcium carbonate precipitates that fill the pores of the sand sample, thereby achieving cementation; S402: Mixing calcium chloride solution, urea solution, and skimmed milk powder solution in a volume ratio of 0.67:1:1 to obtain a cementing solution; and storing the cementing solution at 4° C.; S403: mixing the prepared urease solution and the cementing solution in a volume ratio of 1:4 to obtain a mixed solution; and storing the mixed solution at 4° C.; The S5 includes: S501: Connect the double-cylinder displacement pump (2) and the piston container (3), and then connect the piston container (3) to the liquid inlet of the core holder (11); S502: The mixed solution is placed into the piston container (3); S503: The dual-cylinder displacement pump (2) injects water into the piston container (3), and the water pushes the piston to move. During the movement of the piston, the mixed solution is injected into the core holder (11) to cement the sand sample (10); S504: controlling the first temperature zone (7) of the core holder (11) to heat up to 25-30°C by using the zone temperature controller (6); controlling the second temperature zone (8) of the core holder (11) to heat up to 10°C by using the zone temperature controller (6); controlling the third temperature zone (9) of the core holder (11) to heat up to 25-30°C by using the zone temperature controller (6); and allowing the core holder to stand for 6 hours after the temperature stabilizes. The S9 includes: S901: Connect the double-cylinder displacement pump (2) and the piston container (3), and connect the piston container (3) to the liquid inlet of the core holder (11); S902: Adding formation water prepared according to the target formation into the piston container (3); S903: A double-cylinder displacement pump (2) is used to inject the formation water in the piston container (3) into the core holder (11), displacing the mixed solution in the core holder (11) to obtain saturated carbonate cemented sandstone containing a weak layer; wherein the displacement volume is 10 times the pore volume.

2. The visualization preparation method of sandstone containing weak layers based on EICP technology according to claim 1 is characterized in that: The S6 includes: S601: Connect the double-cylinder displacement pump (2) to the liquid inlet of the core holder (11); S602: A double-cylinder displacement pump (2) is used to inject gas into the core holder (11), and the gas drives the mixed solution in the core holder (11) into the liquid storage tank (12).

3. The visualization preparation method of sandstone containing weak layers based on EICP technology according to claim 2 is characterized in that: The target value of the carbonate cement content in the S8 is 11%~14%.

4. A preparation system for implementing the visualization preparation method of sandstone containing weak layers based on EICP technology according to any one of claims 1 to 3, characterized in that: The invention comprises a double-cylinder displacement pump (2), a piston container (3), a core holder (11), a CT scanning system (5), a pressurizing component and a partition temperature controller (6); the double-cylinder displacement pump (2) is connected to the piston container (3) through a pipeline; the piston container (3) is connected to the liquid inlet of the core holder (11) through a grouting pipe, and the liquid outlet of the core holder (11) is connected to a liquid storage tank (12) through a discharge pipe; the pressurizing component is connected to the core holder (11); the partition temperature controller (6) is installed outside the core holder (11); and the core holder (11) is arranged in the CT scanning system (5).

5. The preparation system of the EICP-based visualization preparation method for sandstone containing weak layers according to claim 4 is characterized by: The pressurizing assembly comprises an axial pressure pump (1) and a confining pressure pump (13); the axial pressure pump (1) is connected to the axial pressure interface of the core holder (11) via a pipeline; and the confining pressure pump (13) is connected to the confining pressure interface of the core holder (11) via a pipeline.

6. The preparation system of the EICP-based visualization preparation method for sandstone containing weak layers according to claim 5, characterized in that: The liquid discharge pipe is provided with a liquid discharge valve (14).

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