Visual preparation method and system for sandstone containing soft layer based on EICP (Enhanced Inductively Coupled Plasma) technology

Abstract

The invention discloses a weak layer-containing sandstone visual preparation method and system based on an EICP technology, belongs to the technical field of carbon sequestration, and solves the problem of high difficulty in obtaining a sandstone sample of a target stratum in carbon sequestration research. The method specifically comprises the following steps: filling quartz sand into a core holder to form a sand sample; the axial pressure and the confining pressure of the core holder are increased; mixing the prepared urease solution and the cementing solution to obtain a mixed solution; driving the mixed solution into a rock core holder by adopting a double-cylinder displacement pump, and cementing the sand sample; and finally displacing the mixed solution in the sand sample by using formation water to obtain the saturated soft-layer-containing carbonate cemented sandstone. According to the invention, the axial pressure and the confining pressure of the core holder are increased to simulate the influence of the stratum stress on the sample cementing process, which is more in line with the natural sandstone sample forming process; a large amount of soft-layer-containing carbonate sandstone can be rapidly obtained in a short time, and the economic cost and the time cost for obtaining research samples are saved.

Description

Technical Field

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

[0002] Large amounts of fuel energy extraction and use cause CO 2 Excessive emissions, atmospheric CO 2 The concentration has increased sharply, leading to increasingly serious environmental problems such as global warming and greenhouse effect. Carbon capture and geological storage (CCS) can achieve low-carbon technology and carbon neutrality technology without changing the current energy and industrial structure. It is an effective means to stabilize the concentration of greenhouse gases in the atmosphere and alleviate the problem of global warming. 2 Geological storage is the process of storing captured CO 2 Compressed and injected into deep formations to achieve long-term isolation from the atmosphere, thereby reducing CO 2 Directly released into the atmosphere.

[0003] At present, in the seabed carbon storage project, there are non-negligible sandstone reservoirs mainly cemented by carbonates in the target reservoirs; the strength of carbonate-cemented sandstone is weak and the structure is loose. On-site sampling is not only costly but also difficult to obtain a large number of representative samples. At the same time, the cementation of sandstone in deep reservoirs is uneven and prone to forming weak interlayers. Therefore, it is urgent to propose a visualization preparation system and method for carbonate-cemented sandstone with weak layers under in-situ stress. Summary of the invention

[0004] In view of the deficiencies in the prior art, 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 of 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: using an axial pressure pump and a 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 scanning 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 loaded into a piston container, and the mixed solution is driven into the core holder by a double-cylinder displacement pump to cement the sand sample; and the temperature of the sand sample is increased by a zoned temperature controller of 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 sand samples and 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 time, saving the economic cost and time cost of obtaining research samples.

[0017] Furthermore, in S2, the axial pressure pump and the confining pressure pump gradually increase the axial pressure and the confining pressure of the core holder to the target pressure value by 0.2 MPa per stage, 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 make the two stresses fully superimposed, 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 in an environment of 4°C;

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

[0022] S403: Mix the prepared urease solution and the cementing solution in a volume ratio of 1:4 to obtain a mixed solution; and store 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 precipitation to fill the pores of the sand sample to achieve cementation.

[0024] Furthermore, S5 includes:

[0025] S501: Connect the double-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: The dual-cylinder displacement pump injects water into the piston container, and 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 through the zone temperature controller; control the second temperature zone of the core holder to heat up to 10°C through the zone temperature controller; control the third temperature zone of the core holder to heat up to 25-30°C through the 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 liquid 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 double-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 similar in properties to the target formation sandstone, thereby achieving rapid preparation of sandstone samples in the target formation.

[0038] In the second aspect, the present invention provides a visual preparation system for sandstone containing weak layers based on the EICP technology based on the first aspect, including a double-cylinder displacement pump, a piston container, a core clamp, a CT scanning system, a pressurizing component and a zoned temperature controller; the double-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 means of devices such as a dual-cylinder displacement pump, a core clamp, a pressurizing assembly, a CT scanning system, and a zoned temperature controller. This realizes the zoned cementation of carbonate under high stress conditions, and can achieve quantitative control of the carbonate cement content. The entire preparation process is visualized, 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 discharge valve is provided on the discharge pipe.

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

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

[0044] Figure 1This is a schematic diagram of the structure of a visualized preparation system for sandstone containing weak layers based on the 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 is further described below in conjunction with the accompanying drawings and specific embodiments. The specific implementation of the present invention is described below to facilitate the understanding of the present invention by those skilled in the art, but it should be clear that the present invention is not limited to the scope of the specific implementation. For those of ordinary skill in the art, as long as various changes are within the spirit and scope of the present invention defined and determined by the attached claims, these changes are obvious, and all inventions and creations using the concept 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, which simulates the natural conditions for the formation of sandstone in the target stratum and can quickly prepare carbonate cemented sandstone containing weak layers with properties similar to those of sandstone mined in the target stratum; specifically, the following steps are included:

[0050] S1: quartz sand is screened according to the target particle size, the screened quartz sand is 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 according to the quartz sand density and the volume of the sand sample 10 after filling, and 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 stage 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; wherein 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 in an environment of 4°C;

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

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

[0058] S5: putting the mixed solution into the piston container 3, and driving the mixed solution into the core holder 11 by the double-cylinder displacement pump 2 to cement the sand sample 10; and raising the temperature of the sand sample 10 by the zone temperature controller 6 of the core holder 11; specifically including:

[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: Fill the mixed solution into the piston container 3;

[0061] 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; wherein 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 comprising:

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

[0065] S602: injecting gas into the core holder 11 using the double-cylinder displacement pump 2, 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 enter S9; wherein 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 process includes:

[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 weak layers; 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, through which carbonate zoning cementation under high stress conditions can be achieved, and the content of carbonate cement can be quantitatively controlled; it specifically includes:

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

[0077] Among them, the pressure control range of the double-cylinder displacement pump 2 is 0-30MPa, and the minimum control flow rate is 0.001ml / min; 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 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 component 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 0-50MPa, and the minimum control pressure is 0.01MPa; the axial pressure pump 1 is connected to the axial pressure interface of the core clamp 11 through a pipeline; the confining pressure pump 13 is connected to the confining pressure interface of the core clamp 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 should be understood that the protection scope of the present invention is not limited to such specific statements and embodiments. Those skilled in the art can make various other specific variations and combinations that do not deviate from the essence of the present invention based on the technical revelations disclosed by the present invention, and these variations and combinations are still within the protection scope 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: preparing quartz sand and filling 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); S3: Scan the sand sample (10) in the core holder (11) using a CT scanning system (5), and use the scanning result as an 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 loaded into the 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 zone 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: Scanning the cemented sand sample (10) using a CT scanning system (5) and calculating 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.

2. The method for visualizing preparation of sandstone containing weak layers based on EICP technology according to claim 1, characterized in that: In S2, the axial pressure pump (1) and the confining pressure pump (13) gradually increase the axial pressure and confining pressure of the core holder (11) to the target pressure value by 0.2 MPa per stage, and then maintain the pressure for 24 hours.

3. The visualization preparation method of sandstone containing weak layers based on EICP technology according to claim 2 is characterized in that: The S4 includes: S401: preparing a urease solution and adjusting the activity of the urease solution to 20 kU; storing the urease solution in an environment of 4°C; S402: mixing the calcium chloride solution, the urea solution and the skimmed milk powder solution at a volume ratio of 0.67:1:1 to obtain a cementing solution; storing the cementing solution in an environment of 4° C.; S403: Mix the prepared urease solution and the cementing solution in a volume ratio of 1:4 to obtain a mixed solution; and store the mixed solution in an environment of 4°C.

4. The method for visualizing and preparing sandstone containing weak layers based on EICP technology according to claim 3 is characterized in that: The S5 includes: S501: Connecting the double-cylinder displacement pump (2) and the piston container (3), and then connecting the piston container (3) to the liquid inlet of the core holder (11); S502: Filling the mixed solution 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 means of the zone temperature controller (6); controlling the second temperature zone (8) of the core holder (11) to heat up to 10°C by means of the zone temperature controller (6); controlling the third temperature zone (9) of the core holder (11) to heat up to 25-30°C by means of the zone temperature controller (6); and allowing to stand for 6 hours after the temperature stabilizes.

5. The method for visualizing and preparing sandstone containing weak layers based on EICP technology according to claim 4 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).

6. The method for visualizing and preparing sandstone containing weak layers based on EICP technology according to claim 5 is characterized in that: The target value of the carbonate cement content in the S8 is 11% to 14%.

7. The method for visualizing and preparing sandstone containing weak layers based on EICP technology according to claim 5 is characterized in that: 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: Using a double-cylinder displacement pump (2), the formation water in the piston container (3) is injected 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.

8. A preparation system for implementing the visualized preparation method of sandstone containing weak layers based on EICP technology according to any one of claims 1 to 7, characterized in that: The invention comprises a double-cylinder displacement pump (2), a piston container (3), a core clamp (11), a CT scanning system (5), a pressurizing component and a zoned temperature controller (6); the double-cylinder displacement pump (2) is connected to the piston container (3) via a pipeline; the piston container (3) is connected to the liquid inlet of the core clamp (11) via a grouting pipe, and the liquid outlet of the core clamp (11) is connected to a liquid storage tank (12) via a discharge pipe; the pressurizing component is connected to the core clamp (11); the zoned temperature controller (6) is installed outside the core clamp (11); and the core clamp (11) is arranged in the CT scanning system (5).

9. The preparation system of the visualized preparation method of sandstone containing weak layers based on EICP technology according to claim 8 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.

10. The preparation system of the visualized preparation method of sandstone containing weak layers based on EICP technology according to claim 9, characterized in that: The liquid discharge pipe is provided with a liquid discharge valve (14).

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