Testing device and method for obtaining water exchange capacity between fracture and rock matrix

Abstract

The invention provides a test device and method for obtaining the water exchange capacity between a fracture and a rock matrix. The test device comprises a sample chamber, a lower rock matrix sample, an upper transparent cover plate, a water inlet diversion water tank, a water-oil separation system, a water supply system, an oil supply system, an air exhaust system and four high-speed camera systems. The lower rock matrix sample is arranged in the sample chamber, the upper transparent cover plate is arranged on the lower rock matrix sample, the lifting assembly is used for controlling the upper transparent cover plate to ascend and descend, the water inlet flow dividing water tank is arranged at the height of a corresponding single fracture, and a water outlet is formed in the bottom of the sample chamber. And the water-oil separation system is used for separating a water-oil mixture flowing out of the water outlet. By changing the opening degree of the fracture, the roughness of the fracture surface, the water pressure flowing into the fracture surface and the permeability of the matrix, the water exchange capacity under corresponding conditions can be calculated respectively. According to the device, rock drying, seepage test and saturation are integrated, and rock does not need to be moved for multiple times in the experiment process.

Description

Technical Field

[0001] The present invention relates to the technical field of rock seepage experiments, and particularly to a test device and method for obtaining the water exchange amount between fractures and rock matrix. Background Technique

[0002] Fractured rock mass mainly includes two media: fractures and rock matrix. Fractures are the main flow channels, so the permeability of the rock matrix is usually ignored in research. However, with the advancement of underground engineering and energy development towards deep earth, under the action of high in-situ stress, the permeability of fractures rapidly decays, and the proportion of the permeability of the rock matrix in the fractured rock mass gradually increases. Moreover, there is water exchange between fractures and the rock matrix. At this time, if the permeability of the rock matrix is still ignored, it may reduce the oil and gas extraction efficiency and even induce engineering accidents. Therefore, how to accurately obtain the water exchange process and water exchange amount between fractures and the rock matrix is crucial for ensuring the safety of underground engineering construction and improving the oil and gas resource extraction efficiency.

[0003] However, limited by the existing test equipment and methods, the water exchange between fractures and the rock matrix cannot be quantitatively calculated, and there is a lack of corresponding test equipment and calculation methods.

[0004] In summary, it is indeed necessary to provide a test device and method for quantitatively calculating the water exchange between the rock matrix and fracture water to solve the problem that it is currently impossible to quantitatively obtain the water exchange process and water exchange amount between fractures and the rock matrix.

[0005] Based on this, this case is born. Summary of the Invention

[0006] (1) Technical Problems to be Solved

[0007] Aiming at the deficiencies of the prior art, the present invention provides a test device and method for obtaining the water exchange amount between fractures and the rock matrix, and solves the problems put forward in the above background technique.

[0008] (2) Technical Solutions

[0009] To achieve the above object, the present invention is realized by the following technical solutions: An experimental method for obtaining the water exchange amount between fractures and rock matrix, the experimental device includes a sample chamber, a lower rock matrix sample, an upper transparent cover plate, an inlet water diversion tank, a water-oil separation system, a water supply system, an oil supply system, a gas extraction system, and four high-speed camera systems; the lower rock matrix sample is arranged in the sample chamber, the upper transparent cover plate is placed on the lower rock matrix sample, the lifting assembly is used to control the lifting of the upper transparent cover plate, the inlet water diversion tank is arranged at the height corresponding to a single fracture, the bottom of the sample chamber is provided with an outlet, the water-oil separation system is used to separate the water-oil mixture flowing out from the outlet and divert it into the corresponding water tank two and oil tank two, the water supply system and the oil supply system supply water and oil to the single fracture through the inlet water diversion tank, and an air extraction valve is arranged between the gas extraction system and the sample chamber;

[0010] The experimental method includes the following steps:

[0011] Step 1, place the lower rock matrix sample into the sample chamber;

[0012] Step 2, screw down the nut group on the top of the sample chamber to make the upper transparent cover plate move downward to fit with the lower rock matrix sample to form a single fracture, then inject dyed water into the single fracture through a water pump, and at the same time use the high-speed camera system to capture the seepage process of the dyed water in the single fracture and the process of the dyed water in the single fracture flowing into the lower rock matrix sample;

[0013] Step 3, the dyed water that does not enter the lower rock matrix sample will flow into the water-oil separator through the outlet, and by calculating the value of water tank two minus water tank one, the flow rate of the fracture flowing into the matrix at each time period can be calculated;

[0014] Step 4, screw the nut group on the top of the sample chamber to the topmost position, continue to inject dyed water into the rock through a water pump until the water surface is 20 mm higher than the top surface of the lower rock matrix sample, open the air extraction valve, start the vacuum air extraction system, and the vacuum pressure during air extraction needs to reach 100 kPa, and maintain this vacuum state until no bubbles occur, not less than 4 hours; place the lower rock matrix sample in the original sample chamber, take it out after standing for 4 hours under atmospheric pressure, and wipe off the excess water stains on the surface with a wet gauze;

[0015] Step 5, place the lower rock matrix sample into the sample chamber again, screw down the nut group on the top of the sample chamber to make the upper transparent cover plate move downward to fit with the lower rock matrix sample to form a single fracture, inject oil into the lower rock matrix sample through an oil pump, and use the high-speed camera system to photograph the process of the oil replacing the dyed water from the matrix into the fracture;

[0016] Step 6: The dyed water displaced by the oil and the oil seeping out from the crack will pass through the water outlet from the sample chamber. Through the water-oil separation system, the dyed water and the oil will enter the second water tank and the second oil tank respectively. By calculating the amounts of the two liquids respectively, the water exchange amount between the crack and the rock matrix can be quantitatively calculated.

[0017] Preferably, the water supply system includes a first water tank and a water pump, and the oil supply system includes a first oil tank and an oil pump. The first water tank and the first oil tank are respectively connected to the split water tank at the water inlet through the water pump and the oil pump.

[0018] Preferably, the lifting assembly is a nut group. The bolts of the nut group are threadedly connected to the top of the sample chamber and the bottom end is pivotally connected to the upper transparent cover plate.

[0019] Preferably, the sample chamber is rectangular parallelepiped-shaped, and visible transparent acrylic plates are installed on six sides. The two transparent side cover plates on both sides are connected to the upper transparent cover plate. When the nut group is screwed downwards, a single crack is formed by splicing. When the nut group is screwed upwards, the lower rock matrix sample can be water-saturated.

[0020] Preferably, only half of the rectangular rock core sample containing a through single crack is taken as the upper rock matrix sample, and the rough surface generated by the penetration is facing upwards.

[0021] Preferably, four high-speed camera systems are respectively distributed on the top, front, left and right of the rock sample for capturing the water exchange process between the crack and the rock matrix.

[0022] (III) Beneficial effects

[0023] The present invention provides a test device and method for obtaining the water exchange amount between a crack and a rock matrix, having the following beneficial effects:

[0024] 1. For the test device and method for obtaining the water exchange amount between a crack and a rock matrix, by changing the aperture of the crack, the roughness of the crack surface, the water pressure flowing into the crack surface, and the permeability of the matrix (i.e., the rock type), the water exchange amounts under corresponding conditions can be respectively calculated. This device integrates rock drying, seepage test, and saturation, and there is no need to move the rock multiple times during the experiment.

[0025] 2. For the test device and method for obtaining the water exchange amount between a crack and a rock matrix, while obtaining the water exchange amount between the crack and the rock matrix, the whole process of water exchange can be visually observed. All six sides of the device are acrylic glass, and 4 cameras are installed, which are respectively distributed on the top, front, left and right of the rock sample for capturing the water exchange process between the crack and the rock matrix. The computer in the data acquisition system is connected to the pressure pump and the high-speed camera through data lines to realize the automatic control of pressure and shooting, and at the same time automatically collect data such as pressure and flow rate. Description of the drawings

[0026] Figure 1 is the overall planar structure schematic diagram of the present invention;

[0027] Figure 2 is the axonometric drawing of the test chamber of the present invention;

[0028] Figure 3 is the longitudinal sectional view when the seepage test is carried out in the test chamber of the present invention;

[0029] Figure 4 is the transverse sectional view when the seepage test is carried out in the test chamber of the present invention;

[0030] Figure 5 is the longitudinal sectional view when the specimen saturation is carried out in the test chamber of the present invention;

[0031] Figure 6 is the transverse sectional view when the specimen saturation is carried out in the test chamber of the present invention;

[0032] Figure 7 is the curve diagram of the evolution of the water exchange amount between the fracture and the rock matrix of the present invention with the fracture aperture;

[0033] Figure 8 is the curve diagram of the evolution of the water exchange amount between the fracture and the rock matrix of the present invention with the fractal dimension;

[0034] Figure 9 is the curve diagram of the evolution of the water exchange amount between the fracture and the rock matrix of the present invention with time;

[0035] Figure 10 is the curve diagram of the evolution of the water exchange amount between the fracture and the rock matrix of the present invention with the matrix permeability.

[0036] In the figure: 1 specimen chamber, 2 lower rock matrix specimen, 3 upper transparent cover plate, 4 water inlet shunt water tank, 5 water-oil separation system, 601 water tank one, 602 oil tank one, 603 water tank two, 604 oil tank two, 7 pressure pump, 8 air extraction system, 9 air extraction valve, 10 nut group, 11 transparent side cover plate, 121 high-speed camera system one, 122 high-speed camera system two, 123 high-speed camera system three, 124 high-speed camera system four, 13 data acquisition system, 14 water outlet, 15 single fracture. Detailed implementation manners

[0037] The embodiment of the present invention provides a test device and method for obtaining the water exchange amount between a fracture and a rock matrix, as Figures 1-10As shown in the figure, the test device includes a specimen chamber 1, a lower rock matrix specimen 2, an upper transparent cover plate 3, an inlet water diversion tank 4, a water-oil separation system 5, a water supply system, an oil supply system, an air extraction system 8, four high-speed camera systems, and a data acquisition system 13. The water supply system includes a water tank 601 and a water pump 701, and the oil supply system includes an oil tank 602 and an oil pump 702.

[0038] The lower rock matrix specimen 2 is arranged in the specimen chamber 1, and the upper transparent cover plate 3 is placed on the lower rock matrix specimen 2. A lifting assembly is used to control the lifting of the upper transparent cover plate 3. The lifting assembly is a nut group 10. The bolts of the nut group 10 are threadedly connected to the top of the specimen chamber 1 and the bottom end is pivotally connected to the upper transparent cover plate 3. The upper transparent cover plate 3 is a transparent acrylic plate. By controlling the up and down movement of the upper transparent cover plate 3 through the nut group 10, when the nut group 10 is screwed downwards, a single fracture 15 is formed by splicing, so as to carry out a seepage experiment. When the nut group 10 is screwed upwards, the upper transparent cover plate 3 is separated from the lower rock matrix specimen 2, and the lower rock matrix specimen 2 can be water-saturated. At this time, the distance between the upper transparent cover plate 3 and the lower rock matrix specimen 2 is 30 mm.

[0039] The water tank 601 and the oil tank 602 are respectively connected to the inlet water diversion tank 4 through the water pump 701 and the oil pump 702. The water supply system and the oil supply system supply water and oil to the single fracture 15 through the inlet water diversion tank 4. The water tank 601 is filled with dyed water. By using the dyed water for the seepage experiment, the water exchange process between the fracture and the rock matrix can be visualized. The oil tank 602 is filled with edible oil. After the lower rock matrix specimen 2 is water-saturated, at this time, the edible oil in the oil tank 602 is evenly injected into the inlet water diversion tank 4 through the oil pump 702 and then enters the single fracture 15, and the water in the rock matrix can be exchanged out.

[0040] The inlet water diversion tank 4 is arranged at the height corresponding to the single fracture 15. An outlet 14 is arranged at the bottom of the specimen chamber 1. The water-oil separation system 5 is used to separate the water-oil mixture flowing out from the outlet 14 and divert it into the corresponding water tank 603 and oil tank 604. The water tank 603 is used to collect the water separated from the water-oil separation system 5. When calculating the water exchange amount from the fracture to the rock matrix, the value obtained by subtracting the water tank 601 from the water tank 603 is calculated. The oil tank 604 is used to collect the oil separated from the water-oil separation system 5. When calculating the water-oil exchange amount at each time point, the value of the water tank 603 and the value obtained by subtracting the oil tank 604 from the oil tank 602 can be used to calculate the water-oil exchange amount.

[0041] The sample chamber 1 is cuboid-shaped, with visible transparent acrylic plates on its six faces. The two transparent side covers 11 on both sides are connected to the upper transparent cover 3. When the nut group 10 is screwed downwards, a single fracture 15 is formed by splicing. When the nut group 10 is screwed upwards, the lower rock matrix sample 2 can be water-saturated. When the nut group 10 is screwed downwards for the seepage experiment, the transparent side covers 11 will drop. The width between the two transparent side covers 11 on both sides is exactly the width of the rock, ensuring that after the dyed water enters the sample chamber 1, the water flow all goes through the fracture of the lower rock matrix sample 2.

[0042] For the upper rock matrix sample 2, only half of the cuboid core sample containing the through single fracture is taken, with the rough surface generated by the penetration facing upwards. The sample chamber 1 is a cuboid box with transparent acrylic plates on all six faces, ensuring a vacuum environment.

[0043] When the nut group 10 on the top of the sample chamber 1 is screwed to the bottommost state where it cannot be screwed further, the fracture aperture is equal to 1 mm at this time. Every time the nut group 10 is loosened by one turn, the aperture will increase by 1 mm. Therefore, this device can change the fracture aperture between the fracture and the rock matrix to obtain the water exchange process and water exchange volume between the fracture and the rock matrix under different fracture apertures.

[0044] The water inlet shunt water tank 4 has three water inlets. After the incoming water flow pumps the dyed water in the water tank 1 601 into the water inlet shunt water tank 4 through the water pump 701, it then flows into the single fracture 15 formed by the lower rock matrix sample 2 and the upper transparent cover 3. The water flow rate will become stable before the water passes through the water inlet shunt water tank 4 and enters the single fracture 15 formed by the lower rock matrix sample 2 and the upper transparent cover 3.

[0045] The water pump 701 and the oil pump 702 are fully automatic booster pumps, which can change the water pressure of the dyed water entering the lower rock matrix sample 2. Therefore, this device can change the incoming water pressure of the fracture-rock matrix to obtain the water exchange process and water exchange volume between the fracture and the rock matrix under different water flow rates.

[0046] The four high-speed camera systems include the high-speed camera system one 121, the high-speed camera system two 122, the high-speed camera system three 123, and the high-speed camera system four 124. The four high-speed camera systems are respectively distributed on the top, front, left, and right of the rock sample, and are used to capture the water exchange process between the fracture and the rock matrix.

[0047] An air extraction valve 9 is provided between the air extraction system 8 and the sample chamber 1; the air extraction system 8 is used to evacuate the sample chamber 1 with this air extraction system 8 before the lower rock matrix sample 2 is saturated, so that the lower rock matrix 2 can be water-saturated. The air extraction valve 9 is only opened when the air extraction system 8 is extracting air, and is in the closed state at other times.

[0048] The computer in the data acquisition system 13 is connected to the pressure pump 7 and the high-speed camera through a data cable.

[0049] The test method includes the following steps:

[0050] Step 1: Place the lower rock matrix specimen 2 into the specimen chamber 1.

[0051] Step 2: Screw down the nut group 10 on top of the specimen chamber 1 to move the upper transparent cover plate 3 downward to fit with the lower rock matrix specimen 2 to form a single fracture 15. Then, inject dyed water into the single fracture 15 through the water pump 701. At the same time, use the high-speed imaging system to capture the seepage process of the dyed water in the single fracture 15 and the process of the dyed water in the single fracture 15 flowing into the lower rock matrix specimen 2.

[0052] Step 3: The dyed water that does not enter the lower rock matrix specimen 2 will flow into the water-oil separator 5 through the water outlet 14. By calculating the value of water tank two 603 minus water tank one 601, the flow rate of the fracture into the matrix at each time period can be calculated.

[0053] Step 4: Screw the nut group 10 on top of the specimen chamber 1 to the topmost position. Continue to inject dyed water into the rock through the water pump 701 until the water surface is 20 mm above the top surface of the lower rock matrix specimen 2. Open the air extraction valve 9 and start the vacuum extraction system 8. The vacuum pressure during extraction needs to reach 100 kPa, and maintain this vacuum state until no bubbles occur, for at least 4 hours. Place the lower rock matrix specimen 2 in the original specimen chamber 1, take it out after standing for 4 hours under atmospheric pressure, and wipe off the excess water stains on the surface with a wet gauze.

[0054] Step 5: Place the lower rock matrix specimen 2 into the specimen chamber 1 again. Screw down the nut group 10 on top of the specimen chamber 1 to move the upper transparent cover plate 3 downward to fit with the lower rock matrix specimen 2 to form a single fracture 15. Inject oil into the lower rock matrix specimen 2 through the oil pump 702, and use the high-speed camera system to photograph the process of the oil replacing the dyed water from the matrix into the fracture.

[0055] Step 6: The dyed water exchanged by the oil and the oil seeping out from the fracture will pass through the water outlet 14 from the specimen chamber 1. The dyed water and the oil will enter water tank two 603 and oil tank two 604 respectively through the water-oil separation system 5. By calculating the amounts of the two liquids respectively, the water exchange amount between the fracture and the rock matrix can be quantitatively calculated.

[0056] The water exchange amount between the fracture and the rock matrix with different fracture apertures obtained from the test is as Figure 7 shown. Seepage experiments were carried out at different fracture apertures. By changing the tightening length of the nut group 10, the fracture aperture size between the upper transparent cover plate 3 and the lower rock matrix specimen 2 was changed. Under the condition that other conditions remain unchanged, from Figure 7It can be observed that as the fracture aperture increases, the water exchange volume between the fracture and the rock matrix also gradually increases, and the increasing rate also gradually increases.

[0057] The water exchange volume between the fracture and the rock matrix with different fractal dimensions obtained from the experiment is as Figure 8 shown. Seepage experiments with different fractal dimensions were carried out. By changing the roughness of the fracture surface of the lower rock matrix specimen 2, under the condition that other conditions remain unchanged, from Figure 8 It can be observed that as the fractal dimension increases, the water exchange volume between the fracture and the rock matrix also gradually increases. When the fractal dimension is greater than 2.6, the increasing rate of the water exchange volume between the fracture and the rock matrix is faster than that when the fractal dimension is less than 2.6.

[0058] The water exchange volume between the fracture and the rock matrix at different times obtained from the experiment is as Figure 9 shown. Seepage experiments at different times were carried out. Under the condition that other conditions remain unchanged, from Figure 9 It can be observed that as time increases, the water exchange volume between the fracture and the rock matrix gradually increases. After 0.8 h, the value of the water exchange volume between the fracture and the rock matrix tends to be stable.

[0059] The water exchange volume between the fracture and the rock matrix with different matrix permeabilities obtained from the experiment is as Figure 10 shown. Seepage experiments with different matrix permeabilities were carried out. Under the condition that other conditions remain unchanged, only the type of rock was changed, and three kinds of rock samples with different permeabilities, namely limestone, sandstone, and mudstone, were used for the experiment. From Figure 10 It can be observed that as the matrix permeability increases, the water exchange volume between the fracture and the rock matrix gradually increases.

[0060] Although the embodiments of the present invention have been shown and described, for those of ordinary skill in the art, it can be understood that various changes, modifications, substitutions, and variations can be made to these embodiments without departing from the principles and spirit of the present invention. The scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. An experimental method for obtaining the amount of water exchange between fractures and rock matrix, characterized in that: The method adopts the following test device, which comprises a sample chamber (1), a lower rock matrix sample (2), an upper transparent cover plate (3), a water inlet diversion water tank (4), a water-oil separation system (5), a water supply system, an oil supply system, an air extraction system (8) and four high-speed camera systems; the lower rock matrix sample (2) is arranged in the sample chamber (1), the upper transparent cover plate (3) is placed on the lower rock matrix sample (2), the lifting component is used to control the lifting of the upper transparent cover plate (3), the water inlet diversion water tank (4) is used to control the lifting of the upper transparent cover plate (3), and the water inlet diversion water tank (5) is used to control the lifting of the upper transparent cover plate (3). The water flow box (4) is arranged at a height corresponding to the single fissure (15); a water outlet (14) is arranged at the bottom of the sample chamber (1); the water-oil separation system (5) is used to separate the water-oil mixture flowing out of the water outlet (14) and divert it into the corresponding water tank 2 (603) and oil tank 2 (604); the water supply system and the oil supply system divert the water tank (4) through the water inlet to supply water and oil to the single fissure (15); and an air extraction valve (9) is arranged between the air extraction system (8) and the sample chamber (1); The test method includes the following steps: Step 1, placing a lower rock matrix sample (2) into a sample chamber (1); Step 2: Screw down the nut assembly (10) on the top of the sample chamber (1) to move the upper transparent cover plate (3) downward to assemble with the lower rock matrix sample (2) to form a single fissure (15), and then inject dye water into the single fissure (15) through a water pump (701), and use a high-speed camera system to capture the seepage process of the dye water in the single fissure (15) and the process of the dye water in the single fissure (15) flowing into the lower rock matrix sample (2); Step 3: The dye water that has not entered the lower rock matrix sample (2) will flow into the water-oil separator (5) through the water outlet (14). The value of water tank 2 (603) minus the value of water tank 1 (601) is calculated, and the flow rate of the cracks flowing into the matrix in each time period can be calculated; Step 4: Screw the nut group (10) on the top of the sample chamber (1) to the top, continue to inject dye water into the rock through the water pump (701) until the water level is 20 mm higher than the top surface of the lower rock matrix sample (2), open the air extraction valve (9), start the vacuum extraction system (8), and the vacuum pressure must reach 100 kPa during the extraction. Maintain this vacuum state until no bubbles are generated, for no less than 4 hours; place the lower rock matrix sample (2) in the original sample chamber (1), leave it to stand for 4 hours under atmospheric pressure, then take it out and wipe off the excess water stains on the surface with a wet gauze; Step 5: Place the lower rock matrix sample (2) into the sample chamber (1), screw down the nut assembly (10) on the top of the sample chamber (1), move the upper transparent cover plate (3) downward to assemble with the lower rock matrix sample (2) to form a single fracture (15), inject oil into the lower rock matrix sample (2) through the oil pump (702), and use a high-speed camera system to record the process of oil exchanging dye water from the matrix into the fracture; In step six, the dye water exchanged with the oil and the oil that permeates from the cracks will pass through the water outlet (14) from the sample chamber (1) through the water-oil separation system (5). The dye water and oil will enter the water tank 2 (603) and the oil tank 2 (604) respectively. By calculating the amount of the two liquids respectively, the amount of water exchange between the cracks and the rock matrix can be quantitatively calculated.

2. The test method for obtaining the amount of water exchange between fractures and rock matrix according to claim 1, characterized in that: The water supply system comprises a water tank (601) and a water pump (701), and the oil supply system comprises an oil tank (602) and an oil pump (702). The water tank (601) and the oil tank (602) are connected to the water inlet diversion tank (4) via the water pump (701) and the oil pump (702) respectively.

3. The test method for obtaining the amount of water exchange between fractures and rock matrix according to claim 1, characterized in that: The lifting assembly is a nut group (10), the bolts of which are threadedly connected to the top of the sample chamber (1) and the bottom end of which is pivotally connected to the upper transparent cover plate (3).

4. A test method for obtaining the amount of water exchange between fractures and rock matrix according to claim 3, characterized in that: The sample chamber (1) is in the shape of a rectangular parallelepiped, with visible transparent acrylic plates installed on six faces, and two transparent side cover plates (11) on both sides connected to the upper transparent cover plate (3). When the nut group (10) is screwed downward, a single crack (15) is formed by splicing, and when the nut group (10) is screwed upward, the lower rock matrix sample (2) can be saturated with water.

5. The test method for obtaining the water exchange amount between fracture and rock matrix according to claim 1, characterized in that: The upper rock matrix sample (2) only takes half of the rectangular parallelepiped core sample containing a single fracture penetrating therethrough, with the rough surface produced by the penetration facing upwards.

6. The test method for obtaining the amount of water exchange between fractures and rock matrix according to claim 1, characterized in that: Four high-speed camera systems are located on the top, front, left and right sides of the rock specimen to capture the water exchange process between the fractures and the rock matrix.

Images