CN104155226B - Reservoir permeating medium heat flow piercement heterogeneous fluid pressure break-seepage flow experiment system - Google Patents

Abstract

The invention discloses a heat-fluid-solid coupling multiphase fluid fracturing-seepage experimental system for reservoir seepage medium, which comprises a frame; a moving trolley is arranged at the lower part of the frame; a lifting mechanism is arranged on the frame; the lifting mechanism is connected with a pressure chamber ;The middle part of the frame is fixed with an oil cylinder; the pressure chamber includes a bottom cover that can be placed on the mobile trolley; the bottom cover is connected with an upper seat by bolts; the upper end of the upper seat is fixed with a guide cover; the center of the guide cover is equipped with a pressure rod; A first water hole and a first air hole are arranged parallel to the axial direction; the lower end of the first water hole is threaded with an upper pressure head; the center of the bottom cover is fixed with a pressure seat; the pressure seat is fixed with a column; the upper end of the column is fixed with a lower The pressure head; the pressure seat, the column and the lower pressure head are provided with a through hole; the bottom cover is provided with a water outlet; the frame is fixed on the heating oil tank; the heating oil tank is equipped with an oil temperature sensor, a heating pipe and a circulation pump. The present invention can carry out more experiment modes, and the experiment precision is higher.

Description

Thermal-fluid-solid coupled multiphase fluid fracturing-seepage experimental system for reservoir permeable media

technical field

The invention relates to an experimental system, in particular to an experimental system for studying the combined action mechanism of unconventional gas fracturing and extraction.

Background technique

With the rapid development of the economy and the continuous progress of human society, the current large-scale production and large-scale utilization of conventional energy supply is increasingly unable to meet market demand. Under this severe energy situation, unconventional natural gas has shown huge resource potential, and my country's unconventional natural gas resources are very rich and have broad prospects for development. Unconventional natural gas will inevitably become an important source of future energy supply. Permeability of unconventional natural gas reservoirs is a physical parameter that reflects the difficulty of fluid seepage in the reservoir. Burial depth, permeable medium structure and geoelectric field are closely related, and the size of reservoir permeability plays an important role in the storage and drainage of natural gas and the distribution of fluid pressure. Therefore, it is very necessary to conduct experimental research on the mechanical deformation characteristics and seepage characteristics of unconventional natural gas reservoirs and gas reservoirs under mining conditions.

Generally speaking, unconventional natural gas includes tight sandstone gas, coalbed methane, shale gas and natural gas hydrate, etc. my country's unconventional natural gas reserves are very rich and have great potential for development. However, the geological conditions are complex, the burial is deep, and the mining cost is high. In the process of developing unconventional natural gas, hydraulic fracturing is a key technology to improve efficiency and reduce costs. At present, scholars at home and abroad have begun to conduct some research on the damage mechanism of hydraulic fracturing, fracture propagation geometry and fracture propagation law. However, due to the lack of systematic scientific research, the lack of relevant hydraulic fracturing mechanisms, and the failure to quantify the relevant main parameters affecting the fracturing effect, the application and development of this technology in the field of unconventional natural gas reservoir permeability enhancement has been restricted. A certain degree of restriction.

The existing experimental devices mainly have the following deficiencies: 1) The factors affecting the permeability considered are relatively single, and multi-physics field coupling experiments considering the stress field, seepage field, temperature field, etc. cannot be carried out; 2) If the permeability needs to be measured, The core needs to be taken out and carried out on another experimental equipment. At this time, the cracks in the core due to fracturing will be closed again, and the change of permeability before and after fracturing of the in-situ core cannot be measured quantitatively and accurately; 3) Most of the seepage experiments carried out It is a single water-phase or gas-phase seepage experiment, and the respective flow rates of water and gas cannot be accurately measured; 4) The vacuum degree inside the test piece cannot be measured, which is not accurate enough for experiments with gas adsorption; 5) The installation process is basically carried by hand , is inconvenient and the process is not stable enough, which has a certain impact on the specimen.

Therefore, it is of great significance for the application and promotion of hydraulic fracturing to establish a scientific unconventional gas fracturing-seepage experimental test system to explore the fracture damage and permeability enhancement mechanism of reservoir permeable media under hydraulic fracturing.

Contents of the invention

In view of the above-mentioned defects in the prior art, the technical problem to be solved by the present invention is to provide a fracturing-seepage experimental system capable of accurately measuring the permeability change of a test piece before and after fracturing under multi-field coupling conditions.

In order to achieve the above object, the present invention provides a thermal-fluid-solid coupling multiphase fluid fracturing-seepage experimental system for reservoir seepage medium, including a frame; the lower part of the frame is provided with parallel guide rails; the parallel guide rails are provided with The mobile trolley; the frame is provided with a lifting mechanism; the lifting mechanism is connected with the pressure chamber; the middle part of the frame is fixed with an oil cylinder; the piston of the oil cylinder is fixed with a displacement sensor; the protruding end of the piston A pressure sensor is fixed;

The pressure chamber includes a bottom cover that can be placed on the mobile trolley; an upper seat is connected with bolts on the bottom cover; a guide cover is fixed on the upper end of the upper seat;

The center of the guide cover is matched with a pressure rod; the first water hole and the first air hole are arranged in parallel in the axial direction in the pressure rod; the first water hole is located at the center of the pressure rod;

The lower end of the first water hole is threaded with an upper pressure head; the center of the upper pressure head is provided with a second water hole communicating with the first water hole; The second air hole connected to the first air hole;

The lower end of the second water hole is threaded with a fracturing head;

The center of the bottom cover is fixed with a press seat; the press seat is fixed with a column; the upper end of the column is fixed with a lower indenter; the lower indenter is provided with a number of third air holes facing the side of the test piece;

The pressure seat, the column and the lower pressure head are provided with a through outlet hole; the third air hole is connected with the outlet hole; the bottom cover is provided with a water outlet hole; the end of the outlet hole is connected with an air outlet and water outlet connector;

The frame is fixed on the heating oil tank; an oil temperature sensor, a heating pipe and a circulating pump are arranged in the heating oil tank.

Preferably, the lifting mechanism includes a lifting reduction motor; the power of the lifting reduction motor is transmitted to the pulleys symmetrically arranged on the top of the frame through a transmission belt; the pulleys are fixed on the transmission screw rod; the transmission wire The rod extends to the bottom of the frame and is fixed with the upper part of the upper seat.

For easy operation, a positioning rod is fixed on the bottom cover; a positioning hole corresponding to the positioning rod is provided on the guide cover.

In order to accurately measure water flow and gas flow, the outlet hole is connected to a water-gas separation measurement system; the water-gas separation measurement system includes a three-way valve connected to the air outlet and water outlet; the three-way valve is also connected to a second A shut-off valve and a second shut-off valve; the second shut-off valve is connected to the gas-liquid separator; the gas-liquid separator is connected to the four-way valve; the four-way valve is connected to the third shut-off valve; The third cut-off valve is connected with the flow meter; the flow meter is connected with the data acquisition instrument at the same time.

In order to facilitate the vacuuming of the pressure chamber and simplify the pipeline structure, the four-way valve is also connected with a fourth shut-off valve and a fifth shut-off valve; the fourth shut-off valve is connected with a vacuum pump; the fifth shut-off valve is connected with a vacuum gauge ; The vacuum gauge is connected with the data acquisition instrument.

For further accurate experiments, a pressure sensor is connected to the connecting pipeline between the air outlet and water outlet and the three-way valve; the pressure sensor is connected to the data acquisition instrument.

The beneficial effects of the present invention are:

(1) Multi-physics field coupling experiments considering stress field, seepage field, temperature field, etc. can be carried out on different reservoir seepage media, including triaxial compression seepage experiments, hydraulic fracturing experiments and multiphase fluid-solid coupling experiments.

(2) Due to the design of the permeability test system before and after hydraulic fracturing, the in-situ precise measurement of the permeability of the reservoir permeable medium before and after hydraulic fracturing under the action of external stress can be carried out.

(3) Due to the design of the water-air separation measurement system, it is possible to accurately measure the water and air flow respectively.

(4) Due to the design of the vacuum system, the system can more conveniently vacuumize the test piece, and visualize the vacuum degree inside the test piece, making the experimental conditions more accurate.

(5) Fluid pressure monitoring sensors can be designed at the front and rear ends of the test piece, so that the experimental conditions are more accurate.

(6) The size of the pressure rod can be changed to adapt to different specimen sizes by setting guide covers with different inner diameters.

(7) Through the design of the lifting mechanism and the moving trolley, the installation process basically does not require manual handling and is more intelligent.

In a word, the present invention can carry out more experimental modes and higher experimental precision.

Description of drawings

Fig. 1 is a schematic structural view of a specific embodiment of the present invention.

Fig. 2 is a structural schematic diagram of the pressure chamber in Fig. 1 .

FIG. 3 is a schematic diagram of a partially enlarged structure at position I in FIG. 2 .

FIG. 4 is a schematic diagram of a partially enlarged structure at II in FIG. 2 .

Fig. 5 is a schematic diagram of the outlet pipeline structure in a specific embodiment of the present invention.

detailed description

Below in conjunction with accompanying drawing and embodiment the present invention will be further described:

As shown in Figures 1 to 5, a thermal-fluid-solid coupling multiphase fluid fracturing-seepage experimental system for reservoir seepage media includes a frame 1, and a parallel guide rail 2 is arranged on the lower part of the frame 1, and a parallel guide rail 2 is arranged on the parallel guide rail 2. Mobile trolley 3.

The middle part of the frame 1 is fixed with an oil cylinder 6, the piston of the oil cylinder 6 is fixed with a displacement sensor 7, and the protruding end of the piston is fixed with a pressure sensor 8.

The bottom of frame 1 is provided with pressure chamber 100, and pressure chamber 100 comprises the bottom cover 10 that can be placed on mobile trolley 3, and bottom cover 10 is bolted with upper seat 11, and the upper end of upper seat 11 is fixed with guide cover 12. A positioning rod 13 is fixed on the bottom cover 10 , and a positioning hole 12 a corresponding to the positioning rod 13 is provided on the guide cover 12 .

The center of the guide cover 12 is matched with a pressure rod 14 , and a first water hole 14 a and a first air hole 14 b are arranged in parallel in the pressure rod 14 along the axial direction, and the first water hole 14 a is located at the center of the pressure rod 14 .

The lower end of the first water hole 14a is screwed with an upper pressure head 15, and the center of the upper pressure head 15 is provided with a second water hole 15a communicating with the first water hole 14a. 14b communicates with the second air hole 15b.

The lower end of the second water hole 15a is screwed with a fracturing head 16 .

A pressure seat 17 is fixed at the center of the bottom cover 10, a column 18 is fixed on the pressure seat 17, a lower indenter 19 is fixed on the upper end of the column 18, and a plurality of third air holes 19a are arranged on the side of the lower indenter 19 facing the specimen.

The pressure seat 17 , the upright column 18 and the lower pressure head 19 are provided with a through outlet hole 20 , the third air hole 19 a communicates with the outlet hole 20 , and the bottom cover 10 is provided with a water outlet hole 9 . The end of the outlet hole 20 is connected with an air outlet and water outlet joint 29 .

The frame 1 is fixed on the heating oil tank 21, and the heating oil tank 21 is provided with an oil temperature sensor 22, a heating pipe 23 and a circulating pump 24.

The frame 1 is provided with a hoisting mechanism, and the hoisting mechanism includes a lifting reduction motor 25, and the power of the lifting reduction motor 25 is transmitted to the belt pulley 27 symmetrically arranged at the top of the frame 1 by a transmission belt 26. Pulley 27 is fixed on the transmission screw mandrel 28, and transmission screw mandrel 28 extends to the bottom of frame 1 and is fixed with the top of upper seat 11. A limit block 4 can be set on the transmission screw mandrel, and a travel switch 5 can be set near the screw mandrel to facilitate automatic control.

The outlet hole 20 is connected with the water-gas separation measurement system. The water-gas separation measurement system includes a three-way valve 30 connected with the air outlet and water outlet joint 29 , and the three-way valve 30 is connected with a first cut-off valve 31 and a second cut-off valve 32 at the same time.

A pressure sensor 42 is connected to the connecting pipeline between the air outlet and water outlet joint 29 and the three-way valve 30 , and the pressure sensor 42 is connected to the data acquisition instrument 37 .

The second stop valve 32 is connected with the gas-liquid separator 33 , and the gas-liquid separator 33 is connected with the four-way valve 34 at the same time.

The four-way valve 34 is connected with a third stop valve 35 , a fourth stop valve 38 and a fifth stop valve 39 , the third stop valve 35 is connected with a flow meter 36 , and the flow meter 36 is connected with a data acquisition instrument 37 at the same time. The fourth stop valve 38 is connected with the vacuum pump 40 , the fifth stop valve 39 is connected with the vacuum gauge 41 , and the vacuum gauge 41 is connected with the data acquisition instrument 37 .

In order to ensure the accuracy of the test, it is necessary to adopt sealing technology where gas and liquid leakage may occur throughout the system.

Connect the above-mentioned experimental system with the high-pressure gas cylinder, the pump pressure servo booster and the control cabinet to conduct the thermal-fluid-solid coupled fracturing-seepage experiment of coal and rock. The specific steps are as follows:

(1) Test piece preparation. The dense sandstone, shale, raw coal or other rocks or coal blocks obtained from the field as permeable media of the reservoir are sealed with a plastic film and placed in a wooden box of an appropriate size, and then the core is drilled with a core machine, and finally Use a grinder to grind the taken out coal core into a Φ50×100mm raw rock sample or raw coal sample, and place it in an oven to dry. Use a bench drill to drill holes on the end face of the dried test piece, the hole diameter is Φ10mm, and the hole depth is not less than 30mm. Apply a high-strength adhesive (such as AB glue) to the upper part of the special nozzle for hydraulic fracturing, put it into the hole of the test piece, squeeze it properly to make the contact surface flat, and then place it to dry.

(2) Test piece installation. First use 704 silicone rubber to apply a layer of 1mm adhesive layer on the side of the test piece. After the applied adhesive layer is completely dry, screw the special nozzle for hydraulic fracturing into the fracturing head 16, and place the test piece on the upper pressure. Between the head 15 and the lower pressure head 19; align the sides of the test piece with the sides of the indenter, put the outer seal of the test piece in the middle of the test piece first, and use a hair dryer to evenly blow the heat shrinkable tube tightly so that it is in contact with the test piece. The test piece is in close contact; two metal hoops are used to tightly hold the overlapping parts of the heat shrinkable tube, the upper indenter, the lower indenter and the lower indenter. Finally, the chain radial displacement sensor is installed in the middle of the test piece, and the data transmission wiring is connected. After the test piece is installed, the mobile car is returned to its position.

(3) Installation. Align the upper seat 11 of the triaxial pressure chamber with the bottom cover 10, use the down switch on the operation cabinet to start the motor 25, drop the upper seat 11 of the pressure chamber, install the 8 M10 screws in the upper counterbore of the fixed pressure chamber, and then fix and tighten There are 20 M30 screws at the lower end. The two screws at the symmetrical positions should be tightened first, so that the lower cover can touch the pressure chamber smoothly, and then tighten the other screws; connect the corresponding inlet and outlet joints of air and water.

(4) Control temperature and vacuumize. Use the up switch on the operation cabinet to lift the pressure chamber 100, move it out of the mobile trolley, use the down switch on the operation cabinet to drop the pressure chamber into the heating oil tank 21, and set the temperature required for the experiment. After the pressure chamber is positioned, set the vacuum degree (such as 300 Pa) required for the experiment on the vacuum gauge 41, open the inlet valve 43 and the water inlet valve 44 at the upper end of the pressure chamber, and start the vacuum switch of the control cabinet to start the vacuum pump 40. Open the fourth shut-off valve 38 and the fifth shut-off valve 39 to vacuumize, close and open the fourth shut-off valve 38, the fifth shut-off valve 39, the intake valve 43 and the water intake valve 44 when the experimental system reaches the target value, and then stop vacuum pump.

(5) Inflated adsorption equilibrium. According to the stress condition of the original rock, the high-precision servo hydraulic pump station is controlled by the computer, and the oil cylinder 6 is operated to apply axial pressure to the test piece. The second cut-off valve 32 opens the inlet valve 44, adjusts the gas outlet valve of the high-pressure methane cylinder, keeps the gas pressure constant, and inflates the test piece. The inflation time is generally 24 hours.

(6) Determination of the original permeability. After applying the corresponding axial pressure and confining pressure according to the established experimental plan (that is, setting the experimental temperature, gas pressure, water pressure or flow rate, axial pressure and confining pressure according to the original environment of different rocks), open the second The second shut-off valve 32 and the third shut-off valve 35, and close the first shut-off valve 31, read the data of the flow meter 36, and measure the original permeability of the test piece.

(7) Hydraulic fracturing of test pieces. Close the inlet valve 44, the first cut-off valve 31 and the second cut-off valve 32, open the water inlet valve 43, and apply corresponding water pressure or flow through the servo booster to perform fracturing treatment on the test piece.

(8) Measure the permeability after fracturing. Close the water inlet valve 43, open the air inlet valve 44 to feed the gas of corresponding pressure, open the second shut-off valve 32 and the third shut-off valve 35, and close the first shut-off valve 31, read the data of the flow meter 36 and the gas-liquid separation The liquid flow collected by the device 33 can accurately measure the gas flow and liquid flow, so as to accurately measure the permeability of the test piece after fracturing.

(9) Adjust the experimental conditions according to the established experimental plan. Repeat steps (6)-(8) according to the experimental protocol.

(10) Carry out the next round of experiments. After the experiment is completed, the test piece is disassembled, and the above steps are repeated for the next round of experiments.

According to the needs of the test, the test piece can be made into Φ100×200mm. At this time, it is only necessary to replace the guide cover 12 with the corresponding inner diameter.

The main technical parameters of the above experimental system are as follows:

1. Maximum axial force: 1000kN

2. Force measurement accuracy: ±1% of the indicated value

3. Force measurement and classification: automatic shifting

4. Force value control accuracy: ±0.5% of the indicated value (voltage stabilization accuracy)

5. The maximum displacement of the piston: 60mm

6. Axial displacement accuracy: ±1% of indicated value

7. Axial control mode: force control, displacement

8. Confining pressure control range: 0~60MPa (AC servo booster cylinder method)

9. Confining pressure control accuracy: ±1% of indicated value

10. Gas flow rate (outlet): 0～5L/min

11. Specimen temperature range: 0～100℃, temperature fluctuation: ±1℃

12. Gas pressure measurement accuracy: ±1% of the indicated value (using a 0.1-grade pressure sensor)

13. Vacuum degree: 6×10 ^-2 Pa

14. The maximum sealing pressure of the gas circuit: 20MPa

15. Axial force test control method: closed-loop control of load and displacement, which can be converted without impact.

16. Experimental waveform: static, step loading, program-controlled loading

17. Noise: ≤72dB

18. Total power: 6kW

19. Dimensions of the host (length × width × height): 1350 × 960 × 2874mm

20. Dimensions of the hydraulic station (length × width × height): 650 × 600 × 750mm

21. Total weight of equipment: 1300kg

In the above experiment, the hydraulic fracturing and the permeability test were completed continuously on the same equipment, so when the permeability was tested, the cracks in the core caused by fracturing would not be reclosed, and the first air hole 14b could be passed to the first air hole 14b during the permeability test. Inject gas, so that the second air hole 15b "inflates" the surface of the test piece, so that the change of permeability before and after in-situ core fracturing can be measured quantitatively and accurately; and the water flow and gas flow in the experiment can be accurately measured at the same time, thereby improving the accuracy of the experiment .

On the other hand, the vacuum system is ingenious The outlet pipeline is effectively used, so it is more convenient to vacuumize the test piece, and the vacuum degree inside the test piece is visualized to make the experimental conditions more accurate.

At the same time, a flow pressure monitoring sensor can be installed at the outlet of the methane cylinder, used in conjunction with the pressure sensor 42 in the outlet pipeline, to make the experimental conditions more accurate.

The preferred specific embodiments of the present invention have been described in detail above. It should be understood that those skilled in the art can make many modifications and changes according to the concept of the present invention without creative work. Therefore, all technical solutions that can be obtained by those skilled in the art based on the concept of the present invention through logical analysis, reasoning or limited experiments on the basis of the prior art shall be within the scope of protection defined by the claims.

Claims (6)

1. reservoir permeating medium heat flow piercement heterogeneous fluid pressure break-seepage flow experiment system, including frame (1)；The bottom of described frame (1) is provided with closed slide (2)；Mobile dolly (3) it is provided with on described closed slide (2)；Described frame is provided with hoisting mechanism on (1)；Described hoisting mechanism is connected with pressure chamber (100)；Described frame (1) be fixedly arranged in the middle of oil cylinder (6)；It is fixed with displacement transducer (7) on the piston (6a) of described oil cylinder (6)；The external part of described piston (6a) is fixed with pressure transducer (8)；It is characterized in that:

Described pressure chamber (100) includes the bottom (10) being placed on described mobile dolly (3)；The upper bolt of described bottom (10) connects the seat of honour (11)；The upper end at the described seat of honour (11) is fixed with guide cover (12)；

The center of described guide cover (12) is combined with depression bar (14)；The first water hole (14a) and the first pore (14b) it is arranged with vertically in parallel in described depression bar (14)；Described first water hole (14a) is positioned at the center of described depression bar (14)；

The lower end threaded engagement of described first water hole (14a) has seaming chuck (15)；Second water hole (15a) being provided centrally with connecting with described first water hole (14a) of described seaming chuck (15)；Several the second pores (15b) connected with described first pore (14b) it are provided with on described seaming chuck (15)；

The lower end threaded engagement of described second water hole (15a) has fracturing head (16)；

The center of described bottom (10) is fixed with wedge (17)；Column (18) it is fixed with on described wedge (17)；The upper end of described column (18) is fixed with push-down head (19)；Described push-down head (19) is provided with some 3rd pores (19a) towards test specimen side；

Through portal (20) it are provided with on described wedge (17), column (18) and push-down head (19)；Described 3rd pore (19a) portal with described (20) connect；Apopore (9) it is provided with on described bottom (10)；The end of described portal (20) connects water out adapter (29) of giving vent to anger；

Described frame (1) is fixed on heating fuel tank (21)；It is provided with oil temperature sensor (22) in described heating fuel tank (21), adds heat pipe (23) and circulating pump (24).

2. reservoir permeating medium heat flow piercement heterogeneous fluid pressure break-seepage flow experiment system as claimed in claim 1, is characterized in that: described hoisting mechanism includes lifting speed reduction motor (25)；The power of described lifting speed reduction motor (25) is transferred to the symmetrically arranged belt wheel in described frame (1) top (27) by transmission band (26)；Described belt wheel (27) is fixed on drive lead screw (28)；Described drive lead screw (28) is fixed to the extension of the lower section of described frame (1) the top with the described seat of honour (11).

3. reservoir permeating medium heat flow piercement heterogeneous fluid pressure break-seepage flow experiment system as claimed in claim 1, is characterized in that: be fixed with location bar (13) on described bottom (10)；The location hole (12a) corresponding with described location bar (13) it is provided with on described guide cover (12).

4. the reservoir permeating medium heat flow piercement heterogeneous fluid pressure break-seepage flow experiment system as described in claim 1 or 2 or 3, is characterized in that: described in portal (20) be connected with aqueous vapor separating and measuring system；Described aqueous vapor separating and measuring system includes the three-way valve (30) being connected with described water out adapter of giving vent to anger (29)；Described three-way valve (30) has been simultaneously connected with the first stop valve (31) and the second stop valve (32)；Described second stop valve (32) is connected with gas-liquid separator (33)；Described gas-liquid separator (33) is connected with cross valve (34) simultaneously；Described cross valve (34) has been simultaneously connected with the 3rd stop valve (35)；Described 3rd stop valve (35) is connected with effusion meter (36)；Described effusion meter (36) is connected with data collecting instrument (37) simultaneously.

5. reservoir permeating medium heat flow piercement heterogeneous fluid pressure break-seepage flow experiment system as claimed in claim 4, is characterized in that: described cross valve (34) is also associated with the 4th stop valve (38) and the 5th stop valve (39)；Described 4th stop valve (38) is connected with vacuum pump (40)；Described 5th stop valve (39) is connected with vacuometer (41)；Described vacuometer (41) is connected with described data collecting instrument (37).

6. reservoir permeating medium heat flow piercement heterogeneous fluid pressure break-seepage flow experiment system as claimed in claim 5, is characterized in that: described in give vent to anger water out adapter (29) and have pressure transducer (42) with being connected on the connecting line of described three-way valve (30)；Described pressure transducer (42) is connected with described data collecting instrument (37).