Hydraulic fracturing test device and method suitable for pressure driving technology

Abstract

The hydraulic fracturing test device comprises a side oil cylinder and a rock sample on one side of the side oil cylinder, an upper pressing plate and a lower pressing plate are arranged above and below the rock sample respectively, the upper pressing plate and the lower pressing plate are connected through a bearing pull rod and fixed through a bearing nut, a seepage base is arranged at the bottom of the rock sample, and a seepage hole is formed in the seepage base. Sealing plates are arranged on the upper side and the lower side of the rock sample, side pressing plates are arranged on the periphery of the rock sample, the invention further discloses a hydraulic fracturing test method suitable for the pressure driving technology, the hydraulic fracturing test method is suitable for the technical field of oilfield development, an indoor pressure driving large-size rock core physical simulation experiment is achieved, and the hydraulic fracturing test method has great significance in deepening the understanding of a pressure driving mechanism; according to the method, only one flat-plate-shaped test piece needs to be taken from a natural rock core, the cost and time of test piece machining and the whole experiment can be effectively reduced, the adopted flat-plate-shaped test piece does not need to be subjected to secondary sectioning when crack observation is conducted, the experiment difficulty is effectively reduced, and the crack observation effect is improved.

Description

Technical Field

[0001] The present invention belongs to the technical field of oilfield development, and specifically is a hydraulic fracturing test device and method suitable for pressure drive technology. Background Technology

[0002] Entering the 21st century, low permeability oil reservoirs have become one of the most important areas of exploration and development. However, low permeability oil reservoirs are affected by factors such as reservoir properties and water quality. After a period of development, there are generally problems such as high water injection pressure and high under-injection ratio, which leads to the inability to establish effective displacement of oil and water wells and rapid decline in production capacity. Practical experience at home and abroad has shown that hydraulic fracturing is an irreplaceable technology for exploiting low permeability oil reservoirs at this stage. Since 2020, Shengli Oilfield has proposed a new technology for pressure drive technology, which uses low-viscosity clean water as fracturing fluid, and injects it at high pressure and high speed to increase reservoir pressure and improve seepage capacity in a relatively short period of time, thereby increasing oil well production capacity and reservoir recovery.

[0003] Pressure-driven technology uses clean water as the injection medium. The injection fluid has a high degree of filtration loss, which makes it easier to form microcracks, and requires higher observation accuracy for pressure-driven cracks. At present, conventional triaxial tests on rocks use hydraulic oil to apply equal lateral pressure to the specimen in the horizontal direction, which is difficult to simulate the actual stress conditions of the reservoir. The specimens used in true triaxial tests on rocks are usually large-sized cubic specimens. Whether using cores or outcrops to process rock specimens, they face difficulties in obtaining and processing. After the true triaxial hydraulic fracturing test of rocks is completed, the observation of cracks is mostly carried out by indirect means such as acoustic emission combined with core cutting, and the observation accuracy of cracks is low.

[0004] Therefore, developing a new test device and indoor physical simulation method suitable for pressure-driven technology is of great significance for deepening the understanding of pressure-driven mechanism and guiding the practice of oilfield pressure-driven mines. SUMMARY OF THE INVENTION

[0005] The purpose of the present invention is to overcome the defects of the prior art and provide a hydraulic fracturing test device and method suitable for pressure drive technology.

[0006] To achieve the above purpose, the present invention adopts the following technical solutions:

[0007] In the first aspect, a hydraulic fracturing test device suitable for pressure drive technology includes a side oil cylinder and a rock sample on one side thereof, wherein an upper pressure plate and a lower pressure plate are respectively arranged above and below the rock sample, wherein the upper pressure plate and the lower pressure plate are connected by a load-bearing tie rod and fixed by a load-bearing nut, a seepage base is arranged at the bottom of the rock sample, sealing plates are arranged on the upper and lower sides of the rock sample, and side pressure plates are arranged around the rock sample.

[0008] Preferably, the rock specimen adopts a flat plate structure, and a cylindrical blind hole is opened at the center of one end face. The cylindrical blind hole is sealed with a conversion indenter through epoxy resin, and the pressure water seeps into the rock specimen through the conversion indenter via the channel in the injection head.

[0009] Preferably, the injection head is arranged at the center of the top of the seepage base, and the conversion indenter is arranged at the upper end of the injection head. The conversion indenter and the injection head are inserted into the cylindrical blind hole.

[0010] Preferably, the lower pressing plate is arranged on the top of the bottom table, and a main oil cylinder is arranged inside the bottom table.

[0011] Preferably, the side oil cylinder is arranged on the sample support through the rear fixing bracket and the fixing bracket, and both the rear fixing bracket and the fixing bracket are connected to the linear guide rail on the sample support.

[0012] Preferably, the sealing plate is used to block fluid cross-flow.

[0013] Preferably, both the injection head and the seepage base are provided with pressure water channels, and the upper and lower sealing plates are pressed tightly against the upper and lower end faces of the rock specimen by the vertical loading cylinder to block the seepage of pressure water.

[0014] Preferably, the injection head adopts a convex-shaped structure, and there is a sealing ring on the end with a larger diameter to cooperate with the seepage base for sealing. The end with a smaller diameter is inserted into the cylindrical blind hole of the rock specimen through the connecting conversion indenter. Epoxy resin glue is applied on the conversion indenter for sealing, and the pressure water enters the conversion indenter through the channel in the injection head and then seeps into the rock specimen.

[0015] In a second aspect, a hydraulic fracturing test method applicable to the pressure drive technology includes the following steps:

[0016] S1 Preparation and loading of the rock specimen;

[0017] S2 Pressure drive fracturing simulation;

[0018] S3 Tracking the crack morphology.

[0019] Preferably, in the step S1, it specifically includes the following steps:

[0020] S11 Preparation of a flat rock specimen;

[0021] S12 Drilling a blind hole;

[0022] S13 Loading the rock specimen.

[0023] Preferably, in the step S11, the preparation of the flat rock specimen includes:

[0024] On the collected underground core or outcrop rock mass, use a drill press and a cutting machine to preliminarily process the specimen into a flat rock specimen, and use a grinding machine to polish each plane of the flat rock specimen to make it flat and smooth.

[0025] Preferably, in the step S11, the size of the flat rock specimen is 48 - 52 cm in length, 48 - 52 cm in width, and 3 - 5 cm in height.

[0026] Preferably, in the step S12, drilling a blind hole includes:

[0027] Use an electric drill to drill a blind hole at the center position of one side of the specimen. After processing, clean the blind hole to ensure that no residue remains in the hole.

[0028] Preferably, in the step S12, the blind hole adopts a cylindrical structure, with a diameter of 5 - 7 mm and a depth of 1 / 2 of the thickness of the flat specimen, which is 1 - 3 cm, and the diameter of the cylindrical blind hole is larger than the diameter of the small end of the conversion indenter.

[0029] Preferably, in the step S13, loading the rock specimen includes:

[0030] Place a conversion indenter into the rock specimen, and coat epoxy resin glue around the conversion indenter to achieve the bonding of the specimen and the conversion indenter. Let the bonded specimen and conversion indenter stand for a period of time to cure the epoxy resin glue until the bonding is firm; place a lower sealing plate on the seepage base, align the blind hole of the specimen bonded with the conversion indenter with the boss of the seepage base, and place it on the sealing plate; place an upper sealing plate on the upper end face of the specimen, and push the core onto the lower pressing plate.

[0031] Preferably, in the step S2, the pressure-driven fracture simulation includes:

[0032] Use the main oil cylinder pump and side oil cylinder pump of the pressure-driven hydraulic fracturing test machine to apply the pressure in the X, Y, and Z directions of the rock specimen to a predetermined state, apply the water pressure in a flow control mode, and continuously inject the fluid until the specimen ruptures.

[0033] Preferably, in the step S2, the fluid one is a potassium chloride solution with a density of 1.0142 g / cm 3 , and a viscosity of 0.9987 mPa·s.

[0034] Preferably, in the step S3, tracking the crack morphology includes:

[0035] After the specimen ruptures, add an oil-soluble dye one to the fluid two, and continuously stir until the dye one is fully dissolved in the fluid two. Slowly inject the fluid two into the rock specimen in a low-flow mode.

[0036] Preferably, in step S3, fluid two is silicone oil and oil-soluble dye one is oil-soluble blue, in order to effectively trace the crack morphology and prevent the fluid from filtering into the matrix.

[0037] In summary, due to the adoption of the above technical solutions, the beneficial effects of the present invention are as follows:

[0038] In the present invention, a physical simulation experiment of indoor pressure-driven large-size core is realized, which is of great significance for deepening the understanding of the pressure-driven mechanism.

[0039] In the present invention, only a flat specimen needs to be taken from the natural core, which can effectively reduce the cost and time of specimen processing and the whole experiment.

[0040] In the present invention, the flat specimen adopted does not need to be secondarily sectioned when observing cracks. Combined with the above crack tracking method, the crack morphology and distribution range can be intuitively analyzed, effectively reducing the experimental difficulty and improving the crack observation effect. Description of the Drawings

[0041] Figure 1 It is a schematic structural diagram of the device of the present invention.

[0042] Figure 2 It is a cross-sectional view of the rock specimen of the present invention;

[0043] Figure 3 It is a cross-sectional view of the seepage base of the present invention;

[0044] Figure 4 It is a photo of the rock specimen after the pressure-driven simulation experiment completed by the rock true triaxial physical simulation test device of the present invention;

[0045] Figure 5 It is the injection pressure curve in the specific embodiment of the present invention;

[0046] Figure 6 It is the pressure curve after continuous water injection turns to intermittent water injection in the specific embodiment of the present invention;

[0047] Figure 7 It is a photo of the rock specimen after the pressure-driven physical simulation experiment completed in the specific embodiment of the present invention;

[0048] Reference numerals: 1, side oil cylinder; 2, rear end fixing bracket; 3, fixing bracket; 4, linear guide rail; 5, sample bracket; 6, bearing nut; 7, upper pressing plate; 8, bearing pull rod; 9, sealing plate; 10, side pressing plate; 11, seepage base; 12, lower pressing plate; 13, main oil cylinder; 14, bottom table; 15, rock specimen; 16, seepage base; 17, conversion press head; 18, injection head. Detailed Embodiments

[0049] The following is combined with the attachedFigures 1-7 , further illustrate the specific implementation manners of a hydraulic fracturing test device and method applicable to the pressure drive technology according to the present invention. The hydraulic fracturing test device and method applicable to the pressure drive technology according to the present invention are not limited to the descriptions of the following embodiments.

[0050] Example 1:

[0051] A hydraulic fracturing test device applicable to the pressure drive technology, as Figures 1-3 shown, includes a side oil cylinder 1 and a rock sample 15 on one side thereof. An upper pressing plate 7 and a lower pressing plate 12 are respectively arranged above and below the rock sample 15. The upper pressing plate 7 and the lower pressing plate 12 are connected by a bearing pull rod 8 and fixed by a bearing nut 6. A seepage base 13 is arranged at the bottom of the rock sample 15. Sealing plates 9 are arranged on both the upper and lower sides of the rock sample 15. Side pressing plates 10 are arranged around the rock sample 15.

[0052] Furthermore, the rock sample 15 adopts a flat plate structure. A cylindrical blind hole is opened at the center of one end face thereof. The cylindrical blind hole is sealed with a conversion press head 17 through epoxy resin. Pressure water penetrates into the rock sample 15 through the conversion press head 17 via the channel in the injection head 18.

[0053] Furthermore, the injection head 18 is arranged at the center of the top of the seepage base 13, and the conversion press head 17 is arranged at the upper end of the injection head 18. The conversion press head 17 and the injection head 18 are inserted into the cylindrical blind hole.

[0054] Furthermore, the lower pressing plate 12 is arranged on the top of a bottom table 14, and a main oil cylinder 13 is arranged inside the bottom table 14.

[0055] Furthermore, the side oil cylinder 1 is arranged on a sample support 5 through a rear end fixing bracket 2 and a fixing bracket 3. Both the rear end fixing bracket 2 and the fixing bracket 3 are connected to a linear guide rail 4 on the sample support 5.

[0056] Furthermore, the sealing plate 9 is used to block fluid cross - flow.

[0057] Furthermore, both the injection head 18 and the seepage base 13 are provided with pressure water channels. The upper and lower sealing plates 9 are tightly pressed against the upper and lower end faces of the rock sample 15 by a vertical loading cylinder to block the seepage of pressure water.

[0058] Furthermore, the injection head 18 adopts a convex - shaped structure. A sealing ring is arranged on the larger - diameter end thereof to cooperate with the seepage base 13 for sealing. The smaller - diameter end is inserted into the cylindrical blind hole of the rock sample 15 through the connecting conversion press head 17. Epoxy resin glue is applied on the conversion press head 17 for sealing. Pressure water enters the conversion press head 17 through the channel in the injection head 18 and then penetrates into the rock sample 15.

[0059] Example 2:

[0060] A hydraulic fracturing test device applicable to the pressure drive technology, as Figures 1-3 shown. The other structures are similar to those in Embodiment 1. Further, the dimensions of each part of the testing machine are:

[0061] Conversion ram: small end diameter 5.7 mm; large end diameter 10 mm; high-pressure water channel diameter 4 mm;

[0062] Seepage base: diameter 27 mm, internal hole diameter 10 mm, seepage hole diameter 4 mm, injection head boss diameter of the seepage base 23 mm, boss height 6 mm;

[0063] Lower sealing plate: length 580 mm, width 580 mm, height 30 mm;

[0064] Upper sealing plate: length 500 mm, width 500 mm, height 30 mm;

[0065] Fluid channel: diameter 4 mm.

[0066] Embodiment 3:

[0067] A hydraulic fracturing test method applicable to the pressure drive technology includes the following steps:

[0068] S1 Preparation and loading of the rock specimen;

[0069] S2 Pressure drive fracture simulation;

[0070] S3 Tracking the crack morphology.

[0071] Further, in step S1, it specifically includes the following steps:

[0072] S11 Preparation of a flat rock specimen;

[0073] S12 Drilling a blind hole;

[0074] S13 Loading the rock specimen.

[0075] Further, in step S11, the preparation of the flat rock specimen includes:

[0076] On the collected underground core or outcrop rock mass, the specimen is preliminarily processed into a flat rock specimen using a drill press and a cutting machine, and each plane of the flat rock specimen is polished using a grinding machine to make it flat and smooth.

[0077] Further, in step S11, the dimensions of the flat rock specimen are length 48 cm, width 48 cm, and height 3 cm.

[0078] Further, in step S12, the drilling of the blind hole includes:

[0079] Use an electric drill to drill a blind hole at the center position on one side of the specimen. After processing, clean the blind hole to ensure that no residue remains in the hole.

[0080] Further, in step S12, the blind hole has a cylindrical structure with a diameter of 5 mm and a depth of 1 / 2 of the thickness of the flat specimen, which is 1 cm, and the diameter of the cylindrical blind hole is larger than the diameter of the small end of the conversion indenter.

[0081] Further, in step S13, loading the rock specimen includes:

[0082] Place the conversion indenter into the rock specimen and coat epoxy resin glue around the conversion indenter to achieve the bonding of the specimen and the conversion indenter. Let the bonded specimen and the conversion indenter stand for a period of time to cure the epoxy resin glue and make the bonding firm; place the lower sealing plate on the seepage base, align the blind hole of the specimen bonded with the conversion indenter with the boss of the seepage base, and place it on the sealing plate; place the upper sealing plate on the upper end face of the specimen and push the core onto the lower pressing plate.

[0083] Further, in step S2, the pressure-driven fracture simulation includes:

[0084] Use the main cylinder pump and side cylinder pump of the pressure-driven hydraulic fracturing test machine to apply the pressure in the X, Y, and Z directions of the rock specimen to a predetermined state, apply the water pressure in a flow control mode, and continuously inject the fluid until the specimen ruptures.

[0085] Further, in step S2, the fluid one is a potassium chloride solution with a density of 1.0142 g / cm 3 , and a viscosity of 0.9987 mPa·s.

[0086] Further, in step S3, tracking the crack morphology includes:

[0087] After the specimen ruptures, add oil-soluble dye one to the fluid two, continuously stir until the dye one is fully dissolved in the fluid two, and slowly inject the fluid two into the rock specimen in a low-flow mode.

[0088] Further, in step S3, the fluid two is silicone oil, and the oil-soluble dye one is oil-soluble blue, in order to effectively trace the crack morphology and prevent the fluid from filtering into the matrix.

[0089] Example 4:

[0090] A hydraulic fracturing test method applicable to the pressure-driven technology. Other steps are similar to those in Example 3. Further, in step S11, the size of the flat rock specimen is 50 cm in length, 50 cm in width, and 4 cm in height.

[0091] Further, in step S12, the blind hole has a cylindrical structure with a diameter of 6 mm and a depth of 1 / 2 of the thickness of the flat sample, which is 2 cm, and the diameter of the cylindrical blind hole is larger than the diameter of the small end of the conversion indenter.

[0092] Example 5:

[0093] A hydraulic fracturing test method applicable to the pressure drive technology, with other steps similar to those in Example 3. Further, in step S11, the dimensions of the flat rock specimen are 52 cm in length, 52 cm in width, and 5 cm in height.

[0094] Further, in step S12, the blind hole has a cylindrical structure with a diameter of 7 mm and a depth of 1 / 2 of the thickness of the flat sample, which is 3 cm, and the diameter of the cylindrical blind hole is larger than the diameter of the small end of the conversion indenter.

[0095] Example 6:

[0096] The pressure drive simulation experiment completed by the rock true triaxial physical model test device in this example includes the following steps:

[0097] Step 1, sample preparation.

[0098] The experimental selection is a cubic artificial core specimen with side lengths of 300 mm × 300 mm × 300 mm. The raw materials for preparation are cement, water, sand, admixtures, etc. The experimental devices used are mixers, incubators, balances, molds, etc. After setting the mortar mix ratio, mortar preparation is carried out in the laboratory. Using a small mixer, first dry stir the mixture of cement and sand in the small mixer for a period of time, and then add water to the mixer for stirring. A water reducing agent is added during the stirring process. After the mortar is made, it is poured and formed in a steel mold. During pouring, pour according to the experimental design. Pour evenly, slowly, and steadily to prevent affecting the experimental results. When the mortar is injected to the designated position in the mold, add a steel pipe simulating the wellbore to the mold and then pour again. To prevent the wellbore from sinking during pouring, it needs to be fixed at the upper end. For the directionally perforated specimen, ensure that the plastic hose does not deform too much during pouring and ensure that the position of the pipe does not change; to prevent mortar from entering the plastic hose, wrap the simulated perforation with toilet paper moistened with water. For the open-hole specimen, after the mortar in the specimen has slightly solidified, pull out the plastic pipe in it to form an open-hole wellbore. Place the processed core in the mold and let it stand for about 7 days. After it is consolidated and formed, remove the mold and conduct constant temperature and humidity maintenance and strengthening for 21 days.

[0099] Step 2, pressure drive simulation experiment.

[0100] Adopt a true triaxial rock engineering physical model testing machine, a hydraulic fracturing pump servo control system, and acoustic emission three-dimensional space positioning technology. Use a straight wellbore and homogeneous rock sample #1, pour it using the cement stone ratio, with a rock permeability of 5 md and a rock elastic modulus of 20.18 GPa. First, conduct formation water injection, and then increase the displacement to conduct a fracturing physical simulation experiment. The construction displacement is 50 mL / min, the fracturing fluid viscosity is 2.5 mPa·s, and the three-way stress σV / σH / σh = 25 / 20 / 16 Mpa.

[0101] Step 3, experimental result analysis.

[0102] The pump injection pressure presents a stepped rising model, rising to 4 MPa in about 12 s, the pressure fluctuates continuously for about 8 s and then rapidly increases to 13 MPa and stabilizes, and the pressure increases sharply to the maximum pressure value of 22.1 MPa in about 45 s. The total pump injection time is 66.7 seconds. As Figure 4 shown, the observation after cutting the core after fracturing shows that two main fractures parallel to the maximum horizontal principal stress are formed after fracturing, and horizontal fractures appear locally.

[0103] Example 7:

[0104] The pressure-driven physical simulation experiment of this example includes the following steps:

[0105] Step 1, sample preparation.

[0106] Prepare a flat rock specimen with a length of 50 cm, a width of 50 cm, and a height of 4 cm on an outcrop rock sample. Use a diamond drill bit with an outer diameter of 6 mm to drill a blind hole with a depth of 2 cm axially at the center of one end face of the flat specimen. Test the gas permeability of the rock specimen on the parallel sample of the flat rock specimen to be 105 mD.

[0107] Step 2, pressure-driven fracturing simulation.

[0108] Put the prepared rock specimen into the pressure-driven hydraulic fracturing test device, and set the initial pressures applied in the X, Y, and Z directions of the rock specimen to be 1 MPa, 1 MPa, and 10 MPa respectively. Pump potassium chloride solution with a density of 1.0142 g / cm 3 , a viscosity of 0.9987 mPa·s into the core holder, and set the injection speed to start from 1 ml / min and gradually increase the injection speed slowly. As Figure 5 shown, use a pressure sensor to record the pressure change during the injection process in real time until the pump pressure curve shows an obvious drop, indicating that the rock sample has cracked.

[0109] Step 3, track the fracture morphology.

[0110] Add silicone oil into the intermediate container, add an oil-soluble blue solvent into the silicone oil, and stir for 24 hours until the solvent is fully dissolved. Connect the intermediate container to the injection inlet section of the pressure-driven hydraulic fracturing experimental device, and slowly inject at an injection rate of 0.5 ml / min. Stop injecting when the injection pressure rises significantly.

[0111] Example 8:

[0112] The pressure-driven physical simulation experiment of this example includes the following steps:

[0113] Step 1, sample preparation.

[0114] Prepare a flat rock specimen with a length of 50 cm, a width of 50 cm, and a height of 4 cm on an outcrop rock sample. Use a diamond drill bit with an outer diameter of 6 mm to drill a blind hole with a depth of 2 cm axially at the center of one end face of the flat specimen. Test the gas permeability of the rock specimen on the parallel sample of the flat rock specimen, which is 1.12 mD.

[0115] Step 2, pressure-driven fracture simulation.

[0116] Place the prepared rock specimen into the pressure-driven hydraulic fracturing test device, and set the initial pressures applied in the X, Y, and Z directions of the rock specimen to 1 MPa, 1 MPa, and 10 MPa respectively. Pump a potassium chloride solution with a density of 1.0142 g / cm 3 , viscosity of 0.9987 mPa·s into the core holder, set the injection rate to start from 1 ml / min, and gradually and slowly increase the injection rate until a significant drop appears in the pump pressure curve. As Figure 6 shown, stop the pump after the pressure drops, inject water again after relieving the pressure, and observe the pressure change.

[0117] Step 3, track the fracture morphology.

[0118] Add silicone oil into the intermediate container, add an oil-soluble blue solvent into the silicone oil, and stir for 24 hours until the solvent is fully dissolved. Connect the intermediate container to the injection inlet section of the pressure-driven hydraulic fracturing experimental device, and slowly inject at an injection rate of 0.5 ml / min. Stop injecting when the injection pressure rises significantly.

[0119] Example 9:

[0120] The pressure-driven physical simulation experiment of this example includes the following steps:

[0121] Step 1, sample preparation.

[0122] Prepare a flat rock specimen with a length of 50 cm, a width of 50 cm, and a height of 4 cm on the outcrop rock sample. Use a diamond drill bit with an outer diameter of 6 mm to axially drill a blind hole with a depth of 2 cm at the center of one end face of the flat specimen. Test the gas permeability of the rock specimen on the parallel sample of the flat rock specimen, and the gas permeability is 78 mD.

[0123] Step 2, simulation of pressure-driven fracturing.

[0124] Place the prepared rock specimen into the pressure-driven hydraulic fracturing test device, and set the initial pressures applied in the X, Y, and Z directions of the rock sample to 1 MPa, 1 MPa, and 10 MPa respectively. Pump potassium chloride solution with a density of 1.0142 g / cm 3 , a viscosity of 0.9987 mPa·s into the core holder, set the injection speed to start from 1 ml / min, and gradually and slowly increase the injection speed until the pump pressure curve shows a significant drop, indicating that the rock sample has cracked.

[0125] Step 3, track the fracture morphology.

[0126] Add silicone oil to the intermediate container, add an oil-soluble blue solvent to the silicone oil, and stir for 24 hours until the solvent is fully dissolved. Connect the intermediate container to the injection inlet section of the pressure-driven hydraulic fracturing experimental device and slowly inject it at an injection speed of 0.5 ml / min. When the injection pressure rises significantly, stop injecting. As Figure 7 shown, after the injection is completed, pull out the rock specimen from the lower platen and observe the fracture morphology and distribution.

[0127] The above content is a further detailed description of the present invention in combination with specific preferred embodiments. It cannot be determined that the specific implementation of the present invention is only limited to these descriptions. For those of ordinary skill in the technical field to which the present invention belongs, without departing from the concept of the present invention, several simple deductions or substitutions can be made, and all should be regarded as belonging to the protection scope of the present invention.

Claims

1. A hydraulic fracturing test device suitable for pressure drive technology, characterized by: The invention comprises a side oil cylinder (1) and a rock sample (15) on one side thereof, wherein an upper pressure plate (7) and a lower pressure plate (12) are respectively arranged above and below the rock sample (15), wherein the upper pressure plate (7) and the lower pressure plate (12) are connected via a load-bearing tie rod (8) and fixed via a load-bearing nut (6), a seepage base (13) is arranged at the bottom of the rock sample (15), sealing plates (9) are arranged on the upper and lower sides of the rock sample (15), and side pressure plates (10) are arranged around the rock sample (15).

2. A hydraulic fracturing test device suitable for pressure drive technology according to claim 1, characterized in that: The rock sample (15) adopts a flat plate structure, and a cylindrical blind hole is opened at the center of one end surface. The cylindrical blind hole is sealed with a conversion pressure head (17) through epoxy resin, and pressurized water penetrates into the rock sample (15) through the channel in the middle of the injection head (18) and the conversion pressure head (17).

3. A hydraulic fracturing test device suitable for pressure drive technology according to claim 2, characterized in that: The injection head (18) is arranged at the top center of the seepage base (13), the conversion pressure head (17) is arranged at the upper end of the injection head (18), and the conversion pressure head (17) and the injection head (18) are inserted into the cylindrical blind hole.

4. A hydraulic fracturing test device suitable for pressure drive technology according to claim 1, characterized in that: The lower pressure plate (12) is arranged on the top of the bottom table (14), and a main oil cylinder (13) is arranged inside the bottom table (14).

5. A hydraulic fracturing test device suitable for pressure drive technology according to claim 1, characterized in that: The side oil cylinder (1) is arranged on the sample support (5) via a rear end fixed support (2) and a fixed support (3), and the rear end fixed support (2) and the fixed support (3) are both connected to a linear guide rail (4) on the sample support (5).

6. A hydraulic fracturing test device suitable for pressure drive technology according to claim 1, characterized in that: The sealing plate (9) is used to prevent fluid cross-flow.

7. A hydraulic fracturing test device suitable for pressure drive technology according to claim 1, characterized in that: The injection head (18) and the seepage base (13) are both provided with pressure water channels, and the upper and lower sealing plates (9) are pressed tightly against the upper and lower end surfaces of the rock sample (15) by a vertical loading cylinder to block the seepage of pressure water.

8. A hydraulic fracturing test device suitable for pressure drive technology as claimed in claim 1, characterized in that: The injection head (18) adopts a convex structure, wherein a sealing ring is provided on the end with a larger diameter to cooperate with the seepage base (13) for sealing, and the end with a smaller diameter is inserted into the cylindrical blind hole of the rock sample (15) by connecting the conversion pressure head (17). The conversion pressure head (17) is coated with epoxy resin glue for sealing. The pressurized water enters the conversion pressure head (17) through the channel in the middle of the injection head (18) and then penetrates into the rock sample (15).

9. A hydraulic fracturing test method suitable for pressure drive technology, characterized in that: The following steps are involved: S1 Preparation and loading of rock samples; S2 pressure-driven fracturing simulation; S3 tracks crack morphology.

10. A hydraulic fracturing test method suitable for pressure drive technology according to claim 9, characterized in that: The step S1 specifically includes the following steps: S11 Preparation of flat rock specimens; S12 drills blind holes; S13 Loading rock samples.

11. A hydraulic fracturing test method suitable for pressure drive technology according to claim 10, characterized in that: In the step S11, preparing a flat rock specimen includes: The samples of underground cores or outcropping rock bodies are initially processed into flat rock specimens using drilling machines and cutting machines, and each plane of the flat rock specimens is polished using a grinder to make them flat and smooth.

12. A hydraulic fracturing test method suitable for pressure drive technology according to claim 11, characterized in that: In the step S11, the dimensions of the flat rock specimen are 48-52 cm in length, 48-52 cm in width, and 3-5 cm in height.

13. A hydraulic fracturing test method suitable for pressure drive technology according to claim 10, characterized in that: In the step S12, drilling a blind hole comprises: Use an electric drill to drill a blind hole in the center of one side of the test piece. After processing, clean the blind hole to ensure that no residue is left in the hole.

14. A hydraulic fracturing test method suitable for pressure drive technology according to claim 13, characterized in that: In the step S12, the blind hole adopts a cylindrical structure with a diameter of 5 to 7 mm and a depth of 1 / 2 of the thickness of the flat sample, which is 1 to 3 cm. The diameter of the cylindrical blind hole is larger than the diameter of the small end of the conversion pressure head.

15. A hydraulic fracturing test method suitable for pressure drive technology according to claim 10, characterized in that: In the step S13, loading the rock sample comprises: A conversion pressure head is placed in the rock sample, and epoxy resin glue is coated around the conversion pressure head to achieve bonding between the sample and the conversion pressure head. The bonded sample and the conversion pressure head are left to stand for a period of time to allow the epoxy resin glue to solidify and bond firmly; a lower sealing plate is placed on the seepage base, and the blind hole of the sample with the conversion pressure head bonded is aligned with the boss of the seepage base and placed on the sealing plate; an upper sealing plate is placed on the upper end face of the sample, and the core is pushed onto the lower pressure plate.

16. A hydraulic fracturing test method suitable for pressure drive technology according to claim 9, characterized in that: In step S2, the pressure-driven fracturing simulation includes: The main cylinder pump and side cylinder pump of the pressure-driven hydraulic fracturing test machine are used to increase the pressure of the rock sample in the three directions of X, Y and Z to a predetermined state, and water pressure is applied in a flow control mode, and fluid is continuously injected until the specimen is broken.

17. A hydraulic fracturing test method suitable for pressure drive technology according to claim 16, characterized in that: In step S2, the pumped fluid has a density of 1.0142 g / cm 3 , potassium chloride solution with a viscosity of 0.9987mPa·s.

18. A hydraulic fracturing test method suitable for pressure drive technology according to claim 9, characterized in that: In step S3, tracking the crack morphology includes: After the specimen is broken, add oil-soluble dye 1 to fluid 2, continue stirring until dye 1 is fully dissolved in fluid 2, and slowly inject fluid 2 into the rock specimen in a low flow mode.

19. A hydraulic fracturing test method suitable for pressure drive technology according to claim 18, characterized in that: In step S3, the second fluid is silicone oil, and the first oil-soluble dye is oil-soluble blue, in order to effectively trace the fracture morphology and prevent the fluid from being lost to the matrix.

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