Large true triaxial fracturing experiment device

Abstract

The utility model relates to the technical field of hydraulic fracturing, and discloses a large true triaxial fracturing experiment device which comprises a vertical rod upper cap, the bottom side of the vertical rod upper cap is movably connected with an upper pressing plate, the bottom side of the upper pressing plate is movably connected with an upper small pressing plate, the two sides of the upper pressing plate are connected with a long vertical rod and a short vertical rod in a penetrating mode, and the long vertical rod and the short vertical rod are connected in a penetrating mode. A lower large pressing plate is arranged at the bottom end of the upper small pressing plate, and the bottom ends of the long and short vertical rods are connected to the edge of the side wall of the lower large pressing plate in a penetrating mode. Under the simulated true triaxial stress, a hole is drilled in a rock core, a steel pipe is embedded to simulate perforation, liquid is injected to simulate crack initiation and crack extension, acoustic emission monitoring and the like are applied to observe the crack extension form, the influence of horizontal ground stress, rock brittleness, construction parameters and the like on the crack form is researched, and the stress state of underground rock can be simulated more accurately; therefore, the fracturing scheme is optimized, the yield and the recovery ratio of an oil and gas well are increased, the fracturing condition under the extreme geological condition can be simulated, and potential safety hazards can be found in advance.

Description

Technical Field

[0001] The utility model relates to the technical field of hydraulic fracturing, in particular to a large-scale true triaxial fracturing experimental device. Background Art

[0002] Hydraulic fracturing, as one of the main measures to increase oil and gas production, has been widely used in the modern petroleum industry and has played an important role in the production of low-permeability oil and gas reservoirs. The geometry of hydraulic fractures is one of the main factors affecting the effect of fracturing treatment. Economical and effective fracturing should allow fractures to extend in the reservoir as much as possible and prevent them from penetrating water layers and low-pressure permeability layers. This requires optimizing fracturing operation parameters based on a deep understanding of the laws of fracture expansion and taking effective measures to control fracture expansion.

[0003] Since the fracturing process requires a large amount of water in actual operation, it may aggravate the water shortage in some water-scarce areas. Unreasonable hydraulic fracturing may affect the underground stress state. If it is not handled properly during multiple actual tests, it may pollute groundwater and surface water. If the fracturing operation is improper, it may also cause damage to the reservoir, affecting the later oil and gas production efficiency and long-term mining effect. Utility Model Content

[0004] The purpose of the utility model is to solve the problem that unreasonable operation in the actual fracturing process easily causes pollution to groundwater and surface water. The utility model provides a large-scale true triaxial fracturing experimental device.

[0005] In order to achieve the above-mentioned purpose, the present invention specifically adopts the following technical solutions:

[0006] The large-scale true triaxial fracturing experimental device includes a cap on a vertical rod, the bottom side of the cap on the vertical rod is movably connected with an upper pressure plate, the bottom side of the upper pressure plate is movably connected with an upper small pressure plate, long and short vertical rods are connected on both sides of the upper pressure plate, the bottom end of the upper small pressure plate is provided with a lower large pressure plate, the bottom end of the long and short vertical rods is connected to the side wall edge of the lower large pressure plate, the top side of the lower large pressure plate is movably connected with a lower pad, the bottom end of the long and short vertical rods is sleeved with a lower cap, the top side of the lower cap is movably connected to the outer edge of the lower large pressure plate, the inner ring of the long and short vertical rods is provided with a main body, the inner ring of the main body is provided with an arc lining plate and a cylinder, the side wall of the arc lining plate is connected with a piston, the outer side of the piston is slidably connected to the inner side of the cylinder, and the inner sides of the arc lining plate and the piston are connected with angle joints.

[0007] Furthermore, the long and short vertical rods are arranged around the side walls of the upper pressing plate and the lower large pressing plate. The upper pressing plate is located above the lower large pressing plate. The upper pressing plate and the upper small pressing plate support the pressure in the Z-axis direction, and the main body supports the pressure in the X and Y-axis directions.

[0008] Furthermore, the bottom ends of the main body and the arc-shaped lining plate are fixedly connected to the top side of the lower pad, the main body supports pressure in the X and Y axis directions, and the clamping system is made of 45 steel.

[0009] Furthermore, the arc-shaped lining, the piston and the cylinder are arranged in a group on the inner ring of the main body, and the cylinder is located in the inner ring of the main body to form a square shape. The piston and the corner joint are both facing the direction of the inner shaft center of the main body. Under the control of computer software, the high-pressure oil pump injects hydraulic oil into the cylinder body according to experimental requirements, and the hydraulic oil drives the piston to move.

[0010] Furthermore, the upper small pressure plate is located above the inner rings of the cylinder, the upper pressure plate and the upper small pressure plate support the pressure in the Z-axis direction, and the main body supports the pressure in the X- and Y-axis directions.

[0011] Furthermore, the top ends of the long and short vertical poles and the side walls of the upper pressing plate are connected by upper pole caps, and the side walls of the lower large pressing plate and the bottom ends of the long and short vertical poles are connected by lower caps.

[0012] Furthermore, a square hydraulic block is provided on the outside of the cylinder, and three arc-surface pressure blocks are provided on the outer layer of the cylinder. The arc-surface pressure blocks are in close contact with the inner wall of the main body, and the direct contact surface with the rock block is a square hydraulic block with a cylinder inside and three arc-surface pressure blocks on the outer layer, which are in close contact with the inner wall of the main body.

[0013] Compared with the existing technology, the present invention provides a large-scale true triaxial fracturing test device with the following beneficial effects:

[0014] This large-scale true triaxial fracturing experimental device simulates true triaxial stress (rock overburden pressure, minimum and maximum formation stress), drills holes in the rock core and embeds steel pipes to simulate perforation, injects liquid to simulate crack initiation and crack extension, and uses acoustic emission monitoring to observe the crack expansion morphology. It studies the effects of horizontal ground stress, rock brittleness, construction parameters, etc. on crack morphology. It can more accurately simulate the stress state of underground rock, thereby optimizing fracturing plans and increasing the production and recovery rate of oil and gas wells. It can simulate fracturing situations under extreme geological conditions and discover potential safety hazards in advance. It helps researchers evaluate the effects of different fracturing technologies and parameters in the laboratory in advance, avoid unnecessary attempts in actual mining, and thus save a lot of manpower, material and financial resources. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 This is a practical front section view;

[0016] Figure 2 This is a cross-sectional view of the top structure of this utility model.

[0017] In the figure: 1. Upper cap of the vertical pole; 2. Upper pressure plate; 3. Upper small pressure plate; 4. Long and short vertical poles; 5. Lower pad; 6. Lower large pressure plate; 7. Lower cap; 8. Main body; 9. Arc lining plate; 10. Piston; 11. Cylinder; 12. Angle joint. DETAILED DESCRIPTION

[0018] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the embodiments described are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention. Example 1:

[0019] like Figure 1-Figure 2 As shown, the large-scale true triaxial fracturing experimental device includes a cap 1 on the vertical rod, the bottom side of the cap 1 on the vertical rod is movably connected with an upper pressure plate 2, the bottom side of the upper pressure plate 2 is movably connected with an upper small pressure plate 3, and the two sides of the upper pressure plate 2 are penetrated by long and short vertical rods 4, the bottom end of the upper small pressure plate 3 is provided with a lower large pressure plate 6, the bottom end of the long and short vertical rods 4 is penetrated and connected to the side wall edge of the lower large pressure plate 6, and the top side of the lower large pressure plate 6 is movably connected with a lower pad 5, the bottom end of the long and short vertical rods 4 is sleeved with a lower cap 7, and the top side of the lower cap 7 is movably connected to the outer edge of the lower large pressure plate 6, the inner ring of the long and short vertical rods 4 is provided with a main body 8, the inner ring of the main body 8 is provided with an arc lining plate 9 and a cylinder 11, the side wall of the arc lining plate 9 is penetrated by a piston 10, the outer side of the piston 10 is slidably connected to the inner side of the cylinder 11, and the inner sides of the arc lining plate 9 and the piston 10 are penetrated and connected with an angle joint 12.

[0020] like Figure 1-Figure 2 As shown, the long and short vertical rods 4 are arranged around the side walls of the upper pressing plate 2 and the lower large pressing plate 6. The upper pressing plate 2 is located above the lower large pressing plate 6. The bottom ends of the main body 8 and the arc-shaped lining plate 9 are fixedly connected to the top side of the lower pad 5. The upper small pressing plate 3 is located above the inner ring of the cylinder 11. The upper pressing plate 2 and the upper small pressing plate 3 support the pressure in the Z-axis direction, and the main body 8 supports the pressure in the X- and Y-axis directions. The clamping system is made of 45 steel and is quenched and tempered, with high strength and no deformation.

[0021] like Figure 1-Figure 2As shown, four groups of arc-shaped liners 9, pistons 10 and cylinders 11 are arranged on the inner ring of the main body 8. The four groups of cylinders 11 are located in the inner ring of the main body 8 to form a square shape. The pistons 10 and angle joints 12 are all facing the direction of the inner axis center of the main body 8. The hydraulic oil drives the piston 10 to move, and the power surface of the piston 10 loads stress on the rock block through the square hydraulic block. Example 2:

[0022] like Figure 1-Figure 2 As shown, the top of the long and short vertical rods 4 and the side wall of the upper pressing plate 2 are connected by the vertical rod upper cap 1, and the side wall of the lower large pressing plate 6 and the bottom end of the long and short vertical rods 4 are connected by the lower cap 7;

[0023] like Figure 1-Figure 2 As shown, a square hydraulic block is provided on the outside of the cylinder 11, and three arc-surface pressure blocks are provided on the outer layer of the cylinder 11. The arc-surface pressure blocks are in close contact with the inner wall of the main body 8, and the direct contact surface with the rock block is a square hydraulic block with the cylinder 11 inside and three arc-surface pressure blocks on the outer layer, which are in close contact with the inner wall of the main body 8.

[0024] Working principle: Figure 1-Figure 2 As shown, the upper pressing plate 2 and the upper small pressing plate 3 support the pressure in the Z-axis direction, and the main body 8 supports the pressure in the X- and Y-axis directions. The clamping system is made of 45 steel and is quenched and tempered, with high strength and no deformation.

[0025] The surface in direct contact with the rock is a square hydraulic block with an inner cylinder 11 and three outer arc-surface pressure blocks in close contact with the inner wall of the main body 8. Under the control of computer software, a high-pressure oil pump injects hydraulic oil into the cylinder 11 according to experimental requirements. The hydraulic oil drives the piston 10 to move. The power surface of the piston 10 applies stress to the rock through the square hydraulic block, achieving the purpose of clamping and stressing the rock block on six surfaces in the X, Y, and Z directions. Fracturing fluid is injected under true triaxial stress to simulate crack initiation and extension, and the effect of different fluids on fracture network reconstruction under different process and reservoir conditions is studied. Compared with indirect methods such as numerical simulation and fracture detection, the true triaxial fracturing simulation device is the most effective and important means to study the mechanism of fracture propagation and the factors affecting fracture network volume. Under simulated true triaxial stress (rock overburden pressure, minimum and maximum formation stress), the system drills holes in the rock core and inserts steel pipes to simulate perforation. Liquid is injected to simulate crack initiation and fracture extension. Acoustic emission monitoring and other methods are used to observe the fracture propagation morphology, and the influence of horizontal ground stress, rock brittleness, and construction parameters on fracture morphology are studied.

[0026] This supporting device can be used to conduct experiments on the expansion laws of hydraulic fractures on different shale outcrops, providing experimental support for clarifying the dynamics of fracture expansion, the mechanism of fracture expansion, and the three-dimensional fracture morphology.

[0027] The device can achieve:

[0028] a. Fracturing simulation of different types of rock samples (artificial rock samples, natural outcrop rock samples):

[0029] By constructing an experimental environment, fracturing simulations are performed on artificial rock samples and natural outcrop rock samples respectively. Artificial rock samples can be customized according to specific parameters and requirements, which helps to control variables and study fracturing behavior under specific conditions.

[0030] b. Fracturing evaluation of different completion methods (casing completion, open hole completion):

[0031] Compare and evaluate the performance of two common completion methods, cased-hole completion and open-hole completion, during fracturing.

[0032] c. Evaluation of different fluid fracturing (CO2, slick water, linear gel, weak gel, acid, etc.):

[0033] A variety of fracturing fluids were evaluated, each with unique properties and mechanisms of action. CO2 fracturing offers advantages such as low damage and improved oil and gas recovery; slickwater enables large-scale volume fracturing; linear gels and weak gels offer sand-carrying and fracture-forming capabilities; and acid can be used to dissolve rock and improve reservoir permeability.

[0034] d. Evaluation of different three-dimensional stress differential pressure fracturing:

[0035] The effects of hydraulic fracturing and crack propagation patterns under different three-dimensional stress differences are studied. The three-dimensional stress difference has a significant impact on the crack initiation pressure, shape, extension direction, and propagation speed.

[0036] e. Three-dimensional geometric dimension testing and evaluation technology of support cracks:

[0037] Using advanced measurement and analysis techniques, the three-dimensional geometric dimensions of the support cracks, including length, width, height, etc., are accurately obtained and comprehensively evaluated.

[0038] f. Multi-well zipper fracturing simulation and evaluation experimental technology:

[0039] Simulate and evaluate multi-well zipper fracturing, a technique in which fracturing treatments are performed alternately in adjacent wells. This technique can improve operational efficiency and increase reservoir stimulation volume, but it also presents challenges such as operation coordination and fracture control.

[0040] The system collects and processes triaxial pressure values, triaxial displacement, rock stress and strain values, fracturing flow pressure, and acoustic emission signals in real time. The system includes hardware (computer, printer, data acquisition card, and input / output board), software (for instrument control and data acquisition and processing), a workbench, and a control panel. To ensure measurement accuracy and control reliability, the C168H digital acquisition control card is used for digital acquisition and transmission.

[0041] The software runs under Windows 10. The instrument workflow is displayed on the interface, enabling human-computer interaction. Once the operator sets the parameters, the system can be operated unattended. The computer automatically controls three high-pressure hydraulic servo pumps, loading the hydraulic cylinders in the X, Y, and Z axes, and controlling high-flow, high-pressure, constant-speed, and constant-pressure fracturing pumps to fractur e the core. The system automatically collects all triaxial pressure values, triaxial displacement, rock stress and strain values, fracturing flow pressure, and acoustic emission signals, and processes the collected data to generate raw data reports, analysis reports, and graphs. It also generates a database file format for flexible user experience.

Claims

1. A large-scale true triaxial fracturing test device, comprising a vertical pole and a cap (1), characterized in that: The bottom side of the upper cap (1) of the vertical rod is movably connected to an upper pressing plate (2), the bottom side of the upper pressing plate (2) is movably connected to an upper small pressing plate (3), both sides of the upper pressing plate (2) are connected through long and short vertical rods (4), the bottom end of the upper small pressing plate (3) is provided with a lower large pressing plate (6), the bottom end of the long and short vertical rods (4) is connected through the side wall edge of the lower large pressing plate (6), the top side of the lower large pressing plate (6) is movably connected to a lower pad (5), the bottom end of the long and short vertical rods (4) is sleeved with a lower and The top side of the lower cap (7) is movably connected to the outer edge of the lower large pressure plate (6), the inner ring of the long and short vertical rods (4) is provided with a main body (8), the inner ring of the main body (8) is provided with an arc lining plate (9) and a cylinder (11), the side wall of the arc lining plate (9) is penetrated and connected with a piston (10), the outer side of the piston (10) is slidably connected to the inner side of the cylinder (11), and the inner sides of the arc lining plate (9) and the piston (10) are penetrated and connected with an angle joint (12).

2. The large-scale true triaxial fracturing test device according to claim 1, characterized in that: The long and short vertical rods (4) are arranged around the side walls of the upper pressing plate (2) and the lower large pressing plate (6), and the upper pressing plate (2) is located above the lower large pressing plate (6).

3. The large-scale true triaxial fracturing test device according to claim 1, characterized in that: The bottom ends of the main body (8) and the arc-shaped lining plate (9) are fixedly connected to the top side of the lower pad (5).

4. The large-scale true triaxial fracturing test device according to claim 1, characterized in that: The arc-shaped lining plate (9), the piston (10) and the cylinder (11) are arranged in four groups on the inner ring of the main body (8). The four groups of cylinders (11) are located on the inner ring of the main body (8) to form a square shape. The piston (10) and the angle joint (12) are both oriented in the direction of the inner shaft center of the main body (8).

5. The large-scale true triaxial fracturing test device according to claim 1, characterized in that: The upper small pressure plate (3) is located above between the inner rings of the cylinder (11).

6. The large-scale true triaxial fracturing test device according to claim 1, characterized in that: The top ends of the long and short vertical rods (4) and the side walls of the upper pressing plate (2) are connected by the upper caps (1) of the vertical rods, and the side walls of the lower large pressing plate (6) and the bottom ends of the long and short vertical rods (4) are connected by the lower caps (7).

7. The large-scale true triaxial fracturing test device according to claim 1, characterized in that: A square hydraulic block is provided on the outside of the cylinder (11), and three arc-surface pressure blocks are provided on the outer layer of the cylinder (11). The arc-surface pressure blocks are in close contact with the inner wall of the main body (8).

Images