Device and method for simulating dynamic embedding of proppant in crustal stress evolution process

Abstract

The invention relates to a device and a method for simulating dynamic embedding of a proppant in a crustal stress evolution process, and the method comprises the following steps: applying forces with the same magnitude and opposite directions to each symmetric plane of an upper rock plate and a lower rock plate for performing maximum / minimum horizontal principal stress simulation; applying forces with different magnitudes and different directions to each surface of the upper rock plate and the lower rock plate, and dynamically adjusting the horizontal principal stress direction to simulate the ground stress direction reversal in the production stage; the shear stress is applied by controlling the principal stress and displacement control systems on the opposite sides of the upper rock plate and the lower rock plate, so that the upper rock plate and the lower rock plate generate transverse displacement, and the'twisting 'effect of the fracture surface is simulated. According to the invention, collaborative simulation of crustal stress direction change and shear displacement evolution is realized for the first time, and stress-displacement dynamic response in a proppant embedding process is captured in real time by using the displacement sensor, so that the blank of proppant behavior characterization under a dynamic shear stress field in the prior art is filled.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of oil and gas development, and is mainly used for simulating the dynamic embedding of proppants in the process of stress evolution after reservoir fracturing, and particularly relates to a method for simulating the dynamic embedding of proppants in the process of stress evolution. BACKGROUND

[0002] In the development of oil and gas, hydraulic fracturing technology is the core means to improve the permeability of the reservoir and the production of oil and gas. In the process of fracturing, high-viscosity fracturing fluid needs to be injected into the formation to form an artificial fracture, and the fracture is filled with proppants to maintain the conductivity of the fracture channel. However, in the actual reservoir, the stress state is not static, but dynamically evolves with the change of fracturing operation, production and exploitation, and pore pressure. The injection of high-viscosity fracturing fluid during fracturing can significantly change the pore pressure of the reservoir. In the subsequent production stage, the residual fracturing fluid in the fracture is discharged, and the pore pressure of the formation gradually decreases. During this process, the maximum and minimum principal stresses of the reservoir and their directions are dynamically adjusted. This evolution of stress not only directly affects the closure pressure of the fracture, but also causes complex dynamic interactions between the fracture surface and the proppants through shearing, such as embedding, crushing, sliding, shearing and rearrangement of the proppants in the fracture wall, ultimately affecting the long-term stability of the fracture conductivity. Existing research has shown that the dynamic evolution of principal stress and pore pressure not only affects the fracture conductivity, but also directly determines the embedding depth and distribution state of the proppants, thereby affecting the long-term productivity and depletion law of the oil and gas well.

[0003] Traditional proppant embedding experimental devices are mainly based on static loading, which can only simulate the vertical stress in a single direction, and are difficult to truly simulate the continuous evolution process of the magnitude and direction of the principal stress and shear stress before and after the fracturing of the formation. The traditional method ignores the dynamic influence of the direction change of the stress in the real reservoir (such as the reversal of the horizontal principal stress direction) and the shear stress on the behavior of the proppants, and cannot synchronously capture the force-displacement coupling change of the proppants between the rock walls. In addition, the traditional method can only measure the stress or displacement in a single direction, lacks complete monitoring means for the shear dislocation, stress difference change and dynamic embedding process of the double rock plate interface, and is difficult to meet the needs of in-depth research on the "rubbing" effect of the proppants (i.e. the mechanism of small relative sliding under different stress directions and magnitudes).

[0004] These technical defects make it difficult for experimental evaluation results to truly reflect the long-term performance of the proppants under complex stress evolution conditions, thereby affecting the optimization of fracturing design and the accurate prediction of fracture conductivity. SUMMARY

[0005] The present application aims to provide a test device that can simultaneously apply and controllably change the maximum and minimum principal stress magnitude and direction in the laboratory, and realize the relative displacement and shear loading of the double rock plates.

[0006] The technical scheme of the present application is characterized in that: The device for simulating the dynamic embedding of proppants in the process of stress evolution comprises a proppant placement chamber with proppants built-in, and the proppants are located between the upper rock plate and the lower rock plate in the proppant placement chamber; characterized in that the upper rock plate and the lower rock plate are connected with a vertical stress application system, and the front, rear, left and right four sides of the upper rock plate and the lower rock plate are each provided with a principal stress and displacement control system along the horizontal direction.

[0007] The proppant placement chamber is provided with rock plates, gaskets and pressurizing cavities in the proppants built-in from inside to outside on the upper and lower sides in sequence.

[0008] The proppant placement chamber is provided with an upper pressurizing cavity, an upper gasket and an upper rock plate from top to bottom in sequence, a lower rock plate, a lower gasket and a lower pressurizing cavity, and the proppants are located between the upper rock plate and the lower rock plate; the upper pressurizing cavity is provided with an upper pressurizing port, and the lower pressurizing cavity is provided with a lower pressurizing port; further comprising a gas cylinder, the upper pressurizing port is connected to the gas cylinder through an upper pressurizing pipeline, and the lower pressurizing port is connected to the gas cylinder through a lower pressurizing pipeline.

[0009] The principal stress and displacement control system has a total of 8 groups, which are front upper control device, front lower control device, rear upper control device, rear lower control device, left upper control device, left lower control device, right upper control device and right lower control device; each principal stress and displacement control system comprises a hydraulic rod and a pressurizing rod connected in sequence; the pressurizing rod is connected with the upper rock plate / lower rock plate through a gasket.

[0010] The front upper control device comprises a front upper hydraulic rod and a front upper pressure rod connected in sequence, and the front upper pressure rod is connected with the upper rock plate through a front upper gasket; the front lower control device comprises a front lower hydraulic rod and a front lower pressure rod connected in sequence, and the front lower pressure rod is connected with the lower rock plate through a front lower gasket; the rear upper control device comprises a rear upper hydraulic rod and a rear upper pressure rod connected in sequence, and the rear upper pressure rod is connected with the upper rock plate through a rear upper gasket; the rear lower control device comprises a rear lower hydraulic rod and a rear lower pressure rod connected in sequence, and the rear lower pressure rod is connected with the lower rock plate through a rear lower gasket; the left upper control device comprises a left upper hydraulic rod and a left upper pressure rod connected in sequence, and the left upper pressure rod is connected with the upper rock plate through a left upper gasket; the left lower control device comprises a left lower hydraulic rod and a left lower pressure rod connected in sequence, and the left lower pressure rod is connected with the lower rock plate through a left lower gasket; the right upper control device comprises a right upper hydraulic rod and a right upper pressure rod connected in sequence, and the right upper pressure rod is connected with the upper rock plate through a right upper gasket; the right lower control device comprises a right lower hydraulic rod and a right lower pressure rod connected in sequence, and the right lower pressure rod is connected with the lower rock plate through a right lower gasket; wherein the upper gasket, the lower gasket, the front upper gasket, the front lower gasket, the rear upper gasket, the rear lower gasket, the left upper gasket, the left lower gasket, the right upper gasket and the right lower gasket are all internally provided with displacement sensors.

[0011] The front upper hydraulic rod and the front lower hydraulic rod share a front base, the rear upper hydraulic rod and the rear lower hydraulic rod share a rear base, the left upper hydraulic rod and the left lower hydraulic rod share a left base, and the right upper hydraulic rod and the right lower hydraulic rod share a right base.

[0012] The device further comprises a computer connected with each of the principal stress and displacement control systems.

[0013] The device further comprises a computer connected with each of the principal stress and displacement control systems.

[0014] A method for simulating dynamic embedding of proppants in a process of evolution of in-situ stress, using the device for simulating dynamic embedding of proppants in a process of evolution of in-situ stress as described above, the method is used as follows: The proppant placement chamber is filled with proppants, and a gas is injected into the proppant placement chamber through the vertical stress application system to simulate the process of closure of a reservoir fracture; (1) the same size and opposite direction forces are applied to each of the symmetric surfaces of the upper rock plate and the lower rock plate to simulate the maximum / minimum horizontal principal stress; (2) exerting forces of different sizes and different directions on each face of the upper rock plate and the lower rock plate, dynamically adjusting the direction of the horizontal principal stress, to simulate the reversal of the stress direction in the production stage; (3) exerting shear stress by controlling the principal stress and displacement control system located on the opposite side of the upper rock plate and the lower rock plate, to make the upper rock plate and the lower rock plate produce lateral displacement, to simulate the "wringing" effect of the fracture surface.

[0015] A method for simulating the dynamic embedding of proppants in the evolution process of the ground stress, using the device for simulating the dynamic embedding of proppants in the evolution process of the ground stress, the method is as follows: The proppant placement chamber is filled with proppants, and gas is injected into the upper and lower pressurizing cavities through the lower and upper pressurizing pipelines, to simulate the reservoir fracture closure process; The maximum / minimum horizontal principal stress is exerted on the proppant placement chamber (18) through the front upper hydraulic rod (19), the front lower hydraulic rod (21), the rear upper hydraulic rod (14), the rear lower hydraulic rod (15), the left upper hydraulic rod (6), the left lower hydraulic rod (46), the right upper hydraulic rod (25) and the right lower hydraulic rod (24); the force direction and size exerted by the hydraulic rods located on the same face are the same, and the force size exerted by the hydraulic rods located on the symmetrical faces is the same and the directions are opposite; The pressure of the left upper hydraulic rod, the left lower hydraulic rod, the rear upper hydraulic rod, the rear lower hydraulic rod, the front upper hydraulic rod, the front lower hydraulic rod, the right upper hydraulic rod and the right lower hydraulic rod is adjusted, so that the horizontal principal stress exerted by each hydraulic rod is different, the dynamic adjustment of the horizontal principal stress direction is realized, to simulate the reversal of the stress direction in the production stage; The shear stress is exerted by controlling a group of hydraulic rods located on the opposite side and at different heights, to make the upper rock plate produce lateral displacement relative to the lower rock plate, to simulate the "wringing" effect of the fracture surface.

[0016] The technical effect of the present application is that: The upper and lower faces of the double rock plates (the upper rock plate and the lower rock plate) are provided with vertical stress exerting systems, to simulate the reservoir fracture closure process; the four side faces are provided with principal stress and displacement control systems, different horizontal principal stresses are exerted on each face of the double rock plates, and different functions are realized: (1) the same size and opposite directions of force are exerted on each symmetrical face of the upper rock plate and the lower rock plate, to simulate the maximum / minimum horizontal principal stress; (2) forces of different sizes and different directions are exerted on each face of the upper rock plate and the lower rock plate, to dynamically adjust the direction of the horizontal principal stress, to simulate the reversal of the stress direction in the production stage; (3) the shear stress is exerted by controlling the principal stress and displacement control system located on the opposite side of the upper rock plate and the lower rock plate, to make the upper rock plate and the lower rock plate produce lateral displacement, to simulate the "wringing" effect of the fracture surface.

[0017] The application realizes dynamic loading of a closed-shear composite stress field, and significantly improves the reduction degree of experiments on real reservoir stress evolution. The embedding depth, distribution characteristics and shear behavior of the proppant under different stress conditions can be observed and quantified.

[0018] By quantifying the embedding rules of the proppant under different stress paths, direct experimental basis is provided for the selection of proppant particle size, optimization of sanding concentration and adjustment of construction parameters in reservoir fracturing design, and the long-term conductivity of the fracture is improved.

[0019] The application first realizes the coordinated simulation of the change of the ground stress direction and the evolution of the shear displacement, and uses the displacement sensor to capture the stress-displacement dynamic response in the proppant embedding process in real time, thereby filling the gap in the characterization of the proppant behavior under the dynamic shear stress field in the prior art. BRIEF DESCRIPTION OF DRAWINGS

[0020] Figure 1 It is a structural schematic diagram of the application.

[0021] Figure 2 It is a front schematic diagram of the application.

[0022] Figure 3 It is a left schematic diagram of the application.

[0023] The figure legend: 1, gas cylinder; 2, valve; 3, lower pressurizing pipeline; 4, upper pressurizing pipeline; 5, left upper pressurizing rod; 6, left upper hydraulic rod; 7, left upper data line; 8, left base; 9, left lower pressurizing rod; 10, rear data line; 11, control line; 12, computer; 13, rear base; 14, rear upper hydraulic rod; 15, rear lower hydraulic rod; 16, lower pressurizing port; 17, upper pressurizing port; 18, proppant laying chamber; 19, front upper hydraulic rod; 20, front base; 21, front lower hydraulic rod; 22, right upper pressurizing rod; 23, right lower pressurizing rod; 24, right lower hydraulic rod; 25, right upper hydraulic rod; 26, right base; 27, front right data line; 28, right upper data line; 29, lower gasket; 30, lower pressurizing cavity; 31, upper pressurizing cavity; 32, upper rock plate; 33, lower rock plate; 34, proppant; 35, upper gasket; 36, left upper gasket; 37, left lower gasket; 38, rear upper pressurizing rod; 39, rear upper gasket; 40, rear lower pressurizing rod; 41, rear lower gasket; 42, front upper gasket; 43, front upper pressurizing rod; 44, front lower gasket; 45, front lower pressurizing rod; 46, left lower hydraulic rod; 47, right upper gasket; 48, right lower gasket. DETAILED DESCRIPTION

[0024] Example 1 The device for simulating the dynamic embedding of proppants in the stress evolution process comprises a proppant placement chamber 18 with proppants 34 arranged therein between an upper rock plate 32 and a lower rock plate 33; the upper rock plate 32 and the lower rock plate 33 are connected with a vertical stress applying system, and the front, back, left and right four sides of the upper rock plate 32 and the lower rock plate 33 are provided with a main stress and displacement control system along the horizontal direction.

[0025] The specific implementation process of the embodiment is as follows: The upper and lower two sides of the double rock plates (the upper rock plate 32 and the lower rock plate 33) are provided with a vertical stress applying system to simulate the reservoir fracture closure process; the four sides are provided with a main stress and displacement control system, and different horizontal main stresses are applied to each side of the double rock plates to realize different functions. (1) the same force is applied to each side of the upper rock plate 32 and the lower rock plate 33 to simulate the maximum / minimum horizontal main stress; (2) different forces of different directions are applied to each side of the upper rock plate 32 and the lower rock plate 33 to dynamically adjust the horizontal main stress direction to simulate the stress direction reversal in the production stage; (3) the main stress and displacement control system on the opposite side of the upper rock plate 32 and the lower rock plate 33 is controlled to apply shear stress to make the upper rock plate 32 and the lower rock plate 33 produce lateral displacement to simulate the “rubbing” effect of the fracture surface.

[0026] Embodiment 2 Based on the embodiment 1, further comprising: The proppant placement chamber 18 is provided with a rock plate, a gasket and a pressurizing cavity from inside to outside on the upper and lower sides of the proppants 34 arranged therein, and the pressurizing cavity is connected with a gas input device.

[0027] The proppant placement chamber 18 is provided with an upper pressurizing cavity 31, an upper gasket 35 and an upper rock plate 32 from top to bottom, a lower rock plate 33, a lower gasket 29 and a lower pressurizing cavity 30, and the proppants 34 are located between the upper rock plate 32 and the lower rock plate 33; the upper pressurizing cavity 31 is provided with an upper pressurizing port 17, and the lower pressurizing cavity 30 is provided with a lower pressurizing port 16; further comprising a gas cylinder 1, the upper pressurizing port 17 is connected to the gas cylinder 1 through an upper pressurizing pipeline 4, and the lower pressurizing port 16 is connected to the gas cylinder 1 through a lower pressurizing pipeline 3.

[0028] Embodiment 3 Based on the embodiment 2, further comprising: The main stress and displacement control system is composed of 8 groups, namely, front upper control device, front lower control device, rear upper control device, rear lower control device, left upper control device, left lower control device, right upper control device and right lower control device; each main stress and displacement control system comprises a hydraulic rod and a pressure rod connected in sequence; the pressure rod is connected with the upper rock plate 32 / lower rock plate 33 through a gasket.

[0029] The front upper control device comprises a front upper hydraulic rod 19 and a front upper pressure rod 43 connected in sequence, and the front upper pressure rod 43 is connected with the upper rock plate 32 through a front upper gasket 42; the front lower control device comprises a front lower hydraulic rod 21 and a front lower pressure rod 45 connected in sequence, and the front lower pressure rod 45 is connected with the lower rock plate 33 through a front lower gasket 44; the rear upper control device comprises a rear upper hydraulic rod 14 and a rear upper pressure rod 38 connected in sequence, and the rear upper pressure rod 38 is connected with the upper rock plate 32 through a rear upper gasket 39; the rear lower control device comprises a rear lower hydraulic rod 15 and a rear lower pressure rod 40 connected in sequence, and the rear lower pressure rod 40 is connected with the lower rock plate 33 through a rear lower gasket 41; the left upper control device comprises a left upper hydraulic rod 6 and a left upper pressure rod 5 connected in sequence, and the left upper pressure rod 5 is connected with the upper rock plate 32 through a left upper gasket 36; the left lower control device comprises a left lower hydraulic rod 46 and a left lower pressure rod 9 connected in sequence, and the left lower pressure rod 9 is connected with the lower rock plate 33 through a left lower gasket 37; the right upper control device comprises a right upper hydraulic rod 25 and a right upper pressure rod 22 connected in sequence, and the right upper pressure rod 22 is connected with the upper rock plate 32 through a right upper gasket 47; the right lower control device comprises a right lower hydraulic rod 24 and a right lower pressure rod 23 connected in sequence, and the right lower pressure rod 23 is connected with the lower rock plate 33 through a right lower gasket 48; wherein, the upper gasket 35, the lower gasket 29, the front upper gasket 42, the front lower gasket 44, the rear upper gasket 39, the rear lower gasket 41, the left upper gasket 36, the left lower gasket 37, the right upper gasket 47 and the right lower gasket 48 are all internally provided with displacement sensors.

[0030] The front upper hydraulic rod 19 and the front lower hydraulic rod 21 share a front base 20, the rear upper hydraulic rod 14 and the rear lower hydraulic rod 15 share a rear base 13, the left upper hydraulic rod 6 and the left lower hydraulic rod 46 share a left base 8, and the right upper hydraulic rod 25 and the right lower hydraulic rod 15 share a right base 26.

[0031] Example 4 Based on example 3, further comprising: Further comprising a computer 12, which is connected with each main stress and displacement control system respectively; Also includes a computer 12, the computer 12 is connected to the upper left hydraulic rod 6 through the upper left data line 7, connected to the lower left hydraulic rod 46, the upper rear hydraulic rod 14 and the lower rear hydraulic rod 15 through the rear left data line 10, connected to the upper front hydraulic rod 19, the lower front hydraulic rod 21 and the lower right hydraulic rod 24 through the right front data line 27, connected to the upper right hydraulic rod 25 through the upper right data line 28; also connected to the valve 2 provided with the outlet end of the gas cylinder 1 through a control line 11.

[0032] The specific implementation process of the embodiment is: The proppant placement chamber 18 is filled with proppant 34, and the upper pressurizing cavity 31 and the lower pressurizing cavity 30 are injected with gas through the lower pressurizing pipeline 3 and the upper pressurizing pipeline 4 to simulate the reservoir fracture closure process; The upper front hydraulic rod 19, the lower front hydraulic rod 21, the upper rear hydraulic rod 14 and the lower rear hydraulic rod 15 apply the same force, the upper front hydraulic rod 19 and the lower front hydraulic rod 21 apply the same force in the same direction, and the upper rear hydraulic rod 14 and the lower rear hydraulic rod 15 apply the force in the opposite direction; The upper left hydraulic rod 6, the lower left hydraulic rod 46, the upper right hydraulic rod 25 and the lower right hydraulic rod 24 apply the same force, the upper left hydraulic rod 6 and the lower left hydraulic rod 46 apply the same force in the same direction, and the upper right hydraulic rod 25 and the lower right hydraulic rod 24 apply the force in the opposite direction; By adjusting the size and direction of the force applied by the upper left hydraulic rod 6, the lower left hydraulic rod 46, the upper rear hydraulic rod 14, the lower rear hydraulic rod 15, the upper front hydraulic rod 19, the lower front hydraulic rod 21, the upper right hydraulic rod 25 and the lower right hydraulic rod 24, the dynamic adjustment of the horizontal principal stress direction is realized to simulate the reversal of the stress direction during production; By controlling the principal stress and displacement control system located on the opposite side of the upper rock plate 32 and the lower rock plate 33, such as the upper left hydraulic rod 6 and the lower right hydraulic rod 24, the shear stress is applied to make the upper rock plate 32 and the lower rock plate 33 produce lateral displacement, and the "rubbing" effect of the fracture surface is simulated.

[0033] Specific experimental cases A method for simulating the dynamic embedding of proppant in the process of evolution of ground stress, the method is as follows: (1) Experimental material preparation: in order to make the subsequent experimental results reflect the actual situation of oilfield site to the greatest extent, the upper rock plate 32 and the lower rock plate 33 are both of sandstone material, which are processed by line cutting machine from outcrop core of a block in southeast Ordos Basin, with an average porosity of 4.0-8.2% and an average permeability of 0.3-0.6 mD; The upper rock plate 32 and the lower rock plate 33 are combined by a rectangle (middle part) and two semicircles with diameters equal to the length of the short side of the rectangle (located at both ends of the rectangle). After the upper rock plate 32 and the lower rock plate 33 are buckled, a closed interval is formed, the length of which is 17.7 cm, the width is 3.7 cm, the thickness is 1.1 cm, and both ends are semicircular. The built-in proppant 34 is a ceramic proppant 34, the mesh number is 40-70, the average particle size is 351 μm, the bulk density is 1.76 g / cm3, and the breakage rate under 5 MPa is 1.35%.

[0034] (2) Device assembly and inspection, connect cylinder 1, upper pressurizing pipeline 4 and upper pressurizing port 17, connect cylinder 1, lower pressurizing pipeline 3 and lower pressurizing port 16, and check the tightness and leakage of the connection.

[0035] (3) Rock plate installation and proppant 34 filling: fix the upper rock plate 32 in the upper pressurizing cavity 31 and the lower rock plate 33 in the lower pressurizing cavity 30, and ensure that the surfaces are parallel. Put the upper gasket 35 on the upper rock plate 32 and the lower gasket 29 on the lower rock plate 33 to ensure that the stress is applied completely and uniformly to the upper rock plate 32 through the upper gasket 35 and to the lower rock plate 33 through the lower gasket 29 when the vertical stress is applied, and the ceramic proppant 34 with a particle size of 40 / 70 mesh is laid between the upper rock plate 32 and the lower rock plate 33.

[0036] (4) Vertical stress loading: open the valve 2, inject gas into the upper pressurizing cavity 31 and the lower pressurizing cavity 30 through the lower pressurizing pipeline 3 and the upper pressurizing pipeline 4 to simulate the reservoir fracture closure process; adjust the gas pressure to control the size of the vertical closure stress, and set the initial stress to 5 MPa (simulate the initial closure state of the fracture after fracturing).

[0037] (5) Horizontal principal stress loading: the maximum / minimum horizontal principal stress simulation is realized by connecting the left upper hydraulic rod 6 through the computer 12 through the left upper data line 7; connecting the left lower hydraulic rod 46, the rear upper hydraulic rod 14 and the rear lower hydraulic rod 15 through the left rear data line 10; connecting the front upper hydraulic rod 19, the front lower hydraulic rod 21 and the right lower hydraulic rod 24 through the front right data line 27, and connecting to the right upper hydraulic rod 25 through the right upper data line 28 to apply the maximum horizontal principal stress σH=10 MPa and the minimum horizontal principal stress σh=8 MPa.

[0038] (6) By adjusting the size and direction of the applied force of the left upper hydraulic rod 6, the left lower hydraulic rod 46, the rear upper hydraulic rod 14, the rear lower hydraulic rod 15, the front upper hydraulic rod 19, the front lower hydraulic rod 21 and the right lower hydraulic rod 24, the dynamic adjustment of the direction of the horizontal principal stress is realized, and the clockwise rotation of 0°, 15° and 30° is set in this embodiment to simulate the reversal of the in-situ stress direction in the production stage.

[0039] (7) Shear dislocation simulation: control the left upper hydraulic rod 6 and the right lower hydraulic rod 24 to advance synchronously, apply shear stress τ = 3 MPa. Make the upper rock plate 32 generate transverse displacement relative to the lower rock plate 33, the displacement amount is set to Δ = 0.5 mm, Δ = 1 mm, Δ = 1.5 mm, Δ = 2 mm, simulate the "wringing" effect of the crack surface.

[0040] (8) Real-time data monitoring and data analysis, through the high-precision displacement sensor built-in the upper gasket 35, the lower gasket 29, the front upper gasket 42, the front lower gasket 44, the rear upper gasket 39, the rear lower gasket 41, the left upper gasket 36, the left lower gasket 37, the right upper gasket 47 and the right lower gasket 48, the shear displacement amount of the upper rock plate 32 and the lower rock plate 33 and the embedding depth of the proppant 34 are recorded in real time. According to the data, the relationship between the maximum / minimum horizontal principal stress change, the rock plate wringing and the proppant 34 crushing rate, the embedding depth under the consideration of the geostress evolution is analyzed quantitatively, and the fracturing construction parameters (such as the proppant 34 particle size selection is 40 / 70 mesh) are optimized.

[0041] Table 1 Proppant crushing rate and embedding depth experimental results table Through the above steps, the combined effect of geostress direction rotation and shear dislocation is successfully simulated. The experimental data shows that the shear stress leads to the increase of the proppant embedding depth, which verifies that the application can systematically and accurately reproduce the complex influence of the geostress evolution in the reservoir fracturing and production stage on the dynamic embedding of the proppant, and has the accurate characterization ability of the proppant behavior under the dynamic stress field. It provides reliable experimental basis for optimizing the field fracturing design and proppant selection.

Claims

1. An apparatus for simulating the dynamic proppant embedment during in-situ stress evolution, comprising a proppant placement chamber (18) having a proppant (34) disposed therein between an upper rock plate (32) and a lower rock plate (33); wherein, The upper rock plate (32) and the lower rock plate (33) are connected with a vertical stress applying system, and the front, rear, left and right four surfaces of the upper rock plate (32) and the lower rock plate (33) are provided with main stress and displacement control systems in the horizontal direction.

2. The apparatus of claim 1, wherein, The support agent laying chamber (18) is provided with rock plates, gaskets and pressurizing cavities in sequence from inside to outside on the upper and lower sides of the support agent (34) arranged in the support agent laying chamber (18).

3. The apparatus of claim 2, wherein the apparatus is configured to simulate the dynamic proppant embedment during the stress evolution process by: The support agent laying chamber (18) is sequentially provided with an upper pressurizing cavity (31), an upper gasket (35) and an upper rock plate (32) from top to bottom, a lower rock plate (33), a lower gasket (29) and a lower pressurizing cavity (30), and the support agent (34) is located between the upper rock plate (32) and the lower rock plate (33); the upper pressurizing cavity (31) is provided with an upper pressurizing port (17), and the lower pressurizing cavity (30) is provided with a lower pressurizing port (16); the device further comprises a gas cylinder (1), the upper pressurizing port (17) is connected to the gas cylinder (1) through an upper pressurizing pipeline (4), and the lower pressurizing port (16) is connected to the gas cylinder (1) through a lower pressurizing pipeline (3).

4. The apparatus of claim 3, wherein the apparatus is configured to simulate the dynamic proppant embedment during the stress evolution process by: The main stress and displacement control system comprises eight groups of front upper control devices, front lower control devices, rear upper control devices, rear lower control devices, left upper control devices, left lower control devices, right upper control devices and right lower control devices; each main stress and displacement control system comprises a hydraulic rod and a pressurizing rod connected in sequence; the pressurizing rod is connected to the upper rock plate (32) / lower rock plate (33) through a gasket.

5. The apparatus of claim 4, wherein the apparatus is configured to simulate the dynamic proppant embedment during the stress evolution process by: The front upper control device comprises a front upper hydraulic rod (19) and a front upper pressure rod (43) connected in sequence, and the front upper pressure rod (43) is connected with the upper rock plate (32) through a front upper gasket (42); the front lower control device comprises a front lower hydraulic rod (21) and a front lower pressure rod (45) connected in sequence, and the front lower pressure rod (45) is connected with the lower rock plate (33) through a front lower gasket (44); the rear upper control device comprises a rear upper hydraulic rod (14) and a rear upper pressure rod (38) connected in sequence, and the rear upper pressure rod (38) is connected with the upper rock plate (32) through a rear upper gasket (39); the rear lower control device comprises a rear lower hydraulic rod (15) and a rear lower pressure rod (40) connected in sequence, and the rear lower pressure rod (40) is connected with the lower rock plate (33) through a rear lower gasket (41); the left upper control device comprises a left upper hydraulic rod (6) and a left upper pressure rod (5) connected in sequence, and the left upper pressure rod (5) is connected with the upper rock plate (32) through a left upper gasket (36); the left lower control device comprises a left lower hydraulic rod (46) and a left lower pressure rod (9) connected in sequence, and the left lower pressure rod (9) is connected with the lower rock plate (33) through a left lower gasket (37); the right upper control device comprises a right upper hydraulic rod (25) and a right upper pressure rod (22) connected in sequence, and the right upper pressure rod (22) is connected with the upper rock plate (32) through a right upper gasket (47); the right lower control device comprises a right lower hydraulic rod (24) and a right lower pressure rod (23) connected in sequence, and the right lower pressure rod (23) is connected with the lower rock plate (33) through a right lower gasket (29); wherein, the upper gasket (35), the lower gasket (29), the front upper gasket (42), the front lower gasket (44), the rear upper gasket (39), the rear lower gasket (41), the left upper gasket (36), the left lower gasket (37), the right upper gasket (47) and the right lower gasket (48) are all internally provided with displacement sensors.

6. The apparatus of claim 5, wherein, The front upper hydraulic rod (19) and the front lower hydraulic rod (21) share a front base (20), the rear upper hydraulic rod (14) and the rear lower hydraulic rod (15) share a rear base (13), the left upper hydraulic rod (6) and the left lower hydraulic rod (46) share a left base (8), and the right upper hydraulic rod (25) and the right lower hydraulic rod (24) share a right base (26).

7. The apparatus of claim 1, wherein, Further comprising a computer (12), which is connected with each of the principal stress and displacement control systems.

8. The apparatus of claim 5, wherein the apparatus is configured to simulate the dynamic proppant embedment during the stress evolution process. Further comprising a computer (12), which is connected to the left upper hydraulic rod (6) through a left upper data line (7), connected to the left lower hydraulic rod (46), the rear upper hydraulic rod (14) and the rear lower hydraulic rod (15) through a left rear data line (10), connected to the front upper hydraulic rod (19), the front lower hydraulic rod (21) and the right lower hydraulic rod (24) through a front right data line (27), connected to the right upper hydraulic rod (25) through a right upper data line (28), and further connected to a valve (2) provided at the outlet end of the gas cylinder (1) through a control line (11).

9. A method of simulating dynamic proppant embedment during in-situ stress evolution, characterized by, The device for simulating the dynamic embedding of proppants during the evolution of in-situ stress as claimed in claim 1 above is used as follows: The proppant placement chamber (18) is filled with proppants (34), and gas is injected into the upper and lower pressurization cavities (31) and (30) through the lower and upper pressurization pipelines (3) and (4) to simulate the reservoir fracture closure process; (1) The same size and opposite directions of force are applied to each symmetric surface of the upper and lower rock plates (32) and (33) to simulate the maximum / minimum horizontal principal stress; (2) Different sizes and directions of force are applied to each surface of the upper and lower rock plates (32) and (33) to dynamically adjust the direction of the horizontal principal stress and simulate the reversal of the in-situ stress direction during the production stage; (3) Shear stress is applied by controlling the principal stress and displacement control system located on the opposite sides of the upper and lower rock plates (32) and (33) to cause the lateral displacement of the upper and lower rock plates (32) and (33) to simulate the "rubbing" effect of the fracture surface.

10. A method of simulating dynamic proppant embedment during in-situ stress evolution, characterized by, The device for simulating the dynamic embedding of proppants during the evolution of in-situ stress as claimed in claim 5 above is used as follows: The proppant placement chamber (18) is filled with proppants (34), and gas is injected into the upper and lower pressurization cavities (31) and (30) through the lower and upper pressurization pipelines (3) and (4) to simulate the reservoir fracture closure process; The maximum / minimum horizontal principal stress is applied to the proppant placement chamber (18) by the front upper hydraulic rod (19), the front lower hydraulic rod (21), the rear upper hydraulic rod (14), the rear lower hydraulic rod (15), the left upper hydraulic rod (6), the left lower hydraulic rod (46), the right upper hydraulic rod (25), and the right lower hydraulic rod (24); the force direction and size applied by the hydraulic rods located on the same surface are the same, and the force size applied by the hydraulic rods located on the symmetric surfaces is the same but in opposite directions; The pressure of the left upper hydraulic rod (6), the left lower hydraulic rod (46), the rear upper hydraulic rod (14), the rear lower hydraulic rod (15), the front upper hydraulic rod (19), the front lower hydraulic rod (21), the right upper hydraulic rod (25), and the right lower hydraulic rod (24) is adjusted to make the horizontal principal stress applied by each hydraulic rod different, thereby dynamically adjusting the direction of the horizontal principal stress to simulate the reversal of the in-situ stress direction during the production stage; Shear stress is applied by controlling a group of hydraulic rods located on opposite surfaces and at different heights to cause the lateral displacement of the upper rock plate (32) relative to the lower rock plate (33) to simulate the "rubbing" effect of the fracture surface.

Images