CN117723408A - Shear seepage pressure head, true three-dimensional shear seepage integrated test pressure head set and method - Google Patents

Abstract

The invention provides a shear seepage pressure head, a true three-dimensional shear seepage integrated test pressure head group and a method, wherein a fluid channel is arranged in the shear seepage pressure head, the shear seepage pressure head comprises a fixed pressure head and a movable pressure head, the movable pressure head is movably arranged in an installation groove at the front end of the fixed pressure head, a spring is arranged at the bottom of the groove and is positioned behind the movable pressure head, and when the pressure is not applied, the movable pressure head and the front end surface of the fixed pressure head are positioned in the same plane; the true three-dimensional shear seepage integration test pressure head group comprises loading pressure heads in 6 directions, wherein two pairs of loading pressure heads are rigid plane type loading pressure heads, the other pair of loading pressure heads are shear seepage pressure heads, and each loading pressure head is provided with an acoustic emission probe and an ultrasonic probe. The true triaxial ground stress state is considered, so that the permeability test can be performed in the multiaxial ground stress state, the Dan Jianqie-seepage-acoustics integrated test of the reservoir rock under the true three-dimensional stress is realized, and the method has great significance for development and utilization of deep reservoir energy.

Description

Shear seepage pressure head, true three-dimensional shear seepage integrated test pressure head set and method

Technical Field

The invention relates to the technical field of rock mechanics and engineering, in particular to a shear seepage pressure head, a true three-dimensional shear seepage integrated test pressure head group and a method.

Background

Deep reservoirs such as coalbed methane, shale gas, oil and gas and the like are important energy resources. Permeability is the ability of fluids (e.g., natural gas, oil, etc.) in a reservoir to pass through rock pores and cracks, directly affecting the efficiency and yield of energy recovery. Knowing the evolution law of reservoir permeability is significant for the development of reservoir energy. The actual geological reservoir stress state is extremely complex, and the phenomenon of shear stress induced rock mass shear fracture and slip instability usually occurs near the rock mass of the structural surface, so that the understanding of the shear-seepage coupling response characteristics of the rock mass under the three-dimensional stress is very important.

When the permeability of a deep reservoir is researched by the existing experimental testing equipment, the axial permeability test of a rock body under the conventional triaxial stress is mainly adopted, namely a triaxial pressure tester is used under the laboratory condition, horizontal and axial stress is applied to a reservoir rock sample, and the pressure state in the stratum is simulated; and then injecting fluid in the axial direction of the rock core through a reserved fluid injection channel, and measuring the permeability of the rock sample in the axial direction to obtain permeability data. The method only considers the conventional triaxial state, and cannot truly simulate the three-dimensional anisotropic ground stress state of the deep reservoir, in particular to the seepage behavior under the action of shear stress.

Disclosure of Invention

The invention provides a shear seepage pressure head, a true three-dimensional shear seepage integrated test pressure head group and a method for solving the technical problems

The invention is realized by the following technical scheme:

the application provides a shear seepage pressure head, be equipped with fluid channel in the shear seepage pressure head, the shear seepage pressure head is including fixed pressure head and movable pressure head, and fixed pressure head front end is opened there is movable pressure head mounting groove, and movable pressure head movable dress is in movable pressure head mounting groove, installs the spring at the tank bottom, and the spring is located movable pressure head rear, when not receiving pressure, movable pressure head is in same level with fixed pressure head front end face

An acoustic emission probe is arranged on the shear seepage pressure head or not; an ultrasonic probe is arranged on the shear seepage pressure head or not; the middle part periphery of the fixed pressure head is provided with or not provided with a pressure-resistant sealing ring.

Optionally, a bar-shaped limit groove is axially arranged on the side surface of the movable pressure head, and a rivet or pin is inserted into the bar-shaped limit groove through the outside of the fixed pressure head, so that the axial movable displacement of the movable pressure head can be limited in a certain range.

Optionally, the front half of the shear seepage pressure head is movable.

Optionally, a plurality of concentric annular grooves and a plurality of radial grooves which are circumferentially arranged at intervals are formed in the front end face of the shear seepage pressure head, one end of each radial groove is communicated with the front end of the fluid channel, and the other end of each radial groove is communicated with the plurality of annular grooves.

The application provides a true three-dimensional shear seepage integration test pressure head group, including the loading pressure head of 6 directions, X, Y, Z three axle are a pair of respectively, wherein two pairs of loading pressure heads are rigid plane type loading pressure heads, another pair of loading pressure heads be the shear seepage pressure head.

Optionally, pressure-resistant and temperature-resistant acoustic emission probes are arranged on the holes at four corners of each loading pressure head.

Optionally, 2 ultrasonic probes are symmetrically arranged in the middle of the end face of each loading pressure head, one is P wave, and the other is S wave; the ultrasonic transmitting probe 83 and the ultrasonic receiving probe 8 are respectively installed in two opposite directions of one axis.

Optionally, the true three-dimensional shear seepage integrated test pressure head group further comprises 6 LVDT sensors, and the 6 LVDT sensors are in one-to-one correspondence with the 6 loading pressure heads; the corresponding positions of each pair of pressure heads are provided with Y-shaped support clamp members, the end parts of the LVDT sensors can be clamped in the front end openings of the Y-shaped support clamp members, and the front ends of the Y-shaped support clamp members are provided with adjusting nuts to realize the adjustment and the fixation of the positions of the LVDT sensors; the two ends of the LVDT sensor can be respectively fixed on the two opposite loading pressure heads by Y-shaped support clamp components.

Optionally, the true three-dimensional shear seepage integration test pressure head group further comprises a heat shrinkage pipe, the heat shrinkage pipe is used for accommodating a cube test piece, and the two shear seepage pressure heads can respectively extend into the heat shrinkage pipe from pipe orifices at two ends of the heat shrinkage pipe to be in direct contact with two surfaces of the cube test piece.

The true three-dimensional shear seepage integration test method provided by the application adopts test equipment, wherein the test equipment comprises a shaft six-direction loading system, a sealing cavity and the true three-dimensional shear seepage integration test pressure head group, the shaft six-direction loading system comprises 6 hydraulic cylinders, the sealing cavity is respectively provided with a butt joint opening in six directions, and telescopic rods of the 6 hydraulic cylinders respectively extend into the sealing cavity from one of the butt joint openings for butt joint with the rear end of one of the loading pressure heads (4);

the true three-dimensional shear seepage integrated test method comprises the following steps:

preparing a cube test piece;

placing a cube test piece in a high-strength pressure-resistant and temperature-resistant heat-shrinkable tube, placing the heat-shrinkable tube with the cube test piece in a sealed cavity, enabling two shearing seepage pressure heads to extend into the heat-shrinkable tube from tube orifices at two ends of the heat-shrinkable tube respectively to be in direct contact with two surfaces of the cube test piece, and then uniformly heating the heat-shrinkable tube by using a hot air gun to enable the heat-shrinkable tube to be in close contact with the cube test piece; the other four rigid plane loading pressure heads act on the other four surfaces of the cube test piece through the pipe wall of the heat shrinkage pipe;

filling hydraulic oil into the sealed cavity, closing a seepage channel of one shear seepage pressure head, opening a seepage channel of the other shear seepage pressure head, vacuumizing a cube test piece through the opened seepage channel by a vacuum pump, and then closing the seepage channel;

the stress is sequentially and circularly loaded on the cube test piece step by utilizing a triaxial six-way loading system;

fluid adsorption: opening a seepage channel of one shear seepage pressure head, keeping the seepage channel of the other shear seepage pressure head closed, filling fluid into the cube test piece through the opened seepage channel, observing the dynamic change condition of the fluid pressure, and adsorbing for a period of time until adsorption balance after the value of the flowmeter is stable;

measuring seepage parameters: opening a seepage channel of the other shear seepage pressure head as a fluid outflow channel, and loading stress on the cube test piece through the shear seepage pressure head at a certain rate to enable the cube test piece to be subjected to shear fracture until the cube test piece reaches a residual stage; waiting until the fluid flow rate at the outlet of the fluid outflow channel is stable, observing the change rule of the pressure change at the outlet of the fluid outflow channel along with the time, stopping testing after a period of time, and closing the seepage channel of the shear seepage pressure head;

then, modulating X, Y, Z various directional three-dimensional stress, loading mode and fluid pressure, repeating the steps S5-S7, and measuring under different reservoir environment conditions;

stopping the experiment and storing data: discharging external seepage fluid pressure, slowly unloading three-dimensional stress, closing a hydraulic source, and removing a cube test piece;

and dynamically measuring seepage parameters from the beginning of the triaxial six-way loading system to the stopping of the experiment.

Compared with the prior art, the embodiment of the invention has at least the following advantages or beneficial effects:

the shear seepage pressure head can load shear stress and has seepage function, and can be used for shear-seepage integrated test;

2, the true three-dimensional shear seepage integration test pressure head set considers the true triaxial ground stress state, so that the seepage rate test can be performed in the multiaxial ground stress state; by installing the acoustic emission probe and the ultrasonic probe on the loading pressure head, the Dan Jianqie-seepage-acoustic integrated test of the reservoir rock under true three-dimensional stress is realized, and the method has great significance for the development and utilization of deep reservoir energy.

Drawings

In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings that are needed in the embodiments will be briefly described below, it being understood that the following drawings only illustrate some embodiments of the present invention and therefore should not be considered as limiting the scope, and other related drawings may be obtained according to these drawings without inventive effort for a person skilled in the art.

FIG. 1 is a three-dimensional view of a true three-dimensional shear seepage integration test ram set in an embodiment;

FIG. 2 is a cross-sectional view of the YZ plane of a true three-dimensional shear seepage integration test ram set in an embodiment;

FIG. 3 is a three-dimensional view of a heat shrinkable tube after heat shrinkage in the embodiment;

FIG. 4 is a three-dimensional view of a rigid planar loading ram in an embodiment;

FIG. 5 is a three-dimensional view of a shear-seepage ram in an embodiment;

FIG. 6 is a cross-sectional view of a shear-seepage ram in an embodiment;

fig. 7 is a three-dimensional view of a movable ram of a shear osmotic ram in an embodiment.

FIG. 8 is a three-dimensional view of a displacement detection device according to an embodiment;

FIG. 9 is a three-dimensional view of a test apparatus in an embodiment;

FIG. 10 is a cross-sectional view of the test apparatus in the YZ plane in an embodiment;

FIG. 11 is a cross-sectional view of the test apparatus in the XZ plane in an embodiment;

fig. 12 is a three-dimensional view of a sealed chamber in an embodiment.

Detailed Description

For the purpose of making the objects, technical solutions and advantages of the embodiments of the present invention more apparent, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention, and it is apparent that the described embodiments are some embodiments of the present invention, but not all embodiments of the present invention. The components of the embodiments of the present invention generally described and illustrated in the figures herein may be arranged and designed in a wide variety of different configurations.

In addition, the embodiments of the present invention and the features of the embodiments may be combined with each other without collision. It should be noted that, in the present specification, each embodiment is described in a progressive manner, and each embodiment is mainly described as different from other embodiments, and identical and similar parts between the embodiments are all enough to be referred to each other.

In the description of the present invention, it should be noted that, directions or positional relationships indicated by terms such as "upper", "lower", "inner", "outer", etc., are directions or positional relationships based on those shown in the drawings, or directions or positional relationships conventionally put in place when the inventive product is used, or directions or positional relationships conventionally understood by those skilled in the art are merely for convenience of describing the present invention and simplifying the description, and are not indicative or implying that the apparatus or element to be referred to must have a specific direction, be constructed and operated in a specific direction, and thus should not be construed as limiting the present invention. Furthermore, the terms "first," "second," and the like, are used merely to distinguish between descriptions and should not be construed as indicating or implying relative importance.

In the description of the present invention, it should also be noted that, unless explicitly specified and limited otherwise, the terms "disposed," "mounted," "connected," and "connected" are to be construed broadly, and may be, for example, fixedly connected, detachably connected, or integrally connected; can be mechanically or electrically connected; can be directly connected or indirectly connected through an intermediate medium, and can be communication between two elements. The specific meaning of the above terms in the present invention will be understood in specific cases by those of ordinary skill in the art.

In order to simulate the rock mass shearing-seepage mechanical behavior rule of a deep reservoir under the true three-dimensional stress and fluid coupling environment, the embodiment particularly discloses a true three-dimensional shearing-seepage integrated testing pressure head, which mainly comprises a loading pressure head 4 in 6 directions, and a pair of three axes of X and Y, Z, as shown in fig. 1 and 2, wherein two pairs of loading pressure heads 4 are rigid plane loading pressure heads, and the other pair of loading pressure heads 4 are shearing-seepage pressure heads, so that the rock mass shearing fracture characteristics under the three-dimensional stress loading and unidirectional shearing stress can be realized.

The front ends of the 6 loading pressure heads 4 are respectively used for pressing 6 faces of the cube test piece 10, and the rear ends of the 6 loading pressure heads are used for being in butt joint with telescopic rods of the hydraulic cylinders so as to realize triaxial six-way stress loading on the center test piece.

In one possible design, the 4 loading rams 4 in the X, Y axis direction are rigid planar loading rams and the 2 loading rams 4 in the Z axis direction are shear osmotic rams, as shown in fig. 2, 4, 5.

The two shear seepage pressure heads are internally provided with a fluid channel 86, one end of the fluid channel 86 is opened at the center of the front end of the shear seepage pressure head, and the other end of the fluid channel 86 is opened at the side surface of the shear seepage pressure head, so that fluid injection and fluid outflow under shear stress can be realized.

As shown in fig. 5 and 6, the shear seepage pressure head comprises a fixed pressure head 81 and a movable pressure head 82, wherein the front end of the fixed pressure head 81 is provided with a movable pressure head mounting groove, the movable pressure head 82 is movably arranged in the movable pressure head mounting groove, a spring 85 is arranged at the bottom of the groove, the spring 85 is positioned behind the movable pressure head 82, and the movable pressure head 82 and the front end surface of the fixed pressure head 81 can be ensured to be in the same plane when not subjected to pressure; the movable ram 82 can compress the spring 85 to move to the bottom side of the groove when being pressed.

Alternatively, as shown in fig. 7, a bar-shaped limiting groove 822 is axially provided on the side surface of the movable pressure head 82, and a rivet or pin is inserted into the bar-shaped limiting groove 822 through the outside of the fixed pressure head 81, so that the limit of the movable pressure head 82 can be realized, the axial movable displacement of the movable pressure head 82 is limited in a certain range, and the no-load fixation of the movable pressure head 82 can be ensured in combination with the bottom spring 85.

In one possible design, the front half of the shear osmotic head is movable.

In one possible design, a half through hole is axially formed in the middle of the front end of the fixed pressing head 81 to the middle of the fixed pressing head 81; the fixed pressure head 81 is provided with a right-angle through hole, one end of the right-angle through hole is opened on the side surface of the fixed pressure head 81, and the other end of the right-angle through hole is communicated with the half through hole and penetrates through the bottom of the movable pressure head mounting groove; a half through hole 821 matched with the fixed pressure head 81 is arranged in the middle of one side of the movable pressure head 82, the two half through holes 821 can jointly form a round hole, the round hole and a right-angle through hole on the fixed pressure head 81 jointly form a fluid channel 86, and fluid can flow from the measuring circle to the front end of the pressure head; the fluid channel 86 is connected with an external fluid pump to realize injection/outflow of high-pressure fluid and the like, so that the rock mass shearing-seepage environment under the three-dimensional stress is simulated.

In order to improve the sealing performance, the middle periphery of the fixed pressure head 81 is provided with a pressure-resistant sealing ring 80; the pressure resistant seal 80 may be a rubber seal.

Optionally, two springs 85 are arranged below the movable pressure head 82, and the two springs 85 support the movable pressure head, so that the movable pressure head is more stable.

In one possible design, as shown in fig. 5, the front end surface of the shear seepage pressure head is provided with a plurality of concentric annular grooves 88 and a plurality of radial grooves 89 which are circumferentially arranged at intervals, one end of each radial groove 89 is communicated with the front end of the fluid channel 86, the other end of each radial groove 89 is communicated with the plurality of annular grooves 88, and the fluid channel 86, the annular grooves 88 and the radial grooves 89 together form a seepage channel.

As shown in fig. 5 and 6, acoustic emission probe mounting channels are reserved at four corners of each loading pressure head 4, and sensing wire through holes are formed to extend to the rear end of the pressure head; the acoustic emission probe 86 with pressure resistance and temperature resistance is arranged in the acoustic emission probe mounting channel, and the three-axis six-direction pressure head group is provided with 24 acoustic emission probes 86 which are used for comprehensively monitoring the three-dimensional evolution characteristics of the whole damage and rupture process of reservoir rock under the conditions of complex stress, fluid and the like. Two ultrasonic probe sensing wire through holes are formed in the middle of the loading pressure head 4 and extend to the rear end of the loading pressure head 4.

2 ultrasonic probes are symmetrically arranged in the middle of the end face of each loading pressure head 4, wherein one ultrasonic probe is P wave and the other ultrasonic probe is S wave; a total of 12 ultrasound probes. It should be noted that, the ultrasonic transmitting probe 83 and the ultrasonic receiving probe 84 are respectively arranged in two opposite directions of one axis, so that the ultrasonic wave speed evolution rule of the rock sample in the whole deformation and destruction process can be studied.

Optionally, as shown in fig. 1, a Y-shaped groove 810 is designed at the rear end of the loading pressure head 4, so that the acoustic emission probe and the ultrasonic probe sensing wire can be arranged to the edge of the pressure head along the Y-shaped groove 810, thereby facilitating the arrangement and avoiding the wire from being damaged by compression. During testing, the acoustic emission probe 86 is connected to an external acoustic emission monitoring system through its sensing wire, and the ultrasonic probe is connected to an external ultrasonic monitoring system through its sensing wire.

In one possible design, as shown in fig. 2, a circular connecting guide sleeve 6 is installed at the rear end of each loading pressure head 4 through a screw, and one end of the circular connecting guide sleeve 6 is a circular plane for being in butt joint with the rear end of the loading pressure head 4 so as to seal acoustic emission, ultrasonic monitoring wires and bear load; the other end of the circular connecting guide sleeve 6 is in a circular ring shape and is used for sleeving a telescopic rod piece of the hydraulic cylinder 2, so that the loading pressure head 4 is connected with the telescopic rod piece of the hydraulic cylinder 2 to realize force transmission.

In one possible design, the circular connecting guide 6 can be screwed to the telescopic rod of the hydraulic cylinder 2.

As shown in fig. 1 and 2, displacement detection devices are arranged between each pair of loading pressure heads 4, so that deformation of the cube test piece 10 in three directions X, Y, Z can be detected. The displacement detection means comprise an LVDT sensor 7. Optionally, each loading pressure head 4 is provided with 1 LVDT sensor 7, and 6 LVDT sensors 7 are provided, so that 2 deformation data acquisitions in each direction are realized, and accurate measurement of deformation in X, Y, Z directions can be realized.

As shown in fig. 1 and 8, two ends of the LVDT sensor 7 are respectively fixed on two opposite loading pressure heads 4 by a Y-shaped support clamping member 71, the end of the LVDT sensor 7 is clamped in the front opening of the Y-shaped support clamping member 71, and an adjusting nut 72 is installed at the front end of the Y-shaped support clamping member 71 to realize the adjustment and fixation of the position of the LVDT sensor 7.

To test true three-dimensional shear-seepage acoustic multiparameters of geological reservoirs, it is also necessary to use a complete test apparatus, as shown in fig. 9-11, comprising a hydraulic system (not shown), a vertical frame 1, a triaxial six-way loading system and a sealed chamber 3.

The hydraulic system comprises a high-pressure hydraulic pump station and is mainly used for providing loading power for the triaxial six-way loading system.

The triaxial six-way loading system comprises 6 hydraulic cylinders 2, and specifically comprises: two hydraulic cylinders 2 in the X-axis direction, two hydraulic cylinders 2 in the Y-axis direction, and two hydraulic cylinders 2 in the Z-axis direction. The 6 hydraulic cylinders 2 are all provided with multistage telescopic structures, provide loading power through a high-pressure hydraulic pump station, and are connected with an external servo control system to carry out accurate control movement in different modes such as displacement, pressure and the like.

Of course, the hydraulic cylinder 2 is a high-pressure hydraulic cylinder.

The two hydraulic cylinders 2 in the X-axis direction are designed to be open and movable, so that sample installation work, related special experiments and the like are facilitated, a sliding support structure 21 is arranged at the lower part of the two hydraulic cylinders 2 in the X-axis direction, the sliding support structure 21 is in sliding connection with two horizontal sliding rails 103, the horizontal sliding rails 103 are parallel to the X-axis direction, and the two hydraulic cylinders 2 in the X-axis direction can freely slide along the horizontal X-axis direction as required.

As shown in fig. 9, the overall appearance of the vertical frame 1 is a cube structure, the middle part is a circular hollow structure, the horizontal sliding rail 103 can be fixed with the vertical frame 1 through screws, and one end of the horizontal sliding rail 103 extends into the central circular cavity of the vertical frame 1. 4 round holes are reserved in the upper, lower, left and right directions of the periphery of the vertical frame 1, the 4 round holes are respectively used for being in sealing connection with two hydraulic cylinders 2 in the Y-axis direction and two hydraulic cylinders 2 in the Z-axis direction, a plurality of screw holes are reserved on the whole intersecting surface of the vertical frame 1, which is used for being in contact with the hydraulic cylinders 2, and the two pairs of hydraulic cylinders 2 in the Y-axis direction and the Z-axis direction can be connected and fixed through bolts or screws.

The lower part of the vertical frame 1 is supported by 4 circular upright posts 101, and the lower part of the circular upright posts 101 is connected with a plane supporting member 102.

The sealed chamber 3 is positioned in the central circular cavity of the vertical frame 1, and a cavity for containing high-pressure liquid is arranged inside the sealed chamber. As shown in fig. 12, the sealed chambers 3 are each provided with one docking port 31 in six directions for docking with one of the hydraulic cylinders 2, respectively.

Specifically, the telescopic rods of the hydraulic cylinders 2 in the Y-axis direction and the Z-axis direction can be connected into the sealed cavity 3 through the corresponding butt joint ports 31, a plurality of screw holes 33 are formed in the edges of the two butt joint ports 31 in the X-axis direction of the sealed cavity 3, the telescopic rods can be respectively and tightly butted with the cylinder bodies of the two hydraulic cylinders 2 in the X-axis direction, and finally a sealed space is formed inside the sealed cavity 3. Annular high-strength pressure-resistant wear-resistant rubber plastic strips are distributed at intervals at the inner edges of the 6 butt joints 31 of the sealing chamber 3, dynamic sealing can be realized to ensure high-pressure hydraulic oil sealing in the sealing chamber 3, and meanwhile, the telescopic rod piece of the hydraulic cylinder 2 can freely stretch and retract.

A plurality of fluid channels 34 are reserved around the sealed chamber 3, wherein, a part of the fluid channels 34 can be used as injection channels to realize different fluid injection, and the rest of the fluid channels 34 can be used as outflow channels to realize fluid outflow. The injection channel of the sealed chamber 3 is connected with a hydraulic oil injection pump through a hydraulic oil injection valve and a pipeline; the outflow channel of the sealed chamber 3 is connected to a hydraulic oil outflow valve. High-temperature high-pressure hydraulic oil can be injected into the sealed chamber 3 in the experimental process, so that the fluid sealing effect is realized, and further the core permeability test experiment is carried out.

In one possible design, the sealed chamber 3 is a housing structure. Preferably, the sealing chamber 3 is of a spherical shell structure, a spherical cavity is arranged inside, a supporting leg 35 is arranged at the bottom, and a coaxial and integrally manufactured annular flange 32 is arranged at the outer end of the butt joint 31; the wire holes 33 on the periphery of the two butt joint openings 31 in the X-axis direction are uniformly formed in the annular flange 32.

In one possible design, a plurality of sensor connecting channels are reserved around the sealed cavity 3, so that the sensor connecting channels can be connected with an external multi-parameter monitoring system, and the acquisition of related parameters of different physical mechanics of the rock core can be realized.

Of course, the system is also provided with a fluid injection and outflow system in a matched way, and the fluid injection system comprises an external fluid source, an external high-pressure plunger pump, a fluid injection pipeline, a pressure gauge and the like; the outflow system includes fluid outflow pipes, pressure gauges, flow meters, etc.

The embodiment discloses a geological reservoir true three-dimensional shear seepage acoustic multiparameter integrated test method, which comprises the following steps:

s1, preparing a cube test piece 10: and preparing a cubic geological reservoir sample according to experimental requirements.

In one possible design, the side length of the cube test piece 10 is 100±0.02mm, and in order to ensure the sealing effect, 12 edges of the cube test piece 10 are ground to have a chamfer angle of 45 °, and the chamfer angle has a chamfer width of 3±0.02mm.

S2, installing a cube test piece 10: as shown in fig. 1-3, a cube test piece 10 is placed on a bottom shearing seepage pressure head, then the cube test piece 10 is sleeved in a high-strength pressure-resistant and temperature-resistant heat shrinkage tube 5, and a tube orifice at one end of the heat shrinkage tube 5 is sleeved on the bottom shearing seepage pressure head; then the upper shearing seepage pressure head is put into the pipe orifice at the other end of the heat shrinkage pipe 5; then, uniformly heating the heat shrinkage tube 5 by using a hot air gun until the heat shrinkage tube 5 is tightly attached to the cube test piece 10 and the shearing seepage pressure head; simultaneously, the two ends of the heat shrinkage tube 5 tightly cover pressure-resistant sealing rings 80 at the middle part of a pair of shearing seepage pressure heads;

s3, respectively arranging the other 4 loading pressure heads 4 at the front ends of the telescopic rods of the 4 hydraulic cylinders 2, arranging the heat shrinkage tube 5 provided with the cube test piece 10 and the two shearing seepage pressure heads in the sealing chamber 3,

the two hydraulic cylinders 2 in the Z-axis direction are slowly controlled, so that telescopic rods of the two hydraulic cylinders in the Z-axis direction are respectively and directly contacted with the two shearing seepage pressure heads in the Z-axis direction, and the loading pressure head 4 is stressed at about 10 kN; the method comprises the steps of carrying out a first treatment on the surface of the

The two hydraulic cylinders 2 in the Y-axis direction are controlled slowly, so that two rigid plane loading pressure heads in the Y-axis direction act on two surfaces of the cube test piece 10 in the Y-axis direction through the pipe wall of the heat shrinkage pipe 5, and the loading pressure head 4 is stressed at about 10 kN;

then, the cylinder bodies of the two open hydraulic cylinders 2 in the X-axis direction are fixedly connected with the sealing chamber 3 through screws or bolts at two butt joints 31 in the X-axis direction respectively, and then the two hydraulic cylinders 2 in the X-axis direction are slowly controlled, so that two rigid plane loading pressure heads in the X-axis direction act on two faces of the cube test piece 10 in the X-axis direction through the pipe wall of the heat shrinkage pipe 5, and the loading pressure head 4 is stressed at about 10 kN;

displacement detection devices are arranged between each pair of loading pressure heads 4, and deformation of the cube test piece 10 in the X, Y, Z directions can be detected in experiments.

To ensure the sealing effect, the two ends of the heat shrinkage tube 5 may be tightly wound with pressure-resistant adhesive tapes after the heat gun is heated, so that the whole cube test piece 10 is in a completely sealed state during the experiment.

Optionally, the heat shrinkage tube 5 is an organic teflon heat shrinkage tube.

The loading pressure head 4 and the telescopic rod piece of the hydraulic cylinder 2 can be connected through a screw and/or a round connecting guide sleeve 6.

S4, oiling and vacuumizing: filling the sealed chamber 3 with hydraulic oil; closing one seepage channel of the shearing seepage pressure head, opening the seepage channel of the other shearing seepage pressure head, vacuumizing the cube test piece 10 through the opened seepage channel by a vacuum pump for two hours, closing the vacuum pump after the vacuum degree reaches 1000Pa, and closing the seepage channel.

S5, loading three-dimensional stress: starting a high-pressure oil pump of a hydraulic system, injecting oil into the sealing chamber 3 by using an independent high-pressure oil pump to pressurize, and ensuring that the pressure value of hydraulic oil in the sealing chamber 3 is higher than the pressure of seepage fluid by 1MPa, thereby ensuring the sealing effect of a sample; starting an ultrasonic monitoring system and an acoustic emission monitoring system;

the method comprises the steps of sequentially and circularly loading a cube test piece 10 step by using a triaxial six-way loading system in a force control mode, wherein the step numbers of the three directions are equal; to prevent the cube test piece 10 from being crushed by the bias stress and to more accurately simulate the actual working condition;

the loading sequence can be sequentially Z-direction, X-direction, Y-direction and Z-direction, the left-right direction is X-direction, the front-back direction is Y-direction, and the loading sequence is sequentially increased by 1MPa to a preset load value.

S6, fluid adsorption: and opening a seepage channel of one shear seepage pressure head, keeping the seepage channel of the other shear seepage pressure head closed, filling fluid into the cube test piece 10 through the opened seepage channel, observing the dynamic change condition of the fluid pressure, and adsorbing for a period of time until adsorption balance after the flow meter value is stable.

S7, measuring seepage parameters: opening a seepage channel of the other shear seepage pressure head to serve as a fluid outflow channel, and then loading Z-direction stress to the sample at a certain speed by adopting a displacement/stress control mode to generate shear fracture until the sample reaches a residual stage; waiting until the fluid flow rate at the outlet of the fluid outflow channel is stable, observing the change rule of the pressure change at the outlet of the fluid outflow channel along with the time, stopping testing after 10min, and closing the seepage channel of the shear seepage head;

the upper and lower shear rams deform the cubic test piece 10 under the load applied by the upper and lower hydraulic cylinders 2, and as half of the shear seepage rams are movable, the fixed ram 81 is stressed, and the movable ram 82 moves to the rear end along with the compression of the spring 85; whereby only half of the upper and lower surfaces of the cube test piece 10 are subjected to force and the other half are not subjected to force, thereby generating shear stress.

Then, modulating X, Y, Z various directional three-dimensional stress, loading mode and fluid pressure, repeating the steps S5-S7, and measuring under different reservoir environment conditions;

the following parameters were dynamically determined during the process of S5 to S7: the oil pressure of the sealed chamber 3, the XYZ three-way pressure, the fluid pressure, the lateral deformation of the cubic test piece 10, the axial deformation of the cubic test piece 10, the fluid flow rate of the fluid outflow channel.

The stress monitoring device monitors and collects the XYZ three-way pressure passing through the inner surface of the rod piece of the hydraulic cylinder.

It should be noted that, the fluid flow rate refers to the portion of the fluid flowing through the inlet of the side seepage channel, passing through the cube test piece 10 and flowing out through the opposite side seepage channel, and can be measured by the flowmeter.

S8, stopping the experiment and storing the data. The specific operation is as follows: firstly, closing an external fluid source, after the fluid pressure is removed, closing a hydraulic oil injection pump connected with the sealing chamber 3, removing the sealing pressure in the sealing chamber 3, slowly unloading the three-dimensional stress, and finally, closing the hydraulic source, taking out the cube test piece 10, and observing the shape of the cube test piece 10. The unloading sequence of the stress can be Y-direction, X-direction, Z-direction and Y-direction, the cycle is sequentially decreased by 1MPa, and after the loading and unloading are finished, the oil pump corresponding to each hydraulic cylinder 2 is turned off.

It should be noted that the type of the seepage fluid may be selected according to the needs, including but not limited to gas, carbon dioxide, nitrogen, water, etc.

The real triaxial ground stress state is considered, so that the permeability test can be carried out in the multiaxial ground stress state, and the multi-parameter synchronous monitoring of the deformation and fracture process of the rock under the influence of the shear-seepage coupling of the reservoir rock under the real three-dimensional stress field can be realized.

The above is only a preferred embodiment of the present invention, and is not intended to limit the present invention, but various modifications and variations can be made to the present invention by those skilled in the art. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims (10)

1. The shear seepage pressure head is characterized in that a fluid channel (86) is arranged in the shear seepage pressure head, the shear seepage pressure head comprises a fixed pressure head (81) and a movable pressure head (82), the front end of the fixed pressure head (81) is provided with a movable pressure head mounting groove, the movable pressure head (82) is movably arranged in the movable pressure head mounting groove, a spring (85) is arranged at the bottom of the groove, the spring (85) is positioned behind the movable pressure head (82), and when the pressure is not applied, the movable pressure head (82) and the front end surface of the fixed pressure head (81) are positioned on the same plane;

an acoustic emission probe (86) is arranged or not arranged on the shearing seepage pressure head;

an ultrasonic probe is arranged on the shear seepage pressure head or not;

the middle periphery of the fixed pressure head (81) is provided with or not provided with a pressure-resistant sealing ring (80).

2. The shear seepage ram of claim 1, wherein a bar-shaped limit groove (822) is axially provided on the side of the movable ram (82), and a rivet or pin is inserted into the bar-shaped limit groove (822) through the outside of the fixed ram (81), so that the axial movable displacement of the movable ram (82) can be limited within a certain range.

3. A shear seepage ram according to claim 1 or claim 2, wherein the front half of the shear seepage ram is movable.

4. The shear seepage head of claim 1, wherein a plurality of concentric annular grooves (88) and a plurality of circumferentially spaced radial grooves (89) are formed in the front face of the shear seepage head, one end of each radial groove (89) is communicated with the front end of the fluid channel (86), and the other end of each radial groove (89) is communicated with the plurality of annular grooves (88).

5. True three-dimensional shear seepage integration test pressure head group, characterized by comprising a loading pressure head (4) of 6 directions, a pair of X, Y, Z three axes respectively, wherein two pairs of loading pressure heads (4) are rigid plane loading pressure heads, and the other pair of loading pressure heads (4) are the shear seepage pressure heads as claimed in any one of claims 1-4.

6. The true three-dimensional shear seepage integration test pressure head set according to claim 5, wherein the four corner position openings of each loading pressure head (4) are provided with pressure-resistant and temperature-resistant acoustic emission probes (86).

7. The true three-dimensional shear seepage integrated test pressure head set according to claim 5 or 6, wherein 2 ultrasonic probes are symmetrically arranged in the middle of the end face of each loading pressure head (4), one is P wave and the other is S wave; an ultrasonic transmitting probe (83) and an ultrasonic receiving probe (84) are respectively arranged in two opposite directions of one shaft.

8. The true three-dimensional shear seepage integration test pressure head set according to claim 5, further comprising 6 LVDT sensors (7), wherein the 6 LVDT sensors (7) are in one-to-one correspondence with the 6 loading pressure heads (4); the corresponding positions of each pair of pressure heads are provided with Y-shaped support clamp members (71), the end parts of the LVDT sensors (7) can be clamped in the front end openings of the Y-shaped support clamp members (7), and the front ends of the Y-shaped support clamp members (7) are provided with adjusting nuts to realize the adjustment and the fixation of the positions of the LVDT sensors (7);

the two ends of the LVDT sensor (7) can be respectively fixed on the two opposite loading pressure heads (4) by Y-shaped support clamp components (71).

9. The true three-dimensional shear seepage integrated test pressure head set according to claim 5 or 8, further comprising a heat shrinkage tube (5), wherein the heat shrinkage tube (5) is used for accommodating a cube test piece (10), and the two shear seepage pressure heads can extend into the heat shrinkage tube (5) from the pipe orifices at the two ends respectively to be in direct contact with two surfaces of the cube test piece (10).

10. The true three-dimensional shear seepage integration test method is characterized by adopting test equipment, wherein the test equipment comprises a shaft six-way loading system, a sealing chamber (3) and a true three-dimensional shear seepage integration test pressure head set as claimed in any one of claims 5-9, the shaft six-way loading system comprises 6 hydraulic cylinders (2), the sealing chamber (3) is respectively provided with a butt joint opening (31) in six directions, and telescopic rods of the 6 hydraulic cylinders (2) extend into the sealing chamber (3) from one butt joint opening (31) respectively for butt joint with the rear end of one loading pressure head (4);

the true three-dimensional shear seepage integrated test method comprises the following steps:

preparing a cube test piece (10);

the method comprises the steps of (1) arranging a cube test piece (10) in a high-strength pressure-resistant and temperature-resistant heat-shrinkable tube (5), arranging the heat-shrinkable tube (5) provided with the cube test piece (10) in a sealed cavity (3), enabling two shear seepage pressure heads to extend into the heat-shrinkable tube (5) from tube orifices at two ends of the heat-shrinkable tube respectively to be in direct contact with two surfaces of the cube test piece (10), and then uniformly heating the heat-shrinkable tube (5) and the cube test piece (10) by using a hot air gun to enable the heat-shrinkable tube to be in close contact; the other four rigid plane loading pressure heads act on the other four surfaces of the cube test piece (10) through the pipe wall of the heat shrinkage pipe (5);

filling hydraulic oil into the sealing chamber (3), closing a seepage channel of one shear seepage pressure head, opening a seepage channel of the other shear seepage pressure head, vacuumizing a cube test piece (10) through the opened seepage channel by a vacuum pump, and then closing the seepage channel;

the three-axis six-way loading system is utilized to circularly load stress to the cube test piece (10) step by step in sequence;

fluid adsorption: opening a seepage channel of one shear seepage pressure head, keeping the seepage channel of the other shear seepage pressure head closed, filling fluid into a cube test piece (10) through the opened seepage channel, observing the dynamic change condition of the fluid pressure, and adsorbing for a period of time until adsorption balance after the value of the flowmeter is stable;

measuring seepage parameters: opening a seepage channel of another shear seepage pressure head as a fluid outflow channel, and loading stress on the cube test piece (10) at a certain speed through the shear seepage pressure head to enable the cube test piece (10) to be subjected to shear fracture until the cube test piece (10) reaches a residual stage; waiting until the fluid flow rate at the outlet of the fluid outflow channel is stable, observing the change rule of the pressure change at the outlet of the fluid outflow channel along with the time, stopping testing after a period of time, and closing the seepage channel of the shear seepage pressure head;

then, modulating X, Y, Z various directional three-dimensional stress, loading mode and fluid pressure, repeating the steps S5-S7, and measuring under different reservoir environment conditions;

stopping the experiment and storing data: discharging external seepage fluid pressure, slowly discharging three-dimensional stress, closing a hydraulic source, and removing a cube test piece (10);

and dynamically measuring seepage parameters from the beginning of the triaxial six-way loading system to the stopping of the experiment.