A test device and test method for simulating the effect of hydration on rock strength

Abstract

The present invention provides a test device and test method for simulating the effect of hydration on rock strength. The test device includes a liquid injection system, an axial pressure loading system, and a confining pressure loading system. The liquid injection system includes a liquid storage tank and a liquid injection pipeline connected to the liquid storage tank; the axial pressure loading system includes a pressure plate and a first driving device connected to the pressure plate; the confining pressure loading system includes two pressure plates and two second driving devices respectively connected to the two pressure plates, and the two pressure plates surround the outer peripheral wall of the core by buckling. The test method includes: placing the core between the two pressure plates and axially aligning the pressure plates; inserting the liquid injection pipeline into the core; heating the liquid in the liquid storage tank to a set temperature and injecting it into the core; starting the first driving device and the second driving device to apply axial pressure and confining pressure to the core; taking out the core; cutting the core, and performing a point load test on the core block. The present invention can simulate the effect of hydration on rock strength under a real formation pressure environment.

Description

Technical Field

[0001] The invention relates to the technical field of oil and gas drilling engineering, in particular to a test device and a test method for simulating the influence of hydration on rock strength. Background Art

[0002] With the in-depth development of offshore oil and gas resources, conventional vertical wells and directional wells can no longer meet the needs of offshore oil and gas exploration and development. In order to meet production needs, more production wells are shallow and deep large-displacement wells. Since the soil in the shallow layer of the ocean is relatively loose, during the shallow drilling process, the shallow formation is easily affected by hydration and prone to complex wellbore instability problems such as collapse, shrinkage, and block drop, which leads to drill bit jamming, low drilling operation efficiency, and even limited extension length of the large-displacement section wellbore, which has a great adverse impact on the exploration and development of offshore areas. Therefore, it is of great practical significance to accurately understand the influence of hydration on the mechanical properties and failure mechanism of shallow formation rocks, and to judge and predict the wellbore strength, wellbore stability and wellbore collapse cycle for safe drilling engineering.

[0003] At present, the method for indoor testing of the effect of hydration on the strength of formation rocks is: first, soak the core in drilling fluid or formation water at room temperature and pressure for a certain period of time to simulate rock hydration, and then use triaxial test equipment to measure the strength of the rock. In this test method, the liquid freely enters the core, which is far from the real formation pressure environment. In the real formation environment, the core is subjected to both the overlying gravity of the upper formation rock and the fluid therein, and the confining pressure from the formation rock and the fluid. In addition, in the actual drilling process, the drilling fluid invades the formation from the internal wellbore, and the drilling fluid has a certain flow rate and is not static. Therefore, the above test method is a test method that does not conform to the actual situation of wellbore fluid invading the formation. Therefore, it is imperative to study a set of economical, simple and practical indoor test methods and devices to solve the problem of hydration instability of the borehole wall in loose formation drilling. Summary of the invention

[0004] The purpose of the present invention is to provide a test device and a test method for simulating the influence of hydration on rock strength, so as to simulate the influence of hydration on rock strength under real formation pressure environment, thereby facilitating the identification and prediction of wellbore strength, wellbore stability and wellbore collapse cycle.

[0005] To achieve the above-mentioned purpose, the present invention proposes a test device for simulating the influence of hydration on rock strength, which comprises: a liquid injection system, comprising a liquid storage tank for containing liquid, and a liquid injection pipeline connected to the liquid storage tank and capable of injecting liquid into the core; an axial pressure loading system, comprising a pressure plate coaxially arranged with the core, and a first driving device connected to the pressure plate and capable of driving the pressure plate to move toward the core; a confining pressure loading system, comprising two pressure plates arranged on both sides of the core, and two second driving devices respectively connected to the two pressure plates, the two second driving devices can respectively drive the two pressure plates to move toward the core, and the two pressure plates surround the outer peripheral wall of the core by buckling and fit with the outer peripheral wall of the core.

[0006] The test device for simulating the influence of hydration on rock strength as described above, wherein the test device for simulating the influence of hydration on rock strength also includes: a base, on which the core is placed; two bearing seats, connected above the base and respectively located on opposite sides of the core, and the two second drive devices are respectively installed on the two bearing seats; a support seat, connected above the two bearing seats and located above the core, and the support seat has an opening for the pressure plate to pass through; a cylinder, connected above the support seat, the cylinder is connected to the opening, the pressure plate is located in the cylinder, the first drive device is connected to the cylinder, and the first drive device is connected to the pressure plate by extending into the cylinder.

[0007] The test device for simulating the effect of hydration on rock strength as described above, wherein the liquid storage tank is connected above the cylinder, the injection pipeline includes a hose and a liquid guide tube, the pressure plate has a flow channel, one end of the hose is connected to the liquid storage tank, the other end of the hose extends into the cylinder and is connected to the pressure plate, the hose is communicated with the flow channel, one end of the liquid guide tube is connected to the pressure plate and communicated with the flow channel, and the other end of the liquid guide tube extends into the core.

[0008] The test device for simulating the effect of hydration on rock strength as described above, wherein the test device for simulating the effect of hydration on rock strength also includes a heating device for heating the liquid in the liquid storage tank.

[0009] In the test device for simulating the effect of hydration on rock strength as described above, the rock core is cylindrical, and the side of the pressure plate facing the rock core is a semi-cylindrical surface.

[0010] In the test device for simulating the influence of hydration on rock strength as described above, a valve is connected to the injection pipeline.

[0011] The test device for simulating the effect of hydration on rock strength as described above, wherein the first driving device comprises a first motor and a first worm gear screw elevator, the first worm gear screw elevator comprises a first worm connected to the first motor, a first worm wheel meshing with the first worm, and a first screw connected to the first worm wheel by a thread, the first screw is arranged along the axial direction of the core and connected to the pressure plate;

[0012] The second driving device includes a second motor and a second worm gear screw lift, the second worm gear screw lift includes a second worm connected to the second motor, a second worm wheel meshing with the second worm, and a second screw connected to the second worm wheel by a thread, the second screw is connected to the pressure plate and is perpendicular to the first screw.

[0013] In the test device for simulating the effect of hydration on rock strength as described above, the first drive device is a hydraulic cylinder or a linear stepping motor, and the second drive device is a hydraulic cylinder or a linear stepping motor.

[0014] The present invention also provides a test method for simulating the effect of hydration on rock strength, which uses the test device for simulating the effect of hydration on rock strength as described above, and the test method includes the following steps: Step S10: placing a core between the two pressure plates and aligning the core axially with the pressure plates; Step S20: inserting a liquid injection pipeline into the core; Step S30: starting the first drive device and the second drive device, and when the pressure plate contacts the end face of the core, closing the first drive device, and when the two pressure plates are in contact with the outer wall of the core, closing the second drive device; Step S40: heating the liquid in the liquid storage tank to a set temperature, and continuously injecting the heated liquid into the core to soak the core; Step S50: starting the first drive device again The first driving device and the second driving device are configured to apply axial pressure to the core and confining pressure to the core by the first driving device. When the applied axial pressure reaches a set value of the axial pressure, the first driving device is turned off. When the applied confining pressure reaches a set value of the confining pressure, the second driving device is turned off. Step S60: keep injecting liquid into the core until the injection is stopped after the set immersion time is reached, pull the injection pipeline out of the core, and then start the first driving device and the second driving device to move the pressure plate and the pressure plate away from the core respectively to unload the axial pressure and confining pressure, take out the core, and turn off the first driving device and the second driving device. Step S70: cut the core, and perform a point load test on the core block obtained by cutting to determine the strength of the core block.

[0015] The test method for simulating the effect of hydration on rock strength as described above, wherein the test method further includes the following steps: Step S01: before step S10, wrap the core with a heat shrink tube, and then weigh the core to obtain an initial weight W1 of the core; Step S61: before step S70, weigh the core again to obtain a weight W2 of the core after immersion, and the amount of water absorbed W3 during the hydration process of the core is W2-W1.

[0016] The characteristics and advantages of the test device and test method for simulating the influence of hydration on rock strength of the present invention are:

[0017] 1. The test device and test method for simulating the effect of hydration on rock strength of the present invention adopt an axial pressure loading system and a confining pressure loading system to apply axial pressure and confining pressure to the core, and continuously inject liquid into the core to soak the core, which can simulate the effect of hydration on rock strength under the real formation pressure environment, thereby facilitating the identification and prediction of wellbore strength, wellbore stability and wellbore collapse cycle;

[0018] 2. The test device and test method for simulating the effect of hydration on rock strength of the present invention can simulate the invasion of high-temperature drilling fluid into rock during actual drilling by setting a heating device to heat the liquid to the formation temperature, thereby more realistically simulating the effect of hydration on rock strength in the formation environment. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] The following drawings are intended only to illustrate and explain the present invention, and are not intended to limit the scope of the present invention.

[0020] Figure 1 is a schematic diagram of a test device for simulating the effect of hydration on rock strength according to the present invention;

[0021] Figure 2 yes Figure 1 Top view of the middle pressure plate.

[0022] Description of main component numbers:

[0023] 1. Liquid injection system

[0024] 11Liquid storage tank

[0025] 12 injection pipeline 121 hose 122 liquid guide tube

[0026] 13 Valves

[0027] 2-axis compression loading system

[0028] 21 pressure plate 211 flow channel

[0029] 22 First drive device

[0030] 221 first worm 222 first worm wheel 223 first screw

[0031] 3. Confining pressure loading system

[0032] 31 pressure plate 311 semi-cylindrical surface 312 large end

[0033] 313 Little Endian

[0034] 32 Second drive device

[0035] 321 second worm 322 second worm wheel 323 second screw

[0036] 4 Base

[0037] 5 bearing seat

[0038] 6 support seat 61 opening

[0039] 7 cylinder

[0040] 100 cores 101 holes DETAILED DESCRIPTION

[0041] In order to have a clearer understanding of the technical features, purposes and effects of the present invention, the specific embodiments of the present invention are now described with reference to the accompanying drawings. Among them, the use of the adjective or adverbial modifiers "horizontal" and "vertical", "upper" and "lower" is only to facilitate relative reference between multiple groups of terms, and does not describe any specific directional restrictions on the modified terms.

[0042] like Figure 1 As shown, the present invention provides a test device for simulating the effect of hydration on rock strength, or a test device for simulating the effect of hydration on formation rock, which includes a liquid injection system 1, an axial pressure loading system 2 and a confining pressure loading system 3. The liquid injection system 1 includes a liquid storage tank 11 for containing liquid, and a liquid injection pipeline 12 connected to the liquid storage tank 11 and capable of injecting liquid into the core 100. For example, the liquid in the liquid storage tank 11 is drilling fluid. Preferably, a valve 13 is connected to the liquid injection pipeline 12, and the flow of the liquid is controlled by opening or closing the valve 13. By setting the liquid injection system 1, liquid can be injected into the core 100 to simulate the drilling fluid fluid invading the formation from the internal wellbore, thereby simulating the rock hydration.

[0043] The axial pressure loading system 2 includes a pressure plate 21 coaxially arranged with the core 100, and a first driving device 22 connected to the pressure plate 21 and capable of driving the pressure plate 21 to move toward the core 100. Since the pressure plate 21 is coaxially arranged with the core 100, the pressure plate 21 can apply axial pressure to the core 100. By setting the axial pressure loading system 2, the overlying gravity of the upper formation rock and the fluid therein borne by the core 100 under the real formation pressure environment can be simulated;

[0044] The confining pressure loading system 3 includes two pressure plates 31 arranged on both sides of the core 100, and two second driving devices 32 respectively connected to the two pressure plates 31. The two second driving devices 32 can respectively drive the two pressure plates 31 to move toward the core 100. The two pressure plates 31 surround the outer peripheral wall of the core 100 (i.e., the outer peripheral side wall of the core 100) by buckling and fit with the outer peripheral wall of the core 100, thereby applying confining pressure to the core 100. By setting up the confining pressure loading system 3, the confining pressure effect from the formation rock and fluid can be simulated.

[0045] The test device of the present invention can simulate a real formation pressure environment by setting up an axial pressure loading system 2 and a confining pressure loading system 3. While applying axial pressure and confining pressure to the core 100, the liquid injection system 1 is used to inject liquid into the core 100, which can simulate the effect of hydration on rock strength under a real formation pressure environment; by changing the axial pressure and confining pressure, the effect of hydration on rock strength under different formation pressure environments can be simulated.

[0046] Specifically, the core 100 has a hole 101 inside, the hole 101 is used to simulate a wellbore, the hole 101 is a blind hole, and the injection pipeline 12 extends into the hole 101. For example, the hole 101 is a round hole, the core 100 is cylindrical, and the diameter of the hole 101 is 1 / 10 to 1 / 8 of the diameter of the core 100.

[0047] For example Figure 1 As shown, further, the test device for simulating the influence of hydration on rock strength also includes a base 4, two bearing seats 5, a support seat 6 and a cylinder 7. The base 4 is arranged opposite to the axial pressure loading system 2. The core 100 is placed on the base 4 and is located between the base 4 and the pressure plate 21. When the pressure plate 21 applies axial pressure to the core 100, the base 4 also applies axial pressure to the core 100. The base 4 can play a supporting role and a pressurizing role. For example, the base 4 is a flat plate structure.

[0048] The two bearing seats 5 are respectively connected above the base 4 and are respectively located on opposite sides of the core 100. The two second driving devices 32 are respectively installed on the two bearing seats 5. For example, the bearing seat 5 is a structure with a T-shaped cross section. The bearing seat 5 includes a vertical upright plate and a flat plate horizontally placed on the top of the upright plate. The flat plate can be a semicircular plate. The flat plates of the two bearing seats 5 are butt-jointed to form a disc. The disc can be an integrated structure or a split structure. For example, the second driving device 32 is connected to the bearing seat 5 by bolts.

[0049] The support seat 6 is connected above the two bearing seats 5 and is located above the core 100. The support seat 6 has an opening 61 for the pressure plate 21 to pass through. The opening 61 is preferably a circular opening. For example, the support seat 6 is a disc-shaped structure. Both sides of the support seat 6 are respectively connected to the flat plates of the two bearing seats 5 by bolts.

[0050] The cylinder 7 is connected above the support seat 6, the interior of the cylinder 7 is connected to the opening 61, the pressure plate 21 is located in the cylinder 7, the first drive device 22 is connected to the cylinder 7, and the first drive device 22 is connected to the pressure plate 21 by extending into the cylinder 7. For example, the cylinder 7 is a cylinder, the cylinder 7 and the support seat 6 are coaxially arranged, and the inner diameter of the cylinder 7 is equal to the diameter of the opening 61.

[0051] like Figure 1 As shown, further, the liquid storage tank 11 is connected above the cylinder 7, the injection pipeline 12 includes a hose 121 and a liquid guide tube 122, the pressure plate 21 has a flow channel 211, the flow channel 211 runs through the pressure plate 21, one end of the hose 121 is connected to the liquid storage tank 11, the other end of the hose 121 extends into the cylinder 7 and is connected to the pressure plate 21, and the hose 121 is communicated with the flow channel 211, for example, the hose 121 is connected to the pressure plate 21 through a joint, and the hose 121 is connected to the pressure plate 21 through a joint. The length of the tube 121 is greater than the distance between the liquid storage tank 11 and the core 100 so that it can bend or straighten as the pressure plate 21 moves. One end of the liquid guide tube 122 is connected to the pressure plate 21 and communicates with the flow channel 211. For example, the liquid guide tube 122 is threadedly connected to the pressure plate 21, and the other end of the liquid guide tube 122 extends into the core 100. Therefore, the liquid in the liquid storage tank 11 can enter the core 100 via the hose 121, the flow channel 211 and the liquid guide tube 122.

[0052] like Figure 1 , Figure 2 As shown, in a specific embodiment, the core 100 is cylindrical, and the side of the pressure plate 31 facing the core 100 is a semi-cylindrical surface 311, and the semi-cylindrical surfaces 311 of the two pressure plates 31 can jointly surround the outer peripheral wall of the core 100. Preferably, the inner diameter of the semi-cylindrical surface 311 of the pressure plate 31 is slightly smaller than the outer diameter of the core 100, so as to ensure that the two pressure plates 31 can act simultaneously to apply confining pressure to the core 100.

[0053] Furthermore, the side of the pressure plate 31 facing the core 100 is the first side, and the side of the pressure plate 31 connected to the second driving device 32 is the second side. The area of ​​the first side is greater than the area of ​​the second side.

[0054] Furthermore, the pressure plate 31 is wedge-shaped, or the cross section of the pressure plate 31 is trapezoidal, the large end 312 of the pressure plate 31 has a semi-cylindrical surface 311, and the small end 313 thereof is connected to the second driving device 32. However, the present invention is not limited thereto, and the pressure plate 31 may also be a prism-shaped, such as a quadrangular prism-shaped, and the side of the pressure plate 31 facing the core 100 is the bottom surface of the prism with a larger area, and the side of the pressure plate 31 connected to the second driving device 32 is the top surface of the prism with a smaller area.

[0055] The pressure plate 31 of this embodiment can ensure that the pressure applied by the second driving device 32 acts evenly on the side of the pressure plate 31 in contact with the core 100 without causing stress concentration. If the pressure plate 31 is replaced with a structure of a semi-cylinder welded to a cylinder, the force from the second driving device 32 is concentrated on the contact surface between the cylinder and the semi-cylinder, which will cause stress concentration.

[0056] like Figure 1 As shown, in the first feasible technical solution, the first driving device 22 includes a first motor and a first worm gear screw lift, the first worm gear screw lift includes a first worm 221 connected to the first motor, a first worm wheel 222 meshing with the first worm 221, and a first screw 223 connected to the first worm wheel 222 by a thread. For example, a threaded hole is provided in the central axis of the first worm wheel 222, the first screw 223 passes through the threaded hole, the first screw 223 is connected to the pressure plate 21, the first screw 223 is arranged along the axial direction of the core 100, that is, along the axial direction of the pressure plate 21, for example, the first screw 223 is threadedly connected and fixed to the pressure plate 21 for easy disassembly and assembly. During operation, the first motor drives the first worm 221 to rotate, the first worm 221 drives the first worm wheel 222 to rotate, the first worm wheel 222 drives the first screw 223 to move linearly (lift and lower) by rotating, and the first screw 223 drives the pressure plate 21 to move axially (up and down) along the core 100 by linear motion;

[0057] Each second driving device includes a second motor and a second worm gear screw lift, the second worm gear screw lift includes a second worm 321 connected to the second motor, a second worm wheel 322 meshing with the second worm 321, and a second screw 323 connected to the second worm wheel 322 by threading, for example, a threaded hole is provided in the central axis of the second worm wheel 322, the second screw 323 passes through the threaded hole, the second screw 323 is connected to the corresponding pressure plate 31, the second screw 323 is arranged along the radial direction of the core 100, or the second screw 323 and the first screw 223 are perpendicular to each other, for example, the second screw 323 is threadedly connected and fixed to the pressure plate 31 for easy disassembly and assembly. During operation, the second motor drives the second worm 321 to rotate, the second worm 321 drives the second worm wheel 322 to rotate, the second worm wheel 322 drives the second screw 323 to move linearly (horizontally) by rotating, and the second screw 323 drives the pressure plate 31 to move radially along the core 100 by linear motion.

[0058] This embodiment uses a worm gear screw mechanical structure to apply pressure to the core. The pressure loading process is safe and reliable, and can achieve precise pressure loading. It has a simple structure, low cost, and is easy to use.

[0059] In the second feasible technical solution, the first driving device 22 is a hydraulic cylinder or a linear stepping motor, and the second driving device 32 is a hydraulic cylinder or a linear stepping motor. The hydraulic cylinder or the linear stepping motor can drive the pressure plate 21 and the pressure plate 31 to move linearly.

[0060] In another specific embodiment, the test device for simulating the effect of hydration on rock strength further includes a heating device (not shown) for heating the liquid in the liquid storage tank 11. The heating device is used to heat the liquid in the liquid storage tank 11 to a set temperature, which can simulate the high-temperature drilling fluid in the actual drilling process, thereby more realistically simulating the effect of hydration on rock strength.

[0061] Furthermore, all components of the injection system 1 are made of high temperature and high pressure resistant materials to safely inject hot fluid into the core.

[0062] The present invention also provides a test method for simulating the effect of hydration on rock strength, which uses the above-mentioned test device for simulating the effect of hydration on rock strength, such as Figure 1 As shown, the test method includes the following steps performed in sequence:

[0063] Step S10: placing the core 100 between the two pressure plates 31 on the base 4, and aligning the core 100 axially with the pressure plate 21;

[0064] Step S20: inserting the injection pipeline 12 into the core 100. Preferably, the injection pipeline 12 is inserted below the middle of the hole in the core 100, for example, to the lower part of the hole;

[0065] Step S30: start the first driving device 22 and the second driving device 32. When the pressure plate 21 contacts the end surface of the core 100, close the first driving device 22. When the two pressure plates 31 are in contact with the outer wall of the core 100, close the second driving device 32.

[0066] Step S40: The liquid in the liquid storage tank 11 is heated to a set temperature, which is the formation temperature. The valve 13 is opened to continuously inject the heated liquid into the holes in the core 100 to soak the core 100. By continuously injecting liquid into the core 100, the intrusion of drilling fluid from the internal wellbore into the formation during the actual drilling process can be simulated. If the liquid is not continuously injected, the liquid in the hole will be reduced or even disappear after the liquid penetrates into the core. By inserting the injection pipeline 12 to a position below the middle of the hole in the core 100, the liquid will flow back from the lower part of the hole to the upper part of the hole, thereby simulating the circulation state of the drilling fluid during the actual drilling process.

[0067] Step S50: start the first driving device 22 and the second driving device 32 again, so that the first driving device 22 drives the pressure plate 21 to apply axial pressure to the core 100 and the second driving device 32 drives the pressure plate 31 to apply confining pressure to the core 100. When the applied axial pressure reaches the axial pressure setting value, turn off the first driving device 22, and when the applied confining pressure reaches the confining pressure setting value, turn off the second driving device 32;

[0068] Step S60: Keep injecting liquid into the core 100 until the set soaking time is reached and then stop injecting, pull out the injection line 12 from the core 100, start the first drive device 22 and the second drive device 32, make the pressure plate 21 and the pressure plate 31 move away from the core 100 respectively to unload the axial pressure and the confining pressure, take out the core 100, and turn off the first drive device 22 and the second drive device 32; by conducting tests for different set soaking times, the variation law of the formation rock strength under different hydration times can be understood;

[0069] Step S70: Cut the core 100 and perform a point load test on the cut core 100 to determine the strength of the core 100. Since the upper end surface of the core 100 is inevitably soaked in liquid, the upper end surface of the core 100 can be cut off during cutting to make the test result more accurate.

[0070] Further, the test method of the present invention also includes the following steps:

[0071] Step S01: Before step S10, the core 100 is made into a standard rock sample according to the test requirements, and a small hole 101 that does not penetrate the core 100 is processed along the axis direction of the core 100 by a micro drill bit, and the core 100 is wrapped with a heat shrink tube, and then the weight of the core 100 is weighed to obtain the initial weight W1 of the core 100; by wrapping the core 100 with a heat shrink tube, the core 100 can be prevented from being loose and shapeless after pressurization or immersion, and the confining pressure can be evenly applied to the outer wall of the core 100 within the wrapping surface to the greatest extent;

[0072] Step S61: before step S70 and after step S60, the core 100 is weighed again to obtain the weight W2 of the core after soaking, and the water absorption W3 of the core during the hydration process is W2-W1.

[0073] The test method of the present invention is simple and intuitive, and can simulate the real formation pressure system environment. The drilling fluid immersion test is carried out under set confining pressure and axial pressure conditions, and then the strength parameter change law of the core under real formation conditions and different hydration times can be measured through point load test equipment.

[0074] The present invention utilizes an axial pressure loading system and a confining pressure loading system to apply axial pressure and confining pressure to a standard core sample after axis drilling, and while pressurizing, injects drilling fluid heated to the formation temperature into the hole of the core, and keeps injecting the drilling fluid continuously. After pressurized immersion for a set time, the core sample is cut and a block is taken to perform a point load test, and the strength parameters of the core block at different immersion times are measured. Compared with the conventional core immersion test, the present invention is more in line with the actual situation when the drilling fluid in the wellbore invades the formation.

[0075] In the present invention, both the confining pressure and the axial pressure are loaded mechanically, which is safe and accurate. The present invention can control the triaxial loading force very accurately, simulate the real formation pressure conditions, and carry out experimental research on the rock hydration process that conforms to the actual situation on site.

[0076] The above description is only an illustrative specific implementation mode of the present invention and is not intended to limit the scope of the present invention. Any equivalent changes and modifications made by any technician in the field without departing from the concept and principle of the present invention should fall within the scope of protection of the present invention. It should also be noted that the various components of the present invention are not limited to the above-mentioned overall application. The various technical features described in the specification of the present invention can be selected one by one or multiple ones can be selected and used in combination according to actual needs. Therefore, the present invention naturally covers other combinations and specific applications related to the invention point of this case.

Claims

1. A test device for simulating the effect of hydration on rock strength, characterized in that: The test device for simulating the influence of hydration on rock strength comprises: A liquid injection system, comprising a liquid storage tank for containing liquid, and a liquid injection pipeline connected to the liquid storage tank and capable of injecting liquid into the core; An axial pressure loading system, comprising a pressure plate coaxially arranged with the core, and a first driving device connected with the pressure plate and capable of driving the pressure plate to move toward the core; The confining pressure loading system comprises two pressure plates arranged on both sides of the core, and two second driving devices respectively connected to the two pressure plates, the two second driving devices can respectively drive the two pressure plates to move toward the core, the two pressure plates surround the outer peripheral wall of the core by buckling, and fit with the outer peripheral wall of the core, the core is cylindrical, the side of the pressure plate facing the core is a semi-cylindrical surface, and the pressure plate is wedge-shaped; The first driving device includes a first motor and a first worm gear screw elevator, the first worm gear screw elevator includes a first worm connected to the first motor, a first worm wheel meshing with the first worm, and a first screw connected to the first worm wheel by a thread, the first screw is arranged along the axial direction of the core and connected to the pressure plate; The second driving device includes a second motor and a second worm gear screw lift, the second worm gear screw lift includes a second worm connected to the second motor, a second worm wheel meshing with the second worm, and a second screw connected to the second worm wheel by a thread, the second screw is connected to the pressure plate and is perpendicular to the first screw; The test device for simulating the effect of hydration on rock strength also includes a heating device for heating the liquid in the liquid storage tank. The heating device heats the liquid in the liquid storage tank to a set temperature to simulate high-temperature drilling fluid in an actual drilling process.

2. The test device for simulating the effect of hydration on rock strength according to claim 1, characterized in that: The test device for simulating the effect of hydration on rock strength also includes: a base, on which the core is placed; Two bearing seats, connected above the base and respectively located on opposite sides of the core, and the two second driving devices are respectively mounted on the two bearing seats; A support seat connected above the two bearing seats and located above the core, wherein the support seat has an opening for the pressure plate to pass through; The cylinder is connected above the support seat, the cylinder is communicated with the opening, the pressure plate is located in the cylinder, the first drive device is connected to the cylinder, and the first drive device is connected to the pressure plate by extending into the cylinder.

3. The test device for simulating the effect of hydration on rock strength as claimed in claim 2, characterized in that: The liquid storage tank is connected above the cylinder, the liquid injection pipeline includes a hose and a liquid guide tube, the pressure plate has a flow channel, one end of the hose is connected to the liquid storage tank, the other end of the hose extends into the cylinder and is connected to the pressure plate, the hose is communicated with the flow channel, one end of the liquid guide tube is connected to the pressure plate and communicated with the flow channel, and the other end of the liquid guide tube extends into the core.

4. The test device for simulating the effect of hydration on rock strength according to any one of claims 1 to 3, characterized in that: The liquid injection pipeline is connected with a valve.

5. The test device for simulating the effect of hydration on rock strength according to any one of claims 1 to 3, characterized in that: The first driving device is a hydraulic cylinder or a linear stepping motor, and the second driving device is a hydraulic cylinder or a linear stepping motor.

6. A test method for simulating the effect of hydration on rock strength, characterized in that: The test method uses a test device for simulating the effect of hydration on rock strength as claimed in any one of claims 1 to 5, and the test method comprises the following steps: Step S10: placing the core between the two pressure plates and aligning the core axially with the pressure plates; Step S20: inserting the injection pipeline into the core; Step S30: starting the first driving device and the second driving device, and when the pressure plate contacts the end surface of the core, closing the first driving device, and when the two pressure plates are in contact with the outer side wall of the core, closing the second driving device; Step S40: heating the liquid in the liquid storage tank to a set temperature, and continuously injecting the heated liquid into the core to soak the core; Step S50: starting the first driving device and the second driving device again, so that the first driving device applies axial pressure to the core and the second driving device applies confining pressure to the core, and when the applied axial pressure reaches the axial pressure setting value, turning off the first driving device, and when the applied confining pressure reaches the confining pressure setting value, turning off the second driving device; Step S60: keep injecting liquid into the core until the set soaking time is reached and then stop injecting, pull out the injection pipeline from the core, and then start the first driving device and the second driving device to move the pressure plate and the pressure plate away from the core respectively to unload the axial pressure and the confining pressure, take out the core, and close the first driving device and the second driving device; Step S70: cutting the core, and performing a point load test on the core block obtained by cutting to determine the strength of the core block.

7. The test method for simulating the effect of hydration on rock strength according to claim 6, characterized in that: The test method also includes the following steps: Step S01: before step S10, the core is wrapped with a heat shrink tube, and then the core is weighed to obtain an initial weight W1 of the core; Step S61: Before step S70, the core is weighed again to obtain the weight W2 of the core after immersion, and the water absorption W3 of the core during hydration is W2-W1.

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