Experimental device and method for simulating in-situ hydration damage of deep shale reservoir wellbore

Abstract

The present invention discloses a test apparatus and method for simulating in-situ hydration damage to deep shale reservoir wellbores. The test apparatus includes a true triaxial stress chamber for storing shale samples and subjecting them to high-temperature and high-pressure loading, an in-situ hydration assembly for conducting in-situ hydration simulation experiments on the shale samples, and an acquisition device for collecting image data from the shale samples before and after the hydration simulation experiments. This invention comprehensively considers the hydration damage caused by self-imbibition and forced imbibition to the wellbore under the in-situ conditions of high geotemperature and high stress in deep shale reservoirs. It can complete laboratory simulations of the stress concentration characteristics and strain field distribution characteristics caused by in-situ hydration damage, providing technical support and scientific guidance for wellbore stability research related to deep shale gas extraction in my country.

Description

Technical Field

[0001] The present invention relates to the technical field related to shale gas extraction, and in particular to a test device and method for simulating in-situ hydration damage of a deep shale reservoir wellbore. Background Art

[0002] As a new clean energy source, shale gas is attracting significant global attention amidst the increasing depletion of traditional energy sources and the growing demand for clean energy. Shale gas is also expected to play a significant role in global primary energy consumption.

[0003] Horizontal wells and hydraulic fracturing are relatively mature methods for shale gas reservoir reconstruction. These methods involve placing horizontal wells within shale reservoirs and pumping high-pressure water into the wells, which then directly fracture the rock after perforating the wells. However, wellbore instability in shale reservoirs directly impacts the efficient development of shale gas and remains a major technical challenge.

[0004] The main reason for the instability of the wellbore in shale formations is shale hydration damage. Due to the strong hydration characteristics of shale, the contact between drilling fluid and wellbore rock can easily cause strong hydration damage, resulting in reduced wellbore stability and thus engineering disasters such as wellbore collapse and instability.

[0005] The problem of wellbore instability caused by drilling horizontal wells in hard and brittle shale reservoirs is more prominent, which can easily lead to complex underground engineering accidents such as drill sticking and drill burial. In severe cases, it may even cause the current wellbore to be scrapped, resulting in huge economic losses.

[0006] Considering that hydration damage to shale gas reservoir wellbore walls is not only a physical and mechanical behavior but also accompanied by chemical reactions, it is a typical multi-field coupling problem. Especially for deep shale gas reservoirs, the high temperature and high stress in situ environment make hydration damage even more complicated.

[0007] Therefore, understanding the hydration process is crucial for studying the direct impact of each mechanism, especially for deep shale reservoirs. However, there is currently no mature and reliable testing equipment to investigate the hydration damage caused by spontaneous imbibition and forced imbibition in shale horizontal wells under high temperature and high stress conditions.

[0008] In order to fill this technological gap, provide better technical support for my country's deep shale gas exploitation, and ensure energy security, a test equipment that can simulate the hydration damage of deep shale reservoir wells in situ state has great practical significance. Summary of the Invention

[0009] The purpose of the present invention is to address the shortcomings of the existing technology and provide a test device and method that can not only realistically simulate the high temperature and high stress environment of deep shale reservoirs, but also comprehensively study the hydration damage caused by self-imbibition and forced infiltration of the well wall in the shale reservoir and its distribution characteristics under triaxial stress state.

[0010] The test device for simulating in-situ hydration damage in deep shale reservoir wells provided by the present invention includes a true triaxial stress chamber for storing shale samples and subjecting them to high-temperature and high-pressure loading, an in-situ hydration assembly for conducting hydration simulation experiments on shale samples in the in-situ state of the formation, and an acquisition device for collecting image data within the shale samples before and after the hydration simulation experiments.

[0011] The true triaxial stress chamber is formed by a bottom plate, side plates and a top plate, and test holes connecting the inside and outside of the true triaxial stress chamber are symmetrically arranged on the two parallel side plates;

[0012] The shale sample is tightly arranged between the bottom plate, the side plate and the top plate, and a simulated wellbore is horizontally opened in the shale sample to connect the ports in the two test holes;

[0013] The in-situ hydration assembly includes a frame erected outside the true triaxial stress chamber. A drilling fluid tank, a two-way water pump, a control valve, a flow meter, and a flow observation tube are installed on the frame above the test hole, which are sequentially connected from top to bottom. The bottom of the flow observation tube is connected to the interior of the simulated wellbore via a high-temperature and high-pressure hose that passes through the test hole. The high-temperature and high-pressure hose is sealed to the test hole. The drilling fluid in the drilling fluid tank is output through the high-temperature and high-pressure hose to perform a hydration simulation experiment on the shale sample in the true triaxial stress chamber under the in-situ formation state.

[0014] The image acquisition device includes a telescopic rod, at the front end of which is mounted a high-definition camera capable of 360-degree viewing around its axis. The telescopic rod is horizontally mounted on a side panel at one end of the simulated wellbore. The high-definition camera is driven by the telescopic rod to extend into the simulated wellbore to collect image data of the interior of the simulated wellbore before and after the hydration simulation experiment.

[0015] The high temperature and high pressure resistant hose is sealed and connected to the outer port of the test hole through a sealing ring.

[0016] The shale sample is made from a complete shale block taken from a shale gas production area through wire cutting. The shale sample is a cubic sample with a size of 500×500×500 mm.

[0017] The simulated wellbore is drilled by a portable electric drill and has a diameter of 25 to 35 mm.

[0018] Two flow observation tubes arranged at the same height are connected in parallel at the lower end of the flow meter, and the bottoms of the two flow observation tubes are connected one-to-one with two high-temperature and high-pressure resistant hoses placed in each test hole.

[0019] The error of the flow meter is less than 0.1%; the maximum water outlet pressure of the bidirectional water pump is 40MPa, and the maximum water inlet pressure is 10Mpa; the pressure bearing capacity of the high-temperature and high-pressure resistant hose is 55Mpa; the capacity of the flow observation tube is 100-500ml.

[0020] The maximum length of the telescopic rod is 550 mm, the frame rate of the high-definition camera can reach 125 fps per second, and both the telescopic rod and the high-definition camera are in remote wireless control mode.

[0021] A test method for the above test device comprises the following steps:

[0022] S1. Select shale cores from the target shale gas mining area and process them into shale samples with a size of 500 × 500 × 500 mm using wire cutting.

[0023] S2. Use a portable drilling rig to drill a simulated wellbore with a diameter of 25-35 mm in the shale sample, connecting the two test holes;

[0024] S3. Place the shale sample with the simulated wellbore in a well-ventilated constant temperature test room until the shale sample is completely dry;

[0025] S4. Take out the shale sample and place it in a true triaxial stress chamber;

[0026] S5, assembling the in-situ hydration components;

[0027] S6. Start the temperature controller and the three-dimensional stress loading controller of the true triaxial stress chamber, and load the temperature and stress of the shale sample according to the actual in-situ state of the engineering wellbore. When the predetermined temperature and stress state are reached, keep the loading values ​​unchanged.

[0028] S7, start the image acquisition device to acquire images of the entire section of the simulated wellbore, and automatically reset after acquisition is completed;

[0029] S8. Start the in-situ hydration component and conduct a hydration simulation experiment of self-imbibition or forced imbibition on the simulated wellbore in the in-situ state of the formation.

[0030] The specific steps of the self-absorption hydration simulation experiment are as follows:

[0031] SA1. Open the control valve in the in-situ hydration assembly. The drilling fluid in the drilling fluid tank spontaneously penetrates into the simulated wellbore in the in-situ state of the formation due to the height difference.

[0032] SA2. Observe the flow observation tube. When the liquid level in the flow observation tube reaches the upper limit of its capacity scale, close the control valve. Continue observing the flow observation tube. When the liquid level remains unchanged for 2 consecutive minutes, record the capacity value V1 at this time. Continue observing the flow observation tube until the liquid level remains unchanged for 24 consecutive hours, and then record the capacity value V2 at this time.

[0033] SA3: Open the bidirectional water pump in the forward direction to suck the drilling fluid from the simulated wellbore back to the drilling fluid tank. When there is no drilling fluid in the flow observation tube, close the control valve and the bidirectional water pump and wait for the next experiment.

[0034] The specific steps of the forced hydration simulation experiment are as follows:

[0035] SB1. Open the control valve and flowmeter in the in-situ hydration assembly and reversely start the bidirectional water pump. This forces the drilling fluid in the drilling fluid tank to penetrate into the simulated wellbore in the in-situ state of the formation under the dual forces of the height difference and pump pressure.

[0036] SB2. Observe the flow meter. When the flow meter value forms a stable pressure differential, start recording the forced shale hydration and record the value V3 at this time. Continue observing the flow meter until the value remains unchanged for 24 consecutive hours, and then record the value V4 at this time.

[0037] SB3: Start the bidirectional water pump in the forward direction to suck the drilling fluid from the simulated wellbore back to the drilling fluid tank. When there is no drilling fluid in the flow observation tube, close the control valve, bidirectional water pump and flow meter and wait for the next experiment.

[0038] S9, start the image acquisition device to acquire images of the entire section of the simulated wellbore, and automatically reset after acquisition is completed;

[0039] S10. Organize the image data collected in S7 and S9, and use digital speckle technology to analyze the stress concentration and strain distribution of the simulated wellbore section before and after the experiment.

[0040] The specific process of placing the shale sample in the true triaxial stress chamber in step S4 is as follows:

[0041] S41. Place the shale sample on the bottom plate and align the simulated wellbore with the two test holes;

[0042] S42. Move the side plates horizontally until they are close to the periphery of the shale specimen;

[0043] S43. Move the top plate down until it is close to the top surface of the shale sample.

[0044] The assembly process of the in-situ hydration component in step S5 is as follows:

[0045] S51, fixing the frame to the base plate;

[0046] S52. Install the drilling fluid tank, bidirectional water pump, flow meter, and flow observation tube from top to bottom on the frame above the top plate. There are two flow observation tubes, which are arranged one-to-one with the two test holes.

[0047] S53. Connect one end of the bidirectional water pump to the bottom outlet of the drilling fluid tank and the other end to the flow meter inlet through a control valve and a pipeline; connect the outlet of the flow meter to the upper ends of the two flow observation tubes through pipelines, connect the lower ends of the flow observation tubes to the high-temperature and high-pressure hoses, and seal the lower ends of the high-temperature and high-pressure hoses by inserting them into the test hole and connecting them to the simulated wellbore.

[0048] Compared with the prior art, the present invention has the following advantages:

[0049] 1. The present invention comprehensively considers the hydration damage caused by self-imbibition and forced imbibition to the wellbore under the in-situ conditions of high geothermal temperature and high stress in deep shale reservoirs. It can complete the simulation study of the stress concentration characteristics and strain field distribution characteristics caused by hydration damage under in-situ conditions in the laboratory, and can provide technical support and scientific guidance for the research on wellbore stability involved in deep shale gas extraction in my country.

[0050] 2. The present invention can conduct characteristic research on the in-situ hydration damage-induced wellbore instability and destruction under stress adjustment based on the characteristics of different shale reservoirs and drilling processes. It has good application prospects and broad engineering practical significance in the field of shale gas extraction engineering. BRIEF DESCRIPTION OF THE DRAWINGS

[0051] Figure 1 Schematic diagram of the structure of the test device in the present invention.

[0052] The symbols and corresponding component names shown in the figure are:

[0053] 1. Shale sample; 11. Simulated wellbore;

[0054] 2. True triaxial stress chamber; 21. Bottom plate; 22. Side plate; 23. Top plate; 221. Test hole;

[0055] 3. In-situ hydration assembly; 31. Frame; 32. Drilling fluid tank; 33. Bidirectional water pump; 34. Control valve; 35. Flow meter; 36. Flow observation tube; 37. High-temperature and high-pressure resistant hose; 38. Sealing ring;

[0056] 4. Data collection device; 41. Telescopic rod; 42. High-definition camera. DETAILED DESCRIPTION

[0057] from Figure 1It can be seen that the test device for simulating in-situ hydration damage in deep shale reservoir wells of the present invention includes a true triaxial stress chamber 2 for storing a shale sample 1 and subjecting it to high temperature and high pressure loading, an in-situ hydration assembly 3 for conducting a hydration simulation experiment on the shale sample 1 in the true triaxial stress chamber 2 under the in-situ formation state, and an acquisition device 4 for acquiring image data in the shale sample 1 before and after the hydration simulation experiment.

[0058] The shale sample 1 is made from a complete shale block taken from a shale gas producing area by wire cutting. The processed shale sample 1 is a cubic sample of 500×500×500 mm. A horizontally arranged simulated wellbore 11 is drilled through the shale sample 1.

[0059] The true triaxial stress chamber 2 is formed by a bottom plate 21, four side plates 22, and a top plate 23. The shale sample 1 is tightly arranged between the bottom plate 21, the side plates 22, and the top plate 23. Two test holes 221 are symmetrically opened on two parallel side plates 22 to connect the inside and outside of the true triaxial stress chamber 2. The inner ports of the two test holes 221 are respectively connected to one port of the simulated wellbore 11, and the outer ports of the two test holes 221 are arranged on the top of the side plates 22.

[0060] The in-situ hydration assembly 3 includes a frame 31, a drilling fluid tank 32, a two-way water pump 33, a control valve 34, a flow meter 35 and a flow observation tube 36. The frame 31 is mounted on the bottom plate 21 outside the side plate 22 and the top plate 23. The flow meter 35 is installed on the frame 31 above the top. The two-way water pump 33 is installed on the frame 31 above the flow meter 35. The control valve 34 is connected between the upper port of the flow meter 35 and the lower port of the two-way water pump 33 through a pipeline. The drilling fluid tank 32 is installed on the frame 31 above the two-way water pump 33. An outlet connected to the upper port of the two-way water pump 33 is provided at the bottom of the drilling fluid tank 32. There are two flow observation tubes 36 and they are arranged one to one with the two test holes 221. The two flow observation tubes 36 are both made of transparent material and have capacity scale lines. The two flow observation tubes 36 are connected through the pipe The clamp is detachably mounted on the frame 31 between each test hole 221 and the flow meter 35, and two flow observation tubes 36 are arranged at the same height on the frame 31; the upper ends of the two flow observation tubes 36 are connected to the side port of the flow meter 35 through a pipeline, and a high-temperature and high-pressure hose 37 is connected to the lower end of each flow observation tube 36. The lower end of each high-temperature and high-pressure hose 37 passes through the corresponding test hole 221 and is connected to the interior of the simulated wellbore 11. The high-temperature and high-pressure hose 37 is sealed with the test hole 221. The flow observation tube 36, the high-temperature and high-pressure hose 37 and the simulated wellbore 11 together form a communicating vessel; when the control valve 34 is opened, the drilling fluid in the drilling fluid tank 32 is output through the high-temperature and high-pressure hose 37 to perform a hydration simulation experiment on the shale sample 1 in the true triaxial stress chamber 2 under the in-situ formation state;

[0061] The image acquisition device 4 includes a telescopic rod 41 horizontally mounted on the side plate 22 at one end of the simulated wellbore 11. A high-definition camera 42 that can capture a 360° angle around its axis is installed at the front end of the telescopic rod 41. The high-definition camera 42 is driven by the telescopic rod 41 to extend into the simulated wellbore 11 at a constant speed to collect image data inside the simulated wellbore before and after the hydration simulation experiment.

[0062] from Figure 1 It can be seen that a sealing ring 38 for sealing connection is provided between the high temperature and high pressure resistant hose 37 and the outer end of the test hole 221 .

[0063] In the present invention, the simulated wellbore 11 is drilled by a portable electric drill and has a diameter of 25 to 35 mm.

[0064] In the present invention, the maximum water outlet pressure of the bidirectional water pump 33 is 40 MPa, and the maximum water inlet pressure is 10 MPa; the error of the flow meter 35 is less than 0.1%; the capacity of the flow observation tube 36 is 100 to 500 ml; the pressure bearing capacity of the high-temperature and high-pressure resistant hose 37 is 55 MPa, and the length is 30 cm.

[0065] In the present invention, the maximum length of the telescopic rod 41 is 550 mm, the frame rate of the high-definition camera 42 can reach 125 fps per second, and the telescopic rod 411 and the high-definition camera 42 are both in remote wireless control mode; the high-definition camera 42 can adopt the structure of an existing 360-degree panoramic camera to achieve its 360° framing function, or it can adopt the structure described in publication number CN215411095U to achieve its 360° framing function.

[0066] The present invention provides a test method for the above-mentioned test device, comprising the following steps:

[0067] S1. Select shale cores from the target shale gas mining area and process them into shale sample 1 with a size of 500 × 500 × 500 mm cubes by wire cutting.

[0068] S2. Drill a simulated wellbore 11 with a diameter of 25-35 mm on the shale sample 1 using a portable drilling rig to connect the two test holes 221;

[0069] S3. Place the shale sample 1 with the simulated wellbore 11 in a well-ventilated constant temperature test room until the shale sample 1 is completely dry;

[0070] S4, taking out the dried shale sample 1 and placing it in a true triaxial stress chamber 2;

[0071] S5, assembling the in-situ hydration component 3;

[0072] S6. Start the temperature controller and the three-dimensional stress loading controller of the true triaxial stress chamber, and load the temperature and stress of the shale sample according to the actual in-situ state of the engineering wellbore. When the predetermined temperature and stress state are reached, keep the loading values ​​unchanged.

[0073] S7, start the image acquisition device 4 to acquire images of the entire section of the simulated wellbore, and automatically reset after acquisition is completed;

[0074] S8, start the in-situ hydration component to conduct a hydration simulation experiment of self-imbibition or forced imbibition on the simulated wellbore in the in-situ state of the formation, wherein:

[0075] The specific steps of the self-absorption hydration simulation experiment are as follows:

[0076] SA1. Open the control valve 34 in the in-situ hydration assembly. The drilling fluid in the drilling fluid tank 32 spontaneously penetrates into the simulated wellbore 11 in the in-situ state of the formation due to the height difference.

[0077] SA2. Observe the flow observation tube 36. When the liquid level in the flow observation tube reaches the upper limit of its capacity scale, close the control valve. Continue observing the flow observation tube. When the liquid level remains constant for 2 consecutive minutes, record the capacity value V1 at this time. Continue observing the flow observation tube until the liquid level remains constant for 24 consecutive hours, and then record the capacity value V2 at this time.

[0078] SA3: Turn on the bidirectional water pump 33 in the forward direction to suck the drilling fluid from the simulated wellbore back to the drilling fluid tank. When there is no drilling fluid in the flow observation tube, close the control valve and the bidirectional water pump and wait for the next experiment.

[0079] The specific steps of the forced hydration simulation experiment are as follows:

[0080] SB1. Open the control valve 34 and flow meter 35 in the in-situ hydration assembly and reversely start the bidirectional water pump 33, so that the drilling fluid in the drilling fluid tank 32 is forced to penetrate into the simulated wellbore 11 in the in-situ state of the formation under the dual forces of the height difference and the pump pressure;

[0081] SB2. Observe the flow meter. When the flow meter value forms a stable pressure differential, start recording the forced shale hydration and record the value V3 at this time. Continue observing the flow meter until the value remains unchanged for 24 consecutive hours, and then record the value V4 at this time.

[0082] SB3: Start the bidirectional water pump in the forward direction to suck the drilling fluid from the simulated wellbore back to the drilling fluid tank. When there is no drilling fluid in the flow observation tube, close the control valve, bidirectional water pump and flow meter and wait for the next experiment.

[0083] S9, start the image acquisition device 4 to acquire images of the entire section of the simulated wellbore, and automatically reset after acquisition is completed;

[0084] S10. Organize the image data collected in S7 and S9, use digital images to process the imaging photos before and after hydration, use digital speckle technology to analyze the stress concentration and strain distribution of the simulated wellbore section before and after the experiment, and obtain the self-imbibition hydration damage state of the wellbore wall in situ, mainly including important mechanical parameters such as the strain state near the bedding plane.

[0085] The specific process of placing the shale sample 1 in the true triaxial stress chamber 2 in step S4 is as follows:

[0086] S41, placing the shale sample 1 on the bottom plate 21, and aligning the simulated wellbore 11 with the two test holes 221;

[0087] S42, the horizontal driving mechanism pushes each side plate 22 to move horizontally until it is arranged close to the periphery of the shale sample 1;

[0088] S43 , the top plate 23 is pushed downward by the vertical driving mechanism to be arranged close to the top surface of the shale sample 1 .

[0089] The assembly process of the in-situ hydration assembly 3 in step S5 is as follows:

[0090] S51, fixing the frame 31 on the base plate 21;

[0091] S52, install the drilling fluid tank 32, the two-way water pump 33, the flow meter 35 and the flow observation tube 36 from top to bottom on the frame 31 above the top plate 23, wherein there are two flow observation tubes 36 and they are arranged one-to-one with the two test holes 221;

[0092] S53. Connect one end of the two-way water pump 33 to the bottom outlet of the drilling fluid tank 32, and the other end to the inlet of the flow meter 35 through the control valve 34 and the pipeline; connect the outlet of the flow meter 35 to the upper ends of the two flow observation tubes 36 through the pipeline, connect the lower ends of the flow observation tubes 36 to the high-temperature and high-pressure resistant hose 37, and seal the lower end of the high-temperature and high-pressure resistant hose and insert it into the test hole to communicate with the simulated wellbore.

[0093] The present invention can also be implemented according to the actual engineering background of the simulated wellbore hydration, such as the evolution characteristics of hydration damage caused by self-imbibition and forced imbibition under the action of drilling-induced stress adjustment and its impact on wellbore instability and destruction, and can also be implemented by setting stress paths after S8, so as to flexibly utilize the system.

[0094] The present invention can study the self-imbibition and forced imbibition characteristics of shale in situ, and can further reveal the characteristics of its hydration damage evolving during stress adjustment and inducing wellbore instability and destruction, which is of great significance to the study of wellbore stability in deep shale gas extraction in my country.

Claims

1. A test method for simulating in-situ hydration damage in deep shale reservoir wellbores, characterized by: The invention comprises a test device for simulating in-situ hydration damage of a deep shale reservoir wellbore, the test device comprising a true triaxial stress chamber (2) for storing a shale sample (1) and subjecting it to high temperature and high pressure loading, an in-situ hydration component (3) for conducting a hydration simulation experiment on the shale sample under a formation in-situ state, and an image acquisition device (4) for acquiring image data in the shale sample before and after the hydration simulation experiment. The true triaxial stress chamber is formed by a bottom plate (21), a side plate (22) and a top plate (23), and test holes (221) are symmetrically arranged on two parallel side plates to connect the inside and outside of the true triaxial stress chamber. The shale sample is closely arranged between the bottom plate, the side plate and the top plate, and a simulated wellbore (11) is horizontally opened in the shale sample to connect the ports in the two test holes; The in-situ hydration assembly comprises a frame (31) erected outside the true triaxial stress chamber, a drilling fluid tank (32), a two-way water pump (33), a control valve (34), a flow meter (35) and a flow observation tube (36) arranged in a sequential manner from top to bottom are installed on the frame above the test hole, the bottom of the flow observation tube is connected to the inside of the simulated wellbore via a high-temperature and high-pressure hose (37) passing through the test hole, the high-temperature and high-pressure hose is sealedly connected to the test hole, and the drilling fluid in the drilling fluid tank is output through the high-temperature and high-pressure hose to perform a hydration simulation experiment on the shale sample in the true triaxial stress chamber under the in-situ state of the formation; The image acquisition device comprises a telescopic rod (41), a high-definition camera (42) capable of 360° viewing around its axis is mounted on the front end of the telescopic rod, the telescopic rod is horizontally mounted on a side plate at one end of the simulated wellbore, and the high-definition camera is driven by the telescopic rod to extend into the simulated wellbore to collect image data of the interior of the simulated wellbore before and after the hydration simulation experiment; The test method comprises the following steps: S1. Select shale cores from the target shale gas mining area and process them into shale samples (1) with a size of 500 × 500 × 500 mm cubes by wire cutting. S2. Drilling a simulated wellbore (11) with a diameter of 25-35 mm on the shale sample, connecting the two test holes (221); S3. Place the shale sample with the simulated wellbore in a well-ventilated constant temperature test room until the shale sample is completely dry; S4, taking out the shale sample and placing it in the true triaxial stress chamber (2); S5, assembling the in-situ hydration component (3); S6. Start the temperature controller and the three-dimensional stress loading controller of the true triaxial stress chamber, and load the temperature and stress of the shale sample according to the actual in-situ state of the engineering wellbore. When the predetermined temperature and stress state are reached, keep the loading values ​​unchanged. S7, start the image acquisition device (4), collect images of the entire section of the simulated wellbore, and automatically reset after the acquisition is completed; S8. Start the in-situ hydration component and conduct a hydration simulation experiment of self-imbibition or forced imbibition on the simulated wellbore in the in-situ state of the formation. The specific steps of the self-absorption hydration simulation experiment are as follows: SA1, opening the control valve (34) in the in-situ hydration assembly, and the drilling fluid in the drilling fluid tank (32) spontaneously penetrates into the simulated wellbore in the in-situ state of the formation under the action of the height difference; SA2, observe the flow observation tube (36), when the height of the liquid level in the flow observation tube reaches the upper line of its capacity scale, close the control valve; continue to observe the flow observation tube, when the internal liquid level remains unchanged for 2 consecutive minutes, record the capacity value V1 at this time; continue to observe the flow observation tube until the internal liquid level remains unchanged for 24 consecutive hours, and record the capacity value V2 at this time; SA3: Turn on the bidirectional water pump (33) in the forward direction to suck the drilling fluid from the simulated wellbore back to the drilling fluid tank. When there is no drilling fluid in the flow observation tube, close the control valve and the bidirectional water pump and wait for the next experiment. The specific steps of the forced hydration simulation experiment are as follows: SB1, opening the control valve (34) and flow meter (35) in the in-situ hydration assembly, and reversely starting the bidirectional water pump (33), so that the drilling fluid in the drilling fluid tank (32) is forced to penetrate into the simulated wellbore in the in-situ state of the formation under the dual forces of the height difference and the pump pressure; SB2. Observe the flow meter. When the flow meter value forms a stable pressure differential, start recording the forced shale hydration and record the value V3 at this time. Continue observing the flow meter until the value remains unchanged for 24 consecutive hours, and then record the value V4 at this time. SB3: Start the bidirectional water pump in the forward direction to suck the drilling fluid from the simulated wellbore back to the drilling fluid tank. When there is no drilling fluid in the flow observation tube, close the control valve, bidirectional water pump and flow meter and wait for the next experiment. S9, start the image acquisition device (4), collect the whole-section image of the simulated wellbore, and automatically reset after the acquisition is completed; S10. Organize the image data collected in S7 and S9, and use digital speckle technology to analyze the stress concentration and strain distribution of the simulated wellbore section before and after the experiment.

2. The test method for simulating in-situ hydration damage in deep shale reservoir wells according to claim 1, characterized in that: The high temperature and high pressure resistant hose is sealed and connected to the outer port of the test hole via a sealing ring (38).

3. The test method for simulating in-situ hydration damage in deep shale reservoir wells according to claim 1, characterized in that: The shale sample is made from a complete shale block taken from a shale gas production area through wire cutting. The shale sample is a cubic sample with a size of 500×500×500 mm.

4. The test method for simulating in-situ hydration damage in deep shale reservoir wells according to claim 1, characterized in that: The simulated wellbore is drilled by a portable electric drill and has a diameter of 25 to 35 mm.

5. The test method for simulating in-situ hydration damage in deep shale reservoir wells according to claim 1, characterized in that: Two flow observation tubes arranged at the same height are connected in parallel at the lower end of the flow meter, and the bottoms of the two flow observation tubes are connected one-to-one with two high-temperature and high-pressure resistant hoses placed in each test hole.

6. The test method for simulating in-situ hydration damage in deep shale reservoir wells according to claim 1, characterized in that: The error of the flow meter is less than 0.1%; the maximum water outlet pressure of the bidirectional water pump is 40MPa, and the maximum water inlet pressure is 10Mpa; the pressure bearing capacity of the high-temperature and high-pressure resistant hose is 55Mpa; the capacity of the flow observation tube is 100-500ml.

7. The test method for simulating in-situ hydration damage in deep shale reservoir wells according to claim 1, characterized in that: The maximum length of the telescopic rod is 550 mm, the frame rate of the high-definition camera can reach 125 fps per second, and both the telescopic rod and the high-definition camera are in remote wireless control mode.

8. The test method for simulating in-situ hydration damage in deep shale reservoir wells according to claim 1, characterized in that: The specific process of placing the shale sample in the true triaxial stress chamber in step S4 is as follows: S41, placing the shale sample on the bottom plate (21), and aligning the simulated wellbore with the two test holes; S42, horizontally moving the side plate (22) until it is closely arranged around the shale sample; S43, the top plate (23) is moved down to be arranged close to the top surface of the shale sample.

9. The test method for simulating in-situ hydration damage in deep shale reservoir wells according to claim 8, characterized in that: The assembly process of the in-situ hydration component in step S5 is as follows: S51, fixing the frame (31) on the base plate (21); S52, installing the drilling fluid tank (32), the bidirectional water pump (33), the flow meter (35) and the flow observation tube (36) from top to bottom on the frame above the top plate, wherein there are two flow observation tubes and they are arranged one to one with the two test holes; S53, connect one end of the bidirectional water pump to the bottom outlet of the drilling fluid tank, and connect the other end to the flow meter inlet through the control valve (34) and the pipeline; connect the outlet of the flow meter to the upper ends of the two flow observation tubes through the pipeline, connect the lower ends of the flow observation tubes to the high-temperature and high-pressure hose (37), and insert the lower end of the high-temperature and high-pressure hose into the test hole in a sealed manner to communicate with the simulated wellbore.

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