Shale in-situ water saturation testing method
By simulating the physical process of shale cores under reservoir conditions, accurately measuring the in-situ water saturation of shale, solving the problem of inaccurate measurement in the existing technology, and providing more accurate support for shale gas reserve evaluation.
Patent Information
- Application Number
- CN202311725245.6
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2023-12-14
- Publication Date
- 2025-06-17
AI Technical Summary
The method of measuring the water saturation of shale in the prior art cannot accurately obtain the in-situ water saturation under reservoir conditions, resulting in large deviations in resource evaluation and capacity prediction.
The steam method is used to establish the original water saturation of the core to be tested, and the core extraction process is physically simulated by simulating the reservoir saturation gas, drilling fluid invasion and drilling process, and the water saturation at different test locations is determined, and the shale in-situ water saturation test diagram is finally drawn.
The in-situ water saturation of shale under reservoir conditions can be accurately measured through physical simulation methods, which solves the problem of inaccurate conventional analysis methods. The water saturation data of the core core is obtained by normalizing the normal method to ensure that it is close to the in-situ water saturation under reservoir conditions.
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Figure CN120161184A_ABST
Abstract
Description
Technical Field
[0001] The present invention relates to the technical field of shale gas exploration and development, and specifically, to a method for testing in-situ water saturation of shale. Background Art
[0002] Reservoirs under in-situ conditions of shale generally contain water, and gas and water coexist. Taking marine shale in the south as an example, its water-bearing environment is complex, and the water saturation ranges from 10% to 90%. The components of shale reservoirs are complex, mainly including organic matters such as oleophilic kerogen and inorganic matters such as hydrophilic clay minerals. The original water mainly exists in the form of structural water, adsorbed water, interlayer water, etc. between the crystal layers, within the crystal grains, and on the particle surfaces of clay minerals, and the original water saturation is generally lower than the maximum irreducible water saturation. The original water saturation of shale is an important parameter for reserve evaluation. If the influence of the original water saturation in micro / nano pores is ignored or miscalculated, there will be large deviations in resource evaluation and production capacity prediction.
[0003] Currently, most scholars generally use the following two methods to measure the water saturation of shale, namely the conventional retorting method and the nuclear magnetic testing method. The calculation principles of these two methods are clear, and the operations are simple and fast, but both have the defect of inaccurate calculation results. This is because there is an ultra-low water saturation phenomenon in shale, and clay is developed, with strong hydrophilicity and adsorption capacity. When the core is lifted from the reservoir to the ground, the water saturation will be affected by temperature reduction, pressure reduction, and invasion of drilling fluid. Therefore, from the well site to the laboratory, as well as during the preservation and experimental testing in the laboratory, the water saturation of shale will be affected by temperature, humidity, and preservation environment, and the measured water saturation of shale is no longer the in-situ water saturation under reservoir conditions. Summary of the Invention
[0004] Aiming at the technical problem that the water saturation obtained by measuring conventional core samples is not the in-situ water saturation of shale under reservoir conditions in the prior art, the present invention provides a method for testing in-situ water saturation of shale. By using this method, the in-situ water saturation of shale under reservoir conditions can be obtained, and the water saturation of conventional core samples can be corrected, providing technical support for the accurate calculation of shale gas reserves.
[0005] To achieve the above object, the method for testing in-situ water saturation of shale provided by the present invention includes the following steps: establishing the original water saturation of the core to be tested by the steam method; performing physical simulation of the core extraction process on the core to be tested at the original water saturation, and determining the water saturation at different test positions; and determining the in-situ water saturation test chart according to the water saturation at different test positions.
[0006] In an exemplary embodiment of the present invention, the testing method further includes: correcting the water saturation of a conventional core sample using a shale in-situ water saturation test chart to obtain the shale in-situ water saturation under reservoir conditions.
[0007] In an exemplary embodiment of the present invention, the physical simulation of the core extraction process may include: physical simulation of the reservoir gas saturation process, physical simulation of the drilling fluid invasion process, and physical simulation of the core lifting process.
[0008] In an exemplary embodiment of the present invention, the physical simulation of the core extraction process for a core sample to be tested at its original water saturation to determine the water saturation at different test positions may include: performing a physical simulation of the reservoir gas saturation process on the core sample to be tested at its original water saturation to construct a first in-situ state of the core sample in the reservoir; performing a physical simulation of the drilling fluid invasion process on the core sample in the first in-situ state to construct a second in-situ state of the core sample during the drilling fluid invasion process; performing a physical simulation of the core lifting process on the core sample in the second in-situ state to construct a third in-situ state of the core sample during the core lifting process; after the physical simulation of the core lifting process is completed, taking out the core sample in the third in-situ state, crushing the core sample into multiple core fragments according to different test positions, and determining the water saturation at different test positions.
[0009] In an exemplary embodiment of the present invention, the physical simulation of the reservoir gas saturation process for a core sample to be tested at its original water saturation may include: placing the core sample to be tested at its original water saturation into an intermediate container, and filling the core sample with a simulated gas by pressurization until the simulated gas inside the core sample is in a saturated state; wherein, the temperature of the simulated gas is set to the reservoir temperature, and the pressure of the simulated gas is set to the reservoir pressure.
[0010] In an exemplary embodiment of the present invention, the physical simulation of the drilling fluid invasion process for a core sample in the first in-situ state may include: injecting a simulated liquid into the annular space between the core sample and the intermediate container until the annular space is filled with the simulated liquid; wherein, the pressure of the simulated liquid is greater than the pressure of the simulated gas.
[0011] In an exemplary embodiment of the present invention, the physical simulation of the core lifting process for a core sample in the second in-situ state may include: reducing the pressure and temperature inside the intermediate container to normal temperature and pressure, and measuring the gas production volume.
[0012] In an exemplary embodiment of the present invention, the different test positions may include: the core center, the core periphery, and multiple test positions from the core center to the core periphery.
[0013] In an exemplary embodiment of the present invention, the weighing method and the nuclear magnetic method can be used to determine the water saturation at different test positions respectively.
[0014] In an exemplary embodiment of the present invention, the simulated gas can be air or methane.
[0015] In an exemplary embodiment of the present invention, the simulated liquid can be water, drilling fluid or drilling fluid-like fluid.
[0016] Through the technical solution provided by the present invention, the present invention has at least the following technical effects:
[0017] (1) By physically simulating the gas saturation process of the reservoir, the drilling fluid invasion process and the core extraction process, and then immediately knocking out multiple fragments from the center to the periphery of the core to measure the water saturation, the shale in-situ water saturation testing method of the present invention can obtain the water saturation at different test positions. This method can measure the shale in-situ water saturation under reservoir conditions to the greatest extent, and solves the problem that the conventional analysis method is inaccurate in testing the shale in-situ water saturation.
[0018] (2) The shale in-situ water saturation testing method of the present invention draws a shale in-situ water saturation test chart based on the water saturation data at different test positions, and uses this chart to correct the water saturation of the conventional core. It eliminates the influence of factors such as temperature, humidity, and storage environment during the process from extraction at the well site to laboratory testing on the shale water saturation, ensuring that the water saturation measured by the conventional analysis method can also be closest to the in-situ water saturation under reservoir conditions to the greatest extent.
[0019] (3) The present invention can be applied to the determination of the porosity of mud shale, providing technical support for the accurate calculation of shale gas reserves.
[0020] Other features and advantages of the present invention will be described in detail in the subsequent specific implementation part. BRIEF DESCRIPTION OF THE DRAWINGS
[0021] The drawings are used to provide a further understanding of the embodiments of the present invention, and constitute a part of the specification. Together with the following specific implementation manners, they are used to explain the embodiments of the present invention, but do not constitute a limitation to the embodiments of the present invention. In the drawings:
[0022] Figure 1 It is the shale in-situ water saturation test chart provided by the embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION
[0023] The following will describe in detail the specific implementation manners of the embodiments of the present invention with reference to the drawings. It should be understood that the specific implementation manners described here are only used to explain and illustrate the embodiments of the present invention, and are not used to limit the embodiments of the present invention.
[0024] It should be noted that, without conflict, the embodiments in the present invention and the features in the embodiments can be combined with each other.
[0025] In the present invention, unless otherwise stated, the orientation words such as "upper, lower, top, bottom" are usually in terms of the direction shown in the drawings or in terms of the vertical, perpendicular or gravitational direction for describing the relative positional relationship of each component. "First", "second", etc. are only for convenience of description and easy distinction, and cannot be understood as indicating or implying relative importance.
[0026] In the description of the present invention, it should also be noted that, unless otherwise clearly specified and limited, the terms "installation", "connection", etc. should be understood in a broad sense. For example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a direct connection or an indirect connection; it can be a wired connection or a wireless connection. For those of ordinary skill in the art, the specific meanings of the above terms in the present invention can be understood according to specific situations.
[0027] The prior art usually uses the conventional dry distillation method or the nuclear magnetic test method to measure the water saturation of shale. However, due to the ultra-low water saturation phenomenon of shale and its strong hydrophilicity and adsorption capacity, during the process of extracting the core from the reservoir and transporting it to the laboratory, the water saturation of shale will change to a certain extent due to factors such as temperature, humidity, and storage environment, and finally the measured water saturation of shale does not belong to the in-situ water saturation under reservoir conditions. In view of the above problems, the present invention proposes a method for testing the in-situ water saturation of shale in combination with physical simulation.
[0028] The present invention will be described in detail below with reference to the drawings and in combination with embodiments.
[0029] The embodiment of the present invention provides a method for testing the in-situ water saturation of shale, and the method includes the following steps:
[0030] Step S101: Establish the original water saturation of the core to be tested by the steam method.
[0031] Specifically, the process of establishing the original water saturation of the core to be tested by the steam method may include but is not limited to the following sub-steps S1011 to sub-step S1013.
[0032] Sub-step S1011: Select a full-diameter core of the main shale reservoir as the core to be tested, and dry the core to be tested at a certain temperature. During the drying process, it is necessary to measure the weight of the core to be tested multiple times until the weight of the core to be tested no longer changes, and then record the dry weight of the core to be tested and determine the porosity of the core to be tested.
[0033] Sub-step S1012: Place the pre-dried core to be tested in a pre-set humidity oven to ensure that the humidity and temperature in the humidity oven are maintained within the preset range.
[0034] After a certain period of time, the core to be tested will absorb water vapor from the surrounding environment and gradually reach a new water saturation state. At this time, by monitoring the weight change of the core or other appropriate measurement means, the original water saturation of the core can be determined.
[0035] Here, the purpose of step S101 is to simulate the water saturation state of the shale core under in-situ conditions (i.e., actual underground conditions) to better understand the physical properties of the rock and the water adsorption of the rock.
[0036] Step S102: Conduct a physical simulation of the core extraction process on the core to be tested at the original water saturation to determine the water saturation at different test positions.
[0037] Specifically, the physical simulation of the core extraction process may include: physical simulation of the reservoir gas saturation process, physical simulation of the drilling fluid invasion process, and physical simulation of the drill pipe lifting process.
[0038] That is to say, the process of conducting a physical simulation of the core extraction process on the core to be tested at the original water saturation to determine the water saturation at different test positions may include but is not limited to the following sub-steps S1021 to sub-step S1024.
[0039] Sub-step S1021: Conduct a physical simulation of the reservoir gas saturation process on the core to be tested at the original water saturation to construct the first in-situ state of the core to be tested in the reservoir.
[0040] Sub-step S1022: Conduct a physical simulation of the drilling fluid invasion process on the core to be tested in the first in-situ state to construct the second in-situ state of the core to be tested during the drilling fluid invasion process.
[0041] Sub-step S1023: Conduct a physical simulation of the drill pipe lifting process on the core to be tested in the second in-situ state to construct the third in-situ state of the core to be tested during the drill pipe lifting process.
[0042] Sub-step S1024: After the physical simulation of the drill pipe lifting process is completed, take out the core to be tested in the third in-situ state, break the core to be tested into multiple core fragments according to different test positions, and determine the water saturation at different test positions.
[0043] Here, the purpose of step S102 is to simulate the high temperature, high pressure, and saturated gas state during the actual gas well production process of the shale core to better understand the change of water saturation of the shale core under in-situ conditions.
[0044] Step S103: Determine the in-situ water saturation test chart of shale according to the water saturations at different test positions.
[0045] Here, it should be noted that the in-situ water saturation test chart of shale refers to the curve chart showing the variation of water saturation with the test position measured by physical simulation methods. Since the pore structure and water saturation of rocks are not uniformly distributed, there may be differences in pore sizes and water saturations at different parts. By determining the water saturation data at different test positions, it helps to more accurately understand the water content inside the rock and clarify the variation law of shale water saturation with the test position.
[0046] Furthermore, in a possible implementation manner, the test method may further include step S104: Use the in-situ water saturation test chart of shale to correct the water saturation of the conventional core samples, and obtain the in-situ water saturation of shale under reservoir conditions.
[0047] Here, the water saturation of the conventional core samples refers to the water saturation data obtained by conventional analysis methods such as the dry distillation method or nuclear magnetic resonance test method. Since the conventional core samples are taken from the well site to the laboratory, and during the preservation and experimental testing in the laboratory, the water saturation of shale will show a certain degree of deviation due to the influence of temperature, humidity, and preservation environment. The in-situ water saturation test chart of shale obtained by physical simulation methods can, to a certain extent, characterize the variation of water saturation at different positions inside the core when the shale core is extracted from the underground to the ground. Therefore, this in-situ water saturation test chart of shale can be used to correct the water saturation data of the conventional core samples, so as to obtain the in-situ water saturation of shale under reservoir conditions.
[0048] In addition, in order to improve the accuracy of water saturation, it is possible to try to select the position at the very center of the core for testing the water saturation of the conventional core samples, and then use the in-situ water saturation test chart of shale to correct the test results.
[0049] Furthermore, in a possible implementation manner, in sub-step S1021, the specific process of physically simulating the reservoir gas saturation process for the core sample to be tested with the original water saturation may include: placing the core sample to be tested with the original water saturation into an intermediate container, and filling the core sample to be tested with simulated gas by the pressure method until the simulated gas inside the core sample to be tested is in a saturated state.
[0050] Among them, in order to restore the real downhole environment of the shale gas well, the temperature of the simulated gas can be set to the reservoir temperature, and the pressure of the simulated gas can be set to the reservoir pressure. The simulated gas can be set to air or methane.
[0051] Further, in a possible implementation manner, in sub-step S1022, the specific process of physically simulating the drilling fluid invasion process for the core to be measured in the first in-situ state may include: injecting a simulated liquid into the annular space between the core to be measured and the intermediate container until the annular space is filled with the simulated liquid.
[0052] Wherein, in order to ensure that the simulated liquid can enter the core to be measured, the pressure of the simulated liquid should be greater than the pressure of the simulated gas. The simulated liquid can be set as water, drilling fluid or drilling-fluid-like fluid.
[0053] It should be noted that the drilling-fluid-like fluid refers to a chemical liquid used in a laboratory or simulation scenario and similar to the actual drilling fluid.
[0054] Further, in a possible implementation manner, in sub-step S1023, the specific process of physically simulating the process of pulling out the drill for the core to be measured in the second in-situ state may include: reducing the pressure and temperature in the intermediate container to normal temperature and pressure, and measuring the gas production.
[0055] Further, in a possible implementation manner, in sub-step S1024, different test positions can be set as: the core center, the core periphery, and multiple test positions from the core center to the core periphery.
[0056] To better understand the above exemplary embodiments of the present invention, the following further describes them in combination with specific examples and drawings.
[0057] This example provides a shale in-situ water saturation testing device, which includes a heating box, sample tank B, sample tank A, check valve, ISCO pump, gas source, intermediate container for gas measurement, six-way valve 1, six-way valve 2, back pressure valve, water-gas separation intermediate container, water absorption silica gel intermediate container, flowmeter, gas collecting belt and inspection instrument.
[0058] Among them, the sample tank A is used to place the core to be tested and conduct physical simulation of the core extraction process; the sample tank B is used to store water to provide simulated liquid for the physical simulation of the core extraction process; the gas source is used to store air to provide simulated gas for the physical simulation of the core extraction process. The ISCO pump is connected to the sample tank B through a one-way valve, and the sample tank B is connected to the sample tank A through a six-way valve 1, so as to realize injecting the water in the sample tank B into the sample tank A. The gas source is connected to the sample tank A through a gas-metering intermediate container and a six-way valve 1, so as to realize injecting the air in the gas source into the sample tank A. The heating box is used to heat the sample tank A and the sample tank B to control the ambient temperatures in the sample tank A and the sample tube B within a preset temperature range. The sample tank A is also connected to the water-gas separation intermediate container through a six-way valve 2 and a back pressure valve, and is used to collect and separate the water and gas discharged from the core to be tested after the physical simulation of the core extraction process is completed. The water-absorbing silica gel intermediate container is connected to the water-gas separation intermediate container for measuring the water production, and the gas collecting bag is connected to the water-absorbing silica gel intermediate container through a flow meter for measuring the gas production. The inspection instrument is connected to each valve and is used to inspect, measure and record the equipment, system or process, so as to timely detect and eliminate faults or abnormal conditions and improve the reliability and operation efficiency of the equipment.
[0059] Using the above test device, the physical simulation of the core extraction process for the core to be tested at the original water saturation can be completed, and then the in-situ water saturation of shale under reservoir conditions can be obtained. Specifically, the process of testing the in-situ water saturation of shale using the above test device is as follows:
[0060] Step 1: Establish the original water saturation by the steam method.
[0061] Specifically, first place the full-diameter core of the main shale reservoir selected in an oven and dry it at a temperature of 105 °C for at least 72 hours. During the drying process, the weight of the core needs to be measured 3 times until the weight of the core no longer changes, then record the dry weight of the core and measure its porosity.
[0062] Next, place the core in an environment with a humidity of 60% and a temperature of 80 °C to create the original water saturation S w .
[0063] Step 2: Simulate the process of saturating the reservoir with gas.
[0064] Specifically, place the core at the original water saturation S w in the sample tank A, apply pressure to the core in the sample tank A, pressurize and saturate the gas in the gas source into the core, and stabilize for more than 24 hours. Thus, the in-situ state of the core in the reservoir (at this time, the pressure in the core is 40 MPa, the temperature is 80 °C, and the water saturation is S w ) is established.
[0065] Normally, the pressure is increased to 40 MPa. This high-pressure state helps to simulate the pressure environment that the rock experiences in the underground reservoir. Additionally, once the pressure is applied, the core needs to be stabilized in this state for a period of time, usually exceeding 24 hours, to ensure that the core fully reaches the in-situ state in the reservoir. During this process, the core is under a pressure of 40 MPa, and the environmental temperature is maintained at 80 °C through an incubator. Meanwhile, the water saturation S w is also maintained.
[0066] Step 3: Simulate the process of drilling fluid invasion by annular water injection.
[0067] Specifically, water in sample tank B is injected into sample tank A in a pressurized manner through an ISCO pump to simulate the process of mud invasion. The flow rate of water needs to be controlled during this process to ensure that the water in the annular space submerges the core, and the pressure is increased to 41 MPa and maintained to ensure that the water can smoothly enter the annular space. Meanwhile, the environmental temperature needs to be adjusted to 80 °C in advance to simulate the actual operating conditions.
[0068] Here, the core is usually taken from the underground rock formation by drilling. The drill bit forms a cylindrical core sample during the coring process. When the core sample is placed in sample tank A, there is a certain annular gap between the core sample and the inner wall of sample tank A. This annular gap is the annular space for completing the water injection operation in this step. By controlling the water inflow, it can be ensured that the water in the annular space submerges the core, and the pressure and temperature conditions for simulating mud invasion are gradually established. After ensuring that the pressure is increased to 41 MPa, the pressure needs to be maintained stable to simulate the real operating conditions for analyzing and evaluating the properties and reactions of the core.
[0069] Step 4: Simulate the core extraction process.
[0070] Specifically, after completing the physical simulation of the reservoir saturation gas process and the drilling fluid invasion process, the pressure and temperature of sample tank A are reduced. After 8 - 14 hours, the pressure and temperature of sample tank A are reduced to normal temperature and pressure. The gas production volume is measured through equipment such as a water-gas separation intermediate container, and the core is weighed.
[0071] Step 5: Measure the water saturation at multiple measurement points.
[0072] Specifically, the test positions can be set at the core center, 1 cm away from the center, 2 cm away from the center, 3 cm away from the center, and the core periphery. The core is immediately broken into 5 irregular block samples according to the above 5 test positions, and the water saturation of the 5 irregular block samples is measured by the weighing method and the nuclear magnetic method respectively to form a shale in-situ water saturation test chart from the core center to the core periphery.
[0073] Figure 1 It is a test chart of in-situ water saturation of shale drawn based on the water saturation test results of the above 5 irregular block samples. It can be seen from Figure 1 that: (1) The water saturation at the center of the core is 26%, which is close to the in-situ water saturation of 23% of shale under the actual gas well production conditions, verifying the reliability of the experimental scheme; (2) Affected by temperature and pressure reduction, the water saturation decreases by 6% - 9% at a distance of 1 - 2 cm from the center; (3) From 3 cm away from the center to the periphery of the core, affected by the invasion of simulated drilling fluid, the water saturation increases by 3% - 5%.
[0074] Table 1 shows the water saturation analysis results of conventional core samples obtained by the drying method, and Table 2 shows the water saturation analysis results of simulated cores obtained by the test method of this implementation. Combining the analysis results of Table 1 and Table 2, it can be seen that the water saturation obtained by the conventional method is about 36%, which has a large error compared with the in-situ water saturation of 23% of shale under the actual gas well production conditions, while the water saturation obtained by the test method of this application is about 26%, which is closer to the in-situ water saturation of 23% of shale under the actual gas well production conditions. This shows that compared with the method of measuring the water saturation of shale by the conventional dry distillation method or nuclear magnetic test method, the water saturation of shale tested by this application is more accurate and closer to the in-situ water saturation under reservoir conditions.
[0075] Table 1 Analysis Results by Drying Method
[0076] Serial number Sample number Initial state weight (g) Dry sample weight (g) Inlet water mass Water saturation 1 5 11.0774 10.9722 0.1052 36.54％ 2 4 7.0949 7.0532 0.0417 22.54％ 3 3 9.2782 9.2147 0.0635 26.26％ 4 2 12.9017 12.7977 0.1040 30.97％ 5 1 9.2427 9.1651 0.0766 32.27％
[0077] Table 2 Analysis Results by Nuclear Magnetic Resonance
[0078]
[0079] It should be noted that "Sample No. 5" in Table 1 and Table 2 represents the center of the core, "Sample No. 4" represents 1 cm away from the center of the core, "Sample No. 3" represents 2 cm away from the center of the core, "Sample No. 2" represents 3 cm away from the center of the core, and "Sample No. 1" represents 4 cm away from the center of the core.
[0080] The preferred embodiments of the present invention have been described in detail above in conjunction with the accompanying drawings. However, the present invention is not limited to the specific details in the above embodiments. Within the scope of the technical concept of the present invention, various simple modifications can be made to the technical solutions of the present invention, and these simple modifications all fall within the protection scope of the present invention.
[0081] In addition, it should be noted that in the above specific embodiments, the various specific technical features described can be combined in any appropriate manner without conflict. To avoid unnecessary repetition, the present invention will not separately describe various possible combination methods.
[0082] In addition, any combination can be made among various different embodiments of the present invention, as long as it does not violate the idea of the present invention, and it should equally be regarded as the content disclosed by the present invention.
Claims
1. A method for testing in-situ water saturation of shale, characterized in that, The described test method includes: Establishing the original water saturation of the core to be tested through the steam method; Conducting physical simulations of the core extraction process on the core to be tested at the original water saturation to determine the water saturation at different test positions; wherein, the physical simulation of the core extraction process includes: physical simulation of the reservoir gas saturation process, physical simulation of the drilling fluid invasion process, and physical simulation of the core lifting process; Determining the in-situ water saturation test chart of shale according to the water saturation at different test positions.
2. The method for testing in-situ water saturation of shale according to claim 1, characterized in that, The test method further includes: correcting the water saturation of the conventional core samples using the in-situ water saturation test chart of shale to obtain the in-situ water saturation of shale under reservoir conditions.
3. The method for testing in-situ water saturation of shale according to claim 1, characterized in that, The conducting physical simulations of the core extraction process on the core to be tested at the original water saturation to determine the water saturation at different test positions includes: Conducting physical simulation of the reservoir gas saturation process on the core to be tested at the original water saturation to construct the first in-situ state of the core to be tested in the reservoir; Conducting physical simulation of the drilling fluid invasion process on the core to be tested in the first in-situ state to construct the second in-situ state of the core to be tested during the drilling fluid invasion process; Conducting physical simulation of the core lifting process on the core to be tested in the second in-situ state to construct the third in-situ state of the core to be tested during the core lifting process; After the physical simulation of the core lifting process is completed, taking out the core to be tested in the third in-situ state, crushing the core to be tested into multiple core fragments according to different test positions, and determining the water saturation at different test positions.
4. The method for testing in-situ water saturation of shale according to claim 3, characterized in that, The conducting physical simulation of the reservoir gas saturation process on the core to be tested at the original water saturation includes: Placing the core to be tested at the original water saturation into an intermediate container, and filling the core to be tested with a simulated gas by the pressurization method until the simulated gas inside the core to be tested is in a saturated state; Wherein, the temperature of the simulated gas is set to the reservoir temperature, and the pressure of the simulated gas is set to the reservoir pressure.
5. The method for testing in-situ water saturation of shale according to claim 4, characterized in that, The conducting physical simulation of the drilling fluid invasion process on the core to be tested in the first in-situ state includes: Injecting a simulated liquid into the annular space between the core to be tested and the intermediate container until the annular space is filled with the simulated liquid; Wherein, the pressure of the simulated liquid is greater than the pressure of the simulated gas.
6. The method for testing in-situ water saturation of shale according to claim 5, characterized in that, The conducting physical simulation of the core lifting process on the core to be tested in the second in-situ state includes: Reducing the pressure and temperature inside the intermediate container to normal temperature and pressure, and measuring the gas production.
7. The method for testing in-situ water saturation of shale according to claim 1, characterized in that, The different test positions include: the core center, the core periphery, and multiple test positions from the core center to the core periphery.
8. The method for testing in-situ water saturation of shale according to claim 3, characterized in that, The weight method and the nuclear magnetic method are respectively used to determine the water saturation at different test positions.
9. The method for testing in-situ water saturation of shale according to claim 4, characterized in that, The simulated gas is air or methane.
10. The method for testing in-situ water saturation of shale according to claim 5, characterized in that, The simulated liquid is water, drilling fluid, or drilling fluid-like fluid.