Shale oil reservoir mechanical property testing method and system considering fracturing fluid soaking

Abstract

The invention discloses a shale oil reservoir mechanical property testing method and system considering fracturing fluid soaking, and relates to the technical field of petroleum and natural gas, and the shale oil reservoir mechanical property testing method comprises the following steps: processing a coring sample of a shale oil reservoir to be tested into a plurality of shale samples; the method comprises the following steps: putting a plurality of shale samples into a soaking device, and soaking the shale samples in fracturing fluid for different soaking time to obtain soaked shale samples; the temperature of the soaked shale sample is loaded to the temperature of the stratum where the coring sample is located, and the loaded shale sample is obtained; respectively carrying out a mechanical property test on the loaded shale sample to obtain a mechanical test strain curve and a failure load; and calculating the mechanical property parameters of the rock in the shale oil reservoir to be tested based on the mechanical test strain curve and the failure load. The technical problem that errors exist during prediction and design of fracturing engineering in the prior art is relieved.

Description

Technical Field

[0001] The present invention relates to the technical field of petroleum and natural gas, and in particular to a method and system for testing the mechanical properties of shale oil reservoirs taking into account fracturing fluid immersion. Background Art

[0002] Oil and natural gas are of great significance as core resources in the global energy structure. Shale oil reservoirs are an important component of unconventional oil and gas resources. With the advancement of mining technology in recent years, the development potential of shale oil has gradually emerged. However, shale oil reservoirs have complex mechanical properties, which directly affect the fracturing effect and production efficiency. The existing shale oil reservoir mechanical property testing methods and equipment have some shortcomings in studying the mechanical behavior of shale reservoirs, especially in simulating long-term immersion in fracturing fluid and reservoir mechanical changes in formation environment. Since shale oil reservoirs are usually under high temperature and high pressure geological conditions, long-term immersion in fracturing fluid and formation temperature have an important influence on their mechanical properties. Traditional testing methods fail to fully reflect this complexity, resulting in errors in the prediction and design of fracturing projects, affecting the development efficiency and production effect of the reservoir. Summary of the invention

[0003] The purpose of the present invention is to provide a method and system for testing the mechanical properties of shale oil reservoirs taking into account fracturing fluid immersion in order to solve at least one of the above technical problems.

[0004] In the first aspect, an embodiment of the present invention provides a method for testing the mechanical properties of shale oil reservoirs taking into account immersion in fracturing fluid, comprising: processing a core sample of the shale oil reservoir to be tested into multiple shale samples; placing the multiple shale samples into an immersion device, and immersing them in fracturing fluid for different immersion times, respectively, to obtain shale samples after immersion; loading the temperature of the shale samples after immersion to the temperature of the formation where the core sample is located, to obtain the shale samples after loading; performing mechanical property testing experiments on the loaded shale samples, respectively, to obtain mechanical test strain curves and failure loads; and calculating the mechanical property parameters of the rock in the shale oil reservoir to be tested based on the mechanical test strain curves and failure loads.

[0005] Furthermore, the core samples of the shale oil reservoir to be tested are processed into multiple shale samples, including: processing the core samples into standard cylindrical samples with a diameter of 25 mm and a height of 50 mm and Brazilian disc specimens with a diameter of 25 mm and a thickness of 25 mm.

[0006] Furthermore, the soaking time includes 1 day, 3 days, 5 days, 10 days and 15 days.

[0007] Furthermore, drag reducer, drainage aid and fungicide are added to the fracturing fluid.

[0008] Furthermore, the drag reducer is added in an amount of 0.08%-0.12% of the mass of the fracturing fluid, the drainage aid is added in an amount of 0.1% of the mass of the fracturing fluid, and the fungicide is added in an amount of 0.05% of the mass of the fracturing fluid.

[0009] Furthermore, the shale samples include standard cylindrical samples and Brazilian disc specimens; mechanical property tests are performed on the loaded shale samples to obtain mechanical test strain curves and failure loads, including: performing uniaxial loading tests and triaxial loading tests on the standard cylindrical samples to obtain the mechanical test strain curves; and performing Brazilian splitting tests on the Brazilian disc specimens to obtain the failure loads.

[0010] Furthermore, the mechanical test strain curve includes a uniaxial loading stress-strain curve, a uniaxial loading transverse strain curve, a uniaxial loading volumetric strain curve, a triaxial loading stress-strain curve, a triaxial loading transverse strain curve and a triaxial loading volumetric strain curve.

[0011] Furthermore, the mechanical property parameters include elastic modulus, Poisson's ratio, compressive strength value and tensile strength value; based on the mechanical test strain curve and the failure load, the mechanical property parameters of the rock in the shale oil reservoir to be tested are calculated, including: the calculation formulas of the elastic modulus and the Poisson's ratio include:

[0012]

[0013] In the formula, E av is the average elastic modulus of the standard cylindrical specimen, μ av is the average Poisson's ratio of the standard cylindrical specimen, σ a is the stress value at the starting point of the straight line segment on the uniaxial loading stress-strain curve, σ b is the stress value at the end point of the straight line segment on the uniaxial loading stress-strain curve, ε aa The representative stress is σ a The longitudinal strain value at ab The representative stress is σ b The longitudinal strain value at ca The representative stress is σ a The transverse strain value at cb The representative stress is σ b The lateral strain value at the time; the calculation formula of the compressive strength value includes:

[0014] σ c =c+σ3tan(φ)

[0015] In the formula, σ cis the compressive strength value, c and φ are the cohesion and internal friction angle of the shale reservoir rock matrix determined based on the triaxial loading stress-strain curve, and σ3 is the normal stress applied to the standard cylindrical specimen; the calculation formula for the tensile strength value includes:

[0016]

[0017] In the formula, σ t is the tensile strength value, P is the breaking load, D is the diameter of the Brazilian disc specimen, and L is the height of the Brazilian disc specimen.

[0018] In the second aspect, an embodiment of the present invention further provides a shale oil reservoir mechanical property testing system taking into account fracturing fluid immersion, comprising: a processing module, an immersion module, a temperature loading module, a test module and a calculation module; wherein the processing module is used to process the core sample of the shale oil reservoir to be tested into multiple shale samples; the immersion module is used to put the multiple shale samples into an immersion device, and soak them in the fracturing fluid for different immersion times respectively to obtain the shale samples after immersion; the temperature loading module is used to load the temperature of the shale sample after immersion to the temperature of the formation where the core sample is located to obtain the shale sample after loading; the test module is used to perform mechanical property testing on the loaded shale sample respectively to obtain the mechanical test strain curve and the failure load; the calculation module is used to calculate the mechanical property parameters of the rock in the shale oil reservoir to be tested based on the mechanical test strain curve and the failure load.

[0019] Furthermore, the shale sample includes a standard cylindrical sample and a Brazilian disc specimen; the test module is also used to: perform a uniaxial loading test and a triaxial loading test on the standard cylindrical sample to obtain the mechanical test strain curve; and perform a Brazilian splitting test on the Brazilian disc specimen to obtain the destructive load.

[0020] The present invention provides a method and system for testing the mechanical properties of shale oil reservoirs taking into account the immersion of fracturing fluid. By combining the formation temperature and pressure conditions of the shale reservoir and the long-term immersion effect of fracturing fluid, the system can accurately simulate the reservoir environment and reduce the errors in predicting and designing fracturing projects. It alleviates the technical problem that traditional testing methods fail to fully reflect the complexity of the influence of long-term immersion of fracturing fluid and formation temperature on its mechanical properties, resulting in errors in predicting and designing fracturing projects and affecting the development efficiency and production effect of the reservoir. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] In order to more clearly illustrate the implementation methods of the present application or the technical solutions in the prior art, the drawings required for use in the specific implementation methods or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are some implementation methods of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0022] Figure 1 A flow chart of a method for testing mechanical properties of shale oil reservoirs taking into account fracturing fluid immersion provided in an embodiment of the present invention;

[0023] Figure 2 A schematic diagram of the dimensions of a shale sample provided in an embodiment of the present invention;

[0024] Figure 3 A schematic diagram of a temperature loading device provided by an embodiment of the present invention;

[0025] Figure 4 A schematic diagram of a uniaxial loading test provided by an embodiment of the present invention;

[0026] Figure 5 A schematic diagram of a triaxial loading test provided by an embodiment of the present invention;

[0027] Figure 6 A schematic diagram of a Brazilian splitting test provided by an embodiment of the present invention;

[0028] Figure 7 A schematic diagram of a shale oil reservoir mechanical property testing system considering fracturing fluid immersion provided in an embodiment of the present invention. DETAILED DESCRIPTION

[0029] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0030] Embodiment 1

[0031] Figure 1 1 is a flow chart of a method for testing the mechanical properties of shale oil reservoirs taking into account fracturing fluid immersion according to an embodiment of the present invention. Figure 1 As shown, the method specifically comprises the following steps:

[0032] Step S102, processing the core sample of the shale oil reservoir to be tested into multiple shale samples.

[0033] Step S104, placing a plurality of shale samples into a soaking device, and soaking them in the fracturing fluid for different soaking times, respectively, to obtain the soaked shale samples.

[0034] Step S106, loading the temperature of the shale sample after soaking to the temperature of the formation where the core sample is located, to obtain the loaded shale sample.

[0035] Step S108, performing mechanical property tests on the loaded shale samples to obtain mechanical test strain curves and failure loads.

[0036] Step S110, calculating the mechanical property parameters of the rock in the shale oil reservoir to be tested based on the mechanical test strain curve and the failure load.

[0037] Specifically, step S102 includes: processing the cored samples into standard cylindrical samples with a diameter of 25 mm and a height of 50 mm and Brazilian disc samples with a diameter of 25 mm and a thickness of 25 mm.

[0038] Figure 2 Schematic diagram of the dimensions of a shale sample provided according to an embodiment of the present invention. Figure 2 As shown, a standard cylindrical specimen and a Brazilian disc specimen are drilled in the shale oil reservoir to be tested, and the shale oil core samples are processed into a standard cylindrical specimen with a diameter of 25 mm and a height of 50 mm, and a Brazilian disc specimen with a diameter of 25 mm and a thickness of 25 mm. The processed specimens are then standardized to ensure that the size and shape of the specimens meet the test requirements. In the embodiment of the present invention, the standard cylindrical specimen is named Type A specimen 1, and the Brazilian disc specimen is named Type B specimen 2.

[0039] Preferably, the soaking time includes 1 day, 3 days, 5 days, 10 days and 15 days.

[0040] Specifically, step S104 also includes: placing the processed standard cylindrical specimen and Brazilian disc specimen into a special immersion device, applying appropriate uniform pressure through the clamp to ensure that the specimen remains stable and does not deform during the immersion process, simulating the actual stress environment in the reservoir. Before immersion, prepare the fracturing fluid, use the drag reducer CT1-20D (addition mass ratio of 0.08% to 0.12%) to reduce the fluid friction resistance, the drainage aid CT5-12B (addition mass ratio of 0.1%) to improve the drainage performance of the fracturing fluid, and the bactericide CT10-4 (addition mass ratio of 0.05%) to inhibit the growth of microorganisms and prevent the rock from being eroded by microorganisms. The shale samples were soaked in the fracturing fluid for 1 day, 3 days, 5 days, 10 days and 15 days respectively to simulate the impact of the fracturing fluid on the shale reservoir in different time periods.

[0041] Figure 3Schematic diagram of a temperature loading device provided according to an embodiment of the present invention. Figure 3 As shown, step S106 also includes the following steps:

[0042] Step S1061, determine the formation temperature: first, it is necessary to understand the ground temperature of the formation where the core sample is located, which can be obtained through geological exploration data, geothermal logging, etc. Determining the formation temperature is the basis for loading the sample.

[0043] Step S1062, setting the temperature loading module: according to the determined formation temperature, setting the temperature loading module of the test equipment to ensure that the temperature of the sample can be accurately controlled.

[0044] Step S1063, prepare the sample: prepare the shale sample properly, ensure that its size meets the test requirements, and its surface is smooth without obvious defects.

[0045] Step S1064, sample loading: the prepared shale sample is placed in the test equipment, and the temperature is gradually increased through the temperature loading module until the target formation temperature is reached.

[0046] Step S1065, stable heat preservation: when the shale sample reaches the target temperature, it needs to be kept stable for a period of time to ensure that the internal temperature of the shale sample is uniform and stable.

[0047] Specifically, step S108 also includes the following steps:

[0048] Step S1081, perform uniaxial loading test and triaxial loading test on the standard cylindrical specimen respectively to obtain a mechanical test strain curve; specifically, the mechanical test strain curve includes a uniaxial loading stress-strain curve, a uniaxial loading lateral strain curve, a uniaxial loading volumetric strain curve, a triaxial loading stress-strain curve, a triaxial loading lateral strain curve and a triaxial loading volumetric strain curve.

[0049] Step S1082, performing a Brazilian splitting test on the Brazilian disc specimen to obtain a failure load.

[0050] Figure 4 Schematic diagram of a uniaxial loading test provided according to an embodiment of the present invention. Figure 4 As shown, a type A specimen 1 with a diameter of 25 mm and a height of 50 mm is selected and preheated under formation temperature conditions. The specimen is placed at the center of the pressure plate 3 of the testing machine, and an axial load 6 is applied at a speed of 0.5 MPa-1.0 MPa per second until the specimen is destroyed. The axial load F, axial strain εl and radial strain εd at each level are measured and recorded. According to the axial deformation and radial deformation of the type A specimen 1 in the uniaxial compression test, the uniaxial loading stress-strain curve of the specimen is drawn, and the deformation characteristics of the specimen are obtained from the uniaxial loading stress-strain curve.

[0051] Plot the axial stress (σ)-axial strain (ε1) curve (i.e., uniaxial loading stress-strain curve) to obtain the elastic modulus E of type A specimen 1 av and Poisson's ratio μ av .

[0052] The axial stress σ is calculated using the following formula:

[0053]

[0054] Where, F represents the axial load (N); A represents the cross-sectional area of ​​the specimen (mm 2 ).

[0055] Axial strain ε1 and radial strain ε d The following formula is used for calculation:

[0056]

[0057]

[0058] Where, ε1 represents the axial strain value of each level of stress; ε d Represents the radial strain value of the same stress as ε1; ε v represents the volumetric strain value; represents the average axial deformation under each level of load (mm); ΔD represents the The average value of radial deformation under the same load (mm); L represents the specimen height (mm); D represents the specimen diameter (mm).

[0059] According to ε1 and ε v The uniaxial loading transverse strain curve and uniaxial loading volumetric strain curve are plotted respectively, and the uniaxial loading stress-strain curve of the rock is plotted according to the axial deformation and radial deformation of the shale sample in the uniaxial loading test.

[0060] Figure 5 Schematic diagram of a triaxial loading test provided according to an embodiment of the present invention. Figure 5 As shown, a type A specimen 1 with a diameter of 25 mm and a height of 50 mm is selected, and the specimen is placed in the triaxial chamber 4 of the testing machine and preheated under the formation temperature condition. The lateral load 7 and the axial load 6 are applied synchronously at a loading speed of 0.05 MPa to a predetermined lateral pressure value σ3 and the lateral pressure is kept constant. Then, the axial load 6 is applied at a speed of 0.5 MPa-1.0 MPa per second until the specimen is destroyed. The axial failure load P under different lateral pressure conditions is recorded, and the maximum principal stress σ1 is calculated. On the coordinate diagram with σ1 as the ordinate and σ3 as the abscissa, the coordinate points of each specimen are plotted according to the σ1 and σ3 values ​​of each specimen.

[0061] Specifically, the axial (triaxial compressive strength) under different lateral pressures is calculated according to the following formula:

[0062]

[0063] Where: l It represents the axial stress value under different test pressures (MPa); P represents the maximum axial load that causes the specimen to fail under a certain lateral pressure (N); A represents the cross-sectional area of ​​the specimen (mm 2 ).

[0064] Axial strain ε ′ l and radial strain ε ′ d The following formula is used for calculation:

[0065]

[0066] In the formula, ε ′ l Indicates the axial strain value of each level of stress; ε ′ d Represents and ε ′ l The radial strain value of the same stress; ε ′ v represents the volumetric strain value; It represents the average value of axial deformation under each level of load (mm); Representation and The average value of radial deformation under the same load (mm); L' represents the specimen height (mm); D' represents the specimen diameter (mm).

[0067] According to ε ′ l and ε ′ v The triaxial loading lateral strain curve and triaxial loading volumetric strain curve were drawn respectively, and the triaxial loading stress-strain curve of the rock was drawn according to the axial deformation and radial deformation of the shale sample in the triaxial loading test.

[0068] Figure 6 Schematic diagram of a Brazilian splitting test provided according to an embodiment of the present invention. Figure 6As shown, select a B-type specimen 2 with a diameter of 25mm and a thickness of 25mm, place the specimen in the center of the pressure plate 3 of the testing machine, and make the pad 5 and the specimen on the same loading axis. Preheat the specimen under the formation temperature condition, grind the surface of the specimen, and ensure that both sides of the specimen are parallel and smooth. According to the initial formation pressure conditions, determine the size and method of the confining pressure to be applied. After applying the confining pressure, apply a vertical axial force P through the testing machine to cause the specimen to split and fail. During the loading process, it is necessary to record the force and displacement data. Apply an axial load 6 at a speed of 0.3MPa-0.5MPa per second until the specimen fails, and record the failure load P and the phenomena that occur during the loading process.

[0069] Specifically, the mechanical property parameters include elastic modulus, Poisson's ratio, compressive strength value and tensile strength value; in step S110, on the uniaxial loading stress-strain curve, the elastic modulus and Poisson's ratio correspond to 30%-70% of the peak strength range. Specifically, the calculation formulas of the elastic modulus and Poisson's ratio include:

[0070]

[0071]

[0072] In the formula, E av is the average elastic modulus of the standard cylindrical specimen (MPa), μ av is the average Poisson's ratio of the standard cylindrical specimen, σ a is the stress value at the starting point of the straight line segment on the uniaxial loading stress-strain curve (MPa), σ b is the stress value at the end point of the straight line segment on the uniaxial loading stress-strain curve (MPa), ε aa The representative stress is σ a The longitudinal strain value at ab The representative stress is σ b The longitudinal strain value at ca The representative stress is σ a The transverse strain value at cb The representative stress is σ b The transverse strain value at .

[0073] Specifically, according to the Mohr-Coulomb criterion, the linear equation of σ1-σ3 is as follows:

[0074] σ1=Fσ3+R (11)

[0075] In the formula, σ1 is the maximum principal stress (MPa); F is the slope of the σ1-σ3 relationship curve; R is the intercept of the σ1-σ3 relationship curve on σ1, which is equivalent to the uniaxial compressive strength of the specimen (MPa). Through multiple sets of triaxial tests, the σ1-σ3 relationship curve fitting is established to obtain the values ​​of F and R.

[0076] The cohesion c and internal friction angle φ of the shale reservoir rock matrix can be calculated as follows:

[0077]

[0078] Where c is the cohesion of the shale reservoir rock matrix (MPa); φ is the internal friction angle of the shale reservoir rock matrix (°).

[0079] Specifically, the calculation formula for the compressive strength value includes:

[0080] σ c =c+σ3tan(φ) (14)

[0081] In the formula, σ c is the compressive strength value, and σ3 is the normal stress applied on the standard cylindrical specimen.

[0082] Type B specimen 2 has tensile fracture failure along the shale reservoir rock matrix at the center of the disk, and this tensile strength value can be approximated as the tensile strength of the shale reservoir rock matrix.

[0083] Specifically, the calculation formula for the tensile strength value includes:

[0084]

[0085] In the formula, σ t is the tensile strength value (MPa), P is the breaking load (N), D is the diameter of the Brazilian disc specimen (mm), and L is the height of the Brazilian disc specimen (mm).

[0086] Preferably, in the embodiment of the present invention, there are 3-5 type A specimens in each group for uniaxial loading test and triaxial loading test, and 3-5 type B specimens in each group for Brazilian splitting test.

[0087] From the above description, it can be seen that the embodiment of the present invention provides a method for testing the mechanical properties of shale oil reservoirs taking into account the immersion of fracturing fluid. Combined with the formation temperature, pressure conditions and long-term immersion effect of fracturing fluid of the shale reservoir, it can accurately simulate the reservoir environment, reduce the error in predicting and designing fracturing projects, and alleviate the technical problem that the traditional testing method fails to fully reflect the complexity of the influence of long-term immersion of fracturing fluid and formation temperature on its mechanical properties, resulting in errors in predicting and designing fracturing projects, affecting the development efficiency and production effect of the reservoir. At the same time, the operation method of the present invention is simple, which is of great significance to the design, construction and stability evaluation of the mechanical properties of shale oil reservoirs, and can provide more practical testing means for oil and gas exploration and development, and has a positive effect on improving the development efficiency and safety of shale oil reservoirs.

[0088] Embodiment 2

[0089] Figure 7Schematic diagram of a shale oil reservoir mechanical property testing system considering fracturing fluid immersion according to an embodiment of the present invention. Figure 7 As shown, the system includes: a processing module 10 , a soaking module 20 , a temperature loading module 30 , a testing module 40 and a calculation module 50 .

[0090] Specifically, the processing module 10 is used to process the core sample of the shale oil reservoir to be tested into multiple shale samples.

[0091] The soaking module 20 is used to put a plurality of shale samples into a soaking device, soak them in the fracturing fluid for different soaking times, and obtain the soaked shale samples.

[0092] The temperature loading module 30 is used to load the temperature of the shale sample after soaking to the temperature of the formation where the core sample is located, so as to obtain the loaded shale sample.

[0093] The test module 40 is used to perform mechanical property tests on the shale samples after loading to obtain mechanical test strain curves and failure loads.

[0094] The calculation module 50 is used to calculate the mechanical property parameters of the rock in the shale oil reservoir to be tested based on the mechanical test strain curve and the failure load.

[0095] Specifically, the shale samples include standard cylindrical samples and Brazilian disc specimens; the test module 40 is also used to: perform uniaxial loading tests and triaxial loading tests on the standard cylindrical samples to obtain mechanical test strain curves; and perform Brazilian splitting tests on the Brazilian disc specimens to obtain the failure load.

[0096] It will be apparent to those skilled in the art that the invention is not limited to the details of the exemplary embodiments described above and that the invention can be implemented in other specific forms without departing from the spirit or essential features of the invention. Therefore, the embodiments should be considered exemplary and non-limiting in all respects, and the scope of the invention is defined by the appended claims rather than the foregoing description, and it is intended that all variations falling within the meaning and scope of the equivalent elements of the claims be included in the invention. Any reference numeral in a claim should not be considered as limiting the claim to which it relates.

[0097] In addition, it should be understood that although the present specification is described according to implementation modes, not every implementation mode contains only one independent technical solution. This description of the specification is only for the sake of clarity. Those skilled in the art should regard the specification as a whole. The technical solutions in each embodiment may also be appropriately combined to form other implementation modes that can be understood by those skilled in the art.

Claims

1. A method for testing mechanical properties of shale oil reservoirs taking into account fracturing fluid immersion, characterized in that: include: Processing a core sample of a shale oil reservoir to be tested into a plurality of shale samples; placing the plurality of shale samples into a soaking device, and soaking them in the fracturing fluid for different soaking times, respectively, to obtain the soaked shale samples; Loading the temperature of the soaked shale sample to the temperature of the formation where the core sample is located, to obtain the loaded shale sample; Conducting mechanical property tests on the shale samples after loading to obtain mechanical test strain curves and failure loads; Based on the mechanical test strain curve and the failure load, the mechanical property parameters of the rock in the shale oil reservoir to be tested are calculated.

2. The method according to claim 1, characterized in that: The core sample of the shale oil reservoir to be tested is processed into multiple shale samples, including: The cored samples were processed into standard cylindrical samples with a diameter of 25 mm and a height of 50 mm and Brazilian disc specimens with a diameter of 25 mm and a thickness of 25 mm.

3. The method according to claim 1, characterized in that: The soaking time includes 1 day, 3 days, 5 days, 10 days and 15 days.

4. The method according to claim 1, characterized in that: The fracturing fluid is added with a drag reducer, a drainage aid and a bactericide.

5. The method according to claim 4, characterized in that: The drag reducer is added in an amount of 0.08%-0.12% of the mass of the fracturing fluid, the drainage aid is added in an amount of 0.1% of the mass of the fracturing fluid, and the fungicide is added in an amount of 0.05% of the mass of the fracturing fluid.

6. The method according to claim 1, characterized in that: The shale samples include standard cylindrical samples and Brazilian disc samples; mechanical property tests are performed on the loaded shale samples to obtain mechanical test strain curves and failure loads, including: Performing a uniaxial loading test and a triaxial loading test on the standard cylindrical specimen respectively to obtain the mechanical test strain curve; A Brazilian splitting test is performed on the Brazilian disc specimen to obtain the failure load.

7. The method according to claim 6, characterized in that: The mechanical test strain curve includes a uniaxial loading stress-strain curve, a uniaxial loading transverse strain curve, a uniaxial loading volumetric strain curve, a triaxial loading stress-strain curve, a triaxial loading transverse strain curve and a triaxial loading volumetric strain curve.

8. The method according to claim 7, characterized in that: The mechanical property parameters include elastic modulus, Poisson's ratio, compressive strength value and tensile strength value; Based on the mechanical test strain curve and the failure load, the mechanical property parameters of the rock in the shale oil reservoir to be tested are calculated, including: The calculation formulas for the elastic modulus and the Poisson's ratio include: In the formula, E av is the average elastic modulus of the standard cylindrical specimen, μ av is the average Poisson's ratio of the standard cylindrical specimen, σ a is the stress value at the starting point of the straight line segment on the uniaxial loading stress-strain curve, σ b is the stress value at the end point of the straight line segment on the uniaxial loading stress-strain curve, ε aa The representative stress is σ a The longitudinal strain value at ab The representative stress is σ b The longitudinal strain value at ca The representative stress is σ a The transverse strain value at cb The representative stress is σ b The transverse strain value at ; The calculation formula of the compressive strength value includes: s c =c+σ3tan(φ) In the formula, σ c is the compressive strength value, c and φ are the cohesion and internal friction angle of the shale reservoir rock matrix determined based on the triaxial loading stress-strain curve, and σ3 is the normal stress applied to the standard cylindrical specimen; The calculation formula of the tensile strength value includes: In the formula, σ t is the tensile strength value, P is the breaking load, D is the diameter of the Brazilian disc specimen, and L is the height of the Brazilian disc specimen.

9. A shale oil reservoir mechanical property testing system considering fracturing fluid immersion, characterized in that: include: Processing module, immersion module, temperature loading module, test module and calculation module; among them, The processing module is used to process the core sample of the shale oil reservoir to be tested into multiple shale samples; The soaking module is used to place the plurality of shale samples into a soaking device, soak them in the fracturing fluid for different soaking times, and obtain the soaked shale samples; The temperature loading module is used to load the temperature of the shale sample after soaking to the temperature of the formation where the core sample is located, so as to obtain the shale sample after loading; The test module is used to perform mechanical property test on the loaded shale samples to obtain mechanical test strain curves and failure loads; The calculation module is used to calculate the mechanical property parameters of the rock in the shale oil reservoir to be tested based on the mechanical test strain curve and the failure load.

10. The system according to claim 8, characterized in that: The shale samples include standard cylindrical samples and Brazilian disc samples; the test module is also used for: Performing a uniaxial loading test and a triaxial loading test on the standard cylindrical specimen respectively to obtain the mechanical test strain curve; A Brazilian splitting test is performed on the Brazilian disc specimen to obtain the failure load.

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