An analytical method for the bound water salinity of shale clay

Abstract

This application discloses an analytical method for the bound water mineralization of shale clay. First, a reference shale sample is prepared, and its NMR spectrum area and first mass are obtained. Then, the reference shale sample is prepared into a saturated shale sample, and its saturated shale NMR spectrum area and second mass are obtained. Next, the saturated shale sample is centrifuged to prepare a centrifuged shale sample, and the centrifuged shale NMR spectrum area is obtained, and the bound fluid volume is calculated. The centrifuged shale sample is then immersed in a diffusion fluid to obtain the percolating diffusion fluid, and its resistance and temperature parameters are measured. Subsequently, the percolating fluid mineralization is calculated based on the resistance and temperature parameters. Finally, a salt conservation equation for the bound fluid is constructed, and the bound fluid mineralization is calculated based on the salt conservation equation and the bound fluid volume. This method achieves non-destructive testing, reducing the testing difficulty while improving the accuracy of bound fluid mineralization detection.

Description

Technical Field

[0001] This application relates to the field of petroleum exploration technology, specifically to an analytical method for the bound water mineralization of shale clay. Background Technology

[0002] In conventional sandstone, formation water is mostly in a free state, and its mineralization can be chemically analyzed by core sampling or well logging. However, due to the capillary binding of nanopores and the huge specific surface area, shale has extremely low water saturation and the fluid cannot flow, making it impossible to extract sufficient water samples. When using direct methods for detection and calculation, even high-pressure centrifugation can only yield trace amounts of liquid, which is easily affected by phase separation, adsorption, evaporation, and core damage.

[0003] Indirect measurement relies on the natural potential and is also affected by the superposition of multiple factors such as cation exchange membrane potential, organic matter diffusion and adsorption potential, and electrical anisotropy, resulting in severe signal distortion and reduced inversion accuracy.

[0004] Therefore, factors such as ultra-low water content, nano-encapsulation, and complex surface chemistry and electrical properties together cause traditional methods to fail in evaluating the bound water mineralization of shale clay, resulting in low calculation accuracy. Summary of the Invention

[0005] The purpose of this application is to provide an analytical method for the bound water mineralization of shale clay, aiming to overcome the shortcomings of low calculation accuracy in the existing technology.

[0006] This application achieves the above objectives through the following technical solutions:

[0007] An analytical method for the bound water salinity of shale clay includes the following steps:

[0008] A reference shale sample was prepared, and the reference shale sample was subjected to nuclear magnetic resonance (NMR) testing and quality inspection to obtain the NMR spectrum area S of the reference shale. d and the first mass m1;

[0009] A baseline shale sample was prepared as a saturated shale sample. The saturated shale sample was then subjected to nuclear magnetic resonance (NMR) testing and quality inspection to obtain the NMR spectral area S of the saturated shale. a Second mass m2;

[0010] Centrifuged shale samples were prepared by centrifuging the saturated shale samples. Nuclear magnetic resonance (NMR) testing was then performed on the centrifuged shale samples to obtain the NMR spectrum area S of the centrifuged shale samples. c And calculate the bound fluid volume V s ;

[0011] Centrifuged shale samples were immersed in a diffusion fluid. After the salt distribution reached equilibrium, the percolating diffusion fluid was collected and its resistance and temperature parameters were measured. The diffusion fluid was a solution with a mineralization lower than that of the bound fluid in the centrifuged shale samples.

[0012] The mineralization of the percolation fluid is calculated based on the resistance parameters and the temperature parameters.

[0013] Construct the salt conservation equation for the bound fluid, based on the salt conservation equation and the bound fluid volume V. s Calculate the mineralization of the bound fluid.

[0014] Optionally, a reference shale sample is prepared, and the reference shale sample is subjected to nuclear magnetic resonance (NMR) testing and quality inspection to obtain the NMR spectrum area S of the reference shale. d And a first mass m1, including the following steps:

[0015] Select shale samples and dry them to prepare reference shale samples; wherein the drying temperature is 190-210℃.

[0016] The mass parameters of the benchmark shale sample were determined and used as the first mass m1;

[0017] Nuclear magnetic resonance (NMR) tests were performed on a benchmark shale sample to obtain benchmark one-dimensional NMR T1 relaxation time NMR data.

[0018] Inverting the baseline one-dimensional NMR T1 relaxation time NMR data yields the baseline shale NMR spectrum area S. d .

[0019] Optionally, the reference shale sample is prepared into a saturated shale sample, and the saturated shale sample is subjected to nuclear magnetic resonance (NMR) testing and quality inspection to obtain the NMR spectrum area S of the saturated shale. a The second mass m2 includes the following steps:

[0020] The baseline shale sample was immersed in a saturated salt solution;

[0021] A baseline shale sample and a saturated salt solution are vacuum pressurized and the pressure is maintained until the mass of the baseline shale sample remains unchanged to obtain a saturated shale sample; the holding time is no less than 48 hours; the pressurization pressure is 25-35 MPa.

[0022] The mass of the saturated shale sample was measured and taken as the second mass m2;

[0023] Nuclear magnetic resonance (NMR) tests were performed on saturated shale samples to obtain saturated one-dimensional NMR T1 relaxation time NMR data.

[0024] Inverting the saturated one-dimensional NMR T1 relaxation time NMR data yields the saturated shale NMR spectrum area S. a.

[0025] Optionally, the saturated shale sample is centrifuged to prepare a centrifuged shale sample, and the centrifuged shale sample is subjected to nuclear magnetic resonance (NMR) testing to obtain the NMR spectrum area S of the centrifuged shale. c This includes the following steps:

[0026] Saturated shale samples were centrifuged, and the volume of the separated liquid was recorded; the centrifugation speed was 4000-5000 r / min, the centrifugation pressure was 2-3 MPa, and the centrifugation time was 20-30 h.

[0027] Repeat the process of placing the saturated shale sample on a centrifuge and recording the volume of the liquid separated by centrifugation until the volume difference between two consecutive centrifugations is no greater than 2%, and obtain a centrifuged shale sample.

[0028] Nuclear magnetic resonance (NMR) tests were performed on centrifuged shale samples to obtain centrifuged one-dimensional NMR T1 relaxation time NMR data;

[0029] Inverting the centrifuged one-dimensional NMR T1 relaxation time NMR data yields the NMR spectrum area S of the centrifuged shale. c .

[0030] Optionally, the formula for calculating the volume of the bound fluid is: V f The volume of pore fluid is expressed as follows: m1 represents the first mass, and m2 represents the second mass. S represents the density of a saturated salt solution. d S represents the area of ​​the baseline shale NMR spectrum. a S represents the area of ​​the NMR spectrum of saturated shale. c This represents the area of ​​the NMR spectrum of centrifuged shale.

[0031] Optionally, the saturated salt solution includes a NaCl solution or a KCl solution; the diffusion fluid includes purified water or distilled water.

[0032] Optionally, the formula for calculating the mineralization of the percolating fluid is as follows: , where R w The resistivity of formation water is expressed by the following formula: S represents the area of ​​the test electrode, L represents the diameter of the container holding the percolation diffusion liquid, R represents the resistance parameter of the percolation diffusion liquid, and T represents the temperature parameter of the percolation diffusion liquid.

[0033] Optionally, a salt conservation equation for the bound fluid is constructed, and the salinity of the bound fluid is calculated based on the salt conservation equation and the volume of the bound fluid, including the following steps:

[0034] Based on the principle of salt mass conservation, a salt conservation equation for bound fluids is constructed.

[0035] Calculate the salt content of the bound fluid based on the salt conservation equation;

[0036] The mineralization degree of the bound fluid is calculated based on the volume and salt content of the bound fluid, wherein the formula for calculating the mineralization degree of the bound fluid is as follows: , where m s V represents the salt content of the bound fluid. s This indicates the volume of the bound fluid.

[0037] Optionally, the expression for the salt content of the bound fluid is: , where C0 and V0 represent the mineralization and volume of the percolating diffusion fluid, respectively, and C represents the mineralization of the percolating fluid.

[0038] Optionally, the analytical method further includes constructing a quantitative model of bound fluid salinity-resistivity-temperature, comprising the following steps:

[0039] Set different temperature gradient parameters T1, T2, T3, ..., T i , where i represents the number;

[0040] Prepare several salt solutions with known mineralization, heat each salt solution according to each temperature gradient parameter, and measure the actual temperature parameters and actual resistance parameters of the percolating diffusion liquid under each temperature gradient parameter.

[0041] Integrate the parameters to generate several calculation arrays {T1, R1, C'1}, {T2, R2, C'2}, ..., {T i R i C' i}; where C' i This represents the degree of mineralization of the salt solution corresponding to the temperature gradient parameter numbered i.

[0042] Construct a standard three-dimensional coordinate system, and calibrate the reference points in the standard three-dimensional coordinate system according to each calculation array;

[0043] Fit each of the aforementioned reference points to generate a fitted surface, and output the fitted surface as a quantitative model of bound fluid mineralization-resistance-temperature.

[0044] Compared with the prior art, this application has the following beneficial effects:

[0045] This application first prepares a reference shale sample, performs nuclear magnetic resonance (NMR) testing and mass detection on the reference shale sample, and obtains the NMR spectrum area and first mass of the reference shale. Then, the reference shale sample is prepared into a saturated shale sample, and NMR testing and mass detection are performed on the saturated shale sample to obtain the NMR spectrum area and second mass of the saturated shale. Next, the saturated shale sample is centrifuged to prepare a centrifuged shale sample, and NMR testing is performed on the centrifuged shale sample to obtain the NMR spectrum area of ​​the centrifuged shale and calculate the bound fluid volume. Then, the centrifuged shale sample is immersed in a diffusion fluid. After the salt distribution reaches equilibrium, the percolating diffusion fluid is obtained, and its resistance and temperature parameters are measured. The diffusion fluid is a solution with a mineralization lower than that of the bound fluid in the centrifuged shale sample. The mineralization of the percolating fluid is then calculated based on the resistance and temperature parameters. Finally, a salt conservation equation for the bound fluid is constructed, and the mineralization of the bound fluid is calculated based on the salt conservation equation and the bound fluid volume.

[0046] Spontaneous percolation relies on the chemical potential gradient formed by the salt concentration difference between the bound water inside the rock sample and the external distilled water, driving the ions in the bound fluid to diffuse backward to the outside. At the same time, the capillary force of the shale nanopores provides additional traction, causing the ions to migrate continuously, and ultimately increasing the conductivity of the external solution. Based on the above principle, the technical solution described in this application constructs a percolation system using a diffusion fluid with lower mineralization. The above percolation system cleverly utilizes the principle of spontaneous percolation diffusion to "transport" a fixed mass of salt in the bound fluid inside the shale to a sufficiently large, easily accessible and measurable diffusion fluid system.

[0047] Meanwhile, the conductivity of the solution is related to factors such as the concentration of electrolytes, the types of ions, and the temperature. Based on the principle of mass conservation, the total mass of salt remains unchanged before and after percolation. Therefore, the mass conservation law of salt can be constructed. By combining the resistance and temperature measurements of the percolation diffusion liquid, the mineralization of its bound fluid can be calculated.

[0048] Compared with the prior art, the technical solution described in this application does not require crushing, keeps the rock sample intact, allows for repeated testing, simplifies the monitoring process of mineralization, and reduces the testing cost;

[0049] Secondly, the volume and concentration of the diffusion fluid are known, and compared with shale samples, the detection conditions are better, enabling rapid and accurate measurement of various parameters, thereby maximizing the detection accuracy of bound fluid mineralization. Attached Figure Description

[0050] Figure 1 This is a flowchart of a method for analyzing the bound water mineralization of shale clay according to Embodiment 1 of this application;

[0051] Figure 2 The one-dimensional NMR spectrum of the centrifugation process;

[0052] Figure 3 These are one-dimensional NMR spectra before and after osmosis. Detailed Implementation

[0053] The technical solutions of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of this application, and not all of the embodiments. The components of this application described and shown in the accompanying drawings can generally be arranged and designed in various different configurations. Therefore, the following detailed description of the embodiments of this application provided in the accompanying drawings is not intended to limit the scope of the claimed application, but merely represents selected embodiments of this application. All other embodiments obtained by those skilled in the art based on the embodiments of this application without inventive effort are within the scope of protection of this application.

[0054] It should be noted that similar reference numerals and letters in the following figures indicate similar items; therefore, once an item is defined in one figure, it does not need to be further defined and explained in subsequent figures. Furthermore, in the description of this application, terms such as "first," "second," etc., are used only to distinguish descriptions and should not be construed as indicating or implying relative importance.

[0055] Implementation method 1:

[0056] Reference Figures 1 to 3 This embodiment, as an optional implementation of this application, discloses a method for analyzing the bound water salinity of shale clay, comprising the following steps:

[0057] S1. Prepare a reference shale sample, perform nuclear magnetic resonance (NMR) testing and quality inspection on the reference shale sample, and obtain the NMR spectrum area S of the reference shale. d and the first mass m1;

[0058] S11. Select shale samples and dry them to prepare reference shale samples; wherein the drying temperature is 190-210℃.

[0059] Select a standard plunger shale sample (5cm in length, 2.5cm in diameter);

[0060] The selected plunger shale sample was then placed in a drying box or other drying equipment, and the drying temperature was adjusted to 190℃-210℃ for drying. During the drying process, the mass change of the plunger shale sample was continuously observed. When the difference between two adjacent mass tests was found to be within the allowable range or the difference between several mass tests was found to be within the allowable range, the drying was considered to be completed, and a reference shale sample was obtained.

[0061] S12. Determine the mass parameters of the benchmark shale sample and use it as the first mass m1;

[0062] The prepared reference shale sample was taken out of the drying equipment and its mass was measured after the temperature returned to room temperature. The measured value was taken as the first mass m1.

[0063] S13. Perform nuclear magnetic resonance (NMR) tests on the benchmark shale sample to obtain benchmark one-dimensional NMR T1 relaxation time NMR data.

[0064] The reference shale sample was subjected to nuclear magnetic resonance testing using a one-dimensional nuclear magnetic resonance device to obtain the reference one-dimensional nuclear magnetic resonance T1 relaxation time nuclear magnetic resonance data.

[0065] S14. Invert the reference one-dimensional NMR T1 relaxation time NMR data to obtain the reference shale NMR spectrum area S. d .

[0066] S2. Prepare a saturated shale sample from the reference shale sample, and perform nuclear magnetic resonance (NMR) testing and quality inspection on the saturated shale sample to obtain the NMR spectrum area S of the saturated shale. a Second mass m2;

[0067] S21. Immerse the benchmark shale sample in a saturated salt solution;

[0068] The benchmark shale sample was immersed in a saturated salt solution; it should be noted that the saturated salt solution refers to a solution in which the salt reaches its maximum solubility at the target temperature and pressure, and no more of the salt can be dissolved; the saturated salt solution includes NaCl solution or KCl solution;

[0069] S22. Vacuum pressurize the reference shale sample and saturated salt solution, maintaining the pressure until the mass of the reference shale sample remains unchanged, to obtain a saturated shale sample; the holding time shall not be less than 48 hours; the pressurization pressure shall be 25-35 MPa.

[0070] The saturated salt solution containing the reference shale sample was placed in a vacuum drying device, and then the reference shale sample was pressurized at a pressure of 25-35 MPa, preferably 30 MPa, for a time of not less than 48 hours.

[0071] During the pressurization process, the mass change of the entire saturated salt solution and the reference shale sample is measured at intervals. When the difference between two adjacent mass measurements is found to be within the allowable range or the difference between several mass measurements is found to be within the allowable range, the pressurization is considered to be over and a saturated shale sample is obtained.

[0072] S23. Measure the mass of the saturated shale sample and use it as the second mass m2;

[0073] Subsequently, saturated shale samples were taken from the saturated salt solution, their mass was recorded, and the above parameters were used as the second mass m2;

[0074] S24. Perform nuclear magnetic resonance (NMR) tests on saturated shale samples to obtain saturated one-dimensional NMR T1 relaxation time NMR data.

[0075] Saturated shale samples were subjected to nuclear magnetic resonance (NMR) tests using a one-dimensional NMR instrument to obtain saturated one-dimensional NMR T1 relaxation time NMR data.

[0076] S25. Invert the saturated one-dimensional NMR T1 relaxation time NMR data to obtain the saturated shale NMR spectrum area S. a .

[0077] S3. Centrifuge the saturated shale sample to prepare centrifuged shale sample, and perform nuclear magnetic resonance (NMR) testing on the centrifuged shale sample to obtain the NMR spectrum area S of the centrifuged shale sample. c And calculate the bound fluid volume V s ;

[0078] S31. Centrifuge the saturated shale sample and record the volume of the separated liquid; the centrifugation speed is 4000-5000 r / min, the centrifugation pressure is 2-3 MPa, and the centrifugation time is 20-30 h.

[0079] The saturated shale sample obtained in step S2 is placed in a centrifuge and then centrifuged. The centrifugation speed is 4000-5000 r / min, the centrifugation pressure is 2-3 MPa, and the centrifugation time is 20-30 h; preferably, the first centrifugation time is 21.5 h and the second centrifugation time is 26.5 h.

[0080] During centrifugation, the separated liquid is collected continuously, and the liquid volume is recorded.

[0081] S32. Repeat the steps of placing the saturated shale sample on a centrifuge for centrifugation and recording the volume of the liquid separated by centrifugation until the volume difference of the liquid separated by two consecutive centrifugations is no greater than 2%, and obtain the centrifuged shale sample.

[0082] The centrifugation process was repeated. When the volume difference between two consecutive centrifugations of the separated liquid was no greater than 2%, the centrifugation was considered complete, and the centrifuged shale sample was obtained.

[0083] S33. Perform nuclear magnetic resonance (NMR) tests on centrifuged shale samples to obtain centrifuged one-dimensional NMR T1 relaxation time NMR data.

[0084] S34. Invert the centrifuged one-dimensional NMR T1 relaxation time NMR data to obtain the NMR spectrum area S of the centrifuged shale. c .

[0085] S35. Calculate the bound fluid volume V s ;

[0086] The drying process completely evaporates the moisture from the shale sample. Then, a saturated salt solution is injected into the pores of the dried shale sample under pressure to fill the internal pores of the entire shale sample, resulting in a saturated shale sample. The pore fluid volume can be obtained through quality testing.

[0087] The mobile water in the saturated shale sample was then separated by centrifugation, and the remaining water was identified as bound fluid. The volume of the bound fluid could be calculated by comparing the detection parameters of the three nuclear magnetic resonance (NMR) tests before and after the test.

[0088] Therefore, the expression for calculating the volume of the bound fluid is: V f The volume of pore fluid is expressed as follows: m1 represents the first mass, and m2 represents the second mass. S represents the density of a saturated salt solution. d S represents the area of ​​the baseline shale NMR spectrum. a S represents the area of ​​the NMR spectrum of saturated shale. c This represents the area of ​​the NMR spectrum of centrifuged shale.

[0089] S4. Immerse the centrifuged shale sample in the diffusion solution. After the salt distribution is balanced, obtain the percolating diffusion solution and measure its resistance and temperature parameters. The diffusion solution is a solution with a mineralization lower than that of the bound fluid in the centrifuged shale sample.

[0090] The centrifuged shale sample from step S3 is immersed in the diffusion liquid, and the diffusion liquid is heated by a heating device at a set temperature. Then, the entire diffusion liquid is connected to a resistance measuring device, and the resistance change of the diffusion liquid is continuously observed. When the resistance change rate is consistently below 2%, the salt distribution is considered to have reached equilibrium. The resistance and temperature parameters of the diffusion liquid at this time are obtained.

[0091] It should be noted that the diffusion fluid is a solution with a mineralization lower than that of the bound fluid in the centrifuged shale sample; preferably, the diffusion fluid is distilled water or purified water.

[0092] Using distilled water and purified water as diffusion fluids can maximize the concentration difference between them and the bound fluid, thereby improving the efficiency of spontaneous percolation and shortening the experimental time. Furthermore, the spontaneous percolation effect is significant, meaning that the concentration parameters of the diffusion fluid change significantly, which can effectively improve the reliability of data acquisition, eliminate measurement errors of the equipment, and thus improve the accuracy of calculations.

[0093] Secondly, distilled water and purified water are widely available, and their initial mineralization rate can be considered to be 0. This not only reduces costs but also effectively ensures the accuracy of various initial data, which is beneficial to improving calculation accuracy.

[0094] Finally, pure running water and distilled water do not react with other substances during spontaneous osmosis, which can effectively ensure the accuracy of the subsequent salt mass conservation equation.

[0095] S5. Calculate the mineralization of the percolation fluid based on the resistance parameters and the temperature parameters;

[0096] The expression for the formula for calculating the mineralization of the percolating fluid is as follows: , where R w The resistivity of formation water is expressed by the following formula: S represents the area of ​​the test electrode, L represents the diameter of the container holding the percolation diffusion liquid, R represents the resistance parameter of the percolation diffusion liquid, and T represents the temperature parameter of the percolation diffusion liquid.

[0097] It should be noted that the area of ​​the test electrode and the diameter of the container can both be measured; generally, the container is a test tube.

[0098] S6. Construct the salt conservation equation for the bound fluid, based on the salt conservation equation and the bound fluid volume V. s Calculate the mineralization of the bound fluid.

[0099] S61. Based on the principle of salt mass conservation, construct the salt conservation equation for bound fluids;

[0100] In the centrifuged shale sample state, the salt content in the bound fluid and the salt content in the diffusion fluid represent the initial total salt content of the entire system, and its calculation expression is as follows: When a centrifuged shale sample is immersed in a diffusion fluid and the spontaneous infiltration process is completed, the salt content in the bound fluid is equal to the salt content in the infiltrated diffusion fluid, which is the total salt content of the infiltration, and the total infiltration is equal to the initial total salt content.

[0101] The formula for calculating the total salt content by osmosis is as follows: ;

[0102] Since the initial total salt content is equal to the total salt content absorbed, i.e., m i =m f ;

[0103] Therefore, the specific expression for the salt conservation equation is: ;

[0104] S62. Calculate the salt content of the bound fluid according to the salt conservation equation.

[0105] Based on the salt conservation equation obtained in step S61, the formula for calculating the salt content of the bound fluid can be obtained. The expression for the salt content of the bound fluid is as follows: Where C0 and V0 represent the mineralization and volume of the percolation diffusion fluid, respectively; preferably, if distilled water or purified water is used as the diffusion fluid, then C0=0, where C represents the mineralization of the percolation fluid;

[0106] By substituting the corresponding parameters, the mineralization degree of the bound fluid can be obtained.

[0107] S63. Calculate the mineralization degree of the bound fluid based on the volume of the bound fluid and the salt content of the bound fluid, wherein the formula for calculating the mineralization degree of the bound fluid is: , where m s V represents the salt content of the bound fluid. s This indicates the volume of the bound fluid.

[0108] The bound fluid mineralization can be calculated based on the aforementioned calculation results and the formula for calculating bound fluid mineralization. The formula for calculating bound fluid mineralization is as follows: , where m s V represents the salt content of the bound fluid. s This indicates the volume of the bound fluid.

[0109] Based on the aforementioned steps S1-S6, the mineralization of the bound fluid can be obtained. To further improve computational efficiency, this application can also construct a quantitative model of bound fluid mineralization-resistance-temperature through multiple sets of parameters. This quantitative model quantifies the quantitative relationship between mineralization, resistance, and temperature, and the mineralization can be predicted through resistance and temperature, which is beneficial to improving computational efficiency.

[0110] The specific steps for constructing a quantitative model of bound fluid salinity-resistivity-temperature are as follows:

[0111] S7. Construct a quantitative model of bound fluid mineralization-resistance-temperature;

[0112] S71. Set different temperature gradient parameters T1, T2, T3, ..., T i , where i represents the number;

[0113] Set different temperature gradient parameters, such as 50℃, 60℃, 70℃, and 80℃;

[0114] S72. Prepare several salt solutions with known mineralization, heat each salt solution according to each temperature gradient parameter, and measure the actual temperature parameter and actual resistance parameter of the percolating diffusion liquid under each temperature gradient parameter.

[0115] Repeated measurements of the temperature and resistance of the diffusion fluid were performed to obtain multiple sets of actual temperature parameters and actual resistance parameters {T1, R1}, {T2, R2}, ..., {T...}. i R i};

[0116] S73. Integrate the parameters to generate several calculation arrays {T1, R1, C'1}, {T2, R2, C'2}, ..., {T i R i C' i}; where C' i This represents the degree of mineralization of the salt solution corresponding to the temperature gradient parameter numbered i.

[0117] S74. Construct a standard three-dimensional coordinate system, and calibrate the reference points in the standard three-dimensional coordinate system according to each calculation array;

[0118] S75. Fit each of the aforementioned reference points to generate a fitted surface, and output the fitted surface as a quantitative model of bound fluid mineralization-resistance-temperature.

[0119] Spontaneous percolation relies on the chemical potential gradient formed by the salt concentration difference between the bound water inside the rock sample and the external distilled water, driving the ions in the bound fluid to diffuse backward to the outside. At the same time, the capillary force of the shale nanopores provides additional traction, causing the ions to migrate continuously, and ultimately increasing the conductivity of the external solution. Based on the above principle, the technical solution described in this application constructs a percolation system using a diffusion fluid with lower mineralization. The above percolation system cleverly utilizes the principle of spontaneous percolation diffusion to "transport" a fixed mass of salt in the bound fluid inside the shale to a sufficiently large, easily accessible and measurable diffusion fluid system.

[0120] Meanwhile, the conductivity of the solution is related to factors such as the concentration of electrolytes, the types of ions, and the temperature. Based on the principle of mass conservation, the total mass of salt remains unchanged before and after percolation. Therefore, the mass conservation law of salt can be constructed. By combining the resistance and temperature measurements of the percolation diffusion liquid, the mineralization of its bound fluid can be calculated.

[0121] Compared with the prior art, the technical solution described in this application does not require crushing, keeps the rock sample intact, allows for repeated testing, simplifies the monitoring process of mineralization, and reduces the testing cost;

[0122] Secondly, the volume and concentration of the diffusion fluid are known, and compared with shale samples, the detection conditions are better, enabling rapid and accurate measurement of various parameters, thereby maximizing the detection accuracy of bound fluid mineralization.

[0123] The above description is merely one embodiment of this application and is not intended to limit the scope of protection of this application. Various modifications and variations can be made to this application by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this application should be included within the scope of protection of this application.

Claims

1. A method for analyzing the bound water salinity of shale clay, characterized in that, Includes the following steps: A reference shale sample was prepared, and the reference shale sample was subjected to nuclear magnetic resonance (NMR) testing and quality inspection to obtain the NMR spectrum area S of the reference shale. d and the first mass m1; A baseline shale sample was prepared as a saturated shale sample. The saturated shale sample was then subjected to nuclear magnetic resonance (NMR) testing and quality inspection to obtain the NMR spectral area S of the saturated shale. a Second mass m2; Centrifuged shale samples were prepared by centrifuging the saturated shale samples. Nuclear magnetic resonance (NMR) testing was then performed on the centrifuged shale samples to obtain the NMR spectrum area S of the centrifuged shale samples. c And calculate the bound fluid volume V s The formula for calculating the volume of the bound fluid is: V f The volume of pore fluid is expressed as follows: m1 represents the first mass, and m2 represents the second mass. S represents the density of a saturated salt solution. d S represents the area of ​​the baseline shale NMR spectrum. a S represents the area of ​​the NMR spectrum of saturated shale. c Indicates the area of ​​the NMR spectrum of centrifuged shale; Centrifuged shale samples were immersed in a diffusion fluid. After the salt distribution reached equilibrium, the percolating diffusion fluid was collected and its resistance and temperature parameters were measured. The diffusion fluid is a solution with a mineralization lower than that of the bound fluid in the centrifuged shale sample; The mineralization of the percolation fluid is calculated based on the resistance parameters and the temperature parameters. Based on the principle of salt mass conservation, a salt conservation equation for bound fluids is constructed. The salt content of the bound fluid is calculated according to the salt conservation equation; the expression for the salt content of the bound fluid is: Where C0 and V0 represent the mineralization and volume of the percolating diffusion fluid, respectively, and C represents the mineralization of the percolating fluid; The mineralization degree of the bound fluid is calculated based on the volume and salt content of the bound fluid, wherein the formula for calculating the mineralization degree of the bound fluid is as follows: , where m s V represents the salt content of the bound fluid. s This indicates the volume of the bound fluid.

2. The method for analyzing the bound water salinity of shale clay according to claim 1, characterized in that, The preparation of the reference shale sample involves performing nuclear magnetic resonance (NMR) testing and quality inspection on the reference shale sample to obtain the NMR spectrum area S of the reference shale. d And a first mass m1, including the following steps: Select shale samples and dry them to prepare reference shale samples; wherein the drying temperature is 190-210℃. The mass parameters of the benchmark shale sample were determined and used as the first mass m1; Nuclear magnetic resonance (NMR) tests were performed on a benchmark shale sample to obtain benchmark one-dimensional NMR T1 relaxation time NMR data. Inverting the baseline one-dimensional NMR T1 relaxation time NMR data yields the baseline shale NMR spectrum area S. d .

3. The method for analyzing the bound water salinity of shale clay according to claim 1, characterized in that, The process involves preparing a reference shale sample into a saturated shale sample, performing nuclear magnetic resonance (NMR) testing and quality inspection on the saturated shale sample, and obtaining the NMR spectrum area S of the saturated shale. a The second mass m2 includes the following steps: The baseline shale sample was immersed in a saturated salt solution; A baseline shale sample and a saturated salt solution are vacuum pressurized and the pressure is maintained until the mass of the baseline shale sample remains unchanged to obtain a saturated shale sample; the holding time is no less than 48 hours; the pressurization pressure is 25-35 MPa. The mass of the saturated shale sample was measured and taken as the second mass m2; Nuclear magnetic resonance (NMR) tests were performed on saturated shale samples to obtain saturated one-dimensional NMR T1 relaxation time NMR data. Inverting the saturated one-dimensional NMR T1 relaxation time NMR data yields the saturated shale NMR spectrum area S. a .

4. The method for analyzing the bound water salinity of shale clay according to claim 1, characterized in that, The saturated shale sample was centrifuged to prepare centrifuged shale samples. Nuclear magnetic resonance (NMR) testing was then performed on the centrifuged shale samples to obtain the NMR spectrum area S of the centrifuged shale samples. c This includes the following steps: Saturated shale samples were centrifuged, and the volume of the separated liquid was recorded; the centrifugation speed was 4000-5000 r / min, the centrifugation pressure was 2-3 MPa, and the centrifugation time was 20-30 h. Repeat the process of centrifuging the saturated shale sample in a centrifuge and recording the volume of the liquid separated by centrifugation until the volume difference between two consecutive centrifugations is no greater than 2%, and obtain a centrifuged shale sample. Nuclear magnetic resonance (NMR) tests were performed on centrifuged shale samples to obtain centrifuged one-dimensional NMR T1 relaxation time NMR data; Inverting the centrifuged one-dimensional NMR T1 relaxation time NMR data yields the NMR spectrum area S of the centrifuged shale. c .

5. The method for analyzing the bound water salinity of shale clay according to claim 3, characterized in that, The saturated salt solution includes NaCl solution or KCl solution; the diffusion fluid includes purified water or distilled water.

6. The method for analyzing the bound water salinity of shale clay according to claim 1, characterized in that, The expression for the formula for calculating the mineralization of the percolating fluid is as follows: , where R w The resistivity of formation water is expressed by the following formula: S represents the area of ​​the test electrode, L represents the diameter of the container holding the percolation diffusion liquid, R represents the resistance parameter of the percolation diffusion liquid, and T represents the temperature parameter of the percolation diffusion liquid.

7. The method for analyzing the bound water salinity of shale clay according to claim 1, characterized in that, The analytical method also includes constructing a quantitative model of bound fluid mineralization-resistivity-temperature, comprising the following steps: Set different temperature gradient parameters T1, T2, T3, ..., T i , where i represents the number; Prepare several salt solutions with known mineralization, heat each salt solution according to each temperature gradient parameter, and measure the actual temperature parameters and actual resistance parameters of the percolating diffusion liquid under each temperature gradient parameter. Integrate the parameters to generate several calculation arrays {T1, R1, C'1}, {T2, R2, C'2}, ..., {T i R i C' i }; where C' i This represents the degree of mineralization of the salt solution corresponding to the temperature gradient parameter numbered i. Construct a standard three-dimensional coordinate system, and calibrate the reference points in the standard three-dimensional coordinate system according to each calculation array; Fit each of the aforementioned reference points to generate a fitted surface, and output the fitted surface as a quantitative model of bound fluid mineralization-resistance-temperature.

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