A method for calculating shale oil clay pore water salinity on site

Abstract

The application discloses a shale oil clay pore water salinity calculation method for mud logging site, first, a reference core is obtained and total signal area and clay pore water signal area of the reference core are measured; then, the reference core is immersed in a diffusion liquid, a wicking diffusion liquid and a standard core are obtained, the standard core is prepared into a saturated core, core pore water volume is calculated according to the dried mass of the standard core and the saturated mass of the saturated core, the wicking diffusion liquid is detected by two-dimensional nuclear magnetic resonance and oil volume is calculated; then, wicking salinity is calculated according to the resistance value parameter and the temperature parameter of the wicking diffusion liquid, finally, a salt conservation equation of the clay pore water is constructed and clay pore water salinity is calculated; the application diffuses the salt and oil in the clay pore water into the whole wicking diffusion liquid based on the wicking diffusion principle of the concentration difference, realizes natural separation of the oil and the water, fundamentally solves the signal mutual interference problem of the oil and the water, and improves the measurement precision of the clay pore water salinity.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of oil exploration, in particular to a method for calculating shale oil clay pore water salinity on site. BACKGROUND

[0002] In conventional sandstone, formation water is mostly in a free state, and the salinity can be analyzed by chemical analysis of water samples taken by coring or logging; shale has nanometer pore capillary binding and a large specific surface area, and the water saturation is extremely low and the fluid is not flowable, so that sufficient water samples cannot be obtained;

[0003] In shale, oil and water are in a mixed state, and when traditional one-dimensional nuclear magnetic detection is performed, the detection signals of oil and water overlap, which cannot be effectively distinguished, thereby resulting in low calculation precision of shale clay pore water salinity. SUMMARY

[0004] The present application aims to provide a method for calculating shale oil clay pore water salinity on site, and aims to solve the problem that the pore water salinity cannot be accurately detected due to overlapping of oil and water signals in ultra-low water content shale in the prior art.

[0005] The present application achieves the above-mentioned purpose by the following technical solutions:

[0006] A method for calculating shale oil clay pore water salinity on site, comprising the following steps:

[0007] A reference core on site is obtained by pressure-maintained coring, and the reference core is subjected to two-dimensional nuclear magnetic resonance detection several times to obtain a total signal area S a and a clay pore water signal area S s ;

[0008] The reference core is immersed in a diffusion liquid to obtain a standard core and a diffusion liquid; wherein the diffusion liquid is a solution with a salinity lower than that of the clay pore water in the reference core;

[0009] The standard core is prepared into a saturated core, and the core pore water volume is calculated according to the dried mass of the standard core and the saturated mass of the saturated core;

[0010] The diffusion liquid is subjected to two-dimensional nuclear magnetic resonance detection, and the oil volume is calculated according to the detection result;

[0011] The diffusion salinity is calculated according to the resistance value parameter and the temperature parameter of the diffusion liquid;

[0012] A salt conservation equation of clay pore water is constructed, and the clay pore water salinity is calculated according to the salt conservation equation, the core pore water volume, the oil volume, and the diffusion salinity.

[0013] Optionally, a reference core is obtained by pressure-maintaining coring at a logging site, a total signal area S a and a clay pore water signal area S s , comprising the following steps:

[0014] The core obtained at the logging site is placed in a liquid nitrogen tank to prepare the reference core;

[0015] The reference core is subjected to several two-dimensional nuclear magnetic resonance detections to obtain several two-dimensional nuclear magnetic resonance spectra;

[0016] Each of the two-dimensional nuclear magnetic resonance spectra is analyzed, and if the difference between two adjacent two-dimensional nuclear magnetic resonance spectra is not greater than 5%, the test is ended, otherwise the steps of subjecting the reference core to several two-dimensional nuclear magnetic resonance detections to obtain several two-dimensional nuclear magnetic resonance spectra are repeated;

[0017] The total signal area S a and the clay pore water signal area S s are obtained from the two-dimensional nuclear magnetic resonance spectrum obtained by the last two-dimensional nuclear magnetic resonance detection.

[0018] Optionally, the reference core is immersed in a diffusion liquid to obtain a wicking diffusion liquid and a standard core, comprising the following steps:

[0019] The reference core is immersed in a diffusion liquid;

[0020] The resistance value parameter and the temperature parameter of the diffusion liquid are measured, and when the change rate of the resistance value is less than 1%, it is determined that the wicking is ended;

[0021] The wicking diffusion liquid and the standard core are separated and obtained.

[0022] Optionally, the standard core is prepared into a saturated core, and the core pore water volume is calculated according to the dried mass of the standard core and the saturated mass of the saturated core, comprising the following steps:

[0023] The standard core is dried, and its dried mass is measured;

[0024] The filling solution is injected into the standard core under pressure until the mass of the standard core is unchanged to obtain a saturated core; wherein the pressure time is not less than 48 h; the pressure is 25-35 MPa;

[0025] The mass of the saturated core is measured to obtain a saturated mass;

[0026] The core pore water volume is calculated according to the dried mass and the saturated mass, and the calculation formula of the core pore water volume is m1 represents the drying mass, and m2 represents the saturated mass, represents the density of the filling solution.

[0027] Optionally, the filling solution comprises a NaCl solution or distilled water; and the diffusion solution comprises purified water or distilled water.

[0028] Optionally, the imbibed diffusion solution is subjected to two-dimensional nuclear magnetic resonance detection, and the oil volume is calculated according to the detection result, comprising the following steps:

[0029] The displacement liquid volume V is calculated according to the diffusion solution V1 and the imbibed diffusion solution volume V2 c ;

[0030] The imbibed diffusion solution is subjected to two-dimensional nuclear magnetic resonance detection to obtain two-dimensional nuclear magnetic T1-T2 relaxation time nuclear magnetic data;

[0031] The two-dimensional nuclear magnetic T1-T2 relaxation time nuclear magnetic data is subjected to inversion calculation to obtain imbibed nuclear magnetic total signal area S c and oil liquid signal area S o ;

[0032] The oil volume is calculated according to the imbibed diffusion solution volume parameter, imbibed nuclear magnetic total signal area and oil liquid signal area, wherein the calculation expression of the oil volume is , wherein V c represents the displacement liquid volume, and the expression thereof is V c= V2-V1.

[0033] Optionally, the calculation formula of the imbibition salinity is , wherein R w represents the formation water resistivity, and the calculation expression thereof is , S represents the area of the test electrode, L is the diameter of the container containing the imbibed diffusion solution; R represents the resistance value parameter of the imbibed diffusion solution, and T represents the temperature parameter of the imbibed diffusion solution.

[0034] Optionally, a salt conservation equation of clay pore water is constructed, and the clay pore water salinity is calculated according to the salt conservation equation, the core pore water volume, the oil volume and the imbibition salinity, comprising the following steps:

[0035] A salt conservation equation is constructed based on the principle of mass conservation of salt;

[0036] The salt content of the clay pore water is calculated according to the salt conservation equation;

[0037] The clay pore water volume is calculated according to the core pore water volume V f , the total signal area S a and the pore water signal area S s .

[0038] According to the clay pore water volume V s And the clay pore water salinity m s Calculate the clay pore water salinity C s Wherein the expression of the clay pore water salinity is Where m s Indicates the clay pore water salinity, V s Indicates the clay pore water volume.

[0039] Optionally, the calculation expression of the clay pore water salinity is Where C j And V j Indicate the salinity and volume of the diffusion liquid respectively, V0 indicates the oil liquid volume, V s Indicates the clay pore water volume.

[0040] Optionally, the calculation expression of the clay pore water volume is Where V f Indicates the core pore water volume, S s Indicates the clay pore water signal area, S a Indicates the total signal area.

[0041] Compared with the prior art, the present application has the following beneficial effects:

[0042] The present application first obtains a reference core on the logging site, and performs two-dimensional nuclear magnetic resonance detection on it for several times to obtain the total signal area and the clay pore water signal area; then the reference core is immersed in a diffusion liquid to obtain a diffusion liquid and a standard core, the standard core is prepared into a saturated core, the core pore water volume is calculated according to the drying mass of the standard core and the saturation mass of the saturated core, then the diffusion liquid is subjected to two-dimensional nuclear magnetic resonance detection, and the oil liquid volume is calculated according to the detection result; then the diffusion salinity is calculated according to the resistance value parameter and the temperature parameter of the diffusion liquid, and finally the salt conservation equation of the clay pore water is constructed, and the clay pore water salinity is calculated according to the salt conservation equation, the core pore water volume, the oil liquid volume and the diffusion salinity;

[0043] The present application not only ensures the integrity of the reference core as much as possible through the pressure-maintaining coring method to improve the accuracy of subsequent measurement, but also measures the total signal area S a And the clay pore water signal area S s Through nuclear magnetic resonance detection; at the same time, the diffusion liquid and the standard core are prepared by immersing the reference core in the diffusion liquid;

[0044] Since it is extremely difficult to extract and measure the mineralization of clay pore water directly from micro-nano level clay, the technical solution of the present application constructs a wicking system with a diffusion liquid with lower mineralization. The wicking system ingeniously uses the diffusion principle to "transport" the fixed mass of salt in the clay pore water to a large enough and easy-to-contact and measure wicking diffusion liquid system. The conductivity of the solution is related to the concentration of electrolytes, ion types and temperature, etc. Based on the principle of mass conservation, the total mass of salt before and after wicking is unchanged. Therefore, the mass conservation principle of salt can be constructed, and the mineralization of clay pore water can be calculated by measuring the resistance and temperature of the wicking diffusion liquid.

[0045] Compared with the prior art, the technical solution of the present application realizes non-destructive measurement of clay pore water by ingeniously applying the wicking diffusion principle based on the concentration difference, simplifies the entire detection procedure, and uses simpler equipment, thereby reducing the detection cost.

[0046] Secondly, by wicking diffusion, the present application diffuses the salt and oil in the clay pore water into the entire wicking diffusion liquid. In the wicking diffusion liquid, oil and water will naturally separate, thereby fundamentally solving the problem of signal interference between oil and water, and realizing rapid and accurate measurement of the mineralization of clay pore water.

[0047] Finally, the method of the present application can also be applied to the study of fluid properties of other unconventional reservoirs (such as tight sandstone and carbonate rock), and has wide application prospect and promotion value. BRIEF DESCRIPTION OF DRAWINGS

[0048] Figure 1 A flow chart of a method for calculating the mineralization of shale oil clay pore water on site mud logging according to Embodiment 1 of the present application. DETAILED DESCRIPTION

[0049] The technical solutions of the present application will be described in detail below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of the present application, but not all the embodiments. The components of the present application described and shown in the accompanying drawings can be arranged and designed in various different configurations. Therefore, the following detailed description of the embodiments of the present application provided in the accompanying drawings is not intended to limit the scope of the claimed application, but only represents selected embodiments of the present application. Based on the embodiments of the present application, all other embodiments obtained by those skilled in the art without creative work are within the scope of protection of the present application.

[0050] It should be noted that similar reference numerals and letters refer to like items in the accompanying drawings, and that, once an item is defined in one drawing, it should not require further defining and explaining in the subsequent drawings. Meanwhile, in the description of the present application, the terms "first", "second", and the like are merely used to distinguish descriptions, and cannot be understood as indicating or implying relative importance.

[0051] Embodiment 1

[0052] With reference to Figure 1 , the present embodiment discloses a method for calculating shale oil clay pore water salinity on site, comprising the following steps:

[0053] S1, obtaining a reference core on site by pressure-maintaining coring, and performing two-dimensional nuclear magnetic resonance detection on the reference core for several times to obtain total signal area S a and clay pore water signal area S s .

[0054] S11, placing the core obtained on site into a liquid nitrogen tank to prepare the reference core;

[0055] Directly placing the core obtained on site into a liquid nitrogen tank to lock the original oil and water content state of the core, thereby preparing the reference core;

[0056] S12, performing two-dimensional nuclear magnetic resonance detection on the reference core for several times to obtain several two-dimensional nuclear magnetic resonance spectra;

[0057] Taking the reference core out of the liquid nitrogen tank, then loading it into an oil-resistant and temperature-resistant PEEK tube, and placing it in a portable two-dimensional nuclear magnetic instrument to perform two-dimensional nuclear magnetic resonance detection for several times to obtain several two-dimensional nuclear magnetic resonance spectra;

[0058] S13, analyzing each of the two-dimensional nuclear magnetic resonance spectra, if the difference between two adjacent two-dimensional nuclear magnetic resonance spectra is not greater than 5%, the test is ended, otherwise, repeating the step of performing two-dimensional nuclear magnetic resonance detection on the reference core for several times to obtain several two-dimensional nuclear magnetic resonance spectra;

[0059] According to the detection time, generating a time stamp number for each two-dimensional nuclear magnetic resonance spectrum, then analyzing each two-dimensional nuclear magnetic resonance spectrum, when the difference between two adjacent two-dimensional nuclear magnetic resonance spectra is not greater than 5%, determining that the sample has returned to room temperature;

[0060] S14, obtaining total signal area S a and clay pore water signal area S s from the two-dimensional nuclear magnetic resonance spectrum obtained from the last two-dimensional nuclear magnetic resonance detection.

[0061] Record the total signal area S on the two-dimensional nuclear magnetic resonance spectrum obtained from the last two-dimensional nuclear magnetic resonance detection a The clay pore water signal area S s The whole test ends

[0062] S2, immerse the reference core in the diffusion liquid to obtain the imbibition diffusion liquid and the standard core; wherein the diffusion liquid is a solution with a lower salinity than the salinity of the clay pore water in the reference core;

[0063] S21, immerse the reference core in the diffusion liquid;

[0064] Immerse the reference core after the completion of the nuclear magnetic resonance test in the diffusion liquid, which is a solution with a lower salinity than the salinity of the clay pore water in the reference core; preferably, the diffusion liquid is distilled water or purified water;

[0065] Use distilled water and purified water as the diffusion liquid, which can on the one hand maximize the concentration difference with the bound fluid, thereby improving the efficiency of spontaneous imbibition and shortening the experimental time; on the other hand, the spontaneous imbibition effect is obvious, that is, the concentration parameters of the diffusion liquid change significantly, which can effectively improve the reliability of data acquisition, eliminate the measurement error of the equipment, and further improve the accuracy of calculation;

[0066] Secondly, distilled water and purified water have a wide source, and their initial salinity can be identified as 0, which can effectively ensure the accuracy of various initial data while reducing costs, which is conducive to improving the calculation accuracy;

[0067] Finally, distilled water and purified water do not react with other substances during spontaneous imbibition, which can effectively ensure the accuracy of the subsequent salt mass conservation equation.

[0068] S22, measure the resistance value parameter and temperature parameter of the diffusion liquid, and determine that the imbibition is complete when the change rate of the resistance value is less than 1%;

[0069] Read the solution liquid resistance value and temperature with a miniature four-stage probe, obtain a group of parameters every interval time, and determine that the imbibition is complete when the change rate of the resistance value is less than 1%; record the resistance value and temperature at this time;

[0070] S23, separate the imbibition diffusion liquid and the standard core.

[0071] Take out the standard core, and at the same time obtain the imbibition diffusion liquid;

[0072] S3, prepare the standard core into a saturated core, and calculate the core pore water volume according to the dried mass of the standard core and the saturated mass of the saturated core;

[0073] S31, drying the standard core and measuring the dried mass of the standard core;

[0074] The standard core is placed in a drying oven or other drying equipment, and the drying temperature is adjusted to 190-210°C. The mass change of the plunger shale sample is observed during the drying process. When the difference between the mass detected at two adjacent times is within the allowable range or the differences between the mass detected at several times are all within the allowable range, it is determined that the drying is completed, and the standard core is prepared.

[0075] Subsequently, the mass of the standard core is measured again after it is cooled to room temperature to obtain the dried mass.

[0076] S32, pressurized injection of the filling solution into the standard core until the mass of the standard core is unchanged to obtain a saturated core; wherein the pressurized time is not less than 48h; and the pressurized pressure is 25-35MPa.

[0077] The standard core is immersed in the filling solution, which is preferably distilled water. Subsequently, the filling solution and the standard core are placed in a vacuum drying equipment. Then, the reference shale sample is pressurized, and the pressurized pressure is 25-35MPa, preferably 30MPa. The pressurized time is not less than 48h.

[0078] The mass of the entire sample is measured at intervals during the pressurization process. When the difference between the mass detected at two adjacent times is within the allowable range or the differences between the mass detected at several times are all within the allowable range, it is determined that the pressurization is completed, and the saturated core is prepared.

[0079] S33, measuring the mass of the saturated core to obtain the saturated mass.

[0080] The mass of the saturated core is monitored to obtain the saturated mass.

[0081] S34, calculating the core pore water volume according to the dried mass and the saturated mass, wherein the calculation formula of the core pore water volume is , wherein m1 represents the dried mass, m2 represents the saturated mass, and ρ represents the density of the filling solution.

[0082] In the dried state, all the water in the core is discharged. After the water is filled again under pressure, the water can fill all the pores. Then, the core pore water volume is calculated by the mass difference. The calculation formula of the core pore water volume is , wherein m1 represents the dried mass, m2 represents the saturated mass, and ρ represents the density of the filling solution.

[0083] S4, performing two-dimensional nuclear magnetic resonance detection on the imbibition and diffusion liquid, and calculating the oil volume according to the detection result.

[0084] S41, calculating the displacement liquid volume V according to the diffusion liquid V1 and the imbibition diffusion liquid volume V2 c ;

[0085] The imbibition diffusion liquid is obtained, and the volume V2 of the imbibition diffusion liquid is measured. After spontaneous imbibition, part of the oil, water and salt in the core will enter the diffusion liquid, so that the volume of the diffusion liquid is increased. Therefore, the volume of the diffusion liquid can be combined to calculate the displacement liquid volume, and the expression is V c= V2-V1.

[0086] S42, performing two-dimensional nuclear magnetic resonance detection on the imbibition diffusion liquid to obtain two-dimensional nuclear magnetic T1-T2 relaxation time nuclear magnetic data;

[0087] S43, performing inversion calculation on the two-dimensional nuclear magnetic T1-T2 relaxation time nuclear magnetic data to obtain imbibition nuclear magnetic total signal area S c and oil liquid signal area S o ;

[0088] S44, calculating the oil liquid volume according to the imbibition diffusion liquid volume parameter, the imbibition nuclear magnetic total signal area and the oil liquid signal area, wherein the calculation expression of the oil liquid volume is , wherein V c represents the displacement liquid volume, and the expression is V c= V2-V1.

[0089] The imbibition diffusion liquid contains oil and water, and the oil and water are naturally separated, so that the oil liquid volume can be quickly and accurately detected. The calculation expression of the oil liquid volume is , wherein V c represents the displacement liquid volume, and the expression is V c= V2-V1.

[0090] Through imbibition diffusion, the salt and oil in the clay pore water are diffused into the entire imbibition diffusion liquid. In the imbibition diffusion liquid, the oil and water are naturally separated, so that the problem of signal interference between the oil and water is fundamentally solved, and the clay pore water salinity is quickly and accurately measured;

[0091] S5, calculating the imbibition salinity according to the resistance value parameter and the temperature parameter of the imbibition diffusion liquid;

[0092] The calculation formula of the imbibition salinity is , wherein R w represents the formation water resistivity, and the calculation expression is , S represents the area of the test electrode, L is the diameter of the container containing the imbibition diffusion liquid; R represents the resistance value parameter of the imbibition diffusion liquid, and T represents the temperature parameter of the imbibition diffusion liquid.

[0093] The parameter in step S22 is brought into the above calculation formula to obtain the imbibition salinity;

[0094] S6, constructing a salt conservation equation of clay pore water, and calculating the clay pore water salinity according to the salt conservation equation, the core pore water volume, the oil liquid volume and the imbibition salinity.

[0095] S61, constructing a salt conservation equation based on the principle of salt mass conservation;

[0096] The salt content in the oil and water in the reference core and the salt content in the diffusion liquid are the initial total salt content of the whole system, and the calculation expression is: When the reference core is immersed in the diffusion liquid and after the spontaneous imbibition process ends, the salt content of the clay pore water is equal to the salt content in the imbibition diffusion liquid, which is the imbibition total salt content, and the imbibition total salt content is equal to the initial total salt content;

[0097] The calculation expression of the imbibition total salt content is ;

[0098] Since the initial total salt content is equal to the imbibition total salt content, that is, i =m f ;

[0099] Therefore, the specific expression of the salt conservation equation is: ;

[0100] S62, calculating the clay pore water salt content according to the salt conservation equation;

[0101] The calculation expression of the clay pore water salt content is , wherein C j and V j represent the salinity and volume of the diffusion liquid respectively, V0 represents the oil liquid volume, if distilled water is selected as the diffusion liquid, then C j =0, V s represents the clay pore water volume.

[0102] S63, calculating the clay pore water volume according to the core pore water volume V f , the total signal area S a and the pore water signal area S s ;

[0103] The calculation expression of the clay pore water volume is , wherein V f represents the core pore water volume, S s represents the clay pore water signal area, and S a represents the total signal area.

[0104] S64, the clay pore water volume V s and the clay pore water salinity m s calculating the clay pore water salinity C s wherein the expression of the clay pore water salinity is wherein m s represents the clay pore water salinity, V s represents the clay pore water volume.

[0105] The clay pore water salinity can be calculated by combining the relevant parameters obtained in the foregoing steps and the calculation expression of the clay pore water salinity, wherein the expression of the clay pore water salinity is wherein m s represents the clay pore water salinity, V s represents the clay pore water volume.

[0106] The present application not only ensures the integrity of the reference core as much as possible through the method of pressure-maintaining coring, thereby improving the accuracy of subsequent measurement, but also measures the total signal area S a and the clay pore water signal area S s by nuclear magnetic resonance detection.

[0107] Meanwhile, the imbibition diffusion liquid and the standard core are prepared by immersing the reference core in the diffusion liquid.

[0108] Since it is extremely difficult to extract and measure the salinity of the clay bound water at the micro-nano level directly, the technical solution of the present application constructs an imbibition system by using a diffusion liquid with lower salinity. The imbibition system ingeniously utilizes the diffusion principle to "transport" the fixed mass of salt in the clay pore water to a diffusion liquid system that is large enough and easy to contact and measure. Meanwhile, the conductivity of the solution is related to factors such as the concentration of electrolytes, ion types and temperature. Based on the principle of mass conservation, the total mass of salt does not change before and after imbibition. Therefore, the mass conservation theorem of salt can be constructed, and the salinity of the clay pore water can be calculated by combining the resistance and temperature measurement of the imbibition diffusion liquid.

[0109] Compared with the prior art, the technical solution of the present application realizes non-destructive measurement of the clay pore water by ingeniously applying the imbibition diffusion principle based on the concentration difference, simplifies the entire detection procedure, uses simpler equipment, and reduces the detection cost.

[0110] Secondly, by imbibition diffusion, the present application diffuses the salt and oil in the clay pore water into the entire imbibition diffusion liquid. In the imbibition diffusion liquid, the oil and water will naturally separate, thereby fundamentally solving the problem of signal interference between oil and water, and realizing rapid and accurate measurement of the salinity of the clay pore water.

[0111] Finally, the method described in the application can also be extended to the study of fluid properties of other unconventional reservoirs (such as tight sandstone and carbonate rock), and has wide application prospects and promotional value.

[0112] The above only describes the embodiment 1 of the application and is not used to limit the protection scope of the application. For those skilled in the art, the application can have various modifications and changes. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the application shall be included in the protection scope of the application.

Claims

1. A method for calculating shale oil clay pore water salinity on site, characterized in that, The method comprises the following steps: A reference core is obtained by pressure-maintaining coring at a logging site, a two-dimensional nuclear magnetic resonance detection is performed on the reference core for several times, and a total signal area S is obtained a and a clay pore water signal area S s ; immersing the reference core in a diffusion solution to obtain a imbibition diffusion solution and a standard core; wherein the diffusion solution is a solution with a lower salinity than the salinity of the clay pore water in the reference core; drying the standard core and measuring the dried mass of the standard core; injecting a filling solution into the standard core under pressure until the mass of the standard core is unchanged to obtain a saturated core; wherein the pressure injection time is not less than 48 hours; the pressure injection pressure is 25-35 MPa; measuring the mass of the saturated core to obtain a saturated mass; The core pore water volume V is calculated from the dried mass and the saturated mass f wherein the core pore water volume V f is calculated by the expression m1 represents the dried mass, m2 represents the saturated mass, denotes the density of the filling solution; The volume V of the displacement liquid is calculated from the volume V1 of the diffusion liquid and the imbibition diffusion liquid volume V2 c ; performing two-dimensional nuclear magnetic resonance detection on the imbibition diffusion solution to obtain two-dimensional nuclear magnetic T1-T2 relaxation time nuclear magnetic data; Inverting the two-dimensional nuclear magnetic T1-T2 relaxation time nuclear magnetic data to obtain a total nuclear magnetic signal area S of the wicking c and an oil liquid signal area S o ; According to the displacement liquid volume V c , the imbibition NMR total signal area S c and the oil liquid signal area S o , the oil liquid volume V0 is calculated, wherein the calculation expression of the oil liquid volume V0 is , wherein V c represents the displacement liquid volume, and the calculation expression of V c =V2-V1; calculating the imbibition salinity according to the resistance value parameter and the temperature parameter of the imbibition diffusion solution; Based on the principle of salt mass conservation, a salt conservation equation is constructed, and the clay pore water salt content m is calculated according to the salt conservation equation s ; the calculation expression of the clay pore water salt content m s is , wherein C j and V j respectively represent the salinity and volume of the diffusion liquid, V0 represents the oil liquid volume, and V s represents the clay pore water volume; Based on the core pore water volume V f Total signal area S a and the area S of the pore water signal region s Calculate the pore water volume V of clay s The clay pore water volume V s The calculation expression is as follows V f S represents the volume of pore water in the core. s S represents the area of ​​the pore water signal region in clay. a Indicates the total signal area; According to the clay pore water volume V s and the clay pore water salinity m s The clay pore water salinity m s The clay pore water salinity m s The calculation expression of the clay pore water salinity m where m s represents the clay pore water salinity, V s represents the clay pore water volume.

2. The method for calculating shale oil clay pore water salinity on site according to claim 1, characterized in that, The reference core in the logging field is obtained by pressure-keeping coring, the reference core is detected by two-dimensional nuclear magnetic resonance for several times, and total signal area S is obtained a and clay pore water signal area S s , comprising the following steps: placing the core obtained on site into a liquid nitrogen tank to prepare the reference core; performing several times of two-dimensional nuclear magnetic resonance detection on the reference core to obtain several two-dimensional nuclear magnetic resonance spectra; respectively analyzing each of the two-dimensional nuclear magnetic resonance spectra, if the difference between two adjacent two-dimensional nuclear magnetic resonance spectra is not greater than 5%, the test is ended, otherwise, repeating the step of performing several times of two-dimensional nuclear magnetic resonance detection on the reference core to obtain several two-dimensional nuclear magnetic resonance spectra; the total signal area S is obtained from the two-dimensional nuclear magnetic resonance spectrum acquired from the last two-dimensional nuclear magnetic resonance measurement a and the clay pore water signal area S s .

3. The method for calculating shale oil clay pore water salinity on site according to claim 1, characterized in that, the step of immersing the reference core in the diffusion solution to obtain the imbibition diffusion solution and the standard core comprises the following steps: immersing the reference core in the diffusion solution; measuring the resistance value parameter and the temperature parameter of the diffusion solution, and determining that the imbibition is ended when the change rate of the resistance value is less than 1%; separately obtaining the imbibition diffusion solution and the standard core.

4. The method for calculating shale oil clay pore water salinity on site according to claim 1, characterized in that, The filling solution comprises a NaCl solution or distilled water; and the diffusion solution comprises purified water or distilled water.

5. The method for calculating shale oil clay pore water salinity on site according to claim 1, characterized in that, The calculation expression of the imbibition salinity is , wherein R w represents the formation water resistivity, and the calculation expression is S represents the area of the test electrode, L represents the diameter of the container containing the imbibition diffusion liquid; R represents the resistance value parameter of the imbibition diffusion liquid, and T represents the temperature parameter of the imbibition diffusion liquid.

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