Weakly cemented, fragile and hydrolyzable mudstone resistivity measurement method

Abstract

The application discloses a weakly cemented, fragile and easily hydrolyzed mudstone resistivity measurement method, and belongs to the technical field of rock physical experiment, and first, the optimal applicable salinity of a formation water sample is established to improve the integrity of a mudstone core experiment; basic parameters and physical property measurement are performed on the processed mudstone core to provide basic data support for mudstone cores with different saturations; the physical property data of the mudstone core are applied to perform self-imbibition titration on two ends of the mudstone core with different formation water sample saturation degrees in a drying balance by using a needle tube until the titration mass does not change, that is, the mudstone core reaches a final saturation state, and finally, the basic data and actual saturation of the mudstone core under different saturation states are obtained; a laboratory resistivity measurement method is applied to obtain the resistivity values of the mudstone under each saturation, and basic methods and data are provided for subsequent accurate determination of mudstone rock physical experiments; finally, the resistivity of the mudstone reservoir under different saturation states of multiple mudstone core samples is obtained.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of rock physics experiment, and particularly relates to a new method capable of keeping a mudstone core plug sample in an in-situ shape for a long time, fully saturating a formation water sample by using a self-suction method, and obtaining a mudstone resistivity at different saturations. BACKGROUND

[0002] Currently, a method for saturating a mudstone core in resistivity measurement mainly includes a natural water immersion saturation method and a vacuum pressurization saturation method. The first natural water immersion saturation method is the simplest method. After drying, the mudstone core is placed in a formation water sample solution for full immersion, and is left to stand in the solution for 3 days, 5 days, 7 days, and the mudstone core is weighed and fully saturated. The second vacuum pressurization saturation method first performs three hours of vacuum on a container filled with saturated formation water, and then stops. At the same time, a mudstone core container filled with dry mudstone core is also vacuumed for 30 minutes. The connector between the two containers is opened, and the saturated formation water sample enters the mudstone core sample chamber. The vacuum is continuously applied, and the mudstone core is immersed in the formation water sample and left to stand for 3 hours. The saturation is completed.

[0003] The traditional mudstone core sample resistivity experiment is a saturation reduction method. The sample is first saturated to determine the porosity, and then the saturated solution in the rock is displaced by using a centrifugal method and a gas displacement method. The centrifugal method gradually increases the rotation speed of the centrifuge to reduce the saturation of the mudstone core, and then measures the resistivity of the rock under each saturation condition until the mudstone core sample reaches the bound water state. The volume and resistivity of the discharged solution are recorded, and finally the rock resistivity is obtained. The gas displacement method uses gas to displace the formation water sample saturated in the mudstone core, records the volume and resistivity of the discharged solution at different times, and finally determines the rock resistivity by fitting. However, the mudstone core has high clay content, soft texture, weak consolidation, and no obvious recrystallization. The mudstone core obtained from the formation drilling has the characteristics of low strength, easy deformation, and easy water absorption. These characteristics lead to large changes in the shape and water content of the mudstone core during full saturation of the formation water sample, making it difficult to measure the resistivity of the mudstone core. SUMMARY

[0004] The present application provides a new method for measuring the resistivity of weakly consolidated, easily broken and easily hydrolyzed mudstone.

[0005] The technical solution adopted by the present application is as follows:

[0006] A method for measuring the resistivity of weakly consolidated, easily broken and easily hydrolyzed mudstone, comprising the following implementation steps:

[0007] Step 1, pretreatment of drilled mudstone core (pretreatment mainly cutting, polishing), get 3-9 pieces of mudstone core sample; mudstone core sample is wrapped with heat shrink tube, then the length, radius, weight and weight after drying are measured; then the porosity and permeability of the mudstone core sample are measured;

[0008] The mudstone core sample is wrapped with a heat shrink tube, and then the length, radius, weight and weight after drying of the mudstone core sample are measured, and then the porosity and permeability of the mudstone core sample are measured again; the conventional physical property data of the mudstone core sample is measured and obtained according to the process specified in the standard of GB / T 29172-2012 Mudstone Core Analysis Method, and the weight after drying is the weight after drying at a temperature of 105℃ for 24h;

[0009] Step 2: calculate the pore volume of each mudstone core sample, calculate the mass of the mudstone core sample fully saturated by the density of the formation water sample, and calculate the mass of the titration water of different mudstone core samples in the fully saturated state of the formation water sample;

[0010] Step 3: place the mudstone core sample wrapped with a heat shrink tube in a dry balance (or other instruments that can be weighed), use a syringe (or other instruments that can be titrated, such as a dropper) to titrate the formation water sample at a constant speed from both ends of the mudstone core sample wrapped with a heat shrink tube, so that the mudstone core sample wrapped with a heat shrink tube fully absorbs the formation water sample, and at the same time, observe the change of the balance mass, according to the saturation state calculated in step 2, titrate to the specified mass, so that the mudstone core sample wrapped with a heat shrink tube reaches the corresponding saturation, after vacuumizing and standing, measure the resistivity, until the mudstone core sample wrapped with a heat shrink tube reaches a fully saturated state, and a stable resistance value is obtained, stop the experiment;

[0011] Step 4, by the measurement results of steps 1-3 above, apply the Archie model to calculate the reservoir saturation related parameters, and establish the saturation model as follows:

[0012]

[0013] In the formula, S w is the water saturation, %;

[0014] φ is the reservoir porosity, %;

[0015] R w is the resistivity of the formation water sample, unit Ω.m;

[0016] R t is the resistivity of the mudstone core, unit Ω.m.

[0017] a, b, m, n are Alch model rock electricity parameters, dimensionless.

[0018] wherein, S w The calculation formula is:

[0019]

[0020] S w is the water saturation of the mudstone core sample, %; m1 is the mass of the mudstone core sample saturated with the formation water sample, unit g; m0 is the mass of the dried mudstone core sample, unit g; p w is the density of the formation water sample, unit g / cm 3 ; V t is the pore volume of the mudstone core sample, unit cm 3 .

[0021] Preferably, the shrinkage of the heat-shrinkable tube is 1.8-2.2 times, and the heat resistance is 170-180 DEG C.

[0022] According to the experimental requirements and the basic conditions of the mudstone core sample, the heat-shrinkable tube (heat-shrinkable film) wrapping the mudstone core is pre-selected, so that the basic form of the mudstone core sample can be maintained for a long time under different experimental conditions without affecting the experimental results; the diameter of the heat-shrinkable tube in the application is 2.57 cm.

[0023] Preferably, the mineralization type of the formation water sample is CaCl2, and the formation water sample has a mineralization degree of 167000-169000 mg / L; the resistivity of the formation water sample at the corresponding temperature is obtained through the resistivity-temperature relationship diagram or measurement; the density of the formation water sample is obtained according to the calculation and measurement of the resistivity and mineralization degree of the formation water sample. According to the actual data range of the formation water sample in the experimental block, the optimal applicable mineralization degree of the formation water sample is selected through pre-experiment according to the basic properties of the experimental sample; the resistivity of the formation water sample is directly measured or the mineralization degree of the formation water sample is converted into the equivalent mineralization degree of the formation water sample solution, and then the resistivity and mineralization degree of the formation water sample at the corresponding temperature are obtained by checking the corresponding solution mineralization degree-resistivity temperature relationship diagram, and finally the density of the formation water sample is obtained.

[0024] Preferably, the method for increasing the saturation degree is specifically as follows: the mass of the mudstone core sample is measured after each titration of 2-40% water saturation degree; since the clay content in the mudstone is high, the mass does not change during the titration process, and the mass is weighed within 48 hours of standing (the weighing frequency should be not less than 3 times in a strictly standing environment, and the mass difference should be ensured to be ±0.05 g), that is, it is considered to reach the corresponding saturation state; the resistance value and resistivity of the mudstone core sample wrapped with the heat-shrinkable tube are tested under different corresponding saturation degree conditions; the above operation is repeated until the saturation state of the mudstone core sample is sufficient.

[0025] Preferably, the mudstone core sample is titrated with the formation water sample at a water saturation of 5-15% each time.

[0026] Preferably, the method for measuring the resistance value of the mudstone core sample wrapped with the heat shrink tube under different saturation conditions comprises the following steps: loading the mudstone core sample wrapped with the heat shrink tube under different saturation conditions into a holder, pre-applying a specified confining pressure, axial pressure, pore pressure and temperature, recording the resistance value change until the resistance value is stable, and recording the resistance value when the resistance value is stable. The resistance value measurement steps refer to the reference standards of the petroleum and natural gas industry, i.e., the Laboratory Measurement and Calculation Method for Rock Resistivity Parameters (SY-T5385-2007) and the Mudstone Core Analysis Method (GB / T 29172-2012).

[0027] Preferably, the specific method for vacuumizing and standing in step 3 comprises the following steps: placing the mudstone core sample wrapped with the heat shrink tube at a corresponding saturation into a vacuum dish in a humid formation water sample environment, vacuumizing for 10-50 min first, and then standing for 1-5 h, measuring the mass and recording, standing for 1-5 h again, comparing the mass difference of at least two times of standing, ensuring that the mass change is within ±0.05 g, and standing for 8-16 h again under the condition that the mass change is within ±0.05 g.

[0028] Preferably, the mudstone core sample in step 1 is 5-8 pieces, and the mudstone core sample is a plunger sample. The mudstone core is prepared in the form of a plunger sample, and the plunger sample is linearly cut to ensure the flatness of the end face of the plunger sample, facilitating the measurement of the length and radius.

[0029] Compared with the existing technology, the present application has the following advantages:

[0030] 1) The present application provides a laboratory measurement method for mudstone with high shale content, weak cementation and easy hydrolysis in water, which is different from the traditional methods (natural water saturation method and vacuumizing and pressurizing saturation method). The present application measures the rock resistivity under each water saturation state during the saturation process while maintaining the integrity of the mudstone core, which lays a foundation for accurately exploring the petrophysical properties of mudstone and has good popularization and application value and practical significance for rock physical experiments.

[0031] 2) The present application is suitable for weakly cemented, fragile and easily hydrolyzed mudstone cores, which are not easy to contact with the mudstone core in a large area. The heat shrink tube is wrapped around the mudstone core by linear cutting, and the saturation degree is increased by using the self-adsorption titration method, so as to obtain the resistivity of the mudstone core and the corresponding saturation degree parameter data. The method is also suitable for well-cemented mudstone cores, which proves the accuracy and universality of the present application.

[0032] 3) The application ultimately obtains the resistivity of the mudstone reservoir under different saturation conditions of multiple mudstone core samples, obtains the related parameters of the reservoir Archie model, and obtains the actual water saturation of the mudstone reservoir by vacuum self-absorption titration and resistivity measurement on the mudstone core samples. BRIEF DESCRIPTION OF DRAWINGS

[0033] Figure 1 is the specific flowchart of the application;

[0034] Figure 2 is a graph about the relationship between formation factors and porosity obtained by resistivity experiments on the mudstone core samples of the example;

[0035] Figure 3 is a graph about the relationship between the resistivity increase coefficient and water saturation obtained by resistivity experiments on the mudstone core samples of the example. DETAILED DESCRIPTION

[0036] In order to make the purpose, technical scheme and advantages of the application more clear and understandable, the application will be further described in detail. It should be understood that the specific embodiments described herein are only used to explain the application and not to limit the application, that is, the described embodiments are only a part of the embodiments of the application, but not all the embodiments.

[0037] The application aims at the problem that it is difficult to measure the resistivity of mudstone cores due to the characteristics of low strength, easy deformation and easy water absorption of mudstone core samples. A new method for maintaining the weakly cemented and fragile mudstone plug sample prototype form for a long time during the experiment is established by applying the basic data of mudstone cores, and a resistivity measurement method for weakly cemented, fragile and easily hydrolyzed mudstone is provided, which is described in detail in Figure 1 The optimal applicable salinity of the experiment is established by applying the different salinity ranges of the formation water samples in the research area, and the integrity of the mudstone core experiment is improved; the basic parameters and physical properties of the treated mudstone cores are measured to provide basic data support for mudstone cores with different saturations; the needle tube is used to self-absorb and titrate the two ends of the mudstone core with different formation water sample saturations in the dry balance, and the vacuum dish is used for vacuuming and standing, so that the saturation is more sufficient, until the titration quality does not change, that is, the mudstone core reaches the final saturation state, and finally the basic data and actual saturation of the mudstone core under different saturation conditions are obtained; the laboratory resistivity measurement method is applied to obtain the resistivity value of the mudstone under each saturation, which provides a basic method and data for subsequent accurate determination of mudstone rock physics experiments.

[0038] EMBODIMENT:

[0039] A resistivity measurement method for weakly cemented, fragile and easily hydrolyzed mudstone, specifically comprising the following steps:

[0040] Step 1, the drilled mudstone is cut and polished, and the mudstone core is prepared in a plunger shape.

[0041] Through the conventional cutting and polishing of the mudstone core drilled from the gas reservoir mudstone reservoir, a total of 6 plunger samples are obtained, numbered 1, 2, 3, 4, 5 and 6.

[0042] Step 2, according to the experimental requirements and the basic situation of the mudstone core, the linear cutting treatment is carried out on the mudstone core plunger sample to ensure the flatness of the end face, and the pre-selection of the wrapped mudstone core heat shrink film is carried out to keep the basic form of the mudstone core under different experimental conditions for a long time and not to affect the experimental results.

[0043] Through the different situations of the gas reservoir mudstone core, the linear cutting treatment is carried out on the 6 plunger samples to ensure the flatness of the end face, and the pre-experiment optimization of the wrapped heat shrink tube of the mudstone core is carried out. This time, starting from the size and shrinkage rate of the heat shrink tube and the high temperature resistance temperature, the mudstone plunger sample and the heat shrink tube are wrapped and wrapped by using a high temperature constant temperature instrument. A total of 5 kinds of heat shrink tubes are tested in this experiment, and finally a heat shrink tube with a diameter of 2.57 cm, a shrinkage rate of 2 times and a high temperature resistance of 175℃ is selected.

[0044] Step 3, according to the actual data range of the experimental block formation water sample, according to the basic properties of the experimental sample, the optimal applicable formation water sample salinity is selected through pre-experiment.

[0045] According to the formation water sample salinity data and the mudstone core layer information, the formation water sample salinity type is CaCl2, and the final salinity is verified through pre-experiment to be 168000mg / L. Under this salinity, the hydrolysis efficiency of the mudstone core is effectively reduced, which effectively ensures the integrity of the end face of the mudstone core. Combined with the water analysis data, the resistivity of the formation water sample is directly measured or the salinity of the formation water sample is converted into the equivalent salinity of the formation water sample solution, and then the relationship between the solution salinity and the resistivity temperature is measured or directly measured to obtain the resistivity of the formation water sample at the corresponding temperature. In this experiment, the resistivity of the formation water sample is directly measured, and the actual resistivity of the formation water sample is 0.052Ω·m.

[0046] Step 4, the basic parameters of the wrapped heat shrink tube after the mudstone core is wrapped, such as length, radius, weight, etc. and the weight of the mudstone core after drying at 105℃ for 24h are measured. The length, diameter and weight change of the mudstone core before and after drying after the linear cutting of the 6 mudstone cores are measured, and the results are shown in Table 1.

[0047] Table 1 Basic data of 6 mudstone cores and weight change after drying

[0048]

[0049] Step 5, the conventional physical property data of mudstone core is measured according to the process specified in the standard of GB / T 29172-2012 Mudstone Core Analysis Method, including porosity and permeability.

[0050] Through the conventional physical property experiment on the nine mudstone cores of the gas reservoir, the initial porosity and permeability are obtained.

[0051] Step 6, according to the basic parameters and conventional physical properties in steps 4 and 5, the pore volume of each mudstone core is calculated, the fully saturated mass of the mudstone core is calculated through the pore volume and the density of the formation water sample, and the mass of the titration water of the mudstone core under different formation water sample saturation states is calculated.

[0052] Through the calculation and measurement of the resistivity and salinity of the formation water sample, the density of the formation water sample is 1.118 g / cm 3 , and according to the experimental results measured in steps 4 and 5, the pore volume of each mudstone core is obtained, and the fully saturated mass of the mudstone core is calculated through the pore volume and the density of the formation water sample, and the mass of the titration water of the mudstone core under different formation water sample saturation states is calculated. The results are shown in Table 2.

[0053] Table 2 Physical property data, pore volume and saturation mass of six mudstone cores

[0054]

[0055] Step 7: place the mudstone core sample to be saturated in a dry balance, use a needle tube to uniformly titrate the formation water sample at both ends of the mudstone core, allow the mudstone core to fully self-absorb, and observe the change in the balance mass. According to the mass required for self-absorption titration under each saturation state calculated in step 6, titrate to the specified mass to make the mudstone core reach the corresponding saturation Figure 2 );

[0056] Step 8: place the mudstone core with the saturation mass reached in step 7 in a vacuum dish in a humid formation water sample environment, first perform vacuum extraction for 30 min, then start standing for 3 h, perform mass measurement and record, then stand for another 3 h, compare the mass difference of the two standing times, ensure that the mass change is within ±0.05 g, and stand for 12 h under the condition of satisfying the mass reduction, so that the mudstone core sample is fully saturated.

[0057] According to the pre-experiment, the vacuum extraction (3.5 Mpa) should not exceed 30 min, otherwise it will cause damage to the end face of the mudstone core just after saturation. This method only creates a vacuum humid water environment for standing to fully saturate the mudstone core, and the saturation state of each mudstone core is different, so the saturation of each mudstone core needs to be recorded.

[0058] Step 9: Titration measurement is performed on the mudstone core sample every 10% water saturation. Due to the high clay content in the mudstone, the saturation state is considered to be reached when the mass does not change during the titration process;

[0059] According to the experimental procedure requirements, the water saturation of the mudstone core sample can be calculated according to the formula:

[0060]

[0061] In the formula, S w is the water saturation of the mudstone core sample, expressed in percentage;

[0062] m1 is the mass of the mudstone core sample saturated with formation water, in grams (g);

[0063] m0 is the mass of the dried mudstone core sample, in grams (g);

[0064] ρ w is the density of the formation water sample, in grams per cubic centimeter (g / cm3);

[0065] V t is the pore volume of the mudstone core sample, in cubic centimeters (cm3);

[0066] The saturation state of the six mudstone cores in the gas reservoir mudstone reservoir was reached due to the properties of the mudstone cores and the same experimental environment, i.e., the titration mass did not change during the 48h of standing (the number of weighing times should be no less than 3 times in a strictly stationary environment, and the mass difference should be ensured to be within ±0.05g), which is considered to be the saturation state. The specific saturation state of the mudstone cores is shown in Table 3.

[0067] Table 3: Results of self-absorption titration experiment of six mudstone cores

[0068]

[0069]

[0070] Step 10: Test the mudstone core resistance value under different saturation conditions: Use the saturation increasing method in step 7 to saturate the mudstone core, weigh the mudstone core with different saturation, then load it into the holder, pre-apply the specified confining pressure, axial pressure, pore pressure, and temperature, record the resistance value change when the parameters are stable, and record the resistance value when the resistance value is stable. The resistance experiment steps refer to the reference "Laboratory Measurement and Calculation Method for Rock Resistivity Parameters" (SY-T 5385-2007) and "Mudstone Core Analysis Method" (GB / T 29172-2012) of the petroleum and natural gas industry standard.

[0071] Through the resistivity measurement of 6 pieces of mudstone cores of gas reservoir mudstone, the resistivity values of the mudstone cores are obtained.

[0072] Step 11: Repeat the previous step until the resistivity test under all different water saturation conditions is completed or the current experimental method or the current experimental condition cannot further increase the water saturation of the mudstone core, at which time the mudstone core has reached sufficient saturation, and the weight is recorded, the final resistivity value change is recorded when the parameters are stable, the final resistivity value of the saturated mudstone core is recorded, the experiment is stopped, and the results are shown in Table 4.

[0073] Table 4 Laboratory resistivity measurement results of 6 pieces of mudstone cores

[0074]

[0075] Step 12: According to the measurement results of the above steps, the actual water saturation of the reservoir is calculated by applying the Archie model related rock-electricity parameters, and the model is as follows:

[0076]

[0077] In the formula, Sw is the water saturation, %;

[0078] φ is the reservoir porosity, %;

[0079] Rw is the resistivity of formation water sample, unit Ω.m;

[0080] Rt is the resistivity of mudstone core, unit Ω.m;

[0081] a, b, m, n are the rock-electricity parameters of the Archie model, dimensionless; the values of a, b, m, n are obtained by fitting according to Figure 2 and Figure 3 a and m are fitted by Figure 2 b and n are fitted by Figure 3 .

[0082] The above-described embodiments only express the specific implementation of the present application, which is described in detail and specifically, but it should not be understood as a limitation on the protection scope of the present application. It should be noted that for ordinary skilled in the art, without departing from the technical scheme concept of the present application, a number of modifications and improvements can be made, which are all within the protection scope of the present application.

Claims

1. A method for measuring the resistivity of weakly cemented, brittle and easily hydrolyzed mudstone, comprising the following steps: Step 1: Pretreatment of drilled mudstone core to obtain mudstone core sample 3 9 pieces; wrap the mudstone core sample with a heat-shrinkable tube, then measure the length, radius, weight, and weight after drying; then measure the porosity and permeability of the mudstone core sample; Step 2: Calculate the pore volume of each mudstone core sample, and calculate the mass of the mudstone core sample fully saturated with the formation water sample by using the density of the mudstone core sample and the formation water sample, and calculate the mass of the titration water of different mudstone core samples under the condition of full saturation of the formation water sample; Step 3: Place the mudstone core sample wrapped in a heat shrinkable tube in a dry balance, and use a syringe to titrate the formation water sample at a constant rate to both ends of the mudstone core sample wrapped in the heat shrinkable tube, so that the mudstone core sample wrapped in the heat shrinkable tube is fully self-absorbed with the formation water sample, and at the same time, observe the change of the balance mass, according to the mass required for self-absorption titration under the saturation condition calculated in step 2, titrate to the specified mass, so that the mudstone core sample wrapped in the heat shrinkable tube reaches the corresponding saturation, and after vacuumizing and standing, measure the resistivity until the mudstone core sample wrapped in the heat shrinkable tube reaches a fully saturated state, and a stable resistance value is obtained, and the experiment is stopped. Step 4, by the above step 1 3 Measurement results, application of Alchi model to calculate reservoir saturation related parameters, to establish saturation model: In the formula, S w is the water saturation, %; φ is the porosity of the mudstone core sample, %; R w R is the formation water resistivity, in Ω.m; R t R is the resistivity of the mudstone core sample in Ω.m; a, b, m, n are the rock-electricity parameters of the Archie model, dimensionless.

2. The method for resistivity measurement of weakly cemented, friable and hydrolyzable mudstone according to claim 1, characterized in that, The heat shrink tube has a shrinkage of 1.8 2.2 fold, against 170 180 °C high temperature.

3. The method for resistivity measurement of weakly cemented, crumbly and hydrolyzable mudstone according to claim 1, characterized in that, The formation water sample is of CaCl2 type and has a salinity of 167000 169000 mg / L; the resistivity of the formation water sample at the corresponding temperature is obtained from the resistivity-salinity-temperature graph or by measurement; the density of the formation water sample is obtained from the calculated and measured resistivity and salinity of the formation water sample.

4. The method for resistivity measurement of weakly cemented, crumbly and easily hydrolyzed mudstone according to claim 1, characterized in that, The method of increasing saturation degree in step 3 is as follows: 2 After titration at 40% water saturation degree, the mass is measured, and if the mass does not change during titration and the mass is weighed within 24 72 hours, it is considered that the corresponding saturation state is reached; the resistance value of the mudstone core sample wrapped with the heat-shrinkable tube is tested under different corresponding saturation degrees; and the above operation is repeated until the sufficient saturation state of the mudstone core sample is reached.

5. The method for resistivity measurement of weakly cemented, friable and hydrolyzable mudstone according to claim 4, characterized in that, Each mud core sample was subjected to 5 Multiple titrations of 15% aqueous formation water samples.

6. The method for resistivity measurement of weakly cemented, friable and hydrolyzable mudstone according to claim 4, characterized in that, The method for measuring the resistance value of the mudstone core sample wrapped in the heat shrinkable tube under different saturation conditions is as follows: load the mudstone core sample wrapped in the heat shrinkable tube under different saturation conditions into a holder, and pre-apply a specified confining pressure, axial pressure, pore pressure and temperature, record the resistance value change when the parameters are stable, and record the resistance value when the resistance value is stable.

7. The method for resistivity measurement of weakly cemented, crumbly and hydrolyzable mudstone according to claim 1, characterized in that, The specific manner of vacuuming and standing in Step 3 is to place the mudstone core sample wrapped with a heat-shrinkable tube to the corresponding saturation degree in a vacuum dish in a humid formation water sample environment, first vacuumed for 10 50 min, and then stood for 1 5 h, mass determination was performed and recorded, then stood for 1 5 h again, mass difference comparison was performed at least twice to ensure that the mass change was within ±0.05 g, and then stood for 8 16 h under the condition that the mass change was within ±0.05 g.

8. The method for resistivity measurement of weakly cemented, crumbly and hydrolyzable mudstone according to claim 1, characterized in that, The mudstone core sample in Step 1 is 5 8 pieces, the mudstone core sample is a plunger sample.

9. The method for resistivity measurement of weakly cemented, crumbly and hydrolyzable mudstone according to claim 1, characterized in that, S in step 4 w The formula for calculating S is: S w For the shale core samples, the water saturation, %; m1 is the mass of the shale core sample of formation water sample, unit g; m0 is the mass of the dried shale core sample, unit g; p w is the density of the formation water sample, unit g / cm 3 ; V t is the pore volume of the shale core sample, unit cm 3 .

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