Evaluation Methods for Water Absorption and Gas Production in Tight Gas Reservoirs

Abstract

This invention discloses a method for evaluating water absorption and gas production from core samples in tight gas reservoirs. The steps are as follows: 1) Select a core sample, test the basic parameters, and weigh the dry weight of the core sample; 2) Assemble the water absorption and gas production testing device and set the process parameters; 3) Place the core sample into a rubber sleeve and insert it into the inner cavity of the core holder (4); 4) Install the core sample; 5) Start the test and record the corresponding data; 6) Calculate the dynamic water saturation and final water saturation of the core sample; 7) Calculate the dynamic gas production degree and final gas production degree of the core sample; 8) Calculate the gas production rate and water absorption rate of the core sample; 9) End the test, calculate the error between the theoretical saturated water volume and the detected saturated water volume, and obtain the evaluation result of the core sample. This invention belongs to the field of gas reservoir core testing technology, quantifies the feasibility of on-site water injection and gas production in different types of gas reservoirs, and provides a theoretical basis for formulating on-site water injection and gas production measures.

Description

Technical Field

[0001] This invention belongs to the field of gas reservoir core testing technology, and relates to a method for evaluating water absorption and gas production in tight gas reservoir cores. Background Technology

[0002] Natural gas reservoirs primarily rely on natural energy for extraction. When the reservoir's natural energy depletes to its abandoned pressure, the low formation pore pressure differential renders gas flow unviable for industrial extraction. However, a significant amount of natural gas remains buried within the reservoir, requiring external forces to re-accumulate this residual gas. This increases the formation pore pressure differential, enabling gas flow and achieving extraction value. For high water-cut gas reservoirs, drainage production can effectively reduce wellbore pressure, fully utilize formation energy to lift gas, and lower the abandoned pressure of natural gas wells. This method has been widely studied theoretically and applied in the field, and its technology is generally mature. However, this method cannot fundamentally solve the problem of energy depletion in natural gas reservoirs. Finding more economical and effective methods to improve gas recovery is a major challenge in the development of natural gas reservoirs, especially those with low pressure, low permeability, and low porosity.

[0003] Furthermore, most sandstone gas reservoirs have strong hydrophilicity, allowing them to spontaneously draw in external water to replenish reservoir energy under capillary forces. Simultaneously, they concentrate isolated natural gas from small pore throats into larger pore throats. Due to the relatively low flow resistance in larger pores, this concentrated gas is easier to extract, thus improving reservoir recovery. Directly discharging water from gas wells causes pollution. Treating the produced water and reinjecting it into the formation can protect the environment and reuse resources. Therefore, the feasibility of water injection for gas production in mining operations requires preliminary evaluation studies on reservoir applicability conditions, injection and production parameters, and the mechanisms for improving gas recovery, providing technical support for field applications.

[0004] However, there is currently a lack of equipment and methods for evaluating water injection and gas production in gas reservoirs. There is an urgent need to develop a new method that can evaluate the relationship between water injection and gas production in gas reservoirs, the relationship between reservoir water cut and gas production, and accurately obtain parameters such as water injection and gas production per unit time and the final gas production, so as to achieve economical and effective gas reservoir development. Summary of the Invention

[0005] The purpose of this invention is to provide a method for evaluating water absorption and gas production in tight gas reservoir cores. This method solves the problems of existing technologies, such as the lack of equipment for evaluating water injection and gas production in gas reservoirs, the difficulty in evaluating the relationship between water injection and gas production, the relationship between reservoir water cut and gas production, and the difficulty in determining the amount of water injected and gas produced per unit time and the final amount of gas produced.

[0006] The technical solution adopted in this invention is a method for evaluating water absorption and gas production from core samples in tight gas reservoirs, implemented according to the following steps:

[0007] Step 1: Select a core sample, test the basic parameters, and weigh the dry weight W0 of the core sample;

[0008] Step 2: Assemble the water absorption and gas sampling test device and set the process parameters;

[0009] Step 3: Place the core sample into the rubber sleeve and then insert it into the inner cavity of the core holder;

[0010] Step 4: Install the core sample;

[0011] Step 5: Start the test and record the relevant data;

[0012] Step 6: Calculate the dynamic water saturation S of the core sample. wi and final water saturation S w ;

[0013] Step 7: Calculate the dynamic gas recovery degree I of the core sample. i and final gas extraction level I;

[0014] Step 8: Calculate the gas extraction rate S of the core sample. gi and water absorption rate S wi ;

[0015] Step 9: End the test, calculate the theoretical saturated water volume (W1-W0) and the measured saturated water volume (V). w ×ρ w The error η between the two is used to obtain the evaluation results of the core sample.

[0016] The beneficial effects of this invention are that it standardizes the testing of water absorption and gas release capacity of core samples through a water absorption and gas production evaluation device and process. It also allows for comparative analysis of the degree of water absorption and gas release under different reservoir properties, temperature, and pressure conditions, quantitatively evaluating the feasibility of in-situ water injection for gas production in different types of gas reservoirs. This provides a theoretical basis for developing in-situ water injection and gas production measures, and is applicable not only to tight sandstone gas reservoirs but also to strongly hydrophilic gas reservoirs. This water injection and gas production method is an economical and effective gas reservoir development method, enabling the reuse of produced water, conserving water resources, and protecting the environment. Attached Figure Description

[0017] Figure 1 This is a schematic diagram of the water-absorbing gas extraction evaluation device used in the method of the present invention;

[0018] Figure 2 This is the water saturation curve obtained by the method of this invention;

[0019] Figure 3 This is the gas extraction degree curve obtained by the method of this invention;

[0020] Figure 4 This is the water absorption rate curve obtained by the method of this invention.

[0021] In the diagram, 1. Gas collection pipe, 2. Pressurization pump, 3. Water metering pipe, 4. Core holder, 5. Temperature control box, 6. Valve 1, 7. Valve 2, 8. Valve 3, 9. Rubber sleeve. Detailed Implementation

[0022] The present invention will now be described in detail with reference to the accompanying drawings and specific embodiments.

[0023] The tight gas reservoir core water absorption and gas production evaluation method of the present invention obtains water absorption and gas production by detecting the capillary pressure, water absorption and gas exhaust information of the core sample itself, and further analyzes the gas production degree and production rate of the core sample. At the same time, it can further analyze the hydrophilicity of the core sample to achieve the following objectives: (1) simulate formation conditions to conduct water injection and gas production tests under different temperatures and pressures; (2) evaluate the feasibility and reservoir adaptability of gas reservoir relying on its own capillary force to absorb water and produce gas; (3) clarify the relationship between water injection and gas production, determine the amount of water absorbed by the core by capillary force and the amount of gas produced, calculate the reservoir water absorption intensity, predict the final enhanced oil recovery value of the gas reservoir, and provide guidance for the design of application parameters in the mine.

[0024] The testing principle of this invention is as follows: Utilizing the hydrophilic properties of sandstone gas reservoirs, capillary force is used as the driving force. Injected water seeps along the surface of the particles into the micropores, driving isolated gas into larger channels with lower flow resistance for collection and extraction. The test evaluates the water absorption and gas production of core samples under different reservoir temperature and pressure conditions, assesses the feasibility of water injection for gas production, and evaluates the hydrophilicity of the reservoir, providing a basis for designing relevant injection and production parameters.

[0025] Reference Figure 1 The method of the present invention employs a water absorption and gas extraction testing device, the structure of which includes a core holder 4, an inner cavity of which is provided with a rubber sleeve for wrapping the core sample, the outlet of the rubber sleeve being connected to a gas collection pipe 1 via valve 6, and the inlet of the rubber sleeve being connected to a water metering pipe 3 via valve 7, the rubber sleeve being sealed in the core holder 4; the inner cavity of the core holder 4 is connected to a pressure pump 2 via valve 8, and a temperature control box 5 is also provided on the surface of the core holder 4 for heating and heat preservation of the core holder 4.

[0026] The inner cavity of the core holder 4 is called the core sample chamber, in which a cylindrical block-shaped core sample is wrapped in a rubber sleeve.

[0027] The pressurizing pump 2 pressurizes the rubber sleeve in the core holder 4. The pressurizing pump 2 cannot force the water in the water metering tube 3 into the core sample. The core sample is placed in the rubber sleeve in the core holder 4. There is a gap between the rubber sleeve and the wall of the core sample. The pressurizing pump 2 is needed to increase the pressure inside the core holder 4 so that the rubber sleeve fits tightly with the core sample. The water in the water metering tube 3 is drawn into the core sample by capillary force based on the porous medium. After the water enters the core sample, it will displace the original gas in the pores of the core sample and enter the gas collection tube 1.

[0028] The method for evaluating water absorption and gas production in tight gas reservoir cores of the present invention is implemented using the aforementioned water absorption and gas production testing device, following these steps:

[0029] Step 1: Select a cylindrical core sample from a water-absorbing gas-producing well, test the basic parameters of the core sample, dry the core sample in a desiccator, and weigh the dry weight W0 of the core sample (using an electronic balance).

[0030] The basic parameters include porosity, gas permeability, and pore volume, among which V p Represents the pore volume of the core sample, in ml; Indicates the porosity of the core sample, %; K g This represents the gas permeability of the core sample, in mD; (the latter two parameters are physical properties of the core or reservoir, which are fundamental data that directly determine the effectiveness of water absorption and gas production. They are used for analysis and comparison of different samples in subsequent steps, but are not directly used for calculations).

[0031] Step 2: According to Figure 1 Assemble the water absorption and gas sampling test device and set the process parameters. The process parameters to be selected are temperature, confining pressure, and water column height.

[0032] Step 3: First, put the core sample into the rubber sleeve, and then put the core sample and the rubber sleeve together into the inner cavity of the core holder 4;

[0033] Step 4: Install the core sample.

[0034] Fill the water metering tube 3 with a predetermined amount of water, discharge the gas in the pipeline between the water metering tube 3 and the inlet of the rubber sleeve, seal the inlet end face of the rubber sleeve with the inlet end face of the water, and at the same time, seal the outlet end of the rubber sleeve with the inlet end of the gas collecting tube 1.

[0035] Open valve 38 and use pressure pump 2 to pressurize the inner cavity of core holder 4 so that the rubber sleeve is tightly attached to the core sample, preventing water from flowing out of the annular space between the rubber sleeve and the core sample (affecting the self-priming effect). Open temperature control box 5 to keep core holder 4 warm and let it stand for 30 minutes.

[0036] Step 5: Start the test and record the relevant data.

[0037] Record the initial liquid levels in water metering tube 3 and gas collecting tube 1. Open valve 7 and valve 6 sequentially, and simultaneously use a stopwatch to record the time. Read the liquid level values ​​in water metering tube 3 and gas collecting tube 1 at different time points (t) to calculate the water absorption V of the core sample over a certain period. wi Gas production V from core samples at a certain time period gi ;

[0038] When the water absorption and gas production of the core sample remain constant for 10 consecutive hours, the self-absorption test is terminated, and the final water absorption V is recorded. w Total gas production V from core samples g ;

[0039] Step 6: Calculate the dynamic water saturation S of the core sample. wi and final water saturation S w ,

[0040] The dynamic water saturation S of the core sample is calculated using formula (1). wi That is, the change in water saturation of the core sample over time; at the same time, the final water saturation S of the core sample is calculated using formula (2). w That is, the water saturation of the core sample when the water absorption no longer changes over time. The two functions are as follows:

[0041] S wi =V wi / V p ×100% (1)

[0042] S w =V w / V p ×100% (2)

[0043] Among them, S wi Indicates the dynamic water saturation of the core sample, %; S w V represents the final water saturation of the core sample, in %; wi V represents the water absorption of a core sample over a specific period of time, expressed in ml. w Indicates the final water absorption volume, in ml;

[0044] Step 7: Calculate the dynamic gas recovery degree I of the core sample. i and final gas extraction level I,

[0045] The dynamic gas extraction degree I of the core sample is calculated using formula (3). iThis refers to the change in the gas production degree of the core sample over time. Simultaneously, formula (4) is used to calculate the final gas production degree I of the core sample, which is the gas production degree when the gas production of the core sample no longer changes over time. The two functions are as follows:

[0046] I i =V gi / V p ×100% (3)

[0047] I = V g / V p ×100% (4)

[0048] Among them, I i V represents the dynamic gas recovery rate of the core sample, %; I represents the final gas recovery rate of the core sample, %; V gi V represents the cumulative gas production of a core sample over a specific period, expressed in ml. g This indicates the total gas production volume of the core sample, expressed in ml.

[0049] Step 8: Calculate the gas extraction rate S of the core sample. gi and water absorption rate S wi ,

[0050] The gas extraction rate S of the core sample is calculated using formula (5). gi That is, the gas extraction rate per unit volume per unit time; at the same time, the water absorption rate S of the core sample is calculated using formula (6). wi This refers to the amount of water absorbed per unit length per unit time in the core sample. The two functions are as follows:

[0051] S gi =(V wi / t) / V p (5)

[0052] S wi =(V wi / t) / L% (6)

[0053] Among them, S gi Indicates the gas extraction rate of the core sample, ml / min / cm; S wi V represents the water absorption rate of the core sample, in ml / min / cm. wi The value represents the amount of water absorbed by the core sample, in ml; t represents the water absorption time of the core sample, in min; and L represents the length of the core sample, in cm.

[0054] Step 9: End the test. Remove the core sample and rubber sleeve from the core holder 4. Remove the rubber sleeve from the core sample and wipe away the water on the surface of the core sample (at this time, the water on the surface of the core sample is closer to water droplets or small water beads). Weigh the saturated weight W1 of the core sample (using an electronic balance).

[0055] The theoretical saturated water content of the core sample was obtained as (W1-W0) using the law of conservation of mass. The measured saturated water content of the core sample was obtained as (V) using water metering tube 3. w ×ρ w Using formula (7), the theoretical saturated water volume (W1-W0) and the measured saturated water volume (V) are calculated. w ×ρ w The error η between the two is expressed as follows:

[0056]

[0057] Where W0 represents the dry weight of the core sample, g; W1 represents the wet weight of the core sample, g; ρ w The density of water is expressed in g / cm³. 3 Evaluation results were obtained from the core samples.

[0058] Step 10 (Selection Step): Simulate different test results under different conditions, analyze the relationships between them, and obtain evaluation results for different core samples.

[0059] First, repeat steps 1 to 9, changing the physical properties of the core sample (including but not limited to permeability, porosity, wettability, etc., using core samples with different permeabilities and porosities), confining pressure (a technical term referring to the pressure exerted on the core sample by the pressure pump 2), and temperature (the temperature controlled by the temperature control chamber 5) to simulate different reservoir conditions and obtain test results for self-water extraction from the natural gas reservoir.

[0060] Then, based on the changes in basic parameters (such as the aforementioned core permeability, porosity, temperature, and pressure), the influence of these changes on the water saturation, gas production degree, and gas production rate of the core samples is compared and analyzed, providing theoretical support for the formulation of water injection and gas production measures in the field; at the same time, the hydrophilicity of the core samples is compared and evaluated according to the speed of water absorption.

[0061] Example 1

[0062] Step 1: Select core sample #1 from a cylindrical water-absorbing gas production well and test the gas permeability K of core sample #1. g1 pore volume V p1 Porosity The basic parameters are shown in Table 1. The core sample was placed in a desiccator and dried. The dry weight W0 of the core sample was weighed (using an electronic balance).

[0063] Step 2: According to Figure 1 Assemble the water absorption and gas sampling test device and set the process parameters, including temperature and confining pressure parameters.

[0064] Step 3: First, put the core sample into the rubber sleeve, and then put the core sample and the rubber sleeve together into the inner cavity of the core holder 4;

[0065] Step 4: Fill the water metering tube 3 with the predetermined amount of water, purge the gas in the pipeline, load the core sample into the core holder 4, ensuring that its inlet end face is fully in contact with the water inlet end face, open valve 3 8, and use the pressure pump 2 to pressurize and seal the core sample chamber to prevent water from flowing out of the annular space, and let it stand for 30 minutes.

[0066] Step 5: Record the initial liquid levels in the water metering tube 3 and the gas collecting tube 1. First, open valve 2 (7), then open valve 1 (6). Simultaneously, press the stopwatch to record the time. Read the liquid level values ​​in the water metering tube 3 and the gas collecting tube 1 at different times (t), and calculate the water absorption volume V. wi1 and gas extraction volume V gi1 Turn on the temperature control chamber 5 to insulate the core holder 4 with the reservoir temperature (depending on reservoir conditions). The self-absorption test can be ended only when the water absorption and produced gas volume of the core sample remain constant for 10 consecutive hours. Record the final water absorption volume V. w1 Total gas production V from core samples g1 .

[0067] Step 6: Calculate the dynamic water saturation S of the core sample using formulas (1) and (2). wi1 The final water saturation S of the core sample w1 .

[0068] Step 7: Using formulas (3) and (4), calculate the dynamic gas extraction degree I of the core sample. i1 The final gas recovery level I1 of the core sample.

[0069] Step 8: Calculate the gas extraction rate S of the core sample using formulas (5) and (6). gi1 Water absorption rate S of core sample wi1 .

[0070] Step 9: After the test, remove the core sample from the core holder 4, wipe off the water on the surface of the core sample, and weigh and record the weight W of the core sample using an electronic balance. 11 The theoretical saturated water volume (W) obtained by the mass conservation method is calculated using formula (7). 11 -W01 The detection saturated water volume (V) of the core sample read from the water metering tube 3 and the water volume metering tube 3. w1 ×ρ w1 The error η between )

[0071] Step 10: Obtain the test results, analyze the relationships among them, and obtain the evaluation results of the core samples.

[0072] The evaluation results of Example 1 are described below.

[0073] Example 2

[0074] Following the steps in Example 1, the gas permeability K of the #2 core sample was tested. g1 pore volume V p1 Porosity The basic parameters and final result parameters are shown in Table 1. The evaluation results of this Example 2 are described below.

[0075] Example 3

[0076] Following the steps in Example 1, the gas permeability K of the #3 core sample was tested. g1 pore volume V p1 Porosity The basic parameters and final result parameters are shown in Table 1. The evaluation results of this Example 3 are described below.

[0077] Example 4

[0078] Following the steps in Example 1, the gas permeability K of the #4 core sample was tested. g1 pore volume V p1 Porosity The basic parameters and final result parameters are shown in Table 1. The evaluation results of this Example 4 are described below.

[0079] Example 5

[0080] Following the steps in Example 1, the gas permeability K of core sample #5 was tested. g1 pore volume V p1 Porosity The basic parameters and final result parameters are shown in Table 1. The evaluation results of this Example 5 are described below.

[0081] Example 6

[0082] Following the steps in Example 1, core sample #6 was tested. The gas permeability K of core sample #6 was determined. g1 pore volume V p1 Porosity The basic parameters and final result parameters are shown in Table 1. The evaluation results of this Example 6 are described below.

[0083] Table 1. Physical properties and analysis results of core samples from Examples 1-6

[0084]

[0085] (Note: Table 1 includes different permeabilities and porosities. The effects of temperature and pressure are not shown in the examples, but temperature and pressure are also influential factors and are also protected by the method of this invention.)

[0086] Figure 2 These are the water saturation curves of the core samples from the six examples. Figure 3 These are the gas extraction curves of the core samples from the six examples. Figure 4 These are the water absorption rate curves of core samples from six examples. Figure 2 , Figure 3 , Figure 4 As can be seen, the self-absorption rate of the core samples in the six embodiments can reach over 85%, and the gas recovery rate is over 80%. The error rate calculation results of all embodiments are less than 10%, demonstrating good reliability. The above tests show that self-absorption gas production has good applicability in tight sandstone reservoirs and can be used as a potential technology to improve the recovery rate of tight gas reservoirs. Comparing the water absorption rates of different core samples, it can be seen that the water absorption rates of core samples #1, #2, and #6 are significantly faster, which is due to their higher permeability and porosity. However, the final water saturation of core samples #1, #2, and #6 is significantly lower, with core sample #6 having the highest permeability and the lowest. This indicates that a fast water absorption rate is not conducive to the final recovery rate, mainly because a faster water absorption rate creates channeling within the core sample, resulting in trapped gas in unaffected and affected areas, affecting the final gas release effect. Therefore, the method of this invention can provide strong support for the feasibility and parameter optimization of self-absorption gas production technology for improving the recovery rate of tight sandstone reservoirs.

Claims

1. A method for evaluating water absorption and gas production from core samples in tight gas reservoirs, utilizing a water absorption and gas production testing device, comprising a core holder (4), with a rubber sleeve installed inside the core holder (4), the outlet of the rubber sleeve being connected to a gas collection pipe (1) via valve one (6), and the inlet of the rubber sleeve being connected to a water metering pipe (3) via valve two (7), the rubber sleeve being sealed within the core holder (4); a pressure pump (2) being connected inside the core holder (4) via valve three (8), and a temperature control box (5) being installed on the surface of the core holder (4), characterized in that... This method is implemented according to the following steps: Step 1: Select core samples, test basic parameters, and weigh the dry weight of the core samples. W 0, The basic parameters include porosity, gas permeability, and pore volume, among which, V p This indicates the pore volume of the core sample, in ml. φ Porosity of core samples is expressed in % (%). K g This indicates the gas permeability of the core sample, measured in mD. Step 2: Assemble the water absorption and gas sampling test device and set the process parameters; Step 3: Put the core sample into the rubber sleeve and put it into the inner cavity of the core holder (4); Step 4: Install the core sample; Step 5: Start the test and record the relevant data. The specific process is as follows: Record the initial liquid level values ​​in the water metering tube (3) and the gas collection tube (1), open valve two (7) and valve one (6) in sequence, and simultaneously press the stopwatch to record the time. Read the liquid level values ​​in the water metering tube (3) and the gas collection tube (1) at different time t states to calculate the water absorption of the core sample in a certain period of time. V wi Gas production from core samples at a certain time period V gi ; The test was terminated when the water absorption and gas production of the core sample remained constant for 10 consecutive hours, and the final water absorption was recorded. V w Total gas production from core samples V g ; Step 6: Calculate the dynamic water saturation of the core sample. S wi and final water saturation S w ; Step 7: Calculate the dynamic gas recovery degree of the core sample. I i and final gas extraction level I The specific process is as follows: The dynamic gas extraction degree of the core sample is calculated using formula (3). I i Simultaneously, the final gas recovery degree of the core sample was calculated using formula (4). I The two functions are as follows: (3) (4) in, I i The dynamic gas recovery rate of the core sample is expressed in % (%). I Indicates the final gas recovery percentage of the core sample, expressed in % %. V gi This indicates the cumulative gas production of a core sample over a certain period of time, expressed in ml. V g This indicates the total gas production volume of the core sample, expressed in ml. Step 8: Calculate the gas extraction rate of the core sample. S gi and water absorption rate S wi ; Step 9: End the test and calculate the error between the theoretical saturation water volume and the measured saturation water volume. η Evaluation results were obtained from the core samples.

2. The method for evaluating water absorption and gas production from tight gas reservoir cores according to claim 1, characterized in that, In step 4, the specific process is as follows: Fill the water metering tube (3) with a predetermined amount of water, discharge the gas in the pipeline between the water metering tube (3) and the inlet of the rubber sleeve, seal the inlet end face of the rubber sleeve with the inlet end face of the water, and at the same time seal the outlet end of the rubber sleeve with the inlet end of the gas collection tube (1). Open valve three (8) and use the pressurizing pump (2) to pressurize the inner cavity of the core holder (4) so ​​that the rubber sleeve is tightly attached to the core sample; open the temperature control box (5) to keep the core holder (4) warm and let it stand for 30 minutes.

3. The method for evaluating water absorption and gas production from tight gas reservoir cores according to claim 1, characterized in that, In step 6, the specific process is to calculate the dynamic water saturation of the core sample using formula (1). S wi Simultaneously, the final water saturation of the core sample was calculated using formula (2). S w The two functions are as follows: (1) (2) in, S wi This indicates the dynamic water saturation of the core sample, expressed in % (%). S w This indicates the final water saturation of the core sample, expressed in % (%). V wi This indicates the amount of water absorbed by a core sample over a specific period of time, expressed in ml. V w This indicates the final water absorption volume, measured in ml.

4. The method for evaluating water absorption and gas production from tight gas reservoir cores according to claim 1, characterized in that, In step 8, the specific process is as follows: The gas extraction rate of the core sample is calculated using formula (5). S gi Meanwhile, the water absorption rate of the core sample was calculated using formula (6). S wi The two functions are as follows: (5) (6) in, S gi This indicates the gas extraction rate of the core sample, expressed in ml / min / cm. S wi This indicates the water absorption rate of the core sample, expressed in ml / min / cm. V wi This indicates the water absorption of the core sample, in ml. t This indicates the water absorption time of the core sample, in minutes. L This indicates the length of the core sample, in cm.

5. The method for evaluating water absorption and gas production from tight gas reservoir cores according to claim 1, characterized in that, In step 9, the specific process is as follows: Remove the core sample and rubber sleeve from the core holder (4), remove the rubber sleeve from the core sample, wipe away the moisture on the surface of the core sample, and weigh the saturated weight of the core sample. W 1; The theoretical saturated water content of the core sample is obtained by applying the law of conservation of mass. W 1- W 0), the detection saturation water volume of the core sample was read through the water metering tube (3) as ( V w × ρ w ), calculate the theoretical saturated water volume using formula (7) W 1- W 0) and the detection saturation water volume ( V w × ρ w Error between ) η The function is as follows: (7) in, W 0 indicates the dry weight of the core sample, in grams; W 1 represents the wet weight of the core sample, in grams; ρ w The density of water is expressed in g / cm³. 3 .

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