A method, device and storage medium for full-size pore characterization of tight sandstone

Abstract

The application relates to a tight sandstone full-size pore characterization method, device and storage medium, which comprises the following steps: preparing an experimental rock sample and a control rock sample; performing CT scanning test on the experimental rock sample and the control rock sample; performing high-pressure mercury injection test on the experimental rock sample and the control rock sample; weighing the experimental rock sample and the control rock sample and performing nuclear magnetic resonance test; and drawing a tight sandstone full-size pore characterization result according to the test result. The tight sandstone full-size pore characterization method, device and storage medium provided by the application have higher tight sandstone full-size porosity result precision after being obtained through CT, high-pressure mercury injection and weight method multi-measurement, the multi-measurement methods do not have a pore size measurement range overlap phenomenon, and have a self-correction function, so that the method has a wide application prospect.

Description

Technical Field

[0001] This application relates to the field of petroleum exploration and development, and in particular to a method, apparatus and storage medium for characterizing full-size pores in tight sandstone. Background Technology

[0002] With the increasing maturity of oil and gas exploration and development technologies in my country, tight sandstone oil and gas resources have shown enormous development potential and are gradually becoming an important strategic resource for my country. Characterizing the pore-fracture system of tight sandstone oil and gas reservoirs plays a crucial role in the exploration and development of tight oil. Tight oil and gas reservoirs are characterized by widespread micro- and nano-pores, and traditional methods cannot accurately depict their multi-scale pore structure. Currently, commonly used methods for characterizing the pore structure of tight sandstone reservoirs include core observation, gas adsorption, micro- and nano-CT, field emission electron microscopy, mercury intrusion porosimetry, and nuclear magnetic resonance. However, due to limitations in testing instruments and measurement accuracy, a single method cannot accurately provide the full-scale pore structure distribution of tight sandstone. Existing combined measurement techniques suffer from overlapping pore size ranges, resulting in low accuracy of the pore structure characterization results. Therefore, it is necessary to establish a novel multi-scale combined measurement method for characterizing the pore structure of tight sandstone. Summary of the Invention

[0003] To solve the above-mentioned technical problems, or at least partially solve them, this application provides a method, apparatus, and storage medium for characterizing the full-size pores of dense sandstone.

[0004] In a first aspect, this application provides a method for characterizing the full-size pores of dense sandstone, the method comprising the steps of:

[0005] Preparation of experimental and control rock samples;

[0006] The experimental rock samples and the control rock samples were subjected to CT scan tests;

[0007] High-pressure mercury intrusion testing was performed on the experimental rock sample and the control rock sample;

[0008] Weigh the experimental rock sample and the control rock sample and perform nuclear magnetic resonance testing;

[0009] Based on the test results, the full-size pore characterization results of dense sandstone were plotted.

[0010] Preferably, the preparation of experimental and control rock samples includes the following steps:

[0011] Obtain experimental and control rock samples of the same specifications;

[0012] The experimental rock samples were cut into three experimental rock samples of the same size: a first experimental rock sample, a second experimental rock sample, and a third experimental rock sample.

[0013] The reference rock samples were cut into three types of rock samples of the same size: a first reference rock sample, a second reference rock sample, and a third reference rock sample.

[0014] Preferably, the CT scan test of the experimental rock sample and the control rock sample includes the following steps:

[0015] Obtain the first and third experimental rock samples from the experimental rock samples;

[0016] Obtain the first and third control rock samples from the control rock samples;

[0017] Dry the first experimental rock sample, the third experimental rock sample, the first control rock sample, and the third control rock sample;

[0018] The first experimental rock sample, the third experimental rock sample, the first control rock sample, and the third control rock sample were scanned using CT scans.

[0019] Data was extracted from the dataset according to different pore levels.

[0020] Based on the data, a bar chart of the distribution of different pore levels was drawn.

[0021] Preferably, the high-pressure mercury intrusion testing of the experimental rock sample and the control rock sample includes the following steps:

[0022] Obtain the second experimental rock sample from the experimental rock samples;

[0023] Obtain the second control rock sample from the control rock samples;

[0024] Dry the second experimental rock sample and the second control rock sample;

[0025] High-pressure mercury intrusion testing was performed on the second experimental rock sample and the second control rock sample;

[0026] Plot the curve of pore distribution frequency as a function of pore diameter;

[0027] The porosity distribution characteristics of the tight sandstone sample were determined based on the aforementioned variation curve.

[0028] Preferably, the weighing of the experimental rock sample and the control rock sample and the nuclear magnetic resonance test include the following steps:

[0029] Obtain the third experimental rock sample from the experimental rock samples;

[0030] Obtain the third reference rock sample from the reference rock samples;

[0031] Dry the third experimental rock sample and the third control rock sample and weigh them;

[0032] Nuclear magnetic resonance (NMR) tests were performed on the third experimental rock sample and the third control rock sample.

[0033] Preferably, the step of drawing full-size porosity characterization results of tight sandstone based on test results includes the following steps:

[0034] Establish the relationship between nuclear magnetic resonance signal quantity and saturated water porosity calibration of tight sandstone;

[0035] Calculate the nuclear magnetic resonance relaxation time and the spacetime conversion coefficient of pore size.

[0036] Preferably, the step of establishing the relationship between nuclear magnetic resonance signal quantity and the porosity calibration of saturated water in tight sandstone includes the following steps:

[0037] Obtain the third experimental rock sample from the experimental rock samples;

[0038] Obtain the third reference rock sample from the reference rock samples;

[0039] Calculate the saturated water porosity of the tight sandstone samples of the third experimental rock sample and the third control rock sample;

[0040] The NMR signal components of dense sandstone after it is saturated with water are converted into porosity components.

[0041] Plot the relationship between the porosity components and the cumulative porosity components of dense sandstone after saturation with water and the relaxation time.

[0042] Secondly, a full-size pore characterization device for dense sandstone is provided, comprising:

[0043] The rock sample preparation module is used to prepare experimental rock samples and control rock samples;

[0044] A CT scan testing module is used to perform CT scan tests on the experimental rock sample and the control rock sample.

[0045] A high-pressure mercury intrusion testing module is used to perform high-pressure mercury intrusion testing on the experimental rock sample and the control rock sample.

[0046] The nuclear magnetic resonance (NMR) testing module is used to weigh the experimental rock sample and the control rock sample and perform NMR testing.

[0047] The characterization results plotting module is used to plot the full-size pore characterization results of tight sandstone based on the test results.

[0048] Thirdly, an electronic device is provided, the electronic device comprising:

[0049] At least one processor; and,

[0050] A memory communicatively connected to the at least one processor; wherein,

[0051] The memory stores instructions that can be executed by the at least one processor to enable the at least one processor to perform any of the aforementioned methods for characterizing the full-size porosity of tight sandstone.

[0052] Fourthly, a non-transitory computer-readable storage medium is provided, which stores computer instructions for causing the computer to execute any of the aforementioned methods for characterizing the full-size pore size of dense sandstone.

[0053] The technical solutions provided in this application have the following advantages compared with the prior art:

[0054] This application provides a method, apparatus, and storage medium for characterizing the full-size porosity of tight sandstone using a combination of gravimetric and NMR methods. The aim is to precisely depict the micro- and nano-sized full-size pore structure of tight sandstone oil and gas reservoirs. This method leverages the wide porosity measurement range of NMR, using nuclear magnetic resonance as the fundamental technique for characterizing the full-size pore structure of tight sandstone. The combined use of CT, high-pressure mercury intrusion porosimetry, and gravimetric methods yields more accurate full-size porosity results. Furthermore, the combined measurement methods do not exhibit overlapping porosity measurement ranges and possess self-correction capabilities, thus demonstrating broad application prospects. Attached Figure Description

[0055] The accompanying drawings, which are incorporated in and form part of this specification, illustrate embodiments consistent with the invention and, together with the description, serve to explain the principles of the invention.

[0056] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, for those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0057] Figure 1 This is a schematic flowchart of a method for characterizing the full-size pores of dense sandstone provided in an embodiment of the present invention;

[0058] Figure 2 This is a schematic diagram of the structure of a full-size pore characterization device for dense sandstone provided in an embodiment of the present invention;

[0059] Figure 3 This is a schematic diagram of the structure of an electronic device provided by the present invention;

[0060] Figure 4 This is a schematic diagram of the structure of a non-transitory computer-readable storage medium provided by the present invention;

[0061] Figure 5 This is a CT scan result of rock sample #1 in a method for characterizing the full-size pores of dense sandstone provided in an embodiment of the present invention.

[0062] Figure 6 This is a spatiotemporal conversion curve of nuclear magnetic resonance and high-pressure mercury intrusion in a method for characterizing the full-size pores of dense sandstone provided in an embodiment of the present invention. Detailed Implementation

[0063] To make the objectives, technical solutions, and advantages of the embodiments of this application clearer, the technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0064] Figure 1 This is a schematic flowchart illustrating a method for characterizing the full-size pores of dense sandstone, as provided in an embodiment of this application.

[0065] This application provides a method for characterizing the full-size pore size of dense sandstone, the method comprising the following steps:

[0066] S1: Preparation of experimental and control rock samples;

[0067] In this embodiment of the application, the preparation of experimental rock samples and control rock samples includes the following steps:

[0068] Obtain experimental and control rock samples of the same specifications;

[0069] The experimental rock samples were cut into three experimental rock samples of the same size: a first experimental rock sample, a second experimental rock sample, and a third experimental rock sample.

[0070] The reference rock samples were cut into three types of rock samples of the same size: a first reference rock sample, a second reference rock sample, and a third reference rock sample.

[0071] Specifically, two standard plunger-type tight sandstone samples from the same core section of the study block were selected and numbered 1# (experimental sample) and 2# (control sample). The core length was required to be 6 cm, with sample 2# serving as the control sample for the corresponding experiments. Sample 1# was cut into three cores with lengths of 1 cm, 1.5 cm, and 3.5 cm using wire cutting, and numbered 1-1 (first experimental sample), 1-2 (second experimental sample), and 1-3 (third experimental sample) for later use. A 2 mm diameter sample was drilled from core 1-1 for CT scanning, core 1-2 for high-pressure mercury intrusion porosimetry, and core 1-3 for both CT scanning and nuclear magnetic resonance (NMR) testing. The processing procedure for rock sample #2 was the same as that for rock sample #1. Specifically, a rock sample with a diameter of 2 mm was drilled from the core of rock sample 2-1 (first control rock sample) for CT scanning test; the core of rock sample 2-2 (second control rock sample) was used for high pressure mercury intrusion testing; and the core of rock sample 2-3 (third control rock sample) was used for CT scanning test and nuclear magnetic resonance test.

[0072] S2: Perform CT scan tests on the experimental rock sample and the control rock sample;

[0073] In this embodiment of the application, the CT scan test of the experimental rock sample and the control rock sample includes the following steps:

[0074] Obtain the first and third experimental rock samples from the experimental rock samples;

[0075] Obtain the first and third control rock samples from the control rock samples;

[0076] Dry the first experimental rock sample, the third experimental rock sample, the first control rock sample, and the third control rock sample;

[0077] The first experimental rock sample, the third experimental rock sample, the first control rock sample, and the third control rock sample were scanned using CT scans.

[0078] Data was extracted from the dataset according to different pore levels.

[0079] Based on the data, a bar chart of the distribution of different pore levels was drawn.

[0080] Specifically, the prepared compact sandstone samples 1-3 and 2-3 with a diameter of 25 mm, and compact sandstone samples 1-1 and 2-1 with a diameter of 2 mm, were dried according to GB / T 29172-2012 "Core Analysis Methods". Then, CT scanning was used to characterize the pore structure of core samples with a diameter >1 μm from the study block. Data was extracted from the dataset according to different pore levels, and histograms of the distribution of different pore levels were plotted.

[0081] S3: Perform high-pressure mercury intrusion testing on the experimental rock sample and the control rock sample;

[0082] In this embodiment of the application, the high-pressure mercury intrusion testing of the experimental rock sample and the control rock sample includes the following steps:

[0083] Obtain the second experimental rock sample from the experimental rock samples;

[0084] Obtain the second control rock sample from the control rock samples;

[0085] Dry the second experimental rock sample and the second control rock sample;

[0086] High-pressure mercury intrusion testing was performed on the second experimental rock sample and the second control rock sample;

[0087] Plot the curve of pore distribution frequency as a function of pore diameter;

[0088] The porosity distribution characteristics of the tight sandstone sample were determined based on the aforementioned variation curve.

[0089] Specifically, the prepared 1-2 and 2-2 tight sandstone samples were dried according to GB / T 29172-2012 "Core Analysis Methods". After drying, high-pressure mercury intrusion testing was carried out on the samples. The pore distribution frequency versus pore diameter curve was plotted under semi-logarithmic coordinates to determine the pore distribution characteristics of the tight sandstone samples.

[0090] S4: Weigh the experimental rock sample and the control rock sample and perform nuclear magnetic resonance testing;

[0091] In this embodiment of the application, the step of weighing the experimental rock sample and the control rock sample and performing nuclear magnetic resonance testing includes the following steps:

[0092] Obtain the third experimental rock sample from the experimental rock samples;

[0093] Obtain the third reference rock sample from the reference rock samples;

[0094] Dry the third experimental rock sample and the third control rock sample and weigh them;

[0095] Nuclear magnetic resonance (NMR) tests were performed on the third experimental rock sample and the third control rock sample.

[0096] Specifically, 1-3 and 2-3 compact sandstone samples with a diameter of 25 mm were selected, dried and weighed according to GB / T 29172-2012 "Core Analysis Methods"; the dried 1-3 and 2-3 standard rock samples were placed in core holders, and a confining pressure of 2 MPa was applied using a hand pump. Then, a vacuum pretreatment system was used to vacuum the standard rock samples for 48 hours; distilled water for the experiment was placed in a piston container, and an ISCO pump was used to inject the distilled water from the piston container into the core holder containing 1-3 and 2-3 rock samples at constant pressure. During saturation, the injection pressure and confining pressure showed a stepwise relationship. The pressure is increased incrementally while maintaining a constant difference of 2 MPa between the confining pressure and the injection pressure. When the injection pressure reaches the formation pressure of the study block, the saturation process is stopped. The rock sample saturation process is completed in a constant temperature chamber, with the temperature consistent with the formation temperature, and the total saturation time is not less than 48 hours. After saturation with water, rock samples 1-3 and 2-3 are removed from the core holder and their mass is recorded. The nuclear magnetic resonance T2 spectrum of the rock samples after saturation with water is tested. The core sample from step 4) is centrifuged at 10000 r / min for 180 min using a centrifuge, and the nuclear magnetic resonance T2 spectrum is tested after centrifugation.

[0097] S5: Draw the full-size pore characterization results of dense sandstone based on the test results.

[0098] In this embodiment of the application, the step of drawing full-size porosity characterization results of tight sandstone based on test results includes the following steps:

[0099] Establish the relationship between nuclear magnetic resonance signal quantity and saturated water porosity calibration of tight sandstone;

[0100] Calculate the nuclear magnetic resonance relaxation time and the spacetime conversion coefficient of pore size.

[0101] Specifically, establishing the relationship between nuclear magnetic resonance signal quantity and the porosity calibration of saturated water in tight sandstone includes the following steps:

[0102] Obtain the third experimental rock sample from the experimental rock samples;

[0103] Obtain the third reference rock sample from the reference rock samples;

[0104] Calculate the saturated water porosity of the tight sandstone samples of the third experimental rock sample and the third control rock sample;

[0105] The NMR signal components of dense sandstone after it is saturated with water are converted into porosity components.

[0106] Plot the relationship between the porosity components and the cumulative porosity components of dense sandstone after saturation with water and the relaxation time.

[0107] Specifically, ① the saturated water porosity of the compact sandstone samples 1-3 and 2-3 was calculated based on the gravimetric method, and the calculation formula is as follows:

[0108] (1)

[0109] in, — Saturated water porosity of rock sample #i, % — Weight of rock sample i after saturation with water, in g; —Weight of rock sample i after drying, in g; — Water density, g / cm3; — Diameter of rock sample #i, in cm; — Length of rock sample #i, in cm;

[0110] ② Based on the T2 spectrum signal components measured by nuclear magnetic resonance, the T2 spectrum nuclear magnetic resonance signal components of the dense sandstone after saturation with water are converted into porosity components according to formula (2):

[0111] (2)

[0112] in, — Porosity component of rock sample i after water saturation, % — The nuclear magnetic resonance signal component of the T2 spectrum of rock sample i after saturation with water, PU; — Cumulative NMR signal in the T2 spectrum of rock sample i after water saturation, PU; — Cumulative NMR signal in the T2 spectrum of rock sample i after centrifugation, PU;

[0113] ③ Based on the porosity components obtained in step ②, plot the relationship between the porosity components and the cumulative value of porosity components after the dense sandstone is saturated with water and the T2 relaxation time.

[0114] Specifically, the calculation of the nuclear magnetic resonance relaxation time and the spatiotemporal conversion coefficient of the pore size includes the following steps:

[0115] ① Extract the nuclear magnetic resonance T2 relaxation time and nuclear magnetic resonance signal data of rock samples 1-3 and 2-3 after saturation with water, and plot the curve of nuclear magnetic resonance signal quantity as a function of T2 relaxation time under semi-logarithmic coordinates.

[0116] ② Extract the pore diameter and pore distribution frequency data from the high-pressure mercury intrusion test results of rock samples 1-2 and 2-2, and plot the curve of pore distribution frequency versus pore diameter under semi-logarithmic coordinates.

[0117] ③ Integrate the curve data from steps ① and ② into the same coordinate system to establish the spatiotemporal conversion curve between nuclear magnetic resonance and high-pressure mercury intrusion, where the top coordinate of the X-axis is the pore diameter, the main coordinate of the Y-axis is the porosity component distribution frequency, the bottom coordinate of the X-axis is the T2 relaxation time, and the secondary coordinate of the Y-axis is the porosity accumulation.

[0118] ④ The difference in the T2 NMR spectrum between the saturated and centrifuged dense sandstone samples represents the porosity component of the movable fluid within the sample. Therefore, the spatiotemporal conversion coefficient is calculated starting with the relaxation time corresponding to the difference in the T2 NMR spectrum between the saturated and centrifuged samples. When the peak value of the NMR signal corresponds one-to-one with the peak value of the high-pressure mercury intrusion porosity distribution frequency, the NMR relaxation time T2 and the pore diameter d value are recorded at this point. Then, the NMR relaxation time T2 value and the spatiotemporal conversion coefficient of the pore size are calculated. It should be noted that during high-pressure mercury intrusion testing, the initial mercury intrusion point is difficult to determine, resulting in significant errors in the obtained macropore data. Therefore, it is necessary to correct the macropores (diameter > 1 μm) by combining the CT scan test results. Data is extracted from the CT scan data according to different pore levels, and a histogram of macropore distribution at different pore levels is plotted.

[0119] The invention will be further illustrated below with examples:

[0120] 1. Rock sample preparation

[0121] Two standard plunger-type tight sandstone samples from the same core section of Block X were selected and numbered 1# and 2#. The core length was required to be 6 cm, with sample 2# serving as a control for the experiments. Sample 1# was cut into three cores with lengths of 1 cm, 1.5 cm, and 3.5 cm using wire cutting, and numbered 1-1, 1-2, and 1-3 for later use. A 2 mm diameter sample was drilled from core 1-1 for CT scanning; core 1-2 was used for high-pressure mercury intrusion porosimetry (HPMI); and core 1-3 was used for both CT scanning and nuclear magnetic resonance (NMR) testing. Sample 2# underwent the same processing as sample 1#, with a 2 mm diameter sample drilled from core 2-1 for CT scanning; core 2-2 was used for HPMI; and core 2-3 was used for both CT scanning and NMR testing. The basic parameters of the rock samples used in this invention are shown in Table 1.

[0122] Table 1 Basic Parameters of Rock Samples

[0123]

[0124] Under the conditions of this invention, the test results of cores #1 and #2 are very consistent. Therefore, the subsequent implementation process of the example is described based on the results of core sample #1.

[0125] 2. CT scan test

[0126] The prepared compact sandstone samples 1-3 and 2-3 with a diameter of 25 mm, and compact sandstone samples 1-1 and 2-1 with a diameter of 2 mm, were dried according to GB / T 29172-2012 "Core Analysis Methods". Then, CT scanning was used to characterize the pore structure of core samples with a diameter >1 μm from the study block. Data was extracted from the dataset according to different pore levels, and histograms of the distribution of different pore levels were plotted. The statistical results of the pore size distribution of core #1 from 3D CT scanning are shown in Table 2.

[0127] Table 21# Statistical table of pore size distribution in 3D CT scan of core samples

[0128]

[0129] 3. High-pressure mercury intrusion test

[0130] The prepared 1-2 and 2-2 tight sandstone samples were dried according to GB / T 29172-2012 "Core Analysis Methods". High-pressure mercury intrusion porosimetry (HPMI) was then performed on the dried samples. A curve showing the variation of pore distribution frequency with pore diameter was plotted under semi-logarithmic coordinates to determine the pore distribution characteristics of the tight sandstone samples. The HPMI data processing results are attached. Figure 6 .

[0131] 4. Gravimetric method + nuclear magnetic resonance testing

[0132] 1) Select 1-3 and 2-3 compact sandstone samples with a diameter of 25 mm, dry them according to GB / T 29172-2012 "Core Analysis Methods" and weigh them;

[0133] 2) Place the dried standard rock samples 1-3 and 2-3 into the core holders respectively, apply a confining pressure of 2MPa using a hand pump, and then use a vacuum pretreatment system to vacuum the standard rock samples for 48 hours.

[0134] 3) Place the distilled water for the experiment in a piston container. Use an ISCO pump to inject the distilled water in the piston container into the core holder containing rock samples 1-3 and 2-3 at constant pressure. During the saturation process, the injection pressure and the confining pressure increase in a stepwise manner, and the difference between the confining pressure and the injection pressure is kept constant at 2 MPa. When the injection pressure reaches the formation pressure of the study block, the saturation process is stopped. The rock sample saturation process is completed in a constant temperature chamber, and the temperature is kept consistent with the formation temperature. The total saturation time is not less than 48 hours.

[0135] 4) Remove rock samples 1-3 and 2-3 from the core holder after water saturation and record their mass. Test the nuclear magnetic resonance T2 spectrum of the rock samples after water saturation.

[0136] 5) Centrifuge the core from step 4) at 10,000 r / min for 180 min and perform nuclear magnetic resonance T2 spectrum analysis after centrifugation.

[0137] 6) Experimental data processing and analysis.

[0138] (1) Establishment of the relationship between nuclear magnetic resonance T2 spectrum signal quantity and saturated water porosity calibration of tight sandstone

[0139] ① The saturated water porosity of the 1-3 tight sandstone samples was calculated using the gravimetric method. The calculation formula is as follows:

[0140] (1)

[0141] in, — Saturated water porosity of rock sample #i, % — Weight of rock sample i after saturation with water, in g; —Weight of rock sample i after drying, in g; — Water density, g / cm3; — Diameter of rock sample #i, in cm; — Length of rock sample #i, in cm;

[0142] ② Based on the T2 spectrum signal components measured by nuclear magnetic resonance, the T2 spectrum nuclear magnetic resonance signal components of the dense sandstone after saturation with water are converted into porosity components according to formula (1):

[0143] (2)

[0144] in, — Porosity component of rock sample i after water saturation, % — The nuclear magnetic resonance signal component of the T2 spectrum of rock sample i after saturation with water, PU; — Cumulative NMR signal in the T2 spectrum of rock sample i after water saturation, PU; — Cumulative NMR signal in the T2 spectrum of rock sample i after centrifugation, PU;

[0145] ③ Based on the porosity components obtained in step ②, plot the relationship between the porosity components and the cumulative porosity components of the tight sandstone after saturation with water and the T2 relaxation time, as shown in the attached figure. Figure 3 As shown.

[0146] (2) Calculation of nuclear magnetic resonance relaxation time T2 and spatiotemporal conversion coefficient of pore size

[0147] ① Extract the T2 relaxation time and NMR signal data of rock samples 1-3 after water saturation, and plot the curve of NMR signal quantity as a function of T2 relaxation time under semi-logarithmic coordinates.

[0148] ② Extract the pore diameter and pore distribution frequency data from the high-pressure mercury intrusion test results of rock samples 1-2, and plot the curve of pore distribution frequency versus pore diameter under semi-logarithmic coordinates.

[0149] ③ Integrate the curve data from steps ① and ② into the same coordinate system to establish a spatiotemporal conversion curve between nuclear magnetic resonance (NMR) and high-pressure mercury injection. The top X-axis represents the pore diameter, and the main Y-axis represents the porosity component distribution frequency. The bottom X-axis represents the T² relaxation time, and the secondary Y-axis represents the porosity accumulation. (See attached figure.) Figure 3 As shown.

[0150] ④ The difference in the T2 NMR spectrum between the saturated and centrifuged dense sandstone samples represents the porosity component of the movable fluid within the sample. Therefore, the spatiotemporal conversion coefficient is calculated starting with the relaxation time corresponding to the difference in the T2 NMR spectrum between the saturated and centrifuged samples. When the peak value of the NMR signal corresponds one-to-one with the peak value of the high-pressure mercury injection porosity distribution frequency, the NMR relaxation time T2 and the pore diameter d value at this point are recorded, and then the NMR relaxation time T2 value and the spatiotemporal conversion coefficient of the pore size are calculated. The full-size pore size distribution results of the dense sandstone obtained under the experimental conditions are attached. Figure 3 As shown.

[0151] like Figure 2 A full-size pore characterization device for dense sandstone is provided, comprising:

[0152] Rock sample preparation module 10 is used to prepare experimental rock samples and control rock samples;

[0153] The CT scan testing module 20 is used to perform CT scan tests on the experimental rock sample and the control rock sample.

[0154] The high-pressure mercury intrusion testing module 30 is used to perform high-pressure mercury intrusion testing on the experimental rock sample and the control rock sample.

[0155] Nuclear magnetic resonance testing module 40 is used to weigh the experimental rock sample and the control rock sample and perform nuclear magnetic resonance testing;

[0156] The characterization result plotting module 50 is used to plot the full-size pore characterization results of dense sandstone based on the test results.

[0157] The device for characterizing full-size pores in dense sandstone provided in this application can perform the method for characterizing full-size pores in dense sandstone provided in the above steps.

[0158] It should be understood that the specific embodiments described above are merely illustrative or explanatory of the principles of the invention and do not constitute a limitation thereof. Therefore, any modifications, equivalent substitutions, improvements, etc., made without departing from the spirit and scope of the invention should be included within the protection scope of the invention. Furthermore, the appended claims are intended to cover all variations and modifications falling within the scope and boundaries of the appended claims, or equivalent forms of such scope and boundaries.

[0159] The following is for reference. Figure 3 The diagram illustrates a structural schematic of an electronic device 100 suitable for implementing embodiments of the present disclosure. The electronic devices in the embodiments of the present disclosure may include, but are not limited to, mobile terminals such as mobile phones, laptops, digital broadcast receivers, PDAs (personal digital assistants), PADs (tablet computers), PMPs (portable multimedia players), in-vehicle terminals (e.g., in-vehicle navigation terminals), and fixed terminals such as digital TVs and desktop computers. Figure 3 The electronic device shown is merely an example and should not be construed as limiting the functionality and scope of the embodiments disclosed herein.

[0160] like Figure 3 As shown, the electronic device 100 may include a processing unit (e.g., a central processing unit, a graphics processing unit, etc.) 101, which can perform various appropriate actions and processes according to a program stored in a read-only memory (ROM) 102 or a program loaded from a storage device 108 into a random access memory (RAM) 103. The RAM 103 also stores various programs and data required for the operation of the electronic device 100. The processing unit 101, ROM 102, and RAM 103 are interconnected via a bus 104. An input / output (I / O) interface 105 is also connected to the bus 104.

[0161] Typically, the following devices can be connected to I / O interface 105: input devices 106 including, for example, touchscreens, touchpads, keyboards, mice, image sensors, microphones, accelerometers, gyroscopes, etc.; output devices 107 including, for example, liquid crystal displays (LCDs), speakers, vibrators, etc.; storage devices 108 including, for example, magnetic tapes, hard disks, etc.; and communication devices 109. Communication device 109 allows electronic device 100 to communicate wirelessly or wiredly with other devices to exchange data. Although an electronic device 100 with various devices is shown in the figure, it should be understood that it is not required to implement or possess all of the devices shown. More or fewer devices may be implemented or possessed alternatively.

[0162] In particular, according to embodiments of this disclosure, the processes described above with reference to the flowcharts can be implemented as computer software programs. For example, embodiments of this disclosure include a computer program product comprising a computer program carried on a computer-readable medium, the computer program containing program code for performing the methods shown in the flowcharts. In such embodiments, the computer program can be downloaded and installed from a network via communication device 109, or installed from storage device 108, or installed from ROM 102. When the computer program is executed by processing device 101, it performs the functions defined in the methods of embodiments of this disclosure.

[0163] The following is for reference. Figure 4 The diagram illustrates a structure of a computer-readable storage medium suitable for implementing embodiments of the present disclosure, the computer-readable storage medium storing a computer program that, when executed by a processor, enables the implementation of the full-size porosity characterization method for dense sandstone as described above.

[0164] This application provides a method, apparatus, and storage medium for characterizing the full-size porosity of tight sandstone using a combination of gravimetric and NMR methods. The aim is to precisely depict the micro- and nano-sized full-size pore structure of tight sandstone oil and gas reservoirs. This method leverages the wide porosity measurement range of NMR, using nuclear magnetic resonance as the fundamental technique for characterizing the full-size pore structure of tight sandstone. The combined use of CT, high-pressure mercury intrusion porosimetry, and gravimetric methods yields more accurate full-size porosity results. Furthermore, the combined measurement methods do not exhibit overlapping porosity measurement ranges and possess self-correction capabilities, thus demonstrating broad application prospects.

[0165] It should be noted that, in this document, relational terms such as "first" and "second" are used merely to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitations, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes said element.

[0166] The above description is merely a specific embodiment of the present invention, enabling those skilled in the art to understand or implement the invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the invention. Therefore, the present invention is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features claimed herein.

Claims

1. A method for characterizing the full-size pores of dense sandstone, characterized in that, The method includes the following steps: Preparation of experimental rock samples and control rock samples; the preparation of experimental rock samples and control rock samples includes: obtaining experimental rock samples and control rock samples of the same specifications; cutting the experimental rock samples into first experimental rock samples, second experimental rock samples and third experimental rock samples of the same specifications; cutting the control rock samples into first control rock samples, second control rock samples and third control rock samples of the same specifications; The experimental rock sample and the control rock sample were subjected to CT scan tests. The CT scan tests included: acquiring the first experimental rock sample and the first control rock sample; after drying, using CT scans to extract data from the data body according to different pore levels, and drawing a histogram of the distribution of different pore levels based on the data. High-pressure mercury intrusion testing was performed on the experimental rock sample and the control rock sample. The high-pressure mercury intrusion testing included: obtaining the second experimental rock sample and the second control rock sample; drying them and then performing high-pressure mercury intrusion testing; plotting the pore distribution frequency versus pore diameter curve; and determining the pore distribution characteristics of the tight sandstone rock sample based on the curve. Weigh the third experimental rock sample and the third control rock sample and perform nuclear magnetic resonance (NMR) testing; the NMR testing includes: drying the third experimental rock sample and the third control rock sample and weighing them; performing NMR T2 spectrum testing on the rock sample after it has been saturated with water; and performing NMR T2 spectrum testing on the rock sample after centrifugation. Based on the test results, a full-size porosity characterization result of dense sandstone was drawn; the characterization result included: establishing the relationship between nuclear magnetic resonance signal quantity and the porosity calibration of saturated water in dense sandstone; calculating the nuclear magnetic resonance relaxation time and the spatiotemporal conversion coefficient of pore size. The establishment of the relationship between nuclear magnetic resonance signal quantity and the saturated water porosity calibration of tight sandstone includes: calculating the saturated water porosity of the tight sandstone samples of the third experimental rock sample and the third control rock sample based on the gravimetric method; and calculating the saturated water porosity of the tight sandstone samples based on the T2 spectrum signal component of nuclear magnetic resonance testing, according to the formula... The nuclear magnetic resonance signal components of dense sandstone after saturation with water were converted into porosity components, and the relationship curves of porosity components and cumulative porosity components as a function of relaxation time were plotted. In the formula, — Porosity component of rock sample i after water saturation, % — The nuclear magnetic resonance signal component of the T2 spectrum of rock sample i after saturation with water, PU; — Porosity component of rock sample i after water saturation, % — Cumulative NMR signal in the T2 spectrum of rock sample i after water saturation, PU; — Cumulative NMR signal in the T2 spectrum of rock sample i after centrifugation, PU; The calculation of nuclear magnetic resonance relaxation time and pore size spatiotemporal conversion coefficient includes: extracting the T2 relaxation time and nuclear magnetic resonance signal data of the third experimental rock sample after saturation with water, and plotting the nuclear magnetic resonance signal quantity as a function of T2 relaxation time under semi-logarithmic coordinates; extracting the pore diameter and pore distribution frequency data from the high-pressure mercury intrusion test results of the second experimental rock sample, and plotting the pore distribution frequency as a function of pore diameter under semi-logarithmic coordinates; integrating the above curve data into the same coordinate system to establish the spatiotemporal conversion coefficient between nuclear magnetic resonance and high-pressure mercury intrusion. The spatiotemporal conversion curve is plotted with the top X-axis representing the pore diameter, the main Y-axis representing the porosity component distribution frequency, the bottom X-axis representing the T2 relaxation time, and the secondary Y-axis representing the porosity accumulation. The spatiotemporal conversion coefficient is calculated starting with the relaxation time corresponding to the difference in the T2 spectrum signal component between the saturated water and centrifuged NMR spectrum. When the peak value of the NMR signal corresponds one-to-one with the peak value of the high-pressure mercury injection pore distribution frequency, the NMR relaxation time T2 and the pore diameter d value are recorded, and then the NMR relaxation time T2 value and the spatiotemporal conversion coefficient of the pore size are calculated.

2. The method for characterizing the full-size pores of dense sandstone according to claim 1, characterized in that, The first experimental rock sample and the first control rock sample are rock samples with a diameter of 2 mm drilled from a core with a length of 1 cm; the second experimental rock sample and the second control rock sample are cores with a length of 1.5 cm and a diameter of 2.5 cm; the third experimental rock sample and the third control rock sample are cores with a length of 3.5 cm and a diameter of 2.5 cm.

3. The method for characterizing the full-size pores of dense sandstone according to claim 1, characterized in that, The CT scan test is used to characterize the pore structure features with a diameter greater than 1 μm.

4. The method for characterizing the full-size pores of dense sandstone according to claim 1, characterized in that, The centrifugation conditions for the nuclear magnetic resonance test are: centrifugation at 10000 r / min for 180 min.

5. The method for characterizing the full-size pores of dense sandstone according to claim 1, characterized in that, The saturation process includes: placing the dried rock sample in a core holder, applying a confining pressure of 2 MPa, and vacuuming for 48 hours; injecting distilled water at constant pressure using an ISCO pump, with the injection pressure and confining pressure increasing in a stepwise manner during the saturation process while maintaining a constant difference of 2 MPa between the confining pressure and the injection pressure; stopping saturation when the injection pressure reaches the formation pressure of the study block; the saturation process is completed in a constant temperature chamber, with the temperature consistent with the formation temperature, and the total saturation time is not less than 48 hours.

6. The method for characterizing the full-size pores of dense sandstone according to claim 1, characterized in that, The macropores, defined as pores with a diameter greater than 1 μm, are corrected based on the CT scan test results.

7. A device for characterizing the full-size pore size of dense sandstone, characterized in that, include: The rock sample preparation module is used to prepare experimental rock samples and control rock samples; A CT scan testing module is used to perform CT scan tests on the experimental rock sample and the control rock sample. A high-pressure mercury intrusion testing module is used to perform high-pressure mercury intrusion testing on the experimental rock sample and the control rock sample. The nuclear magnetic resonance (NMR) testing module is used to weigh the experimental rock sample and the control rock sample and perform NMR testing. The characterization results plotting module is used to plot the full-size porosity characterization results of tight sandstone based on the test results; The nuclear magnetic resonance (NMR) testing module includes: a saturated water T2 spectrum testing unit for performing NMR T2 spectrum testing on rock samples after water saturation; and a post-centrifugation T2 spectrum testing unit for performing NMR T2 spectrum testing on rock samples after centrifugation. The characterization result plotting module includes: a calibration relationship establishment unit, used to calculate saturated water porosity based on the gravimetric method and based on the formula... The NMR signal component is converted into a porosity component; where... — Porosity component of rock sample i after water saturation, % — The nuclear magnetic resonance signal component of the T2 spectrum of rock sample i after saturation with water, PU; — Porosity component of rock sample i after water saturation, % — Cumulative NMR signal in the T2 spectrum of rock sample i after water saturation, PU; — Cumulative NMR signal in the T2 spectrum of rock sample i after centrifugation, PU; The spatiotemporal conversion coefficient calculation unit is used to integrate the curve of nuclear magnetic resonance signal quantity with T2 relaxation time and the curve of high pressure mercury intrusion pore distribution frequency with pore diameter into the same coordinate system. When the peak value of nuclear magnetic resonance signal corresponds one-to-one with the peak value of high pressure mercury intrusion pore distribution frequency, the nuclear magnetic resonance relaxation time T2 and pore diameter d value are recorded to calculate the spatiotemporal conversion coefficient.

8. An electronic device, characterized in that, The electronic device includes: At least one processor; and, A memory communicatively connected to the at least one processor; wherein, The memory stores instructions that can be executed by the at least one processor to enable the at least one processor to perform the method for characterizing full-size pores in tight sandstone according to any one of claims 1-6.

9. A non-transitory computer-readable storage medium storing computer instructions for causing the computer to perform the method for characterizing full-size pores in dense sandstone according to any one of claims 1-6.

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