Method and device for determining micro-topology of pores in tight sandstone reservoirs

Abstract

The present specification provides a method and device for determining the micro-topological structure of the pores of a tight sandstone reservoir, which comprises: determining the pore type, pore size and throat type in a plurality of rock sample slices of the tight reservoir; determining the porosity and permeability; performing high-pressure mercury injection experiments and constant-speed mercury injection experiments and recording the experimental data; determining the pore throat size and distribution characteristics and the main combination configuration relationship between the pore type and the throat type according to the experimental data; processing the experimental data to obtain the fractal dimension under the full pore size; and determining the micro-topological structure characteristic table of the pores of the tight sandstone reservoir according to the above parameters. The scheme can comprehensively understand the pore structure characteristics of the reservoir through the multi-type pore throat topological structure pore throat model, finely characterize the scale, precision and pattern of the pore structure, clearly define the pore structure type, mode and the differences in the reservoir quality and the fluid permeation characteristics under different types of pore structure, and can classify the reservoir.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of oil and gas exploration and development, in particular to a method and device for determining the micro-topological structure of pores in a tight sandstone reservoir. BACKGROUND

[0002] With the development of oil and gas exploration and development technology, the proportion of tight oil has been increasing year by year. The exploitation of tight oil is much more difficult than that of conventional crude oil. Compared with conventional sandstone reservoirs, the micro-pore structure of tight reservoirs is more complex, generally characterized by small pore-throat, uneven pore space distribution, and relatively complex pore-throat configuration relationship. The pore-throat of tight reservoirs is mainly in nanometers and microns, and has strong heterogeneity. The micro-pore structure of tight reservoirs has a direct impact on reservoir storage capacity, percolation capacity, and fluid distribution. Therefore, a clearer understanding of the influence of pore structure on the characteristics of tight reservoirs is conducive to a better understanding of the formation mechanism of tight oil reservoirs, control and optimization of oil and gas reservoir development, and better evaluation of oil and gas reservoirs.

[0003] The classification and evaluation of reservoir pore structure is of great significance, as it can help us better understand the quality of the reservoir, better find high-quality reservoirs, and better control and optimize oil production technology, thereby improving oil production efficiency and benefits. The classification and evaluation of reservoir pore structure refers to the process of selecting appropriate pore-throat structure parameters under the premise of characterizing pore structure, using certain classification and evaluation methods and models, and comprehensively using various data to study and classify the pore structure of the reservoir.

[0004] At present, there are many methods and means for characterizing pore structure. These methods can be divided into direct and indirect methods according to the angle of measurement. Direct observation of pore structure is based on direct observation of the three-dimensional characteristics of pore structure through high-resolution analytical equipment. However, a large number of nanoscale pores and throats develop in tight pores, which are below the detection limit of the instrument. Therefore, many pores in tight reservoirs and their connectivity cannot be detected by direct observation, which makes the test results less accurate. Indirect testing methods can obtain pore-throat distribution characteristics through appropriate testing methods, but they cannot directly reflect the pore structure pattern. Different methods have different testing principles, so there are differences in measurement accuracy and range.

[0005] With the deepening of exploration and development, the characterization of pore structure and reservoir quality by a single method cannot meet the needs of current development, so detailed and in-depth research on pore structure and reservoir quality is needed. SUMMARY

[0006] The purpose of the present application is to provide a method and device for determining the micro-topological structure of pores in a tight sandstone reservoir, to provide a more detailed and in-depth research method for the pores in a tight sandstone reservoir.

[0007] To solve the above technical problems, the first aspect of the present specification provides a method for determining the micro-topological structure of pores in a tight sandstone reservoir, comprising: determining the pore type and pore size of a plurality of rock sample slices of the tight reservoir; determining the throat type of the plurality of rock sample slices; determining the porosity and permeability of the plurality of rock samples; recording experimental data when the plurality of rock samples are respectively subjected to high-pressure mercury injection experiments and constant-rate mercury injection experiments; determining the pore throat size and distribution characteristics in the rock samples according to the experimental data; determining the main combination and configuration relationship between the pore type and the throat type of the plurality of rock sample slices; processing the experimental data to obtain the fractal dimension under the full pore size; and determining a micro-topological structure characteristic table of the pores in the tight sandstone reservoir according to the main combination and configuration relationship between the pore type and the throat type, the porosity, the permeability, and the fractal dimension of the full pore size, wherein the micro-topological structure characteristic table includes a plurality of micro-topological structure categories of the tight rock, and the micro-topological structure characteristic table is used to determine an oil and gas exploration or development scheme for a target area.

[0008] In some embodiments, the micro-topological structure category of the pores in the tight sandstone reservoir includes at least one of the following: a ball-stick net-like structure, a star chain net-like structure, a discrete tree-like structure, and a complex tube bundle-like structure.

[0009] In some embodiments, determining the micro-topology class of the tight sandstone reservoir pore includes: determining the micro-topology class of the rock sample as a ball-stick network structure in the case that the main combined configuration relationship of the pore type and the throat type is a large inter-particle pore-wide sheet-shaped throat combination, the porosity is greater than 10%, the permeability is greater than 0.1 mD, the mercury intrusion curve has a platform, the fractal dimension reflecting the large pore is distributed in 2.26-2.4, and the fractal dimension reflecting the wide throat is distributed in 2.04-2.11; and / or determining the micro-topology class of the rock sample as a star-chain network structure in the case that the main combined configuration relationship of the pore type and the throat type is a small-middle inter-particle pore-narrow sheet-shaped throat combination, the porosity is 8%-12%, the permeability is 0.05 mD-0.1 mD, the mercury intrusion curve has a local platform feature, the fractal dimension reflecting the small pore is distributed in 2.46-2.81, and the fractal dimension reflecting the narrow throat is distributed in 2.04-2.16; and / or determining the micro-topology class of the rock sample as a discrete tree structure in the case that the main combined configuration relationship of the pore type and the throat type is an intra-particle pore-narrow sheet-shaped throat combination, the porosity is 5%-10%, the permeability is 0.02 mD-0.06 mD, the mercury intrusion curve does not have a platform, the mercury saturation and the pressure are in an exponential relationship, the fractal dimension reflecting the small pore is distributed in 2.32-2.81, and the fractal dimension reflecting the narrow throat is distributed in 2.04-2.16; and / or determining the micro-topology class of the rock sample as a complex pipe bundle structure in the case that the main combined configuration relationship of the pore type and the throat type is a micro-pore-extremely narrow sheet-shaped and pipe bundle-shaped throat combination, the porosity is 5%, the permeability is less than 0.03 mD, the mercury intrusion curve does not have a platform feature, and the fractal dimension reflecting the extremely narrow throat is distributed in 2.08-2.16.

[0010] In some embodiments, after the micro-topological structure feature table of the dense sandstone reservoir pores is determined, the micro-topological structure category of the dense sandstone reservoir pores in the target area is further determined by the following method: determining the pore type and pore size in the rock sample slice of the target area; determining the throat type in the rock sample slice of the target area; determining the porosity and permeability of the rock sample of the target area; recording the experimental data when the high-pressure mercury injection experiment and the constant-rate mercury injection experiment are respectively performed on the rock sample of the target area; determining the pore throat size and distribution characteristics in the rock sample according to the experimental data; determining the main combination and configuration relationship of the pore type and throat type in the rock sample slice of the target area; processing the fractal dimension of the full-pore throat according to the experimental data; comparing the main combination and configuration relationship of the pore type and throat type, the porosity, the permeability, and the fractal dimension of the full-pore throat of the rock sample of the target area with the micro-topological structure feature table of the dense sandstone reservoir pores, and taking the target micro-topological structure category in the micro-topological structure feature table that is closest to each feature of the rock sample of the target area as the micro-topological structure category of the rock sample of the target area, so as to determine the oil and gas exploration or development scheme according to the micro-topological structure category of the rock sample of the target area.

[0011] In some embodiments, the experimental data is processed to obtain the fractal dimension under the full pore size, including: determining the pore throat size and pore throat type corresponding to each pressure data of the high-pressure mercury injection experiment and the constant-rate mercury injection experiment; taking the pressure data and the mercury saturation data in the experimental data of the high-pressure mercury injection experiment as logarithms to construct a first data set, and the experimental data in the first data set is divided into the following four categories according to the pore throat size and type: large pore, wide throat, small pore, and narrow throat; for the experimental data of each category in the first data set, a fitting straight line of the experimental data is respectively determined to obtain a plurality of fitting straight lines corresponding to the high-pressure mercury injection experiment; the fractal dimension reflecting the corresponding pore throat category is determined according to the slope of the fitting straight line; taking the pressure data and the mercury saturation data in the experimental data of the constant-pressure mercury injection experiment as logarithms to construct a second data set, and the data in the second data set is divided into the following four categories according to the pore throat size and type: large pore, wide throat, small pore, and narrow throat; for the experimental data of each category in the second data set, a fitting straight line of the experimental data is respectively determined to obtain a plurality of fitting straight lines corresponding to the constant-pressure mercury injection experiment; the fractal dimension reflecting the corresponding pore throat category is determined according to the slope of the fitting straight line; the plurality of fitting straight lines corresponding to the high-pressure mercury injection experiment and the plurality of fitting straight lines corresponding to the constant-pressure mercury injection experiment are spliced to obtain the fractal dimension under the full pore size.

[0012] In some embodiments, the plurality of fitting straight lines corresponding to the high-pressure mercury injection experiment and the plurality of fitting straight lines corresponding to the constant-pressure mercury injection experiment are spliced to obtain the fractal dimension under the full pore size, including: splicing the plurality of fitting straight lines corresponding to the high-pressure mercury injection experiment and the plurality of fitting straight lines corresponding to the constant-pressure mercury injection experiment, and the splicing value adopts the average value of the small pore throat and the large pore throat demarcation points rg2 and rh2 corresponding to the plurality of fitting straight lines of the high-pressure mercury injection experiment and the constant-speed mercury injection experiment.

[0013] In some embodiments, the fractal dimension reflecting the corresponding pore throat category is determined according to the slope of the fitting straight line, including: calculating the sum of the slope of the target fitting straight line and 2; and taking the sum as the fractal dimension reflecting the target pore throat category, which is the pore throat category corresponding to the experimental data associated with the target fitting straight line.

[0014] The second aspect of the present specification provides a device for determining the micro-topological structure of the pores of a tight sandstone reservoir, including: a first determination unit configured to determine the pore type and pore size of a plurality of rock sample slices of a tight reservoir; a second determination unit configured to determine the throat type of the plurality of rock sample slices; a third determination unit configured to determine the porosity and permeability of the plurality of rock samples; a recording unit configured to record experimental data when the plurality of rock samples are subjected to high-pressure mercury injection experiments and constant-speed mercury injection experiments respectively; a fourth determination unit configured to determine the pore throat size and distribution characteristics of the rock samples according to the experimental data; a fifth determination unit configured to determine the main combination and configuration relationship between the pore type and the throat type of the plurality of rock sample slices; a processing unit configured to process the experimental data to obtain the fractal dimension under the full pore size; and a sixth determination unit configured to determine a micro-topological structure characteristic table of the pores of the tight sandstone reservoir according to the main combination and configuration relationship between the pore type and the throat type, the porosity, the permeability, and the fractal dimension of the full pore throat, wherein the micro-topological structure characteristic table includes a plurality of micro-topological structure categories of the tight rock, and the micro-topological structure characteristic table is used to determine an oil and gas exploration or development scheme for a target area.

[0015] The third aspect of the present specification provides an electronic device, including: a memory and a processor, which are in communication connection with each other, and the memory stores computer instructions, and the processor implements the steps of the method of any one of the first aspect by executing the computer instructions.

[0016] The fourth aspect of the present specification provides a computer storage medium, which stores computer program instructions, and the computer program instructions are executed to implement the steps of the method of any one of the first aspect.

[0017] The method and device for determining the micro-topological structure of the pores of a tight sandstone reservoir provided by the specification are proposed, and a method for classifying and characterizing the micro-topological structure of the pores of a tight sandstone reservoir based on the topological structure and pore-throat configuration relationship is proposed. Different types of pore network models are based on the topological structure, and the combination relationship of different types of pores and throats in the tight sandstone reservoir is combined with the indirect test results of the pore structure. The pore structure model (i.e., the micro-topological structure category) can directly reflect the pore-throat characteristics, determine the pore and throat types, sizes, configuration relationships, pore-throat distribution characteristics, etc. Different pore structure models (i.e., micro-topological structure categories) based on the topological structure can be comparable to the test results of different methods (such as mercury injection), and different pore structure models (i.e., micro-topological structure categories) can be verified by test data.

[0018] Through the multi-type pore-throat topological structure pore-throat model, the pore structure characteristics of the reservoir are more comprehensively understood, the fine characterization in the scale, precision, and pattern of the pore structure is realized, the pore structure types, modes, and the differences in the reservoir quality and the fluid permeation characteristics under different types of pore structure are determined, the reservoir can be classified, the foundation for the next step of studying the reservoir quality difference mechanism and the difference distribution characteristics is laid, and the characterization and evaluation of the tight reservoir are of great significance, and reliable geological basis can be provided for the later exploration and development of the oilfield. BRIEF DESCRIPTION OF DRAWINGS

[0019] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the drawings needed to be used in the embodiments or the prior art description will be briefly introduced. Obviously, the drawings in the following description are only some embodiments described in the present application, and other drawings can be obtained by those skilled in the art without any creative labor.

[0020] Figure 1 A flowchart of a method for determining the micro-topological structure of the pores of a tight sandstone reservoir provided by the specification is shown;

[0021] Figure 2 A pore type chart of a reservoir (Chang 7 section of the West 233 block) of a certain block (the West 233 block) is shown;

[0022] Figure 3 A pore type distribution histogram of a reservoir (Chang 7 section of the West 233 block) of a certain block (the West 233 block) is shown;

[0023] Figure 4 A throat type chart of a reservoir (Chang 7 section of the West 233 block) of a certain block (the West 233 block) is shown;

[0024] Figure 5 A tight sandstone high-pressure mercury injection capillary pressure graph of a reservoir (Chang 7 section of the West 233 block) of a certain block (the West 233 block) is shown;

[0025] Figure 6 The four types of high-pressure mercury injection capillary pressure curves of tight sandstone of Chang 7 reservoir in a certain block (West 233 block) are shown;

[0026] Figure 7 The high-pressure mercury injection pore throat radius distribution diagram of tight sandstone of 7th member reservoir in a certain block (West 233 block) is shown;

[0027] Figure 8 The type I constant-rate mercury injection curve and throat radius distribution histogram are shown;

[0028] Figure 9 The type II constant-rate mercury injection curve and throat radius distribution histogram are shown;

[0029] Figure 10 The pore radius distribution histogram measured by constant-rate mercury injection in the study area is shown;

[0030] Figure 11 The throat radius distribution histogram measured by constant-rate mercury injection in the study area is shown;

[0031] Figure 12 The pore throat combination type diagram of tight sandstone of Chang 7 reservoir in a certain block (West 233 block) is shown;

[0032] Figure 13 The high-pressure mercury injection fractal dimension fitting curve of tight sandstone sample of Chang 7 member in the study area is shown;

[0033] Figure 14 The constant-rate mercury injection fractal dimension fitting curve of tight sandstone sample of Chang 7 member in the study area is shown;

[0034] Figure 15 The correlation between porosity and high-pressure mercury injection fractal dimension of tight sandstone sample of Chang 7 member in the study area is shown;

[0035] Figure 16 The correlation between porosity and constant-rate mercury injection fractal dimension of tight sandstone sample of Chang 7 member in the study area is shown;

[0036] Figure 17 The full pore size distribution characteristics of high-pressure mercury injection and constant-rate mercury injection of tight sandstone sample of Chang 7 member in the study area are shown;

[0037] Figure 18 The pore throat topology structure of tight sandstone of Chang 7 reservoir in a certain block (West 233 block) is shown;

[0038] Figure 19 The microscopic pore throat topology structure pattern diagram of tight sandstone of 7th member reservoir in a certain block (West 233 block) is shown;

[0039] Figure 20A schematic diagram of a table of micro-topological structure characteristics of a tight sandstone reservoir pore is shown. DETAILED DESCRIPTION

[0040] In order for those skilled in the art to better understand the technical solutions in the present application, the technical solutions in the embodiments of the present application will be clearly and completely described in the following with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, rather than all the embodiments of the present application. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative work should belong to the scope of protection of the present application.

[0041] The present specification provides a method for determining the micro-topological structure of a tight sandstone reservoir pore, as shown in the following steps. Figure 1 The present specification provides a method for determining the micro-topological structure of a tight sandstone reservoir pore, as shown in the following steps.

[0042] S10: Determine the pore type and pore size in the plurality of rock sample slices of the tight reservoir.

[0043] For example, through observation of the casting slices of 45 coring wells in the study area and scanning electron microscope image analysis, the reservoir pore types are more, mainly intergranular pores, intragranular pores and micropores, and there are also microfractures formed due to particle breakage. The pore radius ranges from 2 μm to 115 μm, and the average pore radius is 35 μm. The overall is in the range of small pores, which is a typical tight reservoir.

[0044] The conventional casting slices can only qualitatively to semi-quantitatively characterize the larger pore and throat type, size and occurrence due to the limited magnification, but it is difficult to accurately measure the small pores and throats of the tight reservoir. Therefore, combined with the scanning electron microscope, the micro-pore characteristics and size and combination relationship can be more accurately identified.

[0045] Through observation of the sample casting slices and scanning electron microscope image analysis, the reservoir pore types are determined, the main pore types are determined, and the pore radius range and average pore radius are determined.

[0046] (1) Intergranular pore

[0047] The intergranular pores in the Chang 7 reservoir in the study area are mainly primary residual intergranular pores and mixed intergranular pores, which can be subdivided into large intergranular pores and small intergranular pores according to the pore radius. The intergranular pores are the most common in the study area, but the pore distribution is uneven and the heterogeneity is strong. The primary residual intergranular pores are the pores that are not filled due to the influence of compaction and cementation during burial, and the shape is inverted triangular. Most of the mixed intergranular pores are related to dissolution, and some pores are generated by the dissolution of the contact fluid of the detrital particles or the dissolution of the cement. The intergranular pores have a relatively large radius, generally between 15 μm and 115 μm, and have good connectivity and can easily form favorable reservoir space (as shown in a and b in Figure 2 ).

[0048] (2) Intragranular pores

[0049] The intragranular pores in the study area are mainly intragranular dissolution pores. Due to the easy dissolution of feldspar, rock debris and a small amount of mica, secondary dissolution pores are formed in the interior of the particles. The pore diameter is mainly between 5 μm and 60 μm. The edges of the dissolved detrital particles also show irregular shapes due to the dissolution of the local parts by the fluid. The development degree and distribution characteristics of the intragranular dissolution pores are related to the detrital composition, resulting in uneven distribution. Some feldspar particles can be completely dissolved to form a mold hole (as shown in c and d in Figure 2 ).

[0050] (3) Micro-pores

[0051] The micro-pores develop in the interstitial material and have a small pore diameter, mostly between 2 μm and 10 μm, which is difficult to identify under an ordinary electron microscope and is usually identified by a scanning electron microscope. The micro-pores are mostly distributed in groups to form micro-pore groups, and the connectivity between the pores and the throats is poor (as shown in e in Figure 2 ).

[0052] (4) Micro-fractures

[0053] The micro-fractures are less developed in the study area and develop in local areas. The width of the micro-fractures is generally less than 10 μm, and the connectivity with the surrounding pores is good (as shown in f in Figure 2 ).

[0054] It is found by counting the pore types in the study area that the content of mixed intergranular pores is the highest, followed by the primary residual intergranular pores and the intragranular dissolution pores, and the contents of the micro-pores and the micro-fractures are low (as shown in Figure 3 ). Figure 3 The ordinate in the figure means the content.

[0055] S20: determining the throat types in the plurality of rock sample thin sections.

[0056] The size and shape of the throat affect the flow of fluid in the pore system, thus affecting the permeability of the rock, and further affecting the reservoir performance of the reservoir. The throat type and the main throat type of the reservoir development are determined through cast thin section and scanning electron microscopy analysis.

[0057] The size and shape of the throat affect the flow of fluid in the pore system, thus affecting the permeability of the rock, and further affecting the reservoir performance of the reservoir. The cast thin section and scanning electron microscopy analysis show that the main development of the reservoir in the Chang 7 member of the study area is flaky throat, followed by pipe bundle throat, and less development of necked throat.

[0058] The flaky throat can be flaky or flaky curved in shape (such as a, c shown in Figure 4 According to the width of the throat, it can be divided into wide flaky throat, narrow flaky throat, and very narrow flaky throat. Such throat is mostly related to compaction. The clastic particles are arranged in a certain direction in the reservoir under the action of strong pressure and form flaky throat.

[0059] The pipe bundle throat (such as d shown in Figure 4 ) mainly develops in the cement and matrix. The primary pores are completely filled during burial, resulting in almost complete loss of porosity. The micropores in the matrix and cement can be pores or throats. These micropore groups are connected by small throats, and these throats together form a pipe bundle throat.

[0060] The necked throat (such as b shown in Figure 4 ) generally develops in the parts where dissolution and compaction are relatively strong. The necked throat is formed between the particles. When the particles are compacted during deposition, the particles are in close contact, and the interparticle pores can be partially preserved, but the throats are compressed and narrowed. Such throats are mostly found in reservoirs with point contact and line contact between particles.

[0061] S30: Determine the porosity and permeability of the plurality of rock samples.

[0062] The porosity and permeability can be obtained by existing methods, which will not be described here.

[0063] S40: Record the experimental data when the high-pressure mercury injection experiment and the constant-speed mercury injection experiment are respectively performed on the plurality of rock samples.

[0064] S50: Determine the pore throat size and distribution characteristics in the rock samples according to the experimental data.

[0065] (1) High-pressure mercury injection characterization of pore throat size and distribution characteristics

[0066] By analyzing the morphology of high-pressure mercury intrusion and extrusion curves, as well as the displacement pressure and characteristics of various parameters in tight sandstone samples, mercury intrusion curves can be classified into different types. Using high-pressure mercury intrusion data, the distribution range of pore throat radii can be plotted, and the peak characteristics of the pore throat radius distribution curves can be analyzed to clarify the distribution range and peak value of different types of pore throat radii.

[0067] By analyzing the morphology and parameter characteristics of high-pressure mercury intrusion curves in the tight sandstone samples of the Chang 7 section of the study area, the mercury intrusion curves can be divided into four types: Type I, Type II, Type III, and Type IV. The displacement pressure (i.e., the pressure at which the curves are displaced from Type I to Type IV) is... Figure 5 The average pressure at which mercury begins to enter in large quantities increases significantly, from 0.67 MPa to 5.37 MPa. Meanwhile, the maximum pore throat radius decreases, from 1.097 μm to 0.267 μm. Type I has the highest maximum mercury saturation at 95.54% and a median average pore throat radius of 0.263 μm, while Type IV has the lowest maximum mercury saturation at 48.57% and a median average pore throat radius of 0.03 μm. Figure 5 A collection of high-pressure mercury intrusion capillary pressure maps is shown for tight sandstone reservoirs. Figure 6 The high-pressure mercury capillary pressure maps for types I to IV are shown respectively.

[0068] Based on the correspondence between pressure data and pore throat data, and high-pressure mercury intrusion data, the distribution range of pore throat radius was plotted. This visually demonstrates that the pore throat radius of the seven samples in the study area exhibits a unimodal distribution (e.g., ...). Figure 7 (As shown). The pore throat radii are mainly distributed between 0.0036 μm and 1.566 μm. Type I curves show pore throat radii ranging from 0.267 μm to 1.566 μm, with a peak value of 0.541 μm; Type II curves show pore throat radii ranging from 0.015 μm to 0.541 μm, with a peak value of 0.134 μm; Type III curves show pore throat radii ranging from 0.009 μm to 0.179 μm, with a peak value of 0.067 μm; and Type IV curves show pore throat radii ranging from 0.0036 μm to 0.134 μm, with a peak value of 0.036 μm. Compared to the pore throat sizes analyzed and measured under conventional cast thin sections, high-pressure mercury intrusion can more accurately and precisely identify the pore throat distribution. However, due to the influence of the maximum mercury saturation, some smaller pores are difficult to inject mercury under external pressure, resulting in the inability to characterize pore throats with smaller radii using high-pressure mercury intrusion.

[0069] (2) Constant-rate mercury intrusion characterization of pore throat size and distribution characteristics

[0070] The characteristics of constant-rate mercury intrusion curves and the features of displacement pressure, total throat mercury saturation, final total mercury saturation, average throat radius, porosity, permeability, and maximum connecting throat radius of tight sandstone samples were analyzed.

[0071] By analyzing the constant-rate mercury injection curve characteristics and related pore structure parameters of the tight sandstone samples of the Chang 7 Member in the study area, it is found that there are two types of constant-rate mercury injection curves in the study area. The first type is characterized by low displacement pressure, high total throat mercury saturation and final total mercury saturation, and high average throat radius (as shown in Figure 8 ). The second type is characterized by high displacement pressure, low total throat mercury saturation and final total mercury saturation, and low average throat radius (as shown in Figure 9 ). The porosity of the type I sample is 10.713%, the permeability is 0.087 mD, the maximum connected throat radius is 0.876 μm, the throat mercury saturation and the final total mercury saturation curves are basically consistent when the mercury injection pressure is below 1 MPa, but start to separate as the pressure increases. The final total mercury saturation is 64.103%, and the total throat mercury saturation is 38.483%. The porosity of the type II sample is 6.28%, the permeability is 0.013 mD, the maximum connected throat radius is 0.365 μm, the throat mercury saturation and the final total mercury saturation curves are basically consistent when the mercury injection pressure is below 3 MPa, but start to separate as the pressure increases. The final total mercury saturation is 32.357%, and the total throat mercury saturation is 29.382%. Through the analysis of the constant-rate mercury injection experimental data, it can be concluded that the porosity and permeability of different sandstone samples are different, and the pore radius and throat radius also have great differences (as shown in Figure 10 and Figure 11 ). For the samples with good physical properties, the pore radius mainly ranges from 130 μm to 260 μm, the average radius is about 196.6 μm, the throat range is from 0.2 μm to 0.7 μm, the average throat radius is 0.525 μm, and the maximum connected throat radius is 0.876 μm. For the samples with poor physical properties, the pore radius mainly ranges from 80 μm to 160 μm, the average radius is about 124.2 μm, the throat range is from 0.04 μm to 0.22 μm, the average throat radius is 0.18 μm, and the maximum connected throat radius is 0.365 μm. The research shows that the physical properties of the tight sandstone reservoir of the Chang 7 Member in the West 233 block are mainly affected by the pore radius, throat radius, and maximum connected throat radius.

[0072] S60: determining a main combination configuration relationship of the pore type and the throat type in the plurality of rock sample slices.

[0073] The combination configuration relationship of the pores and the throats is different, which can form different pore structure characteristics. According to the pore and throat characteristics, the reservoir pore-throat configuration relationship is classified by combining the cast slice, scanning electron microscope, high-pressure mercury injection, and other data. For example, the combination of large intergranular pores and wide sheet-shaped throats, the combination of small-medium intergranular pores and narrow sheet-shaped throats, the combination of intragranular pores and narrow sheet-shaped throats, the combination of micro-pores and extremely narrow sheet-shaped and pipe bundle-shaped throats.

[0074] Research shows that the pore structure of tight sandstone is more complex than that of conventional sandstone, and there are various types of pores and throats in the same rock sample at the same depth. Different combinations of these types (i.e. main connection relationship) will form different pore structure characteristics. According to the characteristics of pores and throats, combined with casting thin section, scanning electron microscope, high pressure mercury injection and other data, the pore throat combination relationship of Chang 7 member reservoir in the study area is classified (Table 1). It is mainly divided into four types, which are large intergranular pore-wide sheet throat combination, small-middle intergranular pore-narrow sheet throat combination, intragranular pore-narrow sheet throat combination, micro-pore-extremely narrow sheet, pipe bundle throat combination.

[0075] Table 1 Interpretation standard of pore throat combination relationship of Chang 7 member tight sandstone in west 233 block

[0076]

[0077]

[0078] The large intergranular pore-wide sheet throat combination mainly shows that the pore size is large, and the primary residual intergranular pore and intragranular dissolved pore are mainly developed. The relative content of large intergranular pore is greater than 50%, the content of intragranular dissolved pore is greater than 30%, and the pore radius is between 65 μm and 115 μm. The throat type is mainly wide sheet throat, the content is greater than 50%, the narrow sheet and pipe bundle throats are less than 50% in total, and the necking type throat is occasionally seen. The throat radius is 0.5 μm to 2 μm. This kind of pore throat combination type is often developed in massive fine sandstone facies, cross-bedding fine sandstone facies and parallel bedding fine sandstone facies, and the reservoir property is good (such as a in Figure 12 ).

[0079] The small-middle intergranular pore-narrow sheet throat combination shows that the pore size is small, and the small-middle primary residual intergranular pore is mainly developed, the content is greater than 50%, and the intragranular dissolved pore is less, the content is greater than 20%. The content of large pore intergranular pore and micro-pore is less, and the pore radius is between 25 μm and 65 μm. The throat type is mainly narrow sheet throat, the content is greater than 50%, and the content of wide sheet and pipe bundle throats is relatively small. The throat radius is 0.3 μm to 1 μm. This kind of pore throat combination type is often developed in deformed tectonic siltstone facies and wavy bedding siltstone facies, and a small amount of it is also developed in parallel bedding fine sandstone facies and massive fine sandstone facies. The reservoir property is relatively good (such as b in Figure 12 ).

[0080] Intragranular pore-pore throat combination type: Intragranular dissolved pore is the main type, and its content is more than 50%. Small-medium primary intergranular pore and micropore group are the second, and their contents are less than 20%. The pore radius is small, between 5 μm and 25 μm. The throat type is mainly narrow sheet-shaped throat, and its content is more than 50%. The second is pipe bundle-shaped throat, and its content is relatively less than 30%. Wide sheet-shaped throat and neck-shaped throat are less. The average throat radius is less than 0.5 μm. This pore-throat combination type is often developed in argillaceous pebbly siltstone facies, wavy bedding siltstone facies, argillaceous banded siltstone facies, and a small amount of massive fine sandstone facies. The reservoir property is medium (as shown in c of FIG. 6). Figure 12

[0081] Micropore-extremely narrow sheet-shaped and pipe bundle-shaped throat combination type: Micropore is the main type, and its content is more than 50%. The micropore is mainly developed in clay minerals and argillaceous cement. The micropore radius is less than 5 μm. The throat type is mainly narrow sheet-shaped throat and pipe bundle-shaped throat and part of neck-shaped throat. The average throat radius is less than 0.5 μm. This pore-throat combination type is often developed in horizontal bedding argillaceous siltstone facies, plant debris-containing argillaceous siltstone facies, and a small amount of argillaceous banded siltstone facies. The reservoir property is poor (as shown in d of FIG. 6). Figure 12

[0082] Different pore-throat configuration relationship porosity and permeability can be plotted into a pore-permeability cross plot, and the porosity and permeability characteristics of different pore-throat configuration relationship samples are analyzed to determine the physical property difference of different pore-throat configuration relationship.

[0083] S70: Processing the experimental data to obtain the fractal dimension under the full pore diameter.

[0084] Based on the fractal theory, the fractal dimension of the pore structure is analyzed by using the segmented relationship between the logarithm of the mercury saturation Lg(SHg) and the logarithm of the capillary pressure Lg(Pc) obtained by the high-pressure mercury injection and the constant-speed mercury injection. Moreover, because the mercury injection processes of the high-pressure mercury injection and the constant-speed mercury injection are relatively consistent, the two experimental methods can be combined to obtain the fractal dimension of the full pore diameter of the tight sandstone.

[0085] ​​Most of the fractal researches on the pore structure of tight sandstone are based on single mercury injection technology. However, both high pressure mercury injection and constant rate mercury injection have their own limitations, which makes it difficult to accurately characterize the pore structure of tight sandstone. Constant rate mercury injection can characterize the size and distribution of pore throat, but due to the limitation of the maximum mercury injection pressure, it cannot characterize the pore throat below 0.12 μm. High pressure mercury injection can measure the pore throat below 0.12 μm, but it cannot measure the large pore distribution connected with narrow slit-shaped throat, while constant rate mercury injection can meet the requirement. Therefore, the two methods are combined to characterize the full pore throat characteristics. Since the mercury injection process of high pressure mercury injection and constant rate mercury injection is relatively consistent, it is effective to obtain the fractal dimension of the full pore size of tight sandstone in the study area by combining the two experimental methods.

[0086] Based on the fractal theory, the relationship between the logarithm of mercury saturation Lg(SHg) and the logarithm of capillary pressure Lg(Pc) obtained by high pressure mercury injection and constant rate mercury injection is analyzed to determine the fractal dimension of the pore structure. The following relationship is derived based on the related calculation model of previous studies:

[0087] Lg(SHg) = (D-2)Lg(Pc) + C (1)

[0088] where D is the fractal dimension; S Hg is the mercury saturation; Pc is the capillary pressure; and C is the constant.

[0089] (1) High pressure mercury injection multi-fractal dimension

[0090] Based on the mercury saturation and capillary pressure data obtained by high pressure mercury injection experiment of tight sandstone samples, the characteristics of high pressure mercury injection fractal fitting curve are analyzed. It is determined that the fractal fitting curve can be divided into several sections, and the types of pores and throats corresponding to different fractal intervals are determined. The range of fractal dimension value and the correlation coefficient of fitting curve are also determined.

[0091] The high pressure mercury injection fractal fitting curve often shows four sections, which can be corresponded to large pores, wide throats, small pores and narrow throats, respectively. The correlation coefficient R of each sample fitting curve is large, and the correlation is good, which is greater than 0.80. This indicates that each section has strong representativeness and accuracy and has multi-dimensional fractal characteristics.

[0092] (2) Constant rate mercury injection multi-fractal dimension

[0093] Based on the mercury saturation and capillary pressure data obtained by constant rate mercury injection experiment of tight sandstone samples, the characteristics of constant rate mercury injection fractal fitting curve are analyzed. It is determined that the fractal fitting curve can be divided into several sections, and the types of pores and throats corresponding to different fractal intervals are determined. The range of fractal dimension value and the correlation coefficient of fitting curve are also determined.

[0094] According to the analysis of the data of the high-pressure mercury injection and the constant-speed mercury injection of the tight sandstone samples in the research area, it is found that the fractal fitting curve of the high-pressure mercury injection shows the characteristics of four-section distribution, which can correspond to the large pore, wide throat, small pore and narrow throat respectively (as shown in Figure 13 The correlation coefficient R of each sample fitting curve is relatively large and the correlation is good, which is distributed between 0.85 and 0.99, indicating that each section has strong representativeness and accuracy. Therefore, it can be confirmed that the pore structure of the samples in the research area is relatively complex and has multi-dimensional fractal characteristics. As shown in Table 2 below.

[0095] In Table 2, Dg1 represents the fractal dimension of the fitting curve of the large pore, and R 2 on the right side of Dg1 represents the correlation coefficient of the fitting curve of the large pore and the porosity and permeability; Dg2 represents the fractal dimension of the fitting curve of the wide throat, and R 2 on the right side of Dg2 represents the correlation coefficient of the fitting curve of the wide throat and the porosity and permeability; Dg3 represents the fractal dimension of the fitting curve of the small pore, and R 2 on the right side of Dg3 represents the correlation coefficient of the fitting curve of the small pore and the porosity and permeability; Dg4 represents the fractal dimension of the fitting curve of the narrow throat, and R 2 on the right side of Dg4 represents the correlation coefficient of the fitting curve of the narrow throat and the porosity and permeability.

[0096] Table 2 Fractal dimensions of high-pressure mercury injection of tight sandstone samples in Chang 7 section of the research area

[0097]

[0098] According to the characteristics of the fractal dimension fitting curve of the constant-speed mercury injection of the tight sandstone samples in the Chang 7 section of the research area, it is found that the fitting curve is mainly three-section or four-section. However, whether it is three-section or four-section, it can effectively distinguish the large pore and the wide throat, and the difference is that the three-section small pore and narrow throat are difficult to distinguish on the graph, while the four-section can effectively distinguish the small pore and narrow throat (as shown in Figure 14 Compared with the high-pressure mercury injection, the constant-speed mercury injection has a larger correlation coefficient R and better correlation in characterizing the large pore and wide throat, so it can more effectively identify the larger pores and throats in the tight sandstone reservoir (as shown in Table 3 below).

[0099] In Table 3, Dh1 represents the fractal dimension of the fitting curve of the large pore, and R 2 on the right side of Dh1 represents the correlation coefficient of the fitting curve of the large pore and the porosity and permeability; Dh2 represents the fractal dimension of the fitting curve of the wide throat, and R 2Dh2 represents the correlation coefficient of the fitting curve of the reaction wide throat with porosity and permeability; Dh3 represents the fractal dimension of the fitting curve of the reaction small pore, and R 2 Dh2 represents the correlation coefficient of the fitting curve of the reaction wide throat with porosity and permeability; Dh3 represents the fractal dimension of the fitting curve of the reaction small pore, and R 2 Dh2 represents the correlation coefficient of the fitting curve of the reaction wide throat with porosity and permeability.

[0100] Table 3 Fractal dimension of constant-rate mercury injection of Chang 7 tight sandstone samples in the study area

[0101]

[0102] The size and distribution of pore throats in tight sandstone reservoirs can be quantitatively characterized by high-pressure mercury injection and constant-rate mercury injection experiments. High-pressure mercury injection can characterize large pores, but it has limited ability to characterize small pores and throats. Constant-rate mercury injection has a constant and low injection rate, which can distinguish between pores and throats by pressure changes. Therefore, high-pressure mercury injection and constant-rate mercury injection are combined to characterize the size and distribution characteristics of pores and throats.

[0103] (3) Full pore size fractal dimension combining high-pressure mercury injection and constant-rate mercury injection

[0104] By observing the fractal dimension fitting curve characteristics of high-pressure mercury injection and constant-rate mercury injection, the numerical ranges of large pore fractal dimension (Dg1), wide throat fractal dimension (Dg2), small pore fractal dimension (Dg3), and narrow throat fractal dimension (Dg4) are determined. Since the fractal dimension of the pore structure of tight sandstone is generally between 2 and 3, pores or throat types with fractal dimensions outside this range are removed, and the pore and throat types with analysis characteristics are determined.

[0105] The fractal dimensions of pores and throats with fractal characteristics are correlated with porosity and permeability to determine the fractal dimensions that are better correlated with reservoir porosity and permeability and to determine the influence of different fractal dimension sections on reservoir properties.

[0106] According to the experimental principle, high-pressure mercury injection is better for characterizing small pores and throats, while constant-rate mercury injection is more accurate for characterizing large pores and throats. By comparing the fractal dimension characteristics of high-pressure mercury injection and constant-rate mercury injection and the correlation between fractal dimension and reservoir properties, the two are combined to characterize the full pore size pore structure.

[0107] According to the radii of the intersection points of high-pressure mercury injection and constant-rate mercury injection for large pores, wide throats, small pores, and narrow throats, which correspond to rg1, rg2, rg3, and rh1, rh2, rh3, respectively, high-pressure mercury injection and constant-rate mercury injection are spliced. The splicing value is the average value of the critical point of small pore throat rg2 and large pore throat rh2 measured by high-pressure mercury injection and constant-rate mercury injection, which is used to characterize the full pore size pore structure characteristics.

[0108] By observing the characteristics of high-pressure mercury injection fractal dimension fitting curve, the large pore fractal dimension(Dg1) ranges from 2.26 to 2.64; the wide throat fractal dimension(Dg2) ranges from 2.04 to 2.11; the small pore fractal dimension(Dg3) ranges from 3.32 to 3.46; and the narrow throat fractal dimension(Dg4) ranges from 2.04 to 2.16. Since the fractal dimension of the pore structure of the tight sandstone is generally between 2 and 3 with a fractal characteristic, otherwise it does not have a fractal characteristic. Therefore, the small pore of the tight sandstone reservoir of the Chang 7 member in the study area does not have a fractal characteristic, while the large pore, wide throat and narrow throat have a fractal characteristic. The narrow throat fractal dimension has a good correlation with the porosity(R is-0.754), indicating that Dg4 has a significant influence on the reservoir porosity and permeability(as shown in Figure 15 By analyzing the characteristics of the constant-rate mercury injection fractal dimension fitting curve, the large pore fractal dimension(Dh1) ranges from 2.60 to 2.74; the wide throat fractal dimension(Dh2) ranges from 2.10 to 2.29; the small pore fractal dimension(Dh3) ranges from 3.68 to 4.30; and the narrow throat fractal dimension(Dh4) ranges from 2.29 to 2.50. Similarly, the small pore does not have a fractal characteristic, while the large pore, wide throat and narrow throat have a fractal characteristic. And the wide throat fractal dimension of the constant-rate mercury injection has a good correlation with the porosity(R is 0.908), so Dh2 can accurately reflect the wide throat characteristics of the tight sandstone reservoir(as shown in Figure 16

[0109] By comprehensively comparing the fractal dimension characteristics of high-pressure mercury injection and constant-rate mercury injection and the correlation between the fractal dimension and the reservoir properties, it can be seen that the high-pressure mercury injection is better for small pore throat representation, while the constant-rate mercury injection is more accurate for large pore throat representation, so the two are combined to represent the full pore size pore structure(Table 4). According to the radius at the intersection of the high-pressure mercury injection and constant-rate mercury injection fractal dimension of large pore, wide throat, small pore and narrow throat, it corresponds to r g1 , r g2 , r g3 and r h1 , r h2 , r h3 This paper refers to the method of previous studies to splice high-pressure mercury injection and constant-rate mercury injection, and the splicing value is the average value of the critical point of small pore throat r g2 and large pore throat r h2 measured by high-pressure mercury injection and constant-rate mercury injection, and then to represent the full pore size pore structure characteristics(as shown in Figure 17 ).

[0110] In Table 4, r g1 represents the intersection of the fitting curve reflecting the large pore and the fitting curve reflecting the wide throat, r g2 represents the intersection of the fitting curve reflecting the wide throat and the fitting curve reflecting the small pore, and r g3 ​r represents the intersection point of the fitting curve reflecting the large pore of the reaction and the fitting curve reflecting the wide throat of the reaction, r h1 r represents the intersection point of the fitting curve reflecting the wide throat of the reaction and the fitting curve reflecting the small pore of the reaction, r h2 r represents the intersection point of the fitting curve reflecting the wide throat of the reaction and the fitting curve reflecting the small pore of the reaction, r h3 r represents the intersection point of the fitting curve reflecting the wide throat of the reaction and the fitting curve reflecting the small pore of the reaction, r

[0111] Table 4 Intersection point of high-pressure mercury injection and constant-speed mercury injection fractal dimension of sample of Chang 7 member of tight sandstone in research area

[0112]

[0113] It can be seen that S70 can include the following steps S71 to S76.

[0114] S71: Determine the pore throat size and pore throat type corresponding to each pressure data of the high-pressure mercury injection and constant-speed mercury injection experiment.

[0115] S72: Take the pressure data and mercury saturation data in the experimental data of the high-pressure mercury injection experiment as logarithms, construct a first data set, and divide the experimental data in the first data set into the following four categories according to the pore throat size and type: large pore, wide throat, small pore, and narrow throat.

[0116] S73: For the experimental data of each category in the first data set, determine the fitting straight line of the experimental data respectively, obtain a plurality of fitting straight lines corresponding to the high-pressure mercury injection experiment, and determine the fractal dimension reflecting the corresponding pore throat category according to the slope of the fitting straight line.

[0117] S74: Take the pressure data and mercury saturation data in the experimental data of the constant-pressure mercury injection experiment as logarithms, construct a second data set, and divide the data in the second data set into the following four categories according to the pore throat size and type: large pore, wide throat, small pore, and narrow throat.

[0118] S75: For the experimental data of each category in the second data set, determine the fitting straight line of the experimental data respectively, obtain a plurality of fitting straight lines corresponding to the constant-pressure mercury injection experiment, and determine the fractal dimension reflecting the corresponding pore throat category according to the slope of the fitting straight line.

[0119] S76: Splice the plurality of fitting straight lines corresponding to the high-pressure mercury injection experiment and the plurality of fitting straight lines corresponding to the constant-pressure mercury injection experiment, and obtain the fractal dimension under the full pore diameter.

[0120] Multiple fitted lines corresponding to the high-pressure mercury intrusion test can be spliced ​​with multiple fitted lines corresponding to the constant-pressure mercury intrusion test. The spliced ​​value is the average value of the boundary points rg2 and rh2 between the small pore throat and the large pore throat in the multiple fitted lines corresponding to the high-pressure mercury intrusion test and the constant-rate mercury intrusion test.

[0121] In some embodiments, according to the above formula (1), the fractal dimension reflecting the corresponding pore throat category can be determined based on the slope of the fitted line. Specifically, the slope of the target fitted line can be calculated first, and then the sum of the slope and 2 can be used as the fractal dimension reflecting the target pore throat category, where the target pore throat category is the pore throat category corresponding to the experimental data associated with the target fitted line.

[0122] S80: Based on the main combination and configuration relationship between pore type and throat type, porosity, permeability, and fractal dimension of the full-diameter pore throat, determine the microscopic topological structure characteristic table of tight sandstone reservoir pores. The microscopic topological structure characteristic table includes multiple microscopic topological structure categories of tight rocks. The microscopic topological structure characteristic table is used to determine the oil and gas exploration or development plan for the target area.

[0123] The reservoir space within the tight reservoir matrix is ​​the location of reservoir oil and gas, forming the final part of the path for oil and gas flow within the reservoir. The function of matrix reservoir pores as oil and gas reservoir spaces is similar. However, different development patterns of pore throats in the matrix reservoir can significantly affect the absolute permeability of the reservoir, leading to substantial differences in the degree of oil and gas recovery.

[0124] The pore structure of the matrix reservoir is one of the important factors affecting oil and gas recovery. The residual mercury inclusion S after mercury removal... 残余 With maximum mercury saturation S 饱和 The ratio of [value] to [value] serves as a parameter for the confinement of oil and gas within the matrix reservoir, and consequently as a parameter for estimating the ultimate recovery rate. Differences in mercury intrusion porosimetry curves represent different pore structures, requiring interpretation by a pore structure model (i.e., a category of microscopic topology). The implications of this pore model are also supported by other experimental parameters.

[0125] Tight sandstone has a more complex pore structure than conventional sandstone. This invention proposes to establish a multi-type pore structure model (i.e., micro-topological structure category) based on topological structure by comprehensively studying pore type, throat type, pore-throat configuration, mercury injection curve characteristics, and multifractal dimension when studying its pore structure. This model can characterize different pore structure features. Different pore structure models (i.e., micro-topological structure categories) will lead to differences in reservoir quality and ultimate oil and gas recovery rates. This model can be used for reservoir classification and evaluation, and is also of great significance for predicting tight oil and gas production capacity and ultimate recovery rates.

[0126] The present application is based on the establishment of four kinds of pore structure modes based on topological structure according to different pore types, throat types, pore throat configuration relationship, high pressure mercury injection curve characteristics, constant speed mercury injection curve characteristics, fractal dimension characteristics, etc.

[0127] (1) Ball stick net structure

[0128] Figure 18 The a in the ball stick net structure shows a schematic diagram of the ball stick network structure. Figure 20 The a in the ball stick net structure shows a schematic diagram of the ball stick network structure.

[0129] The ball stick net structure pore is mainly large interparticle pore, containing a small amount of intragranular dissolved pore, the throat type is mainly wide sheet-shaped throat, and the neck type throat and pipe bundle-shaped throat are basically not developed. The pore throat configuration relationship is corresponding to the large interparticle pore-wide sheet-shaped throat combination (as shown by a in Figure 19 The mercury injection curve characteristics are that the threshold pressure is relatively low, less than 0.9 Mpa, the platform is obvious, the skewness is large, and the sorting is good. In the ball stick pore structure model (i.e. micro-topological structure category), there are multiple circulation paths, that is, from a pore, there is one or more paths returning to the pore, and there is no path backtracking.

[0130] The interparticle pore network has many channels between two pores. The displacement of fluid shows the classical seepage characteristics, that is, a small change in capillary pressure will lead to a large change in mercury saturation.

[0131] During the mercury injection process of the mercury injection experiment, when the pressure reaches a certain value, a large amount of mercury will enter the storage space connected by the throats in the sample, forming a whole displacement phenomenon, and the mercury injection curve presents an obvious platform.

[0132] During the mercury withdrawal process, the mercury in the smallest pore throat is first preferentially discharged to the surrounding larger throats. Then, as the pressure decreases, the mercury in the throats connected to the pores is also gradually emptied, and the mercury is discharged to the pores. The mercury in the pores not connected to the external channel will remain in the sample and cannot be discharged, resulting in a high residual mercury content after mercury withdrawal.

[0133] The fractal dimension value of the fractal dimension segment reflecting the large pore, wide throat, and positively correlated with porosity and permeability is high. The pore structure reservoir physical property of this type is good, and the porosity and permeability value is relatively high.

[0134] The mercury injection curve corresponding to the ball-and-stick network structure is type I, with low threshold pressure, obvious platform, and coarse skewness. The fractal dimension D1 reflecting the large pores is distributed in the range of 2.26-2.64, and the fractal dimension D2 reflecting the wide throat is distributed in the range of 2.04-2.11. The corresponding pore-throat combination is large intergranular pore-wide sheet-shaped throat combination, and the pore topology structure is ball-and-stick network structure. The reservoir with this type of pore structure has good physical properties, with porosity greater than 10% and permeability greater than 0.1 mD, and mainly develops in massive fine sandstone facies and cross-bedded fine sandstone facies.

[0135] (2) Star network structure

[0136] Figure 18 Fig. b in the figure shows a schematic diagram of the star network structure. Figure 20 Fig. b in the figure shows a schematic diagram of the star network structure.

[0137] The star network structure pore is mainly small-medium intergranular pore, with less large intergranular pore and part of intragranular dissolved pore. The throat type is mainly narrow sheet-shaped throat, with less neck-type throat and pipe bundle-shaped throat. The pore-throat combination is mainly small-medium intergranular pore-narrow sheet-shaped throat combination. The mercury injection curve characteristics are that the threshold pressure is slightly low, generally less than 1.5 MPa, the mercury injection curve has a local platform feature, the skewness is slightly coarse, and the sorting is medium-good, which corresponds to the small-medium intergranular pore-narrow sheet-shaped throat combination (as shown in Fig. b in the figure). Figure 19

[0138] The mercury injection curve corresponding to the star network structure is type II, with low threshold pressure, relatively obvious platform, slightly coarse skewness, and medium-good sorting. The fractal dimension D3 reflecting the small pores is distributed in the range of 2.46-2.81, and the fractal dimension D4 reflecting the narrow throat is distributed in the range of 2.04-2.16. The corresponding pore-throat combination is intragranular pore-narrow sheet-shaped throat combination, and the pore topology structure is star network structure. The porosity of this type is 8%-12%, the permeability is 0.05 mD-0.1 mD, and it mainly develops in parallel-bedded fine sandstone facies and wavy-bedded coarse siltstone facies.

[0139] In this pore structure model (i.e., micro-topological structure category), there are both intergranular pores with good pore connectivity and multiple circulation paths, and intragranular pores with poor pore connectivity and no circulation pore-throat channel.

[0140] During the mercury injection process, there is a local "drainage" phenomenon at medium pressure, i.e., the mercury injection curve has a local platform feature. This phenomenon occurs in the intergranular pore network part of the sample, where a large amount of mercury enters at a certain narrow pressure. Then at high pressure, the capillary pressure is exponentially related to the mercury saturation, and this capillary pressure curve represents the mercury entering the intragranular micropore part. The larger the proportion of intergranular pores, the more developed the "platform" feature in the capillary pressure curve.​

[0141] The fractal dimension of a segment reflecting large pores and wide throats, which is positively correlated with porosity and permeability, is relatively high. Reservoirs with this type of pore structure have good physical properties, with relatively high porosity and permeability values.

[0142] (3) Discrete tree structure

[0143] Figure 18 c in the diagram illustrates a discrete tree structure. Figure 20 The diagram shows the features corresponding to the discrete tree structure.

[0144] The discrete dendritic pore structure is dominated by intragranular pores, containing a small number of intergranular pores. The throat type is mainly narrow plateau throats, followed by constricted throats. The mercury intrusion porosimetry curves show an increased threshold pressure to 3.2 MPa, a less pronounced plateau, a slightly thinner skewness, and generally moderate sorting, corresponding to the intragranular pore-narrow plateau throat combination (e.g., ...). Figure 19 (as shown in c).

[0145] like Figure 20 As shown, the discrete dendritic structure is dominated by intragranular pores and small intergranular pores, with throats mainly being narrow plate-like throats, followed by constricted throats. The corresponding mercury intrusion porosimetry curve is Type III, with a relatively high threshold pressure, a less obvious plateau, a slightly finer skewness, and moderate sorting. The fractal dimension D3 of the micropores is distributed between 2.32 and 2.81, and the fractal dimension D4 of the narrow throats is distributed between 2.04 and 2.16. The corresponding pore-throat combination is a combination of small-to-medium-grained intergranular pores and narrow plate-like throats, and the pore topology exhibits a discrete dendritic structure. This type has a porosity of 5%–10% and a permeability of 0.02 mD–0.06 mD, and is mainly developed in siltstone facies containing argillaceous gravel and siltstone facies containing argillaceous bands.

[0146] The discrete dendritic pore structure is dominated by intragranular pores, with a small number of intergranular pores. The throat type is mainly narrow plate-shaped throats, followed by necked throats. The pore-throat configuration is mainly a combination of intragranular pores and narrow plate-shaped throats. The mercury intrusion porosimetry (MIP) curve is characterized by an increased threshold pressure to 3.2 MPa, the absence of a plateau in the curve, an exponential relationship between mercury saturation and pressure, and poor pore-throat sorting.

[0147] The discrete tree-shaped pore structure is mainly intragranular pore with unique spatial distribution characteristics. The pore structure is tree-shaped bifurcation, which can be divided into more smaller throats. Compared with the sphere-stick network structure, the tree-shaped pore structure does not have a cycle of channels. That is, a pore has only one way to pass through the network of tree-shaped pore structure and return to the pore, unless it traces back. The absence of channel circulation means that there is only one way for mercury to reach each pore during the mercury injection experiment. Fluids can only enter the narrower throat from the wider throat. These characteristics result in that there is no feature of a large amount of mercury entering the sample at a certain pressure value during the mercury injection process, that is, the capillary curve has no obvious platform. On the contrary, as the capillary pressure increases, the mercury saturation increases. Under the tree-shaped pore network model, the capillary pressure increases exponentially with the increase of the mercury injection saturation.

[0148] As the capillary pressure decreases, mercury is first discharged from the narrowest throat, and then as the capillary pressure continues to decrease, mercury in the wider throat is also gradually discharged. Because there is no circulating path in the pore throat in the tree-shaped pore structure, the large pore throat is continuously bifurcated into small pore throat, and theoretically all the mercury in the tree-shaped pore structure can be discharged, that is, the mercury injection curve and the mercury discharge curve are consistent, so the sample with discrete tree-shaped structure often has high mercury discharge efficiency. This phenomenon is beneficial to the exploitation of oil and gas, because this pore structure has high recovery efficiency.

[0149] The fractal dimension value of the segment reflecting small pores and narrow throats and negatively correlated with porosity and permeability is high. The pore structure of this type of reservoir has poor physical properties, and the porosity and permeability values are relatively low.

[0150] (4) Complex pipe bundle structure

[0151] Figure 18 The schematic diagram of the discrete tree-shaped structure is shown in d of FIG. 1. Figure 20 The characteristics corresponding to the complex pipe bundle structure are shown in d of FIG. 1.

[0152] The complex pipe bundle structure pore is mainly micropore, containing a small amount of small intragranular solution pores, and the throat type is mainly extremely narrow sheet-shaped throat and pipe bundle-shaped throat, and the neck type throat is less. The pore-throat configuration relationship is mainly micropore-extremely narrow sheet-shaped / pipe bundle-shaped throat combination. The mercury injection curve characteristics are that the threshold pressure is relatively large, about 9.6 MPa, the platform is not obvious, the skewness is fine, and the sorting is medium-poor, which corresponds to the micropore-extremely narrow sheet-shaped / pipe bundle-shaped throat combination (as shown in d of FIG. 1). Figure 19

[0153] ​The complex bundle-like structure has a reservoir space mainly composed of micro-pores, and a large pressure is required for mercury to enter the pores. With further increase of the pressure, mercury can enter smaller pores, and the pressure curve is arched, with a fine skewness. Moreover, due to the small pores and complex throat, mercury cannot enter them in large quantities. Therefore, under the same pressure, the mercury saturation is lower than that of other pore structure models (i.e. micro-topological structure categories).

[0154] The fractal dimension of the segment reflecting small pores and narrow throats and negatively correlated with porosity and permeability is high. The IV-type pore structure is mainly composed of micropores and a small amount of small intragranular dissolved pores, and the throat is mainly composed of extremely narrow sheet-like and bundle-like throats, and less necked throats. The corresponding mercury injection curve is IV-type, with a large threshold pressure, an unclear platform, a fine skewness, and a moderate-poor sorting. The fractal dimension D4 reflecting the extremely narrow throat is distributed in 2.08-2.16, and the corresponding pore-throat combination is micropore-extremely narrow sheet-like and bundle-like throat combination, and the pore topological structure is complex bundle-like structure. The porosity of this type is less than 5%, the permeability is generally less than 0.03 mD, and it mainly develops in horizontal bedding argillaceous siltstone facies and plant debris-containing argillaceous siltstone facies.

[0155] Correspondingly, the step S80 can include the following steps S81, S82, S83 and S84.

[0156] S81: in the case that the main combination and configuration relationship of the pore type and the throat type is large intergranular pore-wide sheet-like throat combination, the porosity is greater than 10%, the permeability is greater than 0.1 mD, the fractal dimension reflecting the large pore is distributed in 2.26-2.4, and the fractal dimension reflecting the wide throat is distributed in 2.04-2.11, the micro-topological structure category of the rock sample is determined as a ball-stick net-like structure.

[0157] S82: in the case that the main combination and configuration relationship of the pore type and the throat type is small and medium intergranular pore-narrow sheet-like throat combination, the porosity is 8%-12%, the permeability is 0.05 mD-0.1 mD, the fractal dimension reflecting the small pore is distributed in 2.46-2.81, and the fractal dimension reflecting the narrow throat is distributed in 2.04-2.16, the micro-topological structure category of the rock sample is determined as a star chain net-like structure.

[0158] S83: in the case that the main combination and configuration relationship of the pore type and the throat type is intragranular pore-narrow sheet-like throat combination, the porosity is 5%-10%, the permeability is 0.02 mD-0.06 mD, the fractal dimension reflecting the small pore is distributed in 2.32-2.81, and the fractal dimension reflecting the narrow throat is distributed in 2.04-2.16, the micro-topological structure category of the rock sample is determined as a discrete tree-like structure.

[0159] S84: In the case that the main combination configuration relationship between the pore type and the throat type is micropore-extremely narrow sheet-shaped and bundle-shaped throat combination, the porosity is 5%, the permeability is less than 0.03 mD, and the fractal dimension distribution reflecting the extremely narrow throat is distributed in the range from 2.08 to 2.16, the micro-topological structure category of the rock sample is determined as a complex bundle-shaped structure.

[0160] After obtaining the micro-topological structure characteristic table shown in the formula (1), the micro-topological structure category of the target area tight sandstone reservoir pore can also be determined by the following method: Figure 20

[0161] S91: The pore type and the pore size in the rock sample slice of the target area are determined.

[0162] S92: The throat type in the rock sample slice of the target area is determined.

[0163] S93: The porosity and the permeability of the rock sample of the target area are determined.

[0164] S94: The experimental data are recorded when the high-pressure mercury injection experiment and the constant-speed mercury injection experiment are respectively performed on the rock sample of the target area.

[0165] S95: The pore-throat size and the distribution characteristics in the rock sample are determined according to the experimental data.

[0166] S96: The main combination configuration relationship between the pore type and the throat type in the rock sample slice of the target area is determined.

[0167] S97: The fractal dimension of the full-pore throat is obtained by processing the experimental data.

[0168] S98: The main combination configuration relationship between the pore type and the throat type, the porosity, the permeability, the fractal dimension of the full-pore throat of the rock sample of the target area are compared with the micro-topological structure characteristic table of the tight sandstone reservoir pore, the target micro-topological structure category in the micro-topological structure characteristic table which is the closest to each characteristic of the rock sample of the target area is taken as the micro-topological structure category of the rock sample of the target area, and the oil and gas exploration or development scheme is determined according to the micro-topological structure category of the rock sample of the target area.

[0169] ​The microstructure topology feature table provided in this specification identifies the microstructure characteristics that affect oil and gas production capacity and ultimate recovery rate. Based on this table, oil and gas production capacity and ultimate recovery rate can be predicted more intuitively and accurately from a microstructure perspective. Existing prediction methods typically rely directly on a few test data points (e.g., porosity). Due to the complex nature of formation structures, individual types of test data are insufficient to accurately characterize the formation's oil and gas recovery rate and difficulty. Improper processing of test data or insufficient types of test data can affect prediction results. This approach directly determines microstructure characteristics based on indicators and performs predictions based on the microstructure feature table, resulting in more accurate predictions.

[0170] In the ball-and-stick pore structure model, multiple circulation paths exist, meaning that starting from a pore, one or more paths return to that pore without a retracing path. During oil and gas recovery, the oil and gas in the smallest pore throat are preferentially discharged first, flowing into the surrounding larger throats. Then, they flow into the pores. Oil and gas in pores not connected to external channels remain in the sample and cannot be discharged, resulting in a high residual oil and gas content. Reservoirs with this type of pore structure have good reservoir quality, large pores and throats, and high oil and gas saturation, but the ultimate oil and gas recovery rate is limited.

[0171] Discrete dendritic pore structures are primarily composed of intragranular pores, exhibiting unique spatial distribution characteristics. The pore structure branches in a tree-like pattern, branching into even finer throats. Compared to ball-and-stick structures, dendritic pore structures lack channel circulation. That is, once a pore passes through the dendritic pore structure network, it cannot return to that pore unless it is traced back. The lack of channel circulation means that during oil and gas extraction, there is only one path to each pore. Fluid flows from narrower throats to wider throats before exiting; theoretically, all oil and gas in a dendritic pore structure can be expelled, thus samples with discrete dendritic structures often exhibit higher mercury removal efficiency. This phenomenon is favorable for oil and gas extraction, therefore this pore structure has a higher ultimate oil and gas recovery rate.

[0172] In the star-chain network structure model, there are both intergranular pores with good pore connectivity and multiple circulation paths, and intragranular pores with poor pore connectivity and no circulation throat channels. Therefore, the reservoir quality and hydrocarbon saturation fall between those of the ball-and-stick pore structure model and the discrete tree-like pore structure model, and the ultimate oil and gas recovery rate also falls between those of the ball-and-stick pore structure model and the discrete tree-like pore structure model.

[0173] Complex tubular structures, due to their small pores and complex throats, make it difficult for large quantities of oil and gas to enter the pores and throats. Once oil and gas enter, they are difficult to extract during the extraction process, resulting in poor reservoir quality and ultimately low oil and gas recovery rates.

[0174] The present specification also provides a device for determining the micro-topology of pores in a tight sandstone reservoir, which can be used to implement the method for determining the micro-topology of pores in a tight sandstone reservoir. The device comprises a first determining unit, a second determining unit, a third determining unit, a recording unit, a fourth determining unit, a fifth determining unit, a processing unit, and a sixth determining unit.

[0175] The first determining unit is configured to determine the pore type and pore size in a plurality of rock sample slices of a tight reservoir.

[0176] The second determining unit is configured to determine the throat type in the plurality of rock sample slices.

[0177] The third determining unit is configured to determine the porosity and permeability of the plurality of rock samples.

[0178] The recording unit is configured to record experimental data when performing high-pressure mercury injection experiments and constant-rate mercury injection experiments on the plurality of rock samples, respectively.

[0179] The fourth determining unit is configured to determine the pore throat size and distribution characteristics in the rock samples according to the experimental data.

[0180] The fifth determining unit is configured to determine the main combination and configuration relationship between the pore type and the throat type in the plurality of rock sample slices.

[0181] The processing unit is configured to process the experimental data to obtain the fractal dimension under the full pore size.

[0182] The sixth determining unit is configured to determine a micro-topology feature table of pores in a tight sandstone reservoir according to the main combination and configuration relationship between the pore type and the throat type, the porosity, the permeability, and the fractal dimension of the full pore throat, wherein the micro-topology feature table comprises a plurality of micro-topology categories of the tight rock, and the micro-topology feature table is used to determine an oil and gas exploration or development scheme for a target area.

[0183] The specific description and beneficial effects of the device are described in the corresponding method embodiments, and will not be repeated here.

[0184] The embodiments of the present application also provide an electronic device, which can comprise a processor and a memory, wherein the processor and the memory can be connected through a bus or other means, for example, through a bus.

[0185] The processor can be a central processing unit (CPU). The processor can also be other general-purpose processors, digital signal processors (DSP), application-specific integrated circuits (ASIC), field-programmable gate arrays (FPGA) or other programmable logic devices, discrete gates or transistor logic devices, discrete hardware components, or a combination thereof.

[0186] The memory, as a non-transitory computer readable storage medium, can be used to store non-transitory software programs, non-transitory computer executable programs and modules, such as program instructions / modules (for example, the first determining unit, the second determining unit, the third determining unit, the recording unit, the fourth determining unit, the fifth determining unit, the processing unit and the sixth determining unit) corresponding to the method for determining the micro-topological structure of the tight sandstone reservoir pore. The processor executes various functions of the processor and data classification by running the non-transitory software programs, instructions and modules stored in the memory, that is, implements the method for determining the micro-topological structure of the tight sandstone reservoir pore in the above method embodiments.

[0187] The memory can include a program storage area and a data storage area. The program storage area can store an operating system and application programs required by at least one function. The data storage area can store data created by the processor and the like. In addition, the memory can include a high-speed random access memory, and can also include a non-transitory memory, such as at least one magnetic disk storage device, a flash memory device, or other non-transitory solid-state memory device. In some embodiments, the memory can optionally include a memory remotely arranged with respect to the processor, and these remote memories can be connected to the processor through a network. Examples of the above network include but are not limited to the Internet, an intranet, a local area network, a mobile communication network, and a combination thereof.

[0188] The one or more modules are stored in the memory and, when executed by the processor, perform the above method for determining the micro-topological structure of the tight sandstone reservoir pore.

[0189] The above electronic device specific details can be understood with reference to the relevant description and effects in the corresponding embodiments, which will not be described here.

[0190] The system, device, module or unit illustrated in the above embodiments can be specifically implemented by a computer chip or entity, or by a product with certain functions.

[0191] For ease of description, the above apparatus is described as various units respectively described in function. Of course, in implementing the present application, the functions of the units can be implemented in one or more software and / or hardware.

[0192] The above only describes the embodiments of the present application and is not intended to limit the present application. The present application can have various modifications and changes for those skilled in the art. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the embodiments of the present application shall be included in the scope of claims of the embodiments of the present application.

Claims

1. A method of determining the microscopic topology of the pores of a tight sandstone reservoir, characterized in that, The method comprises the following steps: determining the pore type and pore size of a plurality of rock sample slices of a dense reservoir; determining the throat type of the plurality of rock sample slices; determining the porosity and permeability of the plurality of rock samples; recording experimental data when high-pressure mercury injection experiments and constant-speed mercury injection experiments are respectively performed on the plurality of rock samples; determining the pore throat size and distribution characteristics of the rock samples according to the experimental data; determining the main combination and configuration relationship between the pore type and the throat type of the plurality of rock sample slices; processing the experimental data to obtain the fractal dimension under the full pore size; constructing a micro-topological structure characteristic table of the dense sandstone reservoir pores according to the main combination and configuration relationship between the pore type and the throat type, the porosity, the permeability, the fractal dimension of the full-pore-size pore throat, the mercury injection curve platform characteristics and the mercury withdrawal efficiency, wherein the micro-topological structure characteristic table comprises a plurality of micro-topological structure categories of the dense rock, and the micro-topological structure characteristic table is used to determine an oil and gas exploration or development scheme of a target area; wherein the micro-topological structure categories of the dense sandstone reservoir pores comprise a ball-stick net-like structure, a star-chain net-like structure, a discrete tree-like structure and a complex tube bundle-like structure; the micro-topological structure categories of the dense sandstone reservoir pores are used to qualitatively predict the reservoir quality and the ultimate oil and gas recovery rate; wherein each micro-topological structure category corresponds to the following parameter range: for the ball-stick net-like structure, the main combination and configuration relationship between the pore type and the throat type is a large intergranular pore-wide sheet-shaped throat combination, the porosity is greater than 10%, the permeability is greater than 0.1 mD, the fractal dimension D1 reflecting the large pores is distributed in 2.26-2.4, and the fractal dimension D2 reflecting the wide throat is distributed in 2.04-2.11; the ball-stick net-like structure has a plurality of circulation paths, one or more paths start from a pore and return to the pore without re-tracing; during the oil and gas production, the oil and gas in the smallest pore throat is first discharged to the surrounding larger throat and then to the pore; the oil and gas in the pores not connected with the external channel remains in the sample and cannot be discharged, resulting in a high residual oil and gas content; the reservoir quality of the ball-stick net-like structure is good, the pores and throats are large, the oil and gas saturation is high, but the ultimate recovery rate of the oil and gas is limited; for the star-chain net-like structure, the main combination and configuration relationship between the pore type and the throat type is a small and medium intergranular pore-narrow sheet-shaped throat combination, the porosity is 8%-12%, the permeability is 0.05 mD-0.1 mD, the fractal dimension D3 reflecting the small pores is distributed in 2.46-2.81, and the fractal dimension D4 reflecting the narrow throat is distributed in 2.04-2.16; the star-chain net-like structure has both intergranular pores with good pore connectivity and a plurality of circulation paths and intragranular pores with poor pore connectivity and no circulation pore throat channel; the ultimate recovery rate of the oil and gas of the star-chain net-like structure is between that of the ball-stick pore structure and that of the discrete tree-like structure. The discrete tree structure has a main combined configuration relationship of pore type and throat type, which is a combination of intragranular pores and narrow sheet-shaped throats, a porosity of 5% to 10%, a permeability of 0.02 mD to 0.06 mD, a fractal dimension D3 reflecting small pores distributed in 2.32 to 2.81, and a fractal dimension D4 reflecting narrow throats distributed in 2.04 to 2.16; the discrete tree structure has a tree branch, can branch out smaller throats, has no circulation of channels, one pore cannot return to the pore through a network channel of the tree-shaped pore structure without backtracking, there is only one way to reach each pore during oil and gas production, fluid is discharged from narrow throats to wide throats, and theoretically, oil and gas in the tree-shaped pore structure can be discharged; the discrete tree structure has a high ultimate oil and gas recovery rate; The complex pipe bundle structure has a main combined configuration relationship of pore type and throat type, which is a combination of micropores and extremely narrow sheet-shaped and pipe bundle-shaped throats, a porosity of 5%, a permeability of less than 0.03 mD, and a fractal dimension D4 reflecting extremely narrow throats distributed in 2.08 to 2.16; the complex pipe bundle structure has small pores and complex throats, and oil and gas are difficult to enter the pores and throats in a large amount; the complex pipe bundle structure has poor reservoir quality and an ultimate oil and gas recovery rate.

2. The method of claim 1, wherein, After the micro-topological structure feature table of the dense sandstone reservoir pore is determined, the micro-topological structure category of the dense sandstone reservoir pore in the target area is further determined by the following method: Determine the pore type and pore size in the rock sample slice in the target area; Determine the throat type in the rock sample slice in the target area; Determine the porosity and permeability of the rock sample in the target area; Record the experimental data when the high-pressure mercury injection experiment and the constant-speed mercury injection experiment are respectively performed on the rock sample in the target area; Determine the pore-throat size and distribution characteristics in the rock sample according to the experimental data; Determine the main combined configuration relationship of the pore type and the throat type in the rock sample slice in the target area; Obtain the fractal dimension of the pore-throat of the full pore diameter by processing the experimental data; Compare the main combined configuration relationship of the pore type and the throat type, the porosity, the permeability, and the fractal dimension of the pore-throat of the full pore diameter of the rock sample in the target area with the micro-topological structure feature table of the dense sandstone reservoir pore, and take the target micro-topological structure category in the micro-topological structure feature table that is closest to each feature of the rock sample in the target area as the micro-topological structure category of the rock sample in the target area, so as to determine the oil and gas exploration or development scheme according to the micro-topological structure category of the rock sample in the target area.

3. The method of claim 1, wherein, The experimental data are processed to obtain the fractal dimension under the full pore diameter, including: Determine the pore-throat size and pore-throat type corresponding to each pressure data of the high-pressure mercury injection experiment and the constant-speed mercury injection experiment; Take the pressure data and the mercury saturation data in the experimental data of the high-pressure mercury injection experiment as logarithms respectively to construct a first data set, and the experimental data in the first data set are divided into the following four categories according to the pore-throat size and type: large pores, wide throats, small pores, and narrow throats; For each category of experimental data in the first data set, a fitting straight line of the experimental data is determined respectively, to obtain a plurality of fitting straight lines corresponding to the high-pressure mercury injection experiment; the fractal dimension reflecting the corresponding pore throat category is determined according to the slope of the fitting straight line; The pressure data and mercury saturation data in the experimental data of the constant-pressure mercury injection experiment are taken as logarithms respectively, to construct a second data set, and the data in the second data set is divided into the following four categories according to the pore throat size and category: large pore, wide throat, small pore, and narrow throat; For each category of experimental data in the second data set, a fitting straight line of the experimental data is determined respectively, to obtain a plurality of fitting straight lines corresponding to the constant-pressure mercury injection experiment; the fractal dimension reflecting the corresponding pore throat category is determined according to the slope of the fitting straight line; The plurality of fitting straight lines corresponding to the high-pressure mercury injection experiment and the plurality of fitting straight lines corresponding to the constant-pressure mercury injection experiment are spliced to obtain the fractal dimension under the full pore diameter.

4. The method of claim 3, wherein, The plurality of fitting straight lines corresponding to the high-pressure mercury injection experiment and the plurality of fitting straight lines corresponding to the constant-pressure mercury injection experiment are spliced to obtain the fractal dimension under the full pore diameter, including: The plurality of fitting straight lines corresponding to the high-pressure mercury injection experiment and the plurality of fitting straight lines corresponding to the constant-pressure mercury injection experiment are spliced, and the splicing value adopts the average value of the small pore throat and the large pore throat demarcation points rg2 and rh2 corresponding to the plurality of fitting straight lines of the high-pressure mercury injection experiment and the constant-speed mercury injection experiment.

5. The method of claim 3, wherein, The fractal dimension reflecting the corresponding pore throat category is determined according to the slope of the fitting straight line, including: The sum of the slope of the target fitting straight line and 2 is calculated; The sum value is taken as the fractal dimension reflecting the target pore throat category, and the target pore throat category is the pore throat category corresponding to the experimental data associated with the target fitting straight line.

6. An apparatus for determining the micro-topology of the pores of a tight sand reservoir, characterized by, Including: A first determination unit is configured to determine the pore type and pore size of a plurality of rock sample slices of a dense reservoir; A second determination unit is configured to determine the throat type of the plurality of rock sample slices; A third determination unit is configured to determine the porosity and permeability of the plurality of rock samples; A recording unit is configured to record experimental data when the high-pressure mercury injection experiment and the constant-speed mercury injection experiment are performed on the plurality of rock samples respectively; A fourth determination unit is configured to determine the pore throat size and distribution characteristics of the rock samples according to the experimental data; A fifth determination unit is configured to determine the main combination and configuration relationship between the pore type and the throat type of the plurality of rock sample slices; A processing unit is configured to process the experimental data to obtain the fractal dimension under the full pore diameter; A sixth determination unit is configured to construct a micro-topological structure feature table of the dense sandstone reservoir pores according to the main combination and configuration relationship between the pore type and the throat type, the porosity, the permeability, the fractal dimension of the full-pore-throat, the mercury saturation curve platform characteristics, and the mercury withdrawal efficiency, wherein the micro-topological structure feature table includes a plurality of micro-topological structure categories of the dense rock, and the micro-topological structure feature table is used to determine an oil and gas exploration or development scheme of a target area; wherein the micro-topological structure categories of the dense sandstone reservoir pores include a ball-stick net-like structure, a star-chain net-like structure, a discrete tree-like structure, and a complex tube bundle-like structure. The micro-topology category of the tight sandstone reservoir pore is used for qualitatively predicting the reservoir quality and the ultimate recovery of oil and gas; Wherein, each micro-topology category corresponds to the following parameter range: The main combination configuration relationship of the pore type and the throat type is large intergranular pore-wide sheet-shaped throat combination, the porosity is greater than 10%, the permeability is greater than 0.1 mD, the fractal dimension D1 reflecting the large pore is distributed in 2.26-2.4, and the fractal dimension D2 reflecting the wide throat is distributed in 2.04-2.11; the ball stick net-like structure has multiple circulation paths, one or more paths start from a pore and return to the pore without retraceable paths; in the process of oil and gas production, the oil and gas in the smallest pore throat are firstly discharged, then discharged into the surrounding larger throat, and then discharged into the pore; the oil and gas in the pore not connected with the external channel remain in the sample and cannot be discharged, resulting in a high residual oil and gas content; the reservoir quality of the ball stick net-like structure is good, the pore and throat are large, the oil and gas saturation is high, but the ultimate recovery of oil and gas is limited; The main combination configuration relationship of the pore type and the throat type is small and medium intergranular pore-narrow sheet-shaped throat combination, the porosity is 8%-12%, the permeability is 0.05 mD-0.1 mD, the fractal dimension D3 reflecting the small pore is distributed in 2.46-2.81, and the fractal dimension D4 reflecting the narrow throat is distributed in 2.04-2.16; the star chain net-like structure has both intergranular pores with good pore connectivity and multiple circulation paths and intragranular pores with poor pore connectivity and no circulation pore throat channel; the oil and gas ultimate recovery of the star chain structure is between the ball stick pore structure and the discrete tree structure; The main combination configuration relationship of the pore type and the throat type is intragranular pore-narrow sheet-shaped throat combination, the porosity is 5%-10%, the permeability is 0.02 mD-0.06 mD, the fractal dimension D3 reflecting the small pore is distributed in 2.32-2.81, and the fractal dimension D4 reflecting the narrow throat is distributed in 2.04-2.16; the discrete tree structure is branched into a tree shape, can divide into smaller throats, has no channel circulation, and one pore cannot return to the pore through the tree pore structure network channel without retracing; when the oil and gas is produced, there is only one way to reach each pore; the fluid is discharged from the narrower throat to the wider throat; in theory, all the oil and gas in the tree pore structure can be discharged; the discrete tree structure has a high ultimate recovery of oil and gas; The main combination configuration relationship of the pore type and the throat type is micro-pore-extremely narrow sheet-shaped and pipe bundle-shaped throat combination, the porosity is 5%, the permeability is less than 0.03 mD, and the fractal dimension D4 reflecting the extremely narrow throat is distributed in 2.08-2.16; the complex pipe bundle structure has small pores and complex throats, and it is difficult for oil and gas to enter the pores and throats in large quantities; the reservoir quality and the ultimate oil and gas recovery of the complex pipe bundle structure are poor.

7. An electronic device, comprising: It comprises: A memory and a processor, which are in communication connection with each other, the memory storing computer instructions, and the processor implementing the steps of the method according to any one of claims 1 to 5 by executing the computer instructions.

8. A computer storage medium, characterized in that, The computer storage medium stores computer program instructions, which, when executed, implement the steps of the method according to any one of claims 1 to 5.

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