Porosity evolution recovery method for clastic rock reservoir under tectonic compression background

Abstract

A porosity evolution recovery method for a clastic rock reservoir under a tectonic compression background, comprising: calculating the total compactional porosity loss of each first sample; selecting first samples having similar properties as selected samples; on the basis of the difference between the total compactional porosity losses corresponding to two selected samples having adjacent maximum palaeotectonic stresses, obtaining the lateral compactional porosity loss of the selected sample having the greater maximum palaeotectonic stress; establishing a second functional relationship; calculating the lateral compactional porosity loss in each lateral compression amongst multiple lateral compressions; on the basis of the total compactional porosity loss and the lateral compactional porosity loss of each first sample, calculating a vertical compactional porosity loss, and establishing a board chart of a relationship between the vertical compactional porosity losses and buried depths; and using a back-stripping inversion method to draw a porosity evolution curve in light of the lateral and vertical compactional porosity losses.

Description

Methods for recovering porosity evolution in clastic reservoirs under tectonic compression

[0001] This application claims priority to Chinese Patent Application No. 2025104169252, filed on April 3, 2025, entitled "A Method for Restoring Porosity Evolution of Clastic Rock Reservoirs under Tectonic Compression Background", the entire contents of which are incorporated herein by reference. Technical Field

[0002] This application belongs to the field of oil and gas exploration and development technology, and in particular relates to a method for recovering the porosity evolution of clastic rock reservoirs under tectonic compression. Background Technology

[0003] In recent years, with the increasing exploration of shallow and medium-depth (reservoir depth less than 4500m) oil and gas resources, exploration has gradually extended to deep and ultra-deep (reservoir depth above 4500m). More than 60% of oil and gas resources in deep and ultra-deep reservoirs are distributed in clastic rocks, with foreland basins being one of the most typical examples of deep and ultra-deep clastic rock exploration. The complex tectonic evolution, burial processes, and diagenetic alteration of foreland basins result in highly heterogeneous clastic reservoirs. Reconstructing the reservoir porosity evolution process is crucial for understanding the controlling factors of reservoir development and revealing the formation mechanism of high-quality reservoirs. Existing methods for reconstructing the porosity evolution of clastic reservoirs during geological history are not applicable to reconstructing the porosity evolution of reservoirs under tectonic compression backgrounds. Summary of the Invention

[0004] To address at least one problem existing in the prior art, the first aspect of this application provides a method for recovering the porosity evolution of clastic reservoirs under tectonic compression, comprising the following steps:

[0005] Establish the second functional relationship: Select several first samples from the study area and calculate the total compaction porosity reduction of each first sample; obtain the maximum paleotectonic stress of each first sample; select first samples with similar burial depth, similar rock structure, and different maximum paleotectonic stresses as selected samples; sort the selected samples in descending order of maximum paleotectonic stress, and take the difference between the total compaction porosity reduction of two adjacent selected samples. The difference is taken as the lateral compaction porosity reduction of the selected sample with the larger maximum paleotectonic stress among the two selected samples; establish a functional relationship between the lateral compaction porosity reduction and the maximum paleotectonic stress of all selected samples, i.e., the second functional relationship;

[0006] The term "similar burial depth" refers to the fact that the difference in burial depth between any two selected samples is no greater than 500 meters, such as 450m, 400m, 350m, 300m, or 280m. "Similar rock structure" mainly refers to the fact that the sorting coefficient and cement content of the selected samples are not significantly different; for example, the sorting coefficient is in the range of 1-1.6, preferably in the range of 1.2-1.4; and the cement content is less than 8%, preferably less than 5%.

[0007] Calculate the lateral compaction porosity reduction for each lateral compression: Determine the number of lateral compressions during the diagenesis process in the study area and the maximum paleotectonic stress for each lateral compression. Combined with the second function relationship, calculate the lateral compaction porosity reduction for each lateral compression.

[0008] Establish a relationship chart: Subtract the total compaction porosity reduction of each first sample from its lateral compaction porosity reduction to obtain the vertical compaction porosity reduction of that first sample; based on the vertical distribution characteristics of the vertical compaction porosity reduction of different first samples, establish a relationship chart between the vertical compaction porosity reduction and burial depth under different sediment parameter constraints.

[0009] The vertical distribution characteristic refers to the trend of vertical compaction and pore reduction with burial depth.

[0010] Evolution curves were plotted: the diagenetic stage of the study area was determined, and the porosity evolution curve of clastic reservoirs under tectonic compression was plotted by combining the lateral compaction porosity reduction amount of each lateral compression during the diagenetic process of the study area and the relationship between the vertical compaction porosity reduction amount and the burial depth.

[0011] This evolution curve can be used to screen favorable reservoir areas. More specifically, it is used to determine the degree of porosity development, thereby screening reservoirs with better porosity development to guide oil and gas exploration.

[0012] In one embodiment, the specific steps for calculating the total compaction reduction in pore volume during the step of establishing the second functional relationship are as follows:

[0013] Based on the functional relationship between porosity φ and sorting coefficient So, the original porosity φ of each first sample is calculated. 原 ;

[0014] Obtain the current porosity φ of each first sample. 今 Total face rate φ 面 The porosity of various types of dissolution pores, the porosity of various types of cementitious materials, and the porosity of various types of microcracks; among which, the porosity of the i-th type of dissolution pore is denoted as φ. 面溶i Let i = 1, 2, ..., n, where n is the number of types of dissolution pores; the porosity of the j-th type of cement is denoted as φ. 面胶j j = 1, 2, ..., m, where m is the number of cement types; the porosity of the k-th type of microcrack is denoted as φ.面缝k k = 1, 2, ..., p, where p is the number of types of microcracks;

[0015] Based on the current porosity φ of each first sample 今 With total face rate φ 面 Establish a functional relationship between the current porosity and the total porosity of all first samples, i.e., the first functional relationship;

[0016] Substituting the porosity of various types of dissolution pores, various types of cementitious material porosity, and various types of microcrack porosity into the first functional relationship, the contribution amounts of various types of dissolution pores, various types of cementitious material porosity, and various types of microcrack porosity are calculated. The contribution amount of the i-th type of dissolution pore is denoted as φ. 溶i The porosity contribution of the j-th type of cement is denoted as φ. 胶j The contribution of the kth type of microcrack porosity is denoted as φ. 缝k ;

[0017] Using Formula 3, calculate the total compaction porosity reduction φ for each first sample. 压 :

[0018] In one embodiment, in the step of calculating the lateral compaction reduction amount for each lateral extrusion, the lateral compaction reduction amount φ for the lth lateral extrusion... 侧压l The calculation formula is:

[0019] Where q represents the number of lateral compressions in the study area, and F l F represents the maximum paleotectonic stress during the l-th lateral compression. l-1 F represents the maximum paleotectonic stress during the (l-1)th lateral compression, and F represents the maximum paleotectonic stress in the second functional relationship. In the calculation, F0 is taken as 0 MPa, and F = F q ;φ 侧压 The lateral compaction reduction in porosity corresponding to the maximum paleotectonic stress F is calculated based on the second functional relationship.

[0020] In one embodiment, in the step of establishing the relational map, a first sample with a cement content of less than 5% is selected, and the sediment parameters include sorting coefficient and sediment grain size.

[0021] More specifically, the sediment grain size can be divided into fine sandstone, medium sandstone and coarse sandstone according to the grain size; the grain size ranges are [0.1-0.25) mm, [0.25-0.5) mm and [0.5-2) mm, respectively.

[0022] In one embodiment, the specific steps for determining the diagenetic stages of the study area in the step of plotting the evolution curve are as follows: by analyzing cast thin sections, conducting in-situ micro-element testing and analysis, analyzing fluid inclusions, and performing U-Pb dating analysis, the formation time and sequence of authigenic minerals (i.e., cement), dissolution pores, and fractures in the study area are determined, and a diagenetic evolution sequence is established; by using inclusion homogenization temperature analysis and U-Pb dating analysis, combined with burial history and thermal history analysis, the occurrence time of each diagenetic stage is determined, and the diagenetic stage is determined by combining the occurrence time of each lateral compression.

[0023] In one embodiment, the specific steps for plotting the evolution curve of clastic reservoir porosity under tectonic compression are as follows: Using the projection of the occurrence time of different diagenetic stages onto the burial history map, the paleoburial depth at the beginning and end of each diagenetic stage is obtained; constrained by the diagenetic evolution sequence, through thin section image analysis and inversion stripping method, combined with the lateral compaction porosity reduction and vertical compaction porosity reduction versus burial depth maps of each lateral compression during the diagenetic process in the study area, the reservoir microstructure characteristics of each diagenetic stage are restored, and the porosity and corresponding porosity of the reservoir at each diagenetic stage are obtained; according to geological history, the reservoir porosity evolution curve from the original porosity to the present porosity is plotted.

[0024] In one embodiment, in each diagenetic stage, the recovered porosity of the initial depositional stage is the average of the original porosity of each first sample; the recovered porosity from the initial depositional stage to the final diagenetic stage is obtained by the following formula:

[0025] Porosity recovered from the previous diagenetic stage - (Porosity contribution from destructive diagenesis - Porosity contribution from constructive diagenesis)

[0026] Among them, destructive diagenesis includes vertical compaction, lateral compression, and cementation, with corresponding porosity contributions of vertical compaction porosity reduction, lateral compaction porosity reduction per lateral compression, and porosity contribution of various cements, respectively; constructive diagenesis includes dissolution and microfracture, with corresponding porosity contributions of various dissolution porosity and porosity contribution of various microfractures, respectively.

[0027] The second aspect of this application provides another method for recovering the porosity evolution of clastic reservoirs under tectonic compression, including the following steps:

[0028] Establishing a second functional relationship: Several first samples are selected from the study area, and the total compaction porosity reduction of each first sample is calculated by a processor; the maximum paleotectonic stress of each first sample is obtained through acoustic emission testing and numerical simulation; the processor selects first samples with similar burial depth, similar rock structure, and different maximum paleotectonic stresses from the first samples as selected samples, and sorts the selected samples in descending order of maximum paleotectonic stress. The difference between the total compaction porosity reduction of two adjacent selected samples is taken as the lateral compaction porosity reduction of the selected sample with the larger maximum paleotectonic stress among the two selected samples, thereby establishing a functional relationship between the lateral compaction porosity reduction of all selected samples and the maximum paleotectonic stress, i.e., the second functional relationship.

[0029] Calculate the lateral compaction porosity reduction for each lateral compression: Determine the number of lateral compressions during the diagenesis process in the study area and the maximum paleotectonic stress for each lateral compression. Combined with the second function relationship, calculate the lateral compaction porosity reduction for each lateral compression using a processor.

[0030] Establish a relationship chart: The processor subtracts the total compaction porosity reduction of each first sample from its lateral compaction porosity reduction to obtain the vertical compaction porosity reduction of that sample; Based on the vertical distribution characteristics of the vertical compaction porosity reduction of different first samples, establish a relationship chart between the vertical compaction porosity reduction and burial depth under different sediment parameter constraints.

[0031] Evolution curves were plotted: the diagenetic stages of the study area were determined, and the inversion stripping method was used. Combined with the lateral compaction porosity reduction of each lateral compression during the diagenetic process and the relationship between the vertical compaction porosity reduction and the burial depth, the porosity evolution curve of the clastic reservoir under the tectonic compression background was plotted by the processor. This evolution curve was used to screen favorable reservoir areas.

[0032] A third aspect of this application provides a computer device including a memory, a processor, and a computer program stored in the memory and executable on the processor, wherein the processor, when executing the computer program, implements the porosity evolution and recovery method for clastic reservoirs under tectonic compression as described in any of the preceding claims.

[0033] The fourth aspect of this application provides a computer-readable storage medium having a computer program stored thereon, which, when executed by a processor, implements the porosity evolution recovery method for clastic reservoirs under tectonic compression as described in any of the preceding claims.

[0034] Compared with the prior art, the advantages and beneficial effects of this application are as follows:

[0035] The method for reconstructing the porosity evolution of clastic reservoirs under tectonic compression, provided in at least one embodiment of this application, is based on the calculation of the total compaction porosity reduction of clastic rock samples. It selects samples with similar burial depths, rock structures, and different maximum paleotectonic stresses as chosen samples. By calculating the difference in the total compaction porosity reduction between two selected samples with adjacent maximum paleotectonic stresses, the lateral compaction porosity reduction of the sample with the larger maximum paleotectonic stress is obtained. This establishes a functional relationship between the lateral compaction porosity reduction and the maximum paleotectonic stress, thereby obtaining the lateral and vertical compaction porosity reduction of any sample and establishing a vertical compaction porosity reduction chart. Using the lateral and vertical compaction porosity reduction charts from different compression periods, combined with the "inversion stripping method," the true evolution curve of clastic reservoir porosity under tectonic compression is obtained, achieving quantitative reconstruction of clastic reservoir porosity in foreland basins. This is of great significance for understanding the genetic mechanisms of deep-to-ultra-deep clastic reservoirs.

[0036] The porosity evolution recovery method for clastic reservoirs under tectonic compression background provided in at least one embodiment of this application is applicable to the porosity evolution recovery of reservoirs under tectonic compression background in foreland basins. By determining the lateral compaction porosity reduction amount and the vertical compaction porosity reduction amount, the reservoir porosity obtained by the inversion stripping method is corrected using the lateral compaction porosity reduction amount and the vertical compaction porosity reduction amount, thereby obtaining the true porosity evolution process of clastic reservoirs under tectonic compression background. Attached Figure Description

[0037] Figure 1 is a first function relationship diagram provided in Embodiment 1 of this application;

[0038] Figure 2 is a second function relationship diagram provided in Embodiment 1 of this application;

[0039] Figure 3 is a graph showing the relationship between vertical compaction and hole reduction and burial depth provided in Embodiment 1 of this application;

[0040] Figure 4 is a diagram showing the porosity evolution of clastic reservoirs in the study area under tectonic compression background provided in Example 1 of this application;

[0041] Figure 5 is a schematic diagram of the connection of computer equipment. Detailed Implementation

[0042] The technical solutions in the embodiments of this application will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. Based on the embodiments in this application, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of this application.

[0043] Example 1

[0044] A method for recovering the porosity evolution of clastic reservoirs under tectonic compression includes the following steps:

[0045] (1) Establish the functional relationship between lateral compaction porosity reduction and maximum paleotectonic stress.

[0046] 139 sandstone samples from a certain study area were selected as the first samples (unless otherwise specified in the following text, the samples referred to are mainly the first samples). The sorting coefficient So of each first sample was obtained by laser grain size analysis of sediments. Based on the functional relationship between porosity φ and sorting coefficient So (Formula 1), the original porosity φ of each first sample was calculated. 原 : φ=20.91+22.90 / So (1).

[0047] Each first sample was fabricated into a plunger sample with a diameter of 2.5 cm and a length of 3-5 cm. The current porosity φ of each first sample was obtained by measuring the plunger samples. 今 .

[0048] Each first sample was fabricated into a cast thin section, and the total thin-section porosity (φ) of each sample was obtained by image analysis of the cast thin sections using an optical microscope. 面 The following are categories of porosity: dissolution thin-section porosity, cement thin-section porosity, and micro-fracture thin-section porosity; where the porosity of the i-th type of dissolution porosity is denoted as φ. 面溶i Let i = 1, 2, ..., n, where n is the number of types of dissolution pores; the porosity of the j-th type of cement is denoted as φ. 面胶j j = 1, 2, ..., m, where m is the number of cement types; the porosity of the k-th type of microcrack is denoted as φ. 面缝k k = 1, 2, ..., p, where p is the number of types of microcracks.

[0049] Laser particle size analysis of the sediments can be performed using a laser particle size analyzer, such as the Masterizer-2000 manufactured by Malvern Panalytical. Plunger samples can be prepared using a core drilling machine according to the standard SY / T5336—2019 "Core Analysis Methods"; the measurement of plunger samples can be performed using a helium porosimeter according to SY / T5336—2019 "Core Analysis Methods" and the GB / T23561 series of standards. Cast thin sections can be prepared using equipment such as a slicer, grinder, and vacuum impregnator according to standards such as SY / T5336—2019 "Core Analysis Methods" and DZ / T0130—2017 "Quality Management Standard for Geological and Mineral Laboratory Testing"; this is well known to those skilled in the art.

[0050] In this embodiment, the various types of dissolution pores are mainly classified as: feldspar particle dissolution pores, quartz particle dissolution pores, and quartz cement dissolution pores, where n is at least one of these; the various types of cements are mainly classified as: calcite, dolomite, gypsum, anhydrite, quartz cement, and feldspar cement, where m is at least one of these; the various types of microcracks are mainly tectonic cracks and particle fracture cracks, where p is at least one of these; n, m, and p are all positive integers. For example, for dissolution pores, when they include feldspar particle dissolution pores, quartz particle dissolution pores, and quartz cement dissolution pores, n = 3. In this case, the porosity of the first type of dissolution pore (i = 1, feldspar particle dissolution pores) is calculated and denoted as φ. 面溶1 The porosity of the second type of dissolution porosity (i=2, quartz grain dissolution porosity) is denoted as φ. 面溶2 The porosity of the third type of dissolution pores (i=3, quartz cement dissolution pores) is denoted as φ. 面溶3 Regarding other quantities and types, as well as various types of cementitious materials and various types of microcracks, the definitions follow the same principle. Furthermore, the surface area ratio of cementitious materials described in this application is more precisely about the area ratio of cementitious materials in the image of the cast sheet; the microcracks refer to cracks with a size of 0.01 mm to 1 mm, preferably 0.05 mm to 0.5 mm.

[0051] As shown in Figure 1, based on the current porosity φ of each first sample... 今 With total face rate φ 面 A functional relationship (referred to as the first functional relationship) was established between the current porosity and the total porosity of all first samples, as shown in Equation 2:

[0052] Substituting the porosity of various types of dissolution pores, various types of cementitious material porosity, and various types of microcrack porosity into the first functional relationship (Formula 2), the contribution amounts of various types of dissolution pores, various types of cementitious material porosity, and various types of microcrack porosity are calculated. The contribution amount of the i-th type of dissolution pore is denoted as φ. 溶i The porosity contribution of the j-th type of cement is denoted as φ.胶j The contribution of the kth type of microcrack porosity is denoted as φ. 缝k .

[0053] For example, for one sample out of 139 samples, it contains three types of dissolution pores; thus, the φ of these three types of dissolution pores... 面溶1 φ 面溶2 φ 面溶3 Substituting each into Formula 2, we obtain three φ values. 今 denoted as φ 溶1 φ 溶2 φ 溶3 This represents the contribution of dissolution porosity to the first sample. The contribution of cement porosity and microcrack porosity are calculated in the same or similar ways.

[0054] Using Formula 3, calculate the total compaction porosity reduction φ for each first sample. 压 :

[0055] The maximum paleotectonic stress for each first sample was obtained by performing acoustic emission testing (AET) and numerical simulation. The AET test, conducted using an AE-04 type AET detection system under low-noise and electronic interference-free conditions, was used to obtain the maximum paleotectonic stress. The numerical simulation employed methods such as the finite element method (FEM) and the discrete element method (DEM). These methods for obtaining the maximum paleotectonic stress of a sample or study area are well-known to those skilled in the art.

[0056] Furthermore, in the first sample, medium sandstone samples with a burial depth within 300m, a sorting coefficient So between 1.2 and 1.4, a cement content of less than 5%, and distributed in different regions of maximum paleotectonic stress were selected as the primary samples to minimize the influence of other factors on the compaction porosity reduction. The selected samples were sorted in descending order of maximum paleotectonic stress, and the difference in the total compaction porosity reduction between two selected samples from adjacent regions was taken as the lateral compaction porosity reduction of the sample with the higher maximum paleotectonic stress. This explanation uses medium sandstone as an example; the same or similar treatment was applied to fine and coarse sandstone.

[0057] Based on the 139 initial samples mentioned above, when selecting the final samples, the difference in current burial depth between any two selected samples must be within 300m (i.e., the difference in burial depth between any two selected samples from the study area must be within 300m), the sorting coefficient So of each selected sample must be in the range of 1.2-1.4, the cement content must be less than 5%, and the sample must belong to one of the following types of sandstone: fine sandstone, medium sandstone, or coarse sandstone. Assuming that 100 selected samples meet the above conditions, these 100 selected samples will be divided into zones according to the maximum paleotectonic stress. Specifically, the different maximum paleotectonic stress regions refer to determining the minimum and maximum values ​​of the maximum paleotectonic stress from these 100 selected samples, and dividing the area between the minimum and maximum values ​​into multiple regions. The step size for each region is a value between 5 and 15 MPa, for example, 10 MPa can be chosen as the step size to obtain multiple regions. A step size that is too large may result in insufficient volume for subsequent differentiation, making it difficult to distinguish between regions; a step size that is too small may result in too small differences between values, also making it difficult to distinguish between regions. Therefore, the step size can be selected based on actual data, subsequent effects, and experience. Then, each selected sample is placed into its corresponding region, with at least one selected sample in each region. The samples are sorted according to their maximum paleotectonic stress from largest to smallest. In two adjacent regions, at least one selected sample is selected from each region, and the difference between their total compaction porosity is calculated to obtain the lateral compaction porosity of the selected sample with the larger maximum paleotectonic stress. This allows us to obtain the lateral compaction porosity φ for each selected sample. 侧压 .

[0058] As shown in Figure 2, the lateral compaction porosity reduction φ for all selected samples is established. 侧压 The functional relationship between φ and the maximum paleotectonic stress F (referred to as the second functional relationship) is shown in Equation 4: 侧压 =3.3952ln(F)-9.3104 (4).

[0059] Since the selected sample is representative, the resulting second functional relationship is applicable to calculating the lateral compaction porosity reduction φ of any first sample. 侧压 .

[0060] (2) Calculate the lateral compaction and porosity reduction of each lateral extrusion during multiple lateral extrusion processes.

[0061] In this embodiment, the diagenesis of the study area involved four lateral compressions. Through acoustic emission testing and numerical simulation of the samples, the maximum paleotectonic stresses corresponding to these four lateral compressions were obtained as F1 = 35.2 MPa, F2 = 59.9 MPa, F3 = 74.8 MPa, and F4 = 80.9 MPa, respectively. That is, F1-F4 represent the maximum paleotectonic stresses exerted on the study area (not individual first samples) by each lateral compression; these are shown in Table 1 for diagenetic stages 2, 4, 8, and 9, respectively.

[0062] The lateral compaction reduction in pore size for each lateral extrusion is calculated using Formula 5.

[0063] Where q represents the number of lateral compressions in the study area, and F l F represents the maximum paleotectonic stress during the l-th lateral compression. l-1 F is the maximum paleotectonic stress of the (l-1)th lateral compression, and F is the maximum paleotectonic stress in the second functional relationship (Formula 4). In the calculation, F0 is taken as 0 MPa, and F = F q ;φ 侧压 The lateral compaction reduction in porosity corresponding to the maximum paleotectonic stress F is calculated based on the second functional relationship.

[0064] (3) Establish a graph showing the relationship between vertical compaction reduction and burial depth.

[0065] The lateral compaction porosity reduction φ of any first sample is calculated using Formula 4. 侧压 The total compaction reduction φ of each first sample 压 (Calculated using Formula 3) and the lateral compaction reduction φ 侧压 By subtracting the values, the vertical compaction porosity reduction φ of each first sample is obtained. 垂压 .

[0066] Taking into account parameters such as sorting coefficient and sediment grain size of each first sample, samples with cement content of less than 5% were selected. Based on the vertical distribution characteristics of vertical compaction porosity reduction of different samples, a chart was established to show the relationship between reservoir vertical compaction porosity reduction and burial depth under the constraints of different sediment parameters (sorting coefficient and sediment grain size), as shown in Figure 3.

[0067] In Figure 3, the sorting coefficients of each first sample range from 1.2 to 1.7. Based on sediment grain size, the samples can be divided into fine sandstone, medium sandstone, and coarse sandstone, with the fine sandstone grain size ranging from [0.1-0.25) mm, the medium sandstone grain size ranging from [0.25-0.5) mm, and the coarse sandstone grain size ranging from [0.5-2) mm. Typically, laser grain size analysis is used to measure the grain size. The cement content in this application is generally measured using conventional instruments or methods such as thin-section image analysis, X-ray diffraction (XRD), and scanning electron microscopy (SEM) energy dispersive spectroscopy. This embodiment primarily uses thin-section image analysis.

[0068] In addition, the sorting coefficient and sediment particle size of the first sample were considered when constructing the relationship chart. The first sample with a cement content of less than 5% was selected. Since they are representative, the relationship chart obtained is also suitable for the analysis of other first samples.

[0069] (4) Plot the porosity evolution curves of clastic reservoirs during geological history under tectonic compression.

[0070] For all the first samples, the formation time and chronological order of authigenic minerals, dissolution pores, and fractures in the study area were determined through cast thin section analysis, in-situ trace element analysis, fluid inclusion analysis, and U-Pb dating, thus establishing a diagenetic evolution sequence. Establishing a diagenetic evolution sequence is a standard technique in this field; for example, the industry standard for diagenetic stage classification of clastic rocks (SY / T5477-2024) and the literature Wang et al., 2018 can be referenced.

[0071] The diagenetic evolution sequence of this study area is shown in Table 1, comprising nine diagenetic stages: Stage 1: feldspar dissolution, feldspar cementation, and quartz cementation (Diagenetic Stage 2) → Stage 1: calcite, dolomite, gypsum cementation, and quartz dissolution (Diagenetic Stage 3) → Stage 2: feldspar dissolution and authigenic quartz cementation (Diagenetic Stage 6) → Stage 2: (iron-bearing) calcite, dolomite, and anhydrite cementation (Diagenetic Stage 6) → Stage 2: feldspar dissolution (Diagenetic Stage 9). Lateral or vertical compaction is present in each diagenetic stage.

[0072] Using homogenization temperature analysis and U-Pb dating analysis of inclusions, combined with burial history and thermal history analysis, the occurrence time of each diagenetic stage was determined. Combined with the occurrence time of lateral compaction events, the diagenetic stages were determined, as shown in Table 1.

[0073] By projecting the occurrence times of different diagenetic stages onto the burial history map, the paleoburial depths at the beginning and end of each diagenetic stage were obtained, as shown in column 4 of Table 1. The acquisition of paleoburial depths is a current technique and will not be described in detail here.

[0074] Table 1. Diagenetic evolution sequence and paleoburial depth and paleoporosity reconstruction at different diagenetic stages.

[0075] In the process of paleoporosity reconstruction at different diagenetic stages, the original porosity φ of each first sample is first obtained according to Formula 1. 原 Their average value is the recovered porosity of 37.7% at the initial deposition shown in Table 1.

[0076] In diagenetic stage 1, since only vertical compaction is involved, the total compaction porosity φ of each first sample is reduced. 压 Its lateral compaction reduces the amount of pores φ 侧压 By subtracting the values, the first vertical compaction porosity reduction φ of each first sample is obtained. 垂压 Take their average value A (i.e., the first vertical compaction porosity reduction φ of the 139 first samples). 垂压 After adding them and dividing by 139, we get A (the same below). We then subtract this average value A from the initial recovered porosity of 37.7% to obtain the recovered porosity of diagenetic stage 1, which is 28%.

[0077] In diagenetic stage 2, the first lateral compression, dissolution, and cementation are involved. For the first lateral compression, the lateral compaction porosity reduction B1 of the first lateral compression in this study area is calculated using Formula 5. For dissolution and cementation, the contribution of various types of dissolution porosity and various types of cement porosity of each first sample is calculated using Formula 2, and the average value is taken to obtain the average value B2 for various types of dissolution porosity and the average value B3 for various types of cement porosity. The total average value B is calculated between B1, B2, and B3 using the formula B = B1 + B3 - B2. The recovered porosity of 28% in diagenetic stage 1 is subtracted from B to obtain the recovered porosity of 26% in diagenetic stage 2.

[0078] In diagenetic stage 3, vertical compaction, dissolution, and cementation are involved; for vertical compaction, the porosity φ is reduced by the total compaction of each first sample. 压 Its lateral compaction reduces the amount of pores φ 侧压 By subtracting the values, the second vertical compaction porosity reduction φ of each sample is obtained. 垂压 The average value C1 is taken. For dissolution and cementation, the contribution of various types of dissolution pores and the contribution of various types of cement pores for each first sample are calculated using Formula 2, and the average value is taken to obtain the average value C2 for the contribution of various types of dissolution pores and the average value C3 for the contribution of various types of cement pores. The total average value C is calculated between C1, C2 and C3 using the formula C = C1 + C3 - C2. The recovered porosity of 26% in diagenetic stage 2 is subtracted from C to obtain the recovered porosity of 30.5% in diagenetic stage 3.

[0079] In diagenetic stage 4, vertical compaction and a second lateral compression are involved; for vertical compaction, the porosity φ is reduced by the total compaction of each first sample. 压 Its lateral compaction reduces the amount of pores φ 侧压 By subtracting the values, the third vertical compaction porosity reduction φ of each sample is obtained. 垂压 Take their average value D1; for the second lateral compression, based on the first lateral compression in diagenetic stage 2, use formula 5 to calculate the lateral compaction porosity reduction D2 of the second lateral compression; between D1 and D2, the total average value D is calculated using the formula D=D1+D2, and by subtracting D from the recovered porosity of 30.5% in diagenetic stage 3, the recovered porosity of 29.8% in diagenetic stage 4 is obtained.

[0080] In diagenetic stages 5 to 8, the effects of various diagenetic processes on reservoir porosity were quantitatively calculated using the same or similar methods. These included vertical compaction from the 4th to 6th stages, lateral compression from the 3rd stage, authigenic quartz cementation, and second-stage (iron-bearing) cementation by calcite, dolomite, and anhydrite. The porosity recovery values ​​for diagenetic stages 5 to 8 were 17.7%, 12.4%, 9.4%, and 9.0%, respectively.

[0081] In diagenetic stage 9, vertical compaction, fourth lateral compression, fractures, and feldspar dissolution are involved. For vertical compaction, the porosity φ is reduced by the total compaction of each first sample. 压 Its lateral compaction reduces the amount of pores φ 侧压 By subtracting the values, the porosity reduction φ of the seventh vertical compaction for each sample was obtained. 垂压 The average value E1 is taken. For the fourth lateral compression, based on the third lateral compression in diagenetic stage 8, the lateral compaction porosity reduction E2 of the fourth lateral compression is calculated using formula 5. For fractures, the microfracture porosity contribution of each first sample is calculated using formula 2, and the average value E3 is taken. For feldspar dissolution, the dissolution porosity contribution of each first sample is calculated using formula 2, and the average value E4 is taken. The total average value E is obtained from E1, E2, E3, and E4 using the formula E = E1 + E2 - (E3 + E4). The recovered porosity of diagenetic stage 9 is obtained by subtracting E from the recovered porosity of 9.0% in diagenetic stage 8.

[0082] The overall calculation approach is as follows: In diagenetic stages 1 to diagenetic stages 9, the porosity recovery value of each diagenetic stage = the recovered porosity of the previous diagenetic stage - (porosity contribution of destructive diagenesis - porosity contribution of constructive diagenesis), where destructive diagenesis includes vertical compaction, lateral compression, and cementation, and constructive diagenesis includes dissolution and microfracture.

[0083] In this embodiment, the contribution of various chemical diagenetic events to reservoir porosity (i.e., the contribution of various dissolution porosity, various cement porosity, and various microfracture porosity) is quantitatively calculated using thin section images of the cast body and the first function relationship. Constrained by the diagenetic evolution sequence (diagenetic processes corresponding to each diagenetic stage), the reservoir microstructure characteristics of each diagenetic stage are restored by using the inversion stripping method, combined with the lateral compaction porosity reduction and vertical compaction porosity reduction versus burial depth charts during each lateral compression in the study area during diagenesis. (Results shown in the circles in Figure 4) The porosity and corresponding porosity of the reservoir at each diagenetic stage are obtained. According to geological history, a reservoir porosity evolution curve from the original porosity to the present porosity is plotted (curve in Figure 4), obtaining a porosity evolution process diagram of clastic reservoirs in the study area under tectonic compression, as shown in Figure 4.

[0084] This embodiment clarifies the evolution law of reservoir properties (i.e., the change process of porosity from the original porosity to the present porosity). By analyzing the porosity evolution values ​​and curves, it reveals the evolution characteristics and main controlling factors of pore types, thereby accurately screening favorable reservoir areas—focusing on identifying areas with well-developed porosity and strong secondary dissolution, directly guiding the direction of oil and gas exploration. At the same time, it provides reference and guidance for oil and gas exploration in areas with similar geological backgrounds (similar tectonic compression environments and similar reservoir mineral compositions), guiding others to carry out the screening and exploration of favorable reservoir areas under similar geological backgrounds. It provides reliable data support for the accurate delineation of exploration target areas and the priority deployment of exploration wells, improving the targeting and success rate of oil and gas exploration and avoiding the waste of resources caused by blind exploration.

[0085] Furthermore, the porosity evolution recovery method described in this application embodiment can be implemented by a computer device. Figure 5 is a schematic diagram of the hardware structure of a computer device according to an embodiment of this application. The computer device may include a processor 51 and a memory 52 storing computer program instructions.

[0086] Specifically, the processor 51 may include a central processing unit (CPU), or an application-specific integrated circuit (ASIC), or one or more integrated circuits configured to implement the embodiments of this application. The memory 52 may include a mass storage device for data or instructions. Where appropriate, the memory 52 may include removable or non-removable (or fixed) media; where appropriate, the memory 52 may be internal or external to a data processing device; and so on.

[0087] The memory 52 can be used to store or cache various data files that need to be processed and / or used for communication, as well as possible computer program instructions executed by the processor 51.

[0088] The processor 51 reads and executes computer program instructions stored in the memory 52 to implement any of the porosity evolution recovery methods in the above embodiments.

[0089] In some embodiments, the computer device may further include a communication interface 53 and a bus 50. As shown in FIG5, the processor 51, memory 52, and communication interface 53 are connected through the bus 50 and communicate with each other.

[0090] Furthermore, in conjunction with the porosity evolution recovery method in the above embodiments, this application can provide a computer-readable storage medium for implementation. This computer-readable storage medium stores computer program instructions; when these computer program instructions are executed by a processor, they implement any of the porosity evolution recovery methods in the above embodiments.

Claims

1. A method for recovering the porosity evolution of clastic rock reservoirs under tectonic compression, wherein, Includes the following steps: Establish the second functional relationship: Select several first samples from the study area and calculate the total compaction porosity reduction of each first sample; obtain the maximum paleotectonic stress of each first sample; select first samples with similar burial depth, similar rock structure, and different maximum paleotectonic stresses from the first samples as selected samples; The selected samples are sorted in descending order of maximum paleotectonic stress. The difference between the total compaction porosity of two adjacent selected samples is taken as the lateral compaction porosity of the selected sample with the greater maximum paleotectonic stress. A functional relationship between the lateral compaction porosity and the maximum paleotectonic stress is established, namely the second functional relationship. Calculate the lateral compaction porosity reduction for each lateral compression: Determine the number of lateral compressions during the diagenesis process in the study area and the maximum paleotectonic stress for each lateral compression. Combined with the second function relationship, calculate the lateral compaction porosity reduction for each lateral compression. Establish a relationship chart: Subtract the total compaction porosity reduction of each first sample from its lateral compaction porosity reduction to obtain the vertical compaction porosity reduction of that first sample; based on the vertical distribution characteristics of the vertical compaction porosity reduction of different first samples, establish a relationship chart between the vertical compaction porosity reduction and burial depth under different sediment parameter constraints. Evolution curves were plotted: the diagenetic stage of the study area was determined, and the porosity evolution curve of clastic reservoirs under tectonic compression was plotted by combining the lateral compaction porosity reduction amount of each lateral compression during the diagenetic process of the study area and the relationship between the vertical compaction porosity reduction amount and the burial depth.

2. The method for restoring porosity evolution in clastic reservoirs under tectonic compression as described in claim 1, wherein, In the step of establishing the second functional relationship, the specific steps for calculating the total compaction reduction are as follows: Based on the functional relationship between porosity φ and sorting coefficient So, the original porosity φ of each first sample is calculated. 原 ; Obtain the current porosity φ of each first sample. 今 Total face rate φ 面 The porosity of various types of dissolution pores, the porosity of various types of cementitious materials, and the porosity of various types of microcracks; among which, the porosity of the i-th type of dissolution pore is denoted as φ. 面溶i Let i = 1, 2, ..., n, where n is the number of types of dissolution pores; the porosity of the j-th type of cement is denoted as φ. 面胶j j = 1, 2, ..., m, where m is the number of cement types; the porosity of the k-th type of microcrack is denoted as φ. 面缝k k = 1, 2, ..., p, where p is the number of types of microcracks; Based on the current porosity φ of each first sample 今 With total face rate φ 面 Establish the functional relationship between current porosity and total porosity, i.e., the first functional relationship; Substituting the porosity of various types of dissolution pores, various types of cementitious material porosity, and various types of microcrack porosity into the first functional relationship, the contribution amounts of various types of dissolution pores, various types of cementitious material porosity, and various types of microcrack porosity are calculated. The contribution amount of the i-th type of dissolution pore is denoted as φ. 溶i The porosity contribution of the j-th type of cement is denoted as φ. 胶j The contribution of the kth type of microcrack porosity is denoted as φ. 缝k ; Using Formula 3, calculate the total compaction porosity reduction φ for each first sample. 压 :

3. The method for restoring porosity evolution in clastic reservoirs under tectonic compression as described in claim 1, wherein, In the step of calculating the lateral compaction reduction amount for each lateral extrusion, the lateral compaction reduction amount φ for the lth lateral extrusion... 侧压l The calculation formula is: Where q represents the number of lateral compressions in the study area, and F l F represents the maximum paleotectonic stress during the l-th lateral compression. l-1 F represents the maximum paleotectonic stress during the (l-1)th lateral compression, and F represents the maximum paleotectonic stress in the second functional relationship. In the calculation, F0 is taken as 0 MPa, and F = F q ;φ 侧压 The lateral compaction reduction in porosity corresponding to the maximum paleotectonic stress F is calculated based on the second functional relationship.

4. The method for restoring porosity evolution in clastic reservoirs under tectonic compression as described in claim 1, wherein, In the step of establishing the relational map, a first sample with a cement content of less than 5% is selected, and the sediment parameters include sorting coefficient and sediment grain size.

5. The method for restoring porosity evolution in clastic reservoirs under tectonic compression as described in claim 1, wherein, The specific steps for determining the diagenetic stages in the study area during the process of plotting the evolution curve are as follows: Through thin section analysis of cast bodies, in-situ micro-element testing and analysis, fluid inclusion analysis, and U-Pb dating analysis, the formation time and sequence of authigenic minerals, dissolution pores, and fractures in the study area are determined, thus establishing a diagenetic evolution sequence. Using inclusion homogenization temperature analysis and U-Pb dating analysis, combined with burial history and thermal history analysis, the occurrence time of each diagenetic stage is determined. Combined with the occurrence time of each lateral compression, the diagenetic stage is then determined.

6. The method for restoring porosity evolution in clastic reservoirs under tectonic compression as described in claim 5, wherein, The specific steps for plotting the evolution curve are as follows: Using the projection of the occurrence time of different diagenetic stages onto the burial history map, the paleoburial depth at the beginning and end of each diagenetic stage is obtained; constrained by the diagenetic evolution sequence, through thin section image analysis and inversion stripping method, combined with the lateral compaction porosity reduction and vertical compaction porosity reduction versus burial depth maps of each lateral compression during the diagenetic process in the study area, the reservoir microstructure characteristics of each diagenetic stage are restored, and the porosity and corresponding porosity of the reservoir at each diagenetic stage are obtained; according to geological history, the reservoir porosity evolution curve from the original porosity to the present porosity is plotted.

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