Clastic rock reservoir porosity evolution recovery method under tectonic extrusion background

Abstract

The invention relates to a clastic rock reservoir porosity evolution recovery method under a tectonic extrusion background, and belongs to the technical field of petroleum and natural gas exploration and development. The method comprises the following steps: calculating the total compaction pore reduction amount of clastic rock samples, selecting samples with similar burial depths, similar rock structures and different maximum paleotectonic stresses as selected samples, and calculating the total compaction pore reduction amount of the clastic rock samples according to the difference value of the total compaction pore reduction amount corresponding to two selected samples with adjacent maximum paleotectonic stresses. Obtaining the lateral compaction pore reduction amount of the maximum palaeotectonic stress, and establishing a function relationship between the lateral compaction pore reduction amount and the maximum palaeotectonic stress; the lateral compaction hole reduction amount of each time of lateral extrusion in the multiple lateral extrusion processes is calculated; according to the total compaction hole reduction amount and the lateral compaction hole reduction amount, the vertical compaction hole reduction amount is calculated, and a relation chart of the vertical compaction hole reduction amount and the buried depth is established; and drawing a geological historical period porosity evolution curve of the clastic rock reservoir under the tectonic extrusion background by utilizing an inversion back-stripping method and combining the lateral compaction pore reduction amount and the vertical compaction pore reduction amount. The method solves the problem that the lateral and vertical compaction hole reduction amount cannot be quantitatively calculated in the evolution recovery process of the porosity of the foreland basin reservoir.

Description

Technical Field

[0001] The present invention belongs to the technical field of oil and gas exploration and development, and particularly relates to a method for restoring the porosity evolution of clastic rock reservoirs under the background of tectonic compression. Background Art

[0002] In recent years, with the gradual increase in the exploration degree of medium and shallow oil and gas, oil and gas exploration has gradually extended to deep and ultra-deep layers. More than 60% of the oil and gas resources in deep and ultra-deep layers are distributed in clastic rocks, and the foreland basin is one of the most typical representatives of deep and ultra-deep clastic rock exploration. The complex tectonic evolution, burial process, and diagenetic transformation in the foreland basin make the clastic rock reservoir have strong heterogeneity characteristics. Remodeling the porosity evolution process of the reservoir is the key to understanding the controlling factors of reservoir development and revealing the formation mechanism of high-quality reservoirs. The existing methods for restoring the porosity evolution of clastic rock reservoirs in geological history do not consider the compaction pore reduction caused by lateral compression in the foreland basin and are not applicable to the restoration of reservoir porosity evolution under the background of tectonic compression. Summary of the Invention

[0003] Aiming at the problem that the existing methods for restoring the porosity evolution of clastic rock reservoirs in geological history are not applicable to the restoration of reservoir porosity evolution under the background of tectonic compression in the foreland basin, the present invention provides a method for restoring the porosity evolution of clastic rock reservoirs under the background of tectonic compression, which determines the lateral compaction pore reduction and the vertical compaction pore reduction, and corrects the reservoir porosity obtained by the inverse backstripping method by using the lateral compaction pore reduction and the vertical compaction pore reduction, so as to obtain the true porosity evolution process of the clastic rock reservoir under the background of tectonic compression.

[0004] The present invention provides a method for restoring the porosity evolution of clastic rock reservoirs under the background of tectonic compression, comprising the following steps:

[0005] (1) Select several samples from the study area and calculate the total compaction pore reduction of each sample; obtain the maximum paleo-tectonic stress corresponding to the sample, select samples with similar burial depths, similar rock structures, and different maximum paleo-tectonic stresses in the sample as selected samples, sort the selected samples in descending order of the maximum paleo-tectonic stress, and take the difference between the total compaction pore reductions corresponding to two adjacent selected samples as the lateral compaction pore reduction of the sample with the larger maximum paleo-tectonic stress among the two selected samples; establish a functional relationship between the lateral compaction pore reduction and the maximum paleo-tectonic stress;

[0006] (2) Determine the number of lateral compressions during the diagenetic process in the study area and the paleo-tectonic stress of each lateral compression, and calculate the lateral compaction pore reduction of each lateral compression in combination with the functional relationship between the lateral compaction pore reduction and the maximum paleo-tectonic stress;

[0007] (3) Subtract the total compaction pore reduction of the sample from the lateral compaction pore reduction to obtain the vertical compaction pore reduction of the sample. Based on the vertical distribution characteristics of the vertical compaction pore reduction of different samples, establish a relationship chart of vertical compaction pore reduction and burial depth under different sediment parameter constraints;

[0008] (4) Determine the diagenetic stage of the study area. Using the inverse backstripping method, combined with the lateral compaction pore reduction of each lateral extrusion during diagenesis in the study area and the relationship chart of vertical compaction pore reduction and burial depth, draw the porosity evolution curve of the clastic reservoir during the geological history period under the background of tectonic extrusion.

[0009] In some of these embodiments, in step (1), the specific steps for calculating the total compaction pore reduction are as follows:

[0010] Calculate the original porosity φ of each sample according to the functional relationship between porosity and sorting coefficient So 原 ;

[0011] Obtain the current porosity φ of each sample 今 , total pore area ratio φ 面 , various types of dissolution pore area ratios, various types of cement area ratios, and various types of microfracture area ratios; among them, the area ratio of the i-th type of dissolution pore is denoted as φ 面溶i , i = 1, 2,..., n, where n is the number of types of dissolution pores; the area ratio of the j-th type of cement is denoted as φ 面胶j , j = 1, 2,..., m, where m is the number of types of cements; the area ratio of the k-th type of microfracture is denoted as φ 面缝k , k = 1, 2,..., p, where p is the number of types of microfractures;

[0012] Based on the current porosity φ of the sample 今 and the total pore area ratio φ 面 , establish a functional relationship between the current porosity and the total pore area ratio;

[0013] Substitute the area ratios of various types of dissolution pores, various types of cements, and various types of microfractures into the functional relationship formula of the current porosity and the total pore area ratio, and calculate the contribution amounts of various types of dissolution pores, various types of cement pores, and various types of microfracture pores. Among them, the contribution amount of the i-th type of dissolution pore is denoted as φ 溶i , the contribution amount of the j-th type of cement pore is denoted as φ 胶j , and the contribution amount of the k-th type of microfracture pore is denoted as φ 缝k ;

[0014] Use the formula to calculate the total compaction pore reduction φ of the sample 压 .

[0015] In some of these embodiments, in step (2), the lateral compaction pore reduction φ of the l-th lateral extrusion侧压l The calculation formula is as follows:

[0016]

[0017] Among them, q is the number of lateral extrusion times in the study area, and F l is the paleotectonic stress of the l-th lateral extrusion, and F l-1 is the paleotectonic stress of the (l - 1)-th lateral extrusion, F is the maximum paleotectonic stress. During calculation, F0 is taken as 0 MPa, and F = F q ; φ 侧压 is the pore reduction amount due to lateral compaction corresponding to the maximum paleotectonic stress, which is obtained by calculating according to the functional relationship between the pore reduction amount due to lateral compaction and the maximum paleotectonic stress.

[0018] In some embodiments, in step (3), when establishing the relationship chart between the vertical compaction pore reduction amount and the burial depth, samples with a cement content of less than 5% are selected, and the sediment parameters include the sorting coefficient and the sediment grain size.

[0019] In some embodiments, in step (4), the specific steps for determining the diagenetic stage of the study area are as follows: By means of cast thin section analysis, in-situ trace element and main element test analysis, fluid inclusion analysis, and U-Pb dating analysis, determine the formation time and the sequence of autogenous minerals, dissolution pores, and fractures in the study area, and establish a diagenetic evolution sequence; Use inclusion homogenization temperature analysis and U-Pb dating analysis, combined with burial history and thermal history analysis, to determine the occurrence time of each diagenetic event, and combine with the occurrence time of the lateral compaction event to determine the diagenetic stage.

[0020] In some embodiments, in step (4), the specific steps for plotting the porosity evolution curve of the clastic rock reservoir during the geological history period under the background of tectonic extrusion are as follows: Use the projection of the time of different diagenetic stages on the burial history diagram to obtain the paleo-burial depths at the beginning and end of each diagenetic stage; Constrained by the diagenetic evolution sequence, through cast thin section image analysis and backstripping method, combined with the lateral compaction pore reduction amount of each lateral extrusion during the diagenesis process in the study area and the relationship chart between the vertical compaction pore reduction amount and the burial depth, restore the microscopic appearance characteristics of the reservoir at each diagenetic stage, and obtain the pore face ratio and the corresponding porosity of the reservoir at each diagenetic stage; Plot the porosity evolution curve of the reservoir from the original porosity to the current porosity according to the geological history time.

[0021] Compared with the prior art, the advantages and beneficial effects of the present invention are as follows:

[0022] The method for restoring the porosity evolution of clastic rock reservoirs under the background of tectonic extrusion provided by the present invention, based on the calculation of the total compaction pore reduction amount of clastic rock samples, selects samples with similar burial depths, similar rock structures, and different maximum paleo-tectonic stresses as selected samples. By calculating the difference in the total compaction pore reduction amounts corresponding to two selected samples with adjacent maximum paleo-tectonic stresses, the lateral compaction pore reduction amount of the sample with the larger maximum paleo-tectonic stress is obtained, thereby establishing a functional relationship between the lateral compaction pore reduction amount and the maximum paleo-tectonic stress. Furthermore, the lateral compaction pore reduction amount and the vertical compaction pore reduction amount of any sample are obtained, and a vertical compaction pore reduction amount chart is established. Then, using the lateral compaction pore reduction amount and the vertical compaction pore reduction amount charts in different extrusion periods, combined with the "inversion backstripping method", the true porosity evolution curve of clastic rock reservoirs under the background of tectonic extrusion is obtained, realizing the quantitative restoration of the porosity of clastic rock reservoirs in foreland basins, which is of great significance for understanding the genetic mechanism of deep to ultra-deep clastic rock reservoirs. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 FIG. 6 is a functional relationship diagram between the current porosity and the total pore area ratio provided in Embodiment 1 of the present invention;

[0024] Figure 2 FIG. 10 is a functional relationship diagram between the lateral compaction pore reduction amount and the maximum paleo-tectonic stress provided in Embodiment 1 of the present invention;

[0025] Figure 3 FIG. 14 is a chart showing the relationship between the vertical compaction pore reduction amount and the burial depth provided in Embodiment 1 of the present invention;

[0026] Figure 4 FIG. 18 is a diagram showing the porosity evolution process of clastic rock reservoirs in the study area under the background of tectonic extrusion provided in Embodiment 1 of the present invention. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0027] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all of the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0028] Embodiment 1

[0029] A method for restoring the porosity evolution of clastic rock reservoirs under the background of tectonic extrusion includes the following steps:

[0030] (1) Establish a functional relationship between the lateral compaction pore reduction amount and the maximum paleo-tectonic stress

[0031] Select 139 sandstone samples from a certain research area. Obtain the sorting coefficient So of the samples through sediment laser particle size analysis. According to the functional relationship between porosity and sorting coefficient So, φ = 20.91 + 22.90 / So, calculate the original porosity φ of each sample 原 .

[0032] Make the samples into plug samples with a diameter of 2.5 cm and a length of 3 - 5 cm. Obtain the current porosity φ of each sample through measurement of the plug samples 今 .

[0033] Make the samples into cast thin sections. Obtain the total pore area ratio φ of each sample through image analysis of the cast thin sections by an optical microscope 面 、the pore area ratios of various types of dissolution pores, the pore area ratios of various types of cements, and the pore area ratios of various types of micro - fractures; among them, the pore area ratio of the i - th type of dissolution pore is denoted as φ 面溶i , i = 1, 2, ……, n, where n is the number of types of dissolution pores; the pore area ratio of the j - th type of cement is denoted as φ 面胶j , j = 1, 2, ……, m, where m is the number of types of cements; the pore area ratio of the k - th type of micro - fracture is denoted as φ 面缝k , k = 1, 2, ……, p, where p is the number of types of micro - fractures.

[0034] As Figure 1 shown, according to the current porosity φ 今 of the sample and the total pore area ratio φ 面 , establish the functional relationship between the current porosity and the total pore area ratio as:

[0035] Substitute the pore area ratios of various types of dissolution pores, the pore area ratios of various types of cements, and the pore area ratios of various types of micro - fractures into the above - mentioned functional relationship between the current porosity and the total pore area ratio to calculate the contribution amounts of various types of dissolution pores, the contribution amounts of various types of cement pores, and the contribution amounts of various types of micro - fracture pores. Among them, the contribution amount of the i - th type of dissolution pore is denoted as φ 溶i , the contribution amount of the j - th type of cement pore is denoted as φ 胶j , and the contribution amount of the k - th type of micro - fracture pore is denoted as φ 缝k .

[0036] Use the formula to calculate the total compaction - induced pore reduction amount φ 压 of the sample.

[0037] The maximum paleo-tectonic stress corresponding to the sample is obtained through sample acoustic emission testing and numerical simulation. In the sample, medium sandstone samples with a burial depth within 300 m, a sorting coefficient So in the range of 1.2 - 1.4, a cement content less than 5%, and distributed in different maximum paleo-tectonic compressive stress regions are selected as the selected samples to minimize the influence of other factors on the compaction pore reduction amount. The selected samples are sorted in descending order of the maximum paleo-tectonic stress, and the difference in the total compaction pore reduction amount corresponding to two adjacent selected samples is taken as the lateral compaction pore reduction amount of the sample with the larger maximum paleo-tectonic stress among the two selected samples.

[0038] As Figure 2 shown, the functional relationship between the lateral compaction pore reduction amount φ 侧压 and the maximum paleo-tectonic stress F is: φ 侧压 = 3.3952ln(F) - 9.3104.

[0039] (2) Calculate the lateral compaction pore reduction amount for each lateral extrusion during multiple lateral extrusion processes

[0040] There are 4 lateral extrusions during the diagenesis process in this study area. The maximum paleo-tectonic stresses corresponding to the 4 lateral extrusions obtained through sample acoustic emission testing and numerical simulation are F1 = 35.2 MPa, F2 = 59.9 MPa, F3 = 74.8 MPa, and F4 = 80.9 MPa respectively.

[0041] Use the formula to calculate the lateral compaction pore reduction amount for each lateral extrusion, where q is the number of lateral extrusions in the study area, F l is the paleo-tectonic stress of the l-th lateral extrusion, F l-1 is the paleo-tectonic stress of the (l - 1)-th lateral extrusion, F is the maximum paleo-tectonic stress. When calculating, F0 is taken as 0 MPa, F = F q ; φ 侧压 is the lateral compaction pore reduction amount corresponding to the maximum paleo-tectonic stress, which is calculated according to the functional relationship between the lateral compaction pore reduction amount and the maximum paleo-tectonic stress.

[0042] (3) Establish a relationship chart of the vertical compaction pore reduction amount and the burial depth

[0043] Use the formula φ 侧压 = 3.3952ln(F) - 9.3104 to calculate the lateral compaction pore reduction amount φ 侧压 of any sample. Subtract the lateral compaction pore reduction amount φ 压 from the total compaction pore reduction amount φ 侧压 of the sample to obtain the vertical compaction pore reduction amount φ 垂压 .

[0044] Considering parameters such as the sorting coefficient and sediment grain size comprehensively, samples with a cement content of less than 5% are selected. According to the vertical distribution characteristics of the vertical compaction pore reduction amount of different samples, a relationship chart of the vertical compaction pore reduction amount of the reservoir and the burial depth under the constraint of different sediment parameters is established, as Figure 3 shown.

[0045] (4) Plot the porosity evolution curve of clastic rock reservoirs during the geological history period under the background of tectonic compression

[0046] Through thin-section casting analysis, in-situ trace element testing analysis, fluid inclusion analysis and U-Pb dating analysis, determine the formation time and sequence of authigenic minerals, dissolution pores and fractures in the study area, and establish a diagenetic evolution sequence. The diagenetic evolution sequence of this study area is shown in Table 1, specifically: the first stage of feldspar dissolution / authigenic albite, the first stage of quartz cementation → the first stage of calcite, dolomite, gypsum cementation, quartz dissolution → the second stage of feldspar dissolution, authigenic quartz cementation → the second stage of (iron-bearing) calcite, dolomite, anhydrite cementation → a small amount of feldspar dissolution in the late stage.

[0047] Using fluid inclusion homogenization temperature analysis and U-Pb dating analysis, combined with burial history and thermal history analysis, determine the occurrence time of each diagenetic event, and combined with the occurrence time of lateral compaction events, determine the diagenetic stage, as shown in Table 1.

[0048] Using the projection of the time of different diagenetic stages on the burial history map, obtain the paleo-burial depths at the beginning and end of each diagenetic stage, as shown in Table 1.

[0049] Table 1 Diagenetic evolution sequence and paleo-burial depth and paleo-porosity recovery of different diagenetic stages

[0050]

[0051] Using thin-section casting images and the functional relationship between the current porosity and the total pore area ratio Quantitatively calculate the contribution of various chemical diagenetic events to the reservoir porosity. Constrained by the diagenetic evolution sequence, through the inversion back-stripping method, combined with the lateral compaction pore reduction amount of each lateral extrusion during the diagenesis process in the study area and the relationship chart of the vertical compaction pore reduction amount and the burial depth, restore the microscopic appearance characteristics of the reservoir at each diagenetic stage, and obtain the pore area ratio and corresponding porosity of the reservoir at each diagenetic stage; according to the geological history time, plot the reservoir porosity evolution curve from the original porosity to the current porosity, and obtain the porosity evolution process map of the clastic rock reservoir in the study area under the background of tectonic compression, as Figure 4 shown.

Claims

1. A method for restoring the porosity evolution of clastic rock reservoirs under the background of tectonic compression, characterized in that, It includes the following steps: (1) Select several samples from the study area, and calculate the total compaction pore reduction of each sample; obtain the maximum paleotectonic stress corresponding to the sample, select samples with similar burial depths, similar rock structures, and different maximum paleotectonic stresses in the sample as the selected samples, sort the selected samples in descending order of the maximum paleotectonic stress, and take the difference between the total compaction pore reductions corresponding to two adjacent selected samples as the lateral compaction pore reduction of the sample with the larger maximum paleotectonic stress among the two selected samples; establish the functional relationship between the lateral compaction pore reduction and the maximum paleotectonic stress; (2) Determine the number of lateral compressions during the diagenesis process in the study area and the paleotectonic stress of each lateral compression, and calculate the lateral compaction pore reduction of each lateral compression in combination with the functional relationship between the lateral compaction pore reduction and the maximum paleotectonic stress; (3) Subtract the lateral compaction pore reduction from the total compaction pore reduction of the sample to obtain the vertical compaction pore reduction of the sample, and establish a chart of the relationship between the vertical compaction pore reduction and the burial depth under different sediment parameter constraints according to the vertical distribution characteristics of the vertical compaction pore reduction of different samples; (4) Determine the diagenetic stage of the study area, and use the inverse backstripping method to draw the porosity evolution curve of the clastic rock reservoir during the geological history period under the background of tectonic compression in combination with the lateral compaction pore reduction of each lateral compression during the diagenesis process in the study area and the chart of the relationship between the vertical compaction pore reduction and the burial depth; 2. The method for restoring the porosity evolution of clastic rock reservoirs under the background of tectonic extrusion according to claim 1, characterized in that In step (1), the specific steps for calculating the total compaction pore reduction are as follows: Calculate the original porosity φ of each sample according to the functional relationship between porosity and sorting coefficient So 原 ; Obtain the current porosity φ of each sample 今 , total pore surface area ratio φ 面 , various dissolution pore surface area ratios, various cement surface area ratios, and various microfracture surface area ratios; among them, the surface area ratio of the i-th type of dissolution pore is denoted as φ 面溶i , i = 1, 2,..., n, where n is the number of types of dissolution pores; the surface area ratio of the j-th type of cement is denoted as φ 面胶j , j = 1, 2,..., m, where m is the number of types of cements; the surface area ratio of the k-th type of microfracture is denoted as φ 面缝k , k = 1, 2,..., p, where p is the number of types of microfractures; Based on the current porosity φ of the sample 今 and the total pore surface area ratio φ 面 , establish the functional relationship between the current porosity and the total pore surface area ratio; Substitute the pore surface porosities of various dissolution pores, the pore surface porosities of various cements, and the pore surface porosities of various microfractures into the functional relationship between the current porosity and the total pore surface porosity, and calculate the contribution amounts of various dissolution pores, the contribution amounts of various cement pores, and the contribution amounts of various microfracture pores. Among them, the contribution amount of the i-th type of dissolution pore is denoted as φ 溶i , the contribution amount of the j-th type of cement pore is denoted as φ 胶j , and the contribution amount of the k-th type of microfracture pore is denoted as φ 缝k ; Using the formula calculate the total compaction pore reduction φ of the sample 压 .

3. The method for restoring the porosity evolution of clastic rock reservoirs under the background of tectonic extrusion according to claim 1, characterized in that In step (2), the lateral compaction and pore reduction amount φ of the l-th lateral extrusion 侧压l is calculated by the following formula: Among them, q is the number of lateral extrusion times in the study area, and F l is the paleotectonic stress of the l-th lateral extrusion, and F l-1 is the paleotectonic stress of the (l - 1)-th lateral extrusion. F is the maximum paleotectonic stress. During calculation, F0 is taken as 0 MPa, and F = F q ; φ 侧压 is the pore reduction amount due to lateral compaction corresponding to the maximum paleotectonic stress, which is calculated according to the functional relationship between the pore reduction amount due to lateral compaction and the maximum paleotectonic stress.

4. The method for restoring the porosity evolution of clastic rock reservoirs under the background of tectonic extrusion according to claim 1, characterized in that In step (3), when establishing the chart of the relationship between the vertical compaction pore reduction and the burial depth, select samples with a cement content of less than 5%, and the sediment parameters include the sorting coefficient and sediment grain size.

5. The method for restoring the porosity evolution of clastic rock reservoirs under the background of tectonic extrusion according to claim 1, characterized in that In step (4), the specific steps for determining the diagenetic stage of the study area are as follows: determine the formation time and sequence of authigenic minerals, dissolution pores, and fractures in the study area through cast thin section analysis, in-situ trace element test analysis, fluid inclusion analysis, and U-Pb dating analysis, and establish a diagenetic evolution sequence; use the homogenization temperature analysis of inclusions and U-Pb dating analysis, combined with the burial history and thermal history analysis, to determine the occurrence time of each diagenetic event, and combine the occurrence time of the lateral compaction event to determine the diagenetic stage.

6. The method for restoring the porosity evolution of clastic rock reservoirs under the background of tectonic extrusion according to claim 5, characterized in that In step (4), the specific steps for drawing the porosity evolution curve of the clastic rock reservoir during the geological history period under the background of tectonic compression are as follows: use the projection of the time of different diagenetic stages on the burial history map to obtain the paleo-burial depths at the beginning and end of each diagenetic stage; with the diagenetic evolution sequence as a constraint, through cast thin section image analysis and inverse backstripping method, combined with the lateral compaction pore reduction of each lateral compression during the diagenesis process in the study area and the chart of the relationship between the vertical compaction pore reduction and the burial depth, restore the microscopic appearance characteristics of the reservoir in each diagenetic stage, and obtain the pore face ratio and corresponding porosity of the reservoir in each diagenetic stage; draw the porosity evolution curve of the reservoir from the original porosity to the current porosity according to the geological history time.

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