A geological modeling method and device for coal measure strata tight gas reservoirs

Abstract

A geological modeling method and device for coal measure tight gas reservoirs, the method comprising: determining the characteristics of the coal seams in the target sedimentary reservoir using collected seismic information and geological information, and dividing the target sedimentary reservoir into a plurality of source areas according to the characteristics; the source areas comprising: single source areas and mixed source areas; determining the quality of the upper coal seams in each source area reservoir and the superimposition relationship with the lower limestone according to the distribution characteristics of the lower limestone under the target sedimentary reservoir, and determining the sand body development area of the target sedimentary reservoir in each source area according to the determined quality of the upper coal seams and the superimposition relationship with the lower limestone; determining the reservoir parameters of the sand body development area in each single source area and the reservoir parameters of the sand body development area in the mixed source area; and establishing a reservoir geological model according to the determined reservoir parameters of each source area.

Description

Technical Field

[0001] This article relates to the field of gas field development technology, and in particular to a geological modeling method and apparatus for tight gas reservoirs in coal-bearing strata. Background Technology

[0002] The Shanxi Formation, the main stratum for tight gas reservoir development in the coal-bearing strata of the eastern margin of the Ordos Basin in China, is a deltaic sedimentary formation of marine-continental transitional facies. During the depositional period, this type of reservoir was eroded and incised by underwater distributary channels from different source directions, and laterally migrated and undulated. Sand bodies from different periods were spatially superimposed, resulting in small reservoir size, rapid lateral variation, and strong heterogeneity. In addition, due to the loess-mountain landform, the terrain is highly undulating, the surface structure is complex, crisscrossed by gullies, and thick layers of loess are developed. Seismic wave energy is absorbed and attenuated rapidly, making earthquake prediction of this type of reservoir difficult. However, the upper coal seam and lower limestone, which are sedimentary associated with the reservoir, are relatively stable and easily identifiable in seismic data. Therefore, conducting reservoir provenance studies, collecting sensitive seismic attributes or geological information of the upper sedimentary coal seam and lower limestone, predicting the distribution characteristics of the coal seam and limestone, and statistically analyzing the well logging response of the coal seam and the superposition characteristics of the lower limestone in different provenance areas are of great significance for predicting and characterizing reservoirs in different provenance areas. This is crucial for improving the accuracy of gas reservoir models and enhancing development effectiveness.

[0003] Currently, there are many tight gas modeling methods that focus on reservoir configuration and geological knowledge bases. For example, geological modeling is based on multi-well fine sandbody correlation results, combining well logging results with geological methods, and using methods such as selecting key wells to determine marker layers, which improves the accuracy of depicting the relationship between horizontal well trajectories and formation space. Alternatively, guided by high-resolution sequence stratigraphy and reservoir configuration theory, a "multi-stage constraint, hierarchical facies control, multi-step modeling" approach is adopted, analyzing from different levels, from large to small, incorporating geological constraints into the geological model as much as possible, enhancing the accuracy of inter-well sandbody prediction and improving the reliability of the three-dimensional geological model. Another approach utilizes dense well network data, employing multi-well correlation with small well spacing to predict the distribution of internal reservoir configuration, and using sequential indicator stochastic simulation under internal interface constraints to establish a sedimentary facies configuration model, etc. These techniques effectively solve the problem of fine characterization of reservoir internal structure during oilfield development and have achieved good application results in actual production. However, existing methods have the following problems:

[0004] Firstly, some methods rely on the dense well network data of gas fields, mainly targeting relatively stable sedimentary reservoirs with large sedimentary thicknesses. This is difficult to meet the current situation of small-scale reservoirs in coal-bearing strata, low seismic prediction accuracy, and poor reference value of well data.

[0005] Secondly, the main methods focus on predicting the reservoir itself, conducting detailed geological model studies, and proposing stochastic reservoir modeling under various geological constraints; however, there are few studies that supplement and constrain the reservoir by utilizing the relative relationships between the upper and lower strata that have a genetic relationship with it.

[0006] To address these existing problems, there is an urgent need to propose a high-precision geological modeling method for tight gas reservoirs in coal-bearing strata. Summary of the Invention

[0007] This application provides a geological modeling method and apparatus for tight gas reservoirs in coal-bearing formations. The method is based on collecting the sensitive seismic and geological attributes of the sedimentary coal seams above the reservoir, dividing the sedimentary reservoir into multiple source zones, and determining the sand body development zones within different source zones according to the seismic attributes and logging parameters of the limestone below the reservoir; establishing a lithofacies model based on the characteristic parameters of the sedimentary reservoir; and finally obtaining a high-precision geological model for reservoir prediction based on the lithofacies model.

[0008] This application provides a geological modeling method for tight gas reservoirs in coal-bearing strata, the method comprising:

[0009] The characteristics of coal seams in the target sedimentary reservoir are determined using the collected seismic and geological information, and the target sedimentary reservoir is divided into multiple source regions based on these characteristics; the source regions include: single source regions and mixed source regions;

[0010] Based on the distribution characteristics of the lower limestone of the target sedimentary reservoir, the quality of the upper coal seam and its superposition relationship with the lower limestone of each source area are determined, and the sand body development zone of the target sedimentary reservoir in each source area is determined based on the determined upper coal seam quality and the superposition relationship.

[0011] Determine the reservoir parameters of sand body development zones within each single source region and the reservoir parameters of sand body development zones within a mixed source region;

[0012] A reservoir geological model is established based on the reservoir parameters of each source region.

[0013] In one exemplary embodiment, the step of determining the characteristics of coal seams in a target sedimentary reservoir using acquired seismic and geological information, and dividing the target sedimentary reservoir into multiple source regions based on these characteristics, includes:

[0014] The seismic properties of the overlying coal seam in the target sedimentary reservoir are determined using the collected seismic information;

[0015] The geological properties of the upper coal seam of the target sedimentary reservoir are determined using the collected geological information;

[0016] The response characteristics of the coal seam are determined based on the identified seismic and geological attributes.

[0017] Based on the coal seam response characteristics, the target sedimentary reservoir is divided into multiple single source regions and multiple mixed source regions; wherein, the mixed source region is the transition area between a single-direction source region and an adjacent single-direction source region.

[0018] In one exemplary embodiment, the step of determining the quality of the upper coal seam and its superposition relationship with the lower limestone in each source area based on the distribution characteristics of the lower limestone of the target sedimentary reservoir, and determining the sand body development zone of the target sedimentary reservoir within each source area based on the determined upper coal seam quality and its superposition relationship with the lower limestone, includes:

[0019] Based on the distribution characteristics of the lower limestone of the target sedimentary reservoir, the superposition relationship between the upper coal seam and the lower limestone of each source area reservoir is determined.

[0020] Based on the superposition relationship between the upper coal seam and the lower limestone of each source area reservoir, the distance correction amount between the upper coal seam and the lower limestone of the target sedimentary reservoir is determined, and the distance correction amount is normalized.

[0021] A quality model of the upper coal seam of the target reservoir is established based on the normalized distance correction.

[0022] The sand body development zone of the target reservoir within each source region is determined based on the quality model.

[0023] In one exemplary embodiment, the quality model of the coal seam deposited above the target reservoir is:

[0024]

[0025] In the formula, I R Indicates coal seam quality; V g Indicates the gas content of the coal seam; H c Indicates the effective thickness of the coal seam after deducting interbedded rock; Φ C Indicates coal seam porosity; TVD lime Indicates vertical depth of limestone; TVD coal A represents the vertical depth of the coal seam; A represents the regional empirical coefficient.

[0026] In one exemplary embodiment, determining the sand body development zone of the target reservoir within each source region according to the quality model includes:

[0027] The coal seam quality coefficient of the upper coal seam of the target reservoir is calculated based on the quality model.

[0028] When the coal seam quality coefficient is greater than or equal to 0.4, the target reservoir in the source area is determined to be a sand body development zone.

[0029] In one exemplary embodiment, the reservoir parameters include: source direction;

[0030] The determination of reservoir parameters for sand body development zones in each single source region and sand body development zones in mixed source regions includes:

[0031] Determine the reservoir thickness and source orientation of the sand body development zone in each single source region;

[0032] The source direction of the mixed source region can be determined by using the reservoir thickness and source direction of the sand body development zone in the adjacent source region;

[0033] AZ=H1 / (H1+H2)*AZ1+H2 / (H1+H2)*AZ2

[0034] In the formula, H1 is the average reservoir thickness of the first source region in meters; H2 is the average reservoir thickness of the second source region in meters; AZ1 is the source direction of the first source region in degrees; AZ2 is the source direction of the second source region in degrees; and AZ is the source direction of the mixed source region in degrees.

[0035] In one exemplary embodiment, the reservoir parameters further include: the main range size and the secondary range size;

[0036] The determination of reservoir parameters for sand body development zones in each single source region and sand body development zones in mixed source regions further includes:

[0037] Determine the reservoir thickness and main range of sand body development zones in each single source region;

[0038] The magnitude of the main range of the mixed source region can be determined by using the reservoir thickness and main range magnitude of the sand body development zone in the adjacent source region.

[0039] L=H1 / (H1+H2)*L1+H2 / (H1+H2)*L2

[0040] In the formula, L1 is the main range of the first source region, in meters; L2 is the main range of the second source region, in meters; and L is the main range of the mixed source region, in meters.

[0041] In one exemplary embodiment, determining the reservoir parameters of the sand body development zone in each single source region and the reservoir parameters of the sand body development zone in the mixed source region further includes:

[0042] Determine the reservoir thickness and secondary range of the sand body development zone in each single source region;

[0043] The magnitude of the secondary range of the mixed source region can be determined by using the reservoir thickness and secondary range magnitude of the sand body development zone in the adjacent source region.

[0044] S=H1 / (H1+H2)*S1+H2 / (H1+H2)*S2

[0045] In the formula, S1 is the magnitude of the second range of the first source region, in meters; S2 is the magnitude of the second range of the second source region, in meters; and S is the magnitude of the second range of the mixture source region, in meters.

[0046] In one exemplary embodiment, establishing a reservoir geological model based on the determined reservoir parameters of each source region includes:

[0047] Based on the magnitude of the primary and secondary ranges of each provenance region, different types of lithofacies models are established;

[0048] For each source area sand body development zone, a reservoir geological model is established based on relevant well logging data, the source direction of each source area, and the lithofacies model.

[0049] This application also provides a geological modeling apparatus for tight gas reservoirs in coal-bearing strata. The apparatus includes a memory and a processor. The memory is used to store a program for geological modeling tight gas reservoirs in coal-bearing strata, and the processor is used to read and execute the program for geological modeling tight gas reservoirs in coal-bearing strata, and execute the method described in any of the above embodiments.

[0050] Compared with related technologies, this application provides a geological modeling method and apparatus for tight gas reservoirs in coal-bearing strata. The method includes: determining the characteristics of coal seams in a target sedimentary reservoir using acquired seismic and geological information, and dividing the target sedimentary reservoir into multiple source regions based on these characteristics; the source regions include: single source regions and mixed source regions; determining the quality of the upper coal seam and its superposition relationship with the lower limestone in each source region based on the distribution characteristics of the lower limestone in the target sedimentary reservoir, and determining the sand body development zone of the target sedimentary reservoir within each source region based on the determined upper coal seam quality and its superposition relationship with the lower limestone; determining the reservoir parameters of the sand body development zone in each single source region and the reservoir parameters of the sand body development zone in the mixed source region; and establishing a reservoir geological model based on the determined reservoir parameters of each source region. Through the technical solution of this invention, this method predicts reservoir distribution based on the relative relationship between the upper coal seam and the lower limestone, which has a sedimentary genetic connection with the reservoir, and then establishes a three-dimensional geological model.

[0051] Other features and advantages of this application will be set forth in the following description, and will be apparent in part from the description, or may be learned by practicing the application. Other advantages of this application can be realized and obtained by means of the solutions described in the description and the accompanying drawings. Attached Figure Description

[0052] The accompanying drawings are used to provide an understanding of the technical solutions of this application and constitute a part of the specification. They are used together with the embodiments of this application to explain the technical solutions of this application and do not constitute a limitation on the technical solutions of this application.

[0053] Figure 1 This is a flowchart of a geological modeling method for tight gas reservoirs in coal-bearing strata according to an embodiment of this application;

[0054] Figure 2 This is a schematic diagram of a geological modeling device for tight gas reservoirs in coal-bearing strata, according to an embodiment of this application.

[0055] Figure 3 These are geological modeling methods for tight gas reservoirs in coal-bearing strata in some exemplary embodiments;

[0056] Figure 4 These are sensitive seismic attribute maps extracted from some exemplary embodiments;

[0057] Figure 5 These are source classification diagrams in some exemplary embodiments;

[0058] Figure 6 These are schematic diagrams illustrating the seismic and well logging response characteristics of sand body developed and undeveloped areas in some exemplary embodiments;

[0059] Figure 7 These are distribution characteristic diagrams of coal seams in different source regions in some exemplary embodiments;

[0060] Figure 8 These are lithofacies model diagrams in some exemplary embodiments;

[0061] Figure 9 These are porosity model diagrams in some exemplary embodiments. Detailed Implementation

[0062] This application describes several embodiments, but these descriptions are exemplary and not restrictive, and it will be apparent to those skilled in the art that many more embodiments and implementations are possible within the scope of the embodiments described herein. Although many possible combinations of features are shown in the drawings and discussed in the detailed description, many other combinations of the disclosed features are also possible. Unless specifically limited, any feature or element of any embodiment may be used in combination with, or may replace, any feature or element of any other embodiment.

[0063] This application includes and contemplates combinations of features and elements known to those skilled in the art. The embodiments, features, and elements disclosed in this application may also be combined with any conventional features or elements to form a unique inventive scheme as defined by the claims. Any feature or element of any embodiment may also be combined with features or elements from other inventive schemes to form another unique inventive scheme as defined by the claims. Therefore, it should be understood that any feature shown and / or discussed in this application may be implemented individually or in any suitable combination. Therefore, the embodiments are not limited except by the limitations imposed by the appended claims and their equivalents. Furthermore, various modifications and changes may be made within the scope of the appended claims.

[0064] Furthermore, in describing representative embodiments, the specification may have presented methods and / or processes as a specific sequence of steps. However, the method or process should not be limited to the specific order of steps described herein, to the extent that it does not depend on such a specific order. As will be understood by those skilled in the art, other sequences of steps are also possible. Therefore, the specific order of steps set forth in the specification should not be construed as a limitation of the claims. Moreover, the claims concerning the method and / or process should not be limited to the steps performed in the written order, and those skilled in the art will readily understand that these orders can be varied and still remain within the spirit and scope of the embodiments of this application.

[0065] This disclosure provides a geological modeling method for tight gas reservoirs in coal-bearing strata, such as... Figure 1 As shown, the method includes steps S100-S130, as detailed below:

[0066] S100. Using the collected seismic and geological information, determine the characteristics of the coal seam in the target sedimentary reservoir, and divide the target sedimentary reservoir into multiple source regions based on these characteristics; the source regions include: single source regions and mixed source regions;

[0067] S110. Based on the distribution characteristics of the lower limestone of the target sedimentary reservoir, determine the quality of the upper coal seam of each source area and its superposition relationship with the lower limestone, and determine the sand body development zone of the target sedimentary reservoir in each source area based on the determined quality of the upper coal seam and its superposition relationship with the lower limestone.

[0068] S120. Determine the reservoir parameters of the sand body development zone within each single source region and the reservoir parameters of the sand body development zone within the mixed source region;

[0069] S130. Establish a reservoir geological model based on the reservoir parameters of each source region.

[0070] In one exemplary embodiment, the characteristics of coal seams in a target sedimentary reservoir are determined using acquired seismic and geological information, and the target sedimentary reservoir is divided into multiple source regions based on these characteristics, including:

[0071] Step 1. Determine the seismic properties of the coal seam above the target sedimentary reservoir using the acquired seismic information; in this step, sensitive seismic properties of the coal seam above the target sedimentary reservoir are acquired, which may include one or more of the following: phase, coherence volume, amplitude, etc.

[0072] Step 2. Use the collected geological information to determine the geological properties of the sedimentary coal seam above the target sedimentary reservoir; in this step, the collected geological information to determine the geological properties of the sedimentary coal seam above the target sedimentary reservoir may include heavy minerals, paleocurrent direction, and trace element information.

[0073] Step 3. Determine the coal seam response characteristics based on the determined seismic and geological attributes;

[0074] Step 4. Divide the target sedimentary reservoir into multiple single-source regions and multiple mixed-source regions based on the coal seam response characteristics; wherein, the mixed-source region is the transition area between a single-direction source region and an adjacent single-direction source region. For example: based on the seismic sensitivity attribute plane distribution map, such as... Figure 4 As shown, the dark-colored response areas in the north and south correspond to different source regions and belong to single-source regions; the light-colored portion in the middle of the two dark-colored areas in the north and south belongs to mixed-source regions; coal seams are relatively stable in single-direction source regions, while in mixed-direction source regions, coal seams are affected by source sources from different directions and are relatively unstable, mostly consisting of thin coal seams. Mixed-source regions are transitional areas from one-direction source region to another.

[0075] In one exemplary embodiment, based on the distribution characteristics of the lower limestone of the target sedimentary reservoir, the quality of the upper coal seam and its superposition relationship with the lower limestone of each source area are determined, and the sand body development zone of the target sedimentary reservoir within each source area is determined based on the determined upper coal seam quality and its superposition relationship with the lower limestone, including:

[0076] Step 1. Based on the distribution characteristics of the lower limestone of the target sedimentary reservoir, determine the superposition relationship between the upper coal seam and the lower limestone of each source area reservoir;

[0077] Step 2. Determine the distance correction amount between the upper coal seam and the lower limestone of the target sedimentary reservoir based on the superposition relationship between the upper coal seam and the lower limestone of each source area reservoir, and normalize the distance correction amount.

[0078] Step 3. Establish a quality model of the upper sedimentary coal seam of the target reservoir based on the normalized distance correction value;

[0079] Step 4. Determine the sand body development zone of the target reservoir within each source region based on the quality model.

[0080] In one exemplary embodiment, the quality model of the coal seam deposited above the target reservoir is:

[0081]

[0082] In the formula, I R Coal seam quality, dimensionless; V g Gas content of coal seam, m 3 / kg; This parameter can be determined by combining core samples and logging calibration; H c The effective thickness of the coal seam after deducting interbedded rock, in meters (m); this parameter can be determined through well logging; Φ C Coal seam porosity, unit: dimensionless; this parameter can also be determined through well logging; TVD lime Vertical depth of limestone, unit: m; this parameter can also be obtained through drilling, TVD coal The vertical depth of the coal seam is given in meters (m); this parameter is obtained through drilling. A is a regional empirical coefficient, which can be set to 0.012.

[0083] In one exemplary embodiment, determining the sand body development zone of the target reservoir within each source region based on the quality model includes:

[0084] The coal seam quality coefficient of the upper coal seam of the target reservoir is calculated based on the quality model.

[0085] When the coal seam quality coefficient is greater than or equal to 0.4, the target reservoir in the source area is determined to be a sand body development zone.

[0086] When the coal seam quality coefficient is less than 0.4, the target reservoir in the source area is determined to be a sand body underdeveloped area, i.e., a Class II reservoir.

[0087] In one exemplary embodiment, the reservoir parameters include: source direction;

[0088] The determination of reservoir parameters for sand body development zones in each single source region and sand body development zones in mixed source regions includes:

[0089] Determine the reservoir thickness and source orientation of the sand body development zone in each single source region;

[0090] The source direction of the mixed source region can be determined by using the reservoir thickness and source direction of the sand body development zone in the adjacent source region;

[0091] AZ=H1 / (H1+H2)*AZ1+H2 / (H1+H2)*AZ2

[0092] In the formula, H1 is the average reservoir thickness of the first source region in meters; H2 is the average reservoir thickness of the second source region in meters; AZ1 is the source direction of the first source region in degrees; AZ2 is the source direction of the second source region in degrees; and AZ is the source direction of the mixed source region in degrees.

[0093] In one exemplary embodiment, the reservoir parameters further include: the main range size and the secondary range size;

[0094] The determination of the physical parameters of the sand body development zone in each single source region and the reservoir parameters of the sand body development zone in the mixed source region also includes:

[0095] Determine the reservoir thickness and main range of sand body development zones in each single source region;

[0096] The magnitude of the main range of the mixed source region can be determined by using the reservoir thickness and main range magnitude of the sand body development zone in the adjacent source region.

[0097] L=H1 / (H1+H2)*L1+H2 / (H1+H2)*L2

[0098] In the formula, L1 is the main range of the first source region, in meters; L2 is the main range of the second source region, in meters; and L is the main range of the mixed source region, in meters.

[0099] In one exemplary embodiment, determining the reservoir parameters of the sand body development zone in each single source region and the reservoir parameters of the sand body development zone in the mixed source region further includes:

[0100] Determine the reservoir thickness and secondary range of the sand body development zone in each single source region;

[0101] The magnitude of the secondary range of the mixed source region can be determined by using the reservoir thickness and secondary range magnitude of the sand body development zone in the adjacent source region.

[0102] S=H1 / (H1+H2)*S1+H2 / (H1+H2)*S2

[0103] In the formula, S1 is the magnitude of the second range of the first source region, in meters; S2 is the magnitude of the second range of the second source region, in meters; and S is the magnitude of the second range of the mixture source region, in meters.

[0104] In one exemplary embodiment, a reservoir geological model is established based on the reservoir parameters of each determined source region, including:

[0105] Based on the magnitude of the primary and secondary ranges of each provenance region, different types of lithofacies models are established;

[0106] For each source area sand body development zone, a reservoir geological model is established based on relevant well logging data, the source direction of each source area, and the lithofacies model.

[0107] This application also provides a geological modeling device for tight gas reservoirs in coal-bearing strata, such as... Figure 2 As shown, the device includes a memory 210 and a processor 220; the memory 210 is used to store a program for geological modeling of tight gas reservoirs in coal-bearing strata, and the processor 220 is used to read and execute the program for geological modeling of tight gas reservoirs in coal-bearing strata, and execute the geological modeling method for tight gas reservoirs in coal-bearing strata as described in any of the above embodiments.

[0108] Example 1

[0109] The following example illustrates the geological modeling process for tight gas reservoirs in coal-bearing formations. Figure 3 As shown:

[0110] Step 301. Use relevant seismic and geological information to divide different source areas.

[0111] Sensitive seismic attributes of the upper coal seams of the reservoir, such as phase, coherence, and amplitude, as well as sensitive geological data such as heavy minerals, paleocurrent direction, and trace element information, are collected to classify the sedimentary reservoir into single-direction source areas and mixed-direction source areas controlled by different sources.

[0112] Step 302. Classify reservoirs using the relationship between coal seam quality and underlying limestone superposition.

[0113] Considering the difficulty in accurately obtaining coal seam permeability data during on-site drilling, and the need for subsequent fracturing, permeability was not used as a quality assessment parameter. The distance between the upper coal seam and the lower limestone was corrected and normalized before the reservoir was classified. R The larger the size, the better the coal seam quality. Comprehensive analysis shows that it can be divided into sand body development zones (I...) on a planar surface. R ≥0.4) and Class II reservoirs in undeveloped areas (I) R <0.4), and statistically analyzed reservoir characteristic parameters by source region, including the average length and average width of reservoirs in different source regions. The quality of the overlying coal seam of the established reservoir is shown in the following formula.

[0114]

[0115] In the formula,

[0116] I R Coal seam quality is dimensionless.

[0117] V g Gas content of coal seam, m 3 / kg;

[0118] H c The effective thickness of the coal seam after deducting interbedded gangue, in meters;

[0119] Φ C Coal seam porosity, unit: dimensionless;

[0120] TVD lime Vertical depth of limestone, unit: m;

[0121] TVD coal Vertical depth of coal seam, in meters;

[0122] A is the regional experience coefficient, which can generally be taken as 0.012.

[0123] Step 303. Determine the characteristic parameters of the mixture source region using the parameters of adjacent source regions.

[0124] The parameters required for a geological model include the magnitude and direction of the primary range, and the magnitude and direction of the secondary range. The direction of the primary range is perpendicular to the direction of the secondary range, and it aligns with the source direction. The magnitudes of the primary and secondary ranges correspond to the average length and average width of the reservoir, respectively.

[0125] Step 3031. Determine the reservoir thickness, main range magnitude, and secondary range magnitude of the sand body development zone in each single source region; the main range direction is consistent with the source direction.

[0126] The source direction of this single source region can be determined by combining sensitive seismic data and sensitive geological parameters. The magnitudes of the main and secondary ranges correspond to the average length and average width of the reservoir, respectively; the average length and average width of the single source region can be obtained statistically.

[0127] Step 3032. Determine the source direction of the mixed source region by using the reservoir thickness and source direction of the sand body development zone in the adjacent source region;

[0128] AZ=H1 / (H1+H2)*AZ1+H2 / (H1+H2)*AZ2

[0129] In the formula, H1 is the average reservoir thickness of the first source region, in meters; H2 is the average reservoir thickness of the second source region, in meters; AZ1 is the source direction of the first source region, in degrees; AZ2 is the source direction of the second source region, in degrees; and AZ is the source direction of the mixed source region, in degrees.

[0130] Step 3033. Determine the magnitude of the main range of the mixed source region by utilizing the reservoir thickness and main range magnitude of the sand body development zone in the adjacent source region;

[0131] L=H1 / (H1+H2)*L1+H2 / (H1+H2)*L2

[0132] In the formula, L1 is the main range of the first source region, in meters; L2 is the main range of the second source region, in meters; and L is the main range of the mixed source region, in meters.

[0133] Step 3034. Determine the secondary range of the mixed source region by using the reservoir thickness and secondary range of the sand body development zone in the adjacent source region;

[0134] S=H1 / (H1+H2)*S1+H2 / (H1+H2)*S2

[0135] In the formula, S1 is the magnitude of the second range of the first source region, in meters; S2 is the magnitude of the second range of the second source region, in meters; and S is the magnitude of the second range of the mixture source region, in meters.

[0136] Step 304. Establish a reservoir model for each source region based on the reservoir type.

[0137] Using the average length of the sand body development zone in different source areas as their respective primary range and the average width as their respective secondary range, with the primary range direction being the source direction and the secondary range direction being perpendicular to the source direction, different types of lithofacies models are established. Based on this, for different types of reservoirs, using actual drilled horizontal wells or control wells as the basic data, and employing the sequential indicator stochastic simulation method, porosity models for different types of reservoirs are established on the basis of the lithofacies models, thus obtaining reservoir geological models.

[0138] The technical effects of this embodiment are as follows:

[0139] 1. By combining the sensitive seismic attributes with the relative relationship between the upper coal seam and the lower limestone which are related to the sedimentary genesis of the reservoir, the reservoir can be predicted. This not only avoids the difficulty of direct prediction, but also effectively depicts the true distribution inside the reservoir, making up for the shortcomings of traditional geological models constructed using theoretical sedimentary models.

[0140] 2. The parameters required for modeling were determined separately for different source areas, and lithofacies models of sedimentary reservoirs were established. Based on the lithofacies models, the properties and characteristics of the reservoirs were simulated, which improved the accuracy of reservoir characterization in geological models.

[0141] Example 2

[0142] Taking the DJ gas field as an example, the S sand body in the DJ gas field is a braided river delta front sedimentary type. The geological modeling process and results of the tight gas reservoir in the coal-bearing strata using the technical solution of this application are as follows:

[0143] 1. Use seismic geological data to divide different source areas

[0144] Determine the seismic sensitivity properties of the overlying coal seam, such as Figure 4 The diagram shows a plan view of the sensitive seismic attributes. Based on the determined sensitive seismic attributes and sensitive geological information, the sedimentary reservoirs controlled by different sources are divided into single-direction source areas and mixed-direction source areas (the darker areas in the north and south are single-direction source areas, while the lighter-colored areas in the middle are mixed-direction source areas). The resulting plan view of the source areas is shown below. Figure 5 As shown. There can be multiple source regions in a single direction and multiple source regions in a mixed direction. For example, the DJ gas field can be divided into a northern source region, a southern source region, and a mixed source region in a single direction based on its sensitive seismic attributes. Figure 6 These are seismic profiles of developed and undeveloped sand bodies. Developed sand bodies exhibit significant downcutting characteristics on the seismic attribute profiles, while undeveloped sand bodies do not. Figure 7 This diagram illustrates the relative relationship between coal seams and underlying limestone in different source regions. The reservoir is located between the upper coal seam and the lower limestone. In the southern source region, the coal seam is relatively close to the underlying limestone, and the coal seam is relatively concentrated; in the northern source region, the coal seam is relatively far from the underlying limestone, and the coal seam is relatively concentrated; while in the mixed source region, from the southern source region to the northern source region, the relative distance between the coal seam and the underlying limestone increases, and the coal seam begins to bifurcate.

[0145] 2. Reservoir classification using coal seam quality and seismic response data.

[0146] Based on actual drilling data of vertical and horizontal wells

[0147] Gas content of Vg coal seam, 13.6 x 10⁻⁶ 3 m 3 / kg;

[0148] Hc, after deducting the effective thickness of the coal seam containing interbedded gangue, is 4.6m.

[0149] Kc is the coal seam permeability, 0.0014 mD;

[0150] ΦC represents the porosity of the coal seam, 0.023, dimensionless;

[0151] TVDlime is a vertically deep limestone formation, 1315m deep;

[0152] TVDcoal is the vertical depth of the coal seam, 1280m;

[0153] Calculate the coal seam reservoir quality factor;

[0154]

[0155] 3. Determine the characteristic parameters of the mixture source region by utilizing the interrelationships between adjacent source regions.

[0156] The sediment sources in different areas of the S sand body in the DJ gas field are different. The northern source area comes from the north, and the southern source area comes from the south. With 0° as true north and 180° as the south, the source direction (AZ), main range (L), and secondary range (S) of the mixed area are determined by the following formula.

[0157] H1: Average reservoir thickness in the first source region, 6.7m;

[0158] H2: Average reservoir thickness in the second source region, 3.5m;

[0159] L1: The main variable range of the first source region, 1100m;

[0160] L2: The main range of the second source region, 420m;

[0161] S1: The magnitude of the secondary range in the first source region, 60m

[0162] S2: The magnitude of the secondary range in the second source region, 110m

[0163] AZ1: Source direction of the first source region, 0 degrees;

[0164] AZ2: The source direction of the second source region, 180 degrees;

[0165] AZ=6.7 / (6.7+3.5)*0+3.5 / (6.7+3.5)*180=61.7 degrees

[0166] L=6.7 / (6.7+3.5)*1100+3.5 / (6.7+3.5)*420=866.7m

[0167] S=6.7 / (6.7+3.5)*60+3.5 / (6.7+3.5)*110=77.2m

[0168] 4. Establish reservoir models by differentiating reservoir types based on provenance.

[0169] The average length of sand body development zones in different source areas is taken as their principal range, and the average width as their secondary range. Different types of lithofacies models are then established, such as... Figure 8 As shown in the figure, the dark areas represent sand body development zones. Based on the established lithofacies model, for reservoirs in different source areas, using actual drilled horizontal wells or control wells as base data, a sequential indicator stochastic simulation method is used to establish reservoir porosity models based on the lithofacies model, resulting in a three-dimensional geological model of the reservoir, as shown below. Figure 9 As shown, this three-dimensional geological model can be a porosity model.

[0170] The sedimentary sources differ across different areas of the S sandstone body in the DJ gas field. The northern source area originates from the north, with 0° as the primary range direction and 90° as the secondary range direction; the primary range for sandstone development is 1100 meters in average length, and the secondary range is 60 meters in average width. The southern source area originates from the south, with 180° as the primary range direction and 270° as the secondary range direction; the primary range for sandstone development is 420 meters in average length, and the secondary range is 110 meters in average width. The mixed source area has 61.7° as the primary range direction and 151.7° as the secondary range direction; the primary range for sandstone development is 866.7 meters in average length, and the secondary range is 77.2 meters in average width.

[0171] The geological modeling method for tight gas reservoirs in coal-bearing strata proposed in this application is designed for reservoirs with small scale and high prediction difficulty. The upper part of the reservoir has a stable coal seam, and the lower part has a stable limestone seam. Therefore, it proposes to indirectly use the relative relationship between the upper coal seam and the lower limestone, which has a sedimentary genetic connection with the reservoir, to predict the reservoir distribution and then establish a three-dimensional geological model. The method first collects sensitive seismic attributes and sensitive geological information of the upper coal seam of the reservoir. Based on the coal seam response characteristics, the sedimentary reservoir is divided into single-direction source areas and mixed-direction source areas controlled by different sources. Second, it collects sensitive seismic attributes and well logging parameters of the lower limestone to predict the distribution characteristics of the limestone. It then analyzes the quality of the upper coal seam and its superposition relationship with the lower limestone in detail, and divides the reservoir into two types: sand body developed areas and undeveloped areas within different source areas. Based on the data from vertical or horizontal wells that penetrate the upper coal seam of the reservoir, it statistically analyzes the characteristic parameters used to characterize the two types of sedimentary reservoirs and establishes lithofacies models for the two types of sedimentary reservoirs in different source areas. Finally, based on the lithofacies models, it simulates the attribute characteristics of the two types of reservoirs to obtain a high-precision geological model of the reservoir.

[0172] It will be understood by those skilled in the art that all or some of the steps, systems, or apparatuses disclosed above, and their functional modules / units, can be implemented as software, firmware, hardware, or suitable combinations thereof. In hardware implementations, the division between functional modules / units mentioned above does not necessarily correspond to the division of physical components; for example, a physical component may have multiple functions, or a function or step may be performed collaboratively by several physical components. Some or all components may be implemented as software executed by a processor, such as a digital signal processor or microprocessor, or as hardware, or as an integrated circuit, such as an application-specific integrated circuit (ASIC). Such software may be distributed on a computer-readable medium, which may include computer storage media (or non-transitory media) and communication media (or transient media). As is known to those skilled in the art, the term computer storage media includes volatile and non-volatile, removable and non-removable media implemented in any method or technology for storing information (such as computer-readable instructions, data structures, program modules, or other data). Computer storage media include, but are not limited to, RAM, ROM, EEPROM, flash memory or other memory technologies, CD-ROM, digital versatile disc (DVD) or other optical disc storage, magnetic cartridges, magnetic tape, disk storage or other magnetic storage devices, or any other medium that can be used to store desired information and can be accessed by a computer. Furthermore, it is well known to those skilled in the art that communication media typically contain computer-readable instructions, data structures, program modules, or other data in modulated data signals such as carrier waves or other transmission mechanisms, and may include any information delivery medium.

Claims

1. A geological modeling method for tight gas reservoirs in coal-bearing strata, characterized in that, The method includes: The seismic properties of the overlying coal seam in the target sedimentary reservoir are determined using the acquired seismic information; the geological properties of the overlying coal seam in the target sedimentary reservoir are determined using the acquired geological information; the coal seam response characteristics are determined based on the determined seismic and geological properties; and the target sedimentary reservoir is divided into multiple single source regions and multiple mixed source regions based on the coal seam response characteristics. Based on the distribution characteristics of the lower limestone of the target sedimentary reservoir, the quality of the upper coal seam and its superposition relationship with the lower limestone of each source area are determined, and the sand body development zone of the target sedimentary reservoir in each source area is determined based on the determined upper coal seam quality and the superposition relationship. Determine the reservoir parameters of sand body development zones within each single source region and the reservoir parameters of sand body development zones within a mixed source region; A reservoir geological model is established based on the reservoir parameters of each source region.

2. The geological modeling method for tight gas reservoirs in coal-bearing strata according to claim 1, characterized in that, The mixture source region is a transitional area between a unidirectional source region and an adjacent unidirectional source region.

3. The geological modeling method for tight gas reservoirs in coal-bearing strata according to claim 2, characterized in that, Based on the distribution characteristics of the lower limestone of the target sedimentary reservoir, the quality of the upper coal seam and its superposition relationship with the lower limestone in each source area are determined. Then, based on the determined upper coal seam quality and its superposition relationship with the lower limestone, the sand body development zone of the target sedimentary reservoir within each source area is determined, including: Based on the distribution characteristics of the lower limestone of the target sedimentary reservoir, the superposition relationship between the upper coal seam and the lower limestone of each source area reservoir is determined. Based on the superposition relationship between the upper coal seam and the lower limestone of each source area reservoir, the distance correction amount between the upper coal seam and the lower limestone of the target sedimentary reservoir is determined, and the distance correction amount is normalized. A quality model of the upper coal seam of the target reservoir is established based on the normalized distance correction. The sand body development zone of the target reservoir within each source region is determined based on the quality model.

4. The geological modeling method for tight gas reservoirs in coal-bearing strata according to claim 3, characterized in that, The quality model of the coal seam deposited above the target reservoir is: In the formula, Indicates coal seam quality; Indicates the gas content of the coal seam; This indicates the effective thickness of the coal seam after deducting interbedded rock; Indicates coal seam porosity; TVD lime Indicates vertical depth of limestone; TVD coal A represents the vertical depth of the coal seam; A represents the regional empirical coefficient.

5. The geological modeling method for tight gas reservoirs in coal-bearing strata according to claim 4, characterized in that, The determination of the sand body development zone of the target reservoir within each source region based on the quality model includes: The coal seam quality coefficient of the upper coal seam of the target reservoir is calculated based on the quality model. When the coal seam quality coefficient is greater than or equal to 0.4, the target reservoir in the source area is determined to be a sand body development zone.

6. The geological modeling method for tight gas reservoirs in coal-bearing strata according to claim 5, characterized in that, The reservoir parameters include: source direction; The determination of reservoir parameters for sand body development zones in each single source region and sand body development zones in mixed source regions includes: Determine the reservoir thickness and source orientation of the sand body development zone in each single source region; The source direction of the mixed source region can be determined by using the reservoir thickness and source direction of the sand body development zone in the adjacent source region; AZ=H1 / (H1+H2)*AZ1+H2 / (H1+H2)*AZ2 In the formula, The average reservoir thickness in the first source region is expressed in meters. AZ1 represents the average reservoir thickness of the second source region in meters; AZ2 represents the source direction of the first source region in degrees; AZ3 represents the source direction of the second source region in degrees; and AZ4 represents the source direction of the mixed source region in degrees.

7. The geological modeling method for tight gas reservoirs in coal-bearing strata according to claim 6, characterized in that, The reservoir parameters also include: the main range size and the secondary range size; The determination of reservoir parameters for sand body development zones in each single source region and sand body development zones in mixed source regions further includes: Determine the reservoir thickness and main range of sand body development zones in each single source region; The magnitude of the main range of the mixed source region can be determined by using the reservoir thickness and main range magnitude of the sand body development zone in the adjacent source region. L=H1 / (H1+H2)*L1+H2 / (H1+H2)*L2 In the formula, L1 is the main range of the first source region, in meters; L2 is the main range of the second source region, in meters; and L is the main range of the mixed source region, in meters.

8. The geological modeling method for tight gas reservoirs in coal-bearing strata according to claim 6, characterized in that, The determination of reservoir parameters for sand body development zones in each single source region and sand body development zones in mixed source regions further includes: Determine the reservoir thickness and secondary range of the sand body development zone in each single source region; The magnitude of the secondary range of the mixed source region can be determined by using the reservoir thickness and secondary range magnitude of the sand body development zone in the adjacent source region. S=H1 / (H1+H2)*S1+H2 / (H1+H2)*S2 In the formula, S1 is the magnitude of the second range of the first source region, in meters; S2 is the magnitude of the second range of the second source region, in meters; and S is the magnitude of the second range of the mixture source region, in meters.

9. The geological modeling method for tight gas reservoirs in coal-bearing strata according to claim 8, characterized in that, The process of establishing a reservoir geological model based on the reservoir parameters of each determined source region includes: Based on the magnitude of the primary and secondary ranges of each provenance region, different types of lithofacies models are established; For each source area sand body development zone, a reservoir geological model is established based on relevant well logging data, the source direction of each source area, and the lithofacies model.

10. A geological modeling device for tight gas reservoirs in coal-bearing strata, the device comprising: A memory and a processor; characterized in that the memory is used to store a program for geological modeling of tight gas reservoirs in coal-bearing strata, and the processor is used to read and execute the program for geological modeling of tight gas reservoirs in coal-bearing strata, and execute the method according to any one of claims 1-9.

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