A method and apparatus for estimating shear wave velocity

Abstract

The embodiment of the application discloses a method and device for estimating the shear wave velocity, and belongs to the technical field of oil and gas exploration. After obtaining a rock sample, the porosity width-length ratio curve of the rock sample can be calculated, and then plastic mineral equivalence, brittle mineral equivalence, rock skeleton equivalence, dry rock equivalence, fluid equivalence and fluid replacement are performed, so as to establish a rock physics model of the rock sample. The shear wave velocity of the rock sample can be estimated based on the rock physics model. Since the rock physics model of the rock sample of the shale reservoir which is relatively close to the actual situation is comprehensively established, the estimation of the shear wave velocity of the rock sample is relatively accurate, thereby laying a method foundation for predicting various pressures and ground stresses of the stratum by using seismic data, and providing strong technical support for subsequent shale oil horizontal well selection and reserve increase and production increase.

Description

Technical Field

[0001] This application relates to the field of oil and gas exploration technology, and in particular to a method and apparatus for estimating shear wave velocity. Background Technology

[0002] In the field of shale oil and gas exploration, due to the characteristics of shale reservoirs, vertical well production in shale oil reservoirs is low, and production is mainly increased by horizontal wells. The distribution of in-situ stress is a key factor in the fracturing effect of horizontal wells, determining the stability of the fracturing wellbore and the direction, shape, and orientation of fractures. Pre-stack elastic parameters are used in the calculation of the maximum and minimum horizontal principal stresses, and accurate shear wave velocities are necessary for calculating high-precision pre-stack elastic parameters.

[0003] In related technologies, methods for determining shear wave velocity can be divided into two main categories: one is the empirical formula method, which has the advantages of fast calculation and simple operation, and performs well for conventional sandstone oil and gas reservoirs, but it is difficult to meet the needs of research on complex lithological oil and gas reservoirs. The other is the equivalent theoretical model method, which requires the calculation of various rock physical parameters. Although the calculation process is more complex, the physical meaning is clear. However, existing shale models are mostly biased, highlighting a certain characteristic of shale. Summary of the Invention

[0004] This application provides a method and apparatus for estimating shear wave velocity. The technical solution is as follows:

[0005] According to one aspect of this application, a method for estimating shear wave velocity is provided, the method comprising:

[0006] The rock samples are extracted from the shale reservoir. Based on the sonic transit time curve, density curve and electrical parameters of the rock samples, the data required to build a rock physical model of the rock samples are calculated. The required data includes mineral composition curve, total porosity curve and water saturation curve.

[0007] The pore width-to-length ratio curve of the rock sample is calculated based on the ratio of the target mineral content to the total mineral content.

[0008] Based on the mineral composition of the rock sample, the equivalent modulus of plastic minerals and the equivalent modulus of brittle minerals of the rock sample are obtained by mixing a self-consistent model and a differential equivalent model.

[0009] Based on the equivalent materials of ductile and brittle minerals of the rock sample, a differential equivalent model is used to mix them to obtain the equivalent modulus of the rock skeleton of the rock sample.

[0010] Based on the rock skeleton and porosity of the rock sample, a differential equivalent model is used to mix the samples to obtain the dry rock equivalent modulus of the rock sample.

[0011] Based on the water saturation of the rock sample, the fluid mixing was performed using the Brie index method to obtain the fluid equivalent modulus of the rock sample.

[0012] Based on the dry rock and mixed fluid of the rock sample, the Boris fluid displacement model was used to perform fluid displacement, thereby establishing a rock physics model of the rock sample.

[0013] Based on the rock physics model, the transverse wave velocity of the rock sample was estimated.

[0014] According to another aspect of this application, a transverse wave velocity estimation apparatus is provided, the apparatus comprising:

[0015] The modeling data calculation module is used to extract rock samples from shale reservoirs and calculate the data required to establish a rock physical model of the rock samples based on the sonic transit time curve, density curve and rock electrical parameters of the rock samples. The required data includes mineral composition curves, total porosity curves and water saturation curves.

[0016] The pore width-to-length ratio calculation module is used to calculate the pore width-to-length ratio curve of the rock sample based on the ratio of the target mineral content to the total mineral content in the rock sample.

[0017] A rock matrix equivalent module is used to obtain the equivalent modulus of plastic minerals and the equivalent modulus of brittle minerals of the rock sample by mixing a self-consistent model and a differential equivalent model based on the mineral composition of the rock.

[0018] A rock skeleton equivalent module is used to mix the plastic mineral equivalent material and the brittle mineral equivalent material of the rock sample using a differential equivalent model to obtain the rock skeleton equivalent modulus of the rock sample.

[0019] A dry rock equivalent module is used to obtain the dry rock equivalent modulus of the rock sample by mixing based on the rock skeleton and porosity of the rock sample using a differential equivalent model.

[0020] A fluid equivalent module is used to perform fluid mixing based on the water saturation of the rock sample using the Brie index method to obtain the fluid equivalent modulus of the rock sample.

[0021] The fluid displacement module is used to perform fluid displacement based on the dry rock and mixed fluid of the rock sample using the Boris fluid displacement model, thereby establishing a rock physics model of the rock sample.

[0022] The shear wave velocity estimation module is used to estimate the shear wave velocity of the rock sample based on the rock physics model.

[0023] According to another aspect of this application, a terminal is provided, the terminal including a processor and a memory, the memory storing at least one instruction loaded and executed by the processor to implement the transverse wave velocity estimation method as provided in various aspects of this application.

[0024] According to another aspect of this application, a computer-readable storage medium is provided, wherein at least one instruction is stored therein, the instruction being loaded and executed by a processor to implement the method for estimating transverse wave velocity as provided in various aspects of this application.

[0025] According to one aspect of this application, a computer program product is provided, comprising computer instructions stored in a computer-readable storage medium. A processor of a computer device reads the computer instructions from the computer-readable storage medium and executes the computer instructions, causing the computer device to perform the transverse wave velocity estimation method provided in the various alternative implementations described above.

[0026] The beneficial effects of the technical solutions provided in this application embodiment may include:

[0027] After obtaining the rock sample, the pore width-to-length ratio curve of the sample can be calculated. Then, equivalence models of plastic minerals, brittle minerals, rock skeleton, dry rock, fluid, and fluid displacement are performed to establish a rock physical model of the rock sample. Based on this model, the shear wave velocity of the rock sample can be estimated. Because this application comprehensively establishes a rock physical model of rock samples that closely resembles actual shale reservoirs, the estimation of shear wave velocity is relatively accurate. This lays a methodological foundation for predicting various formation pressures and geostresses using seismic data, and provides strong technical support for subsequent shale oil horizontal well site selection and reserve enhancement. Attached Figure Description

[0028] To more clearly illustrate the technical solutions in the embodiments of this application, the accompanying drawings used in the description of the embodiments of this application will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0029] Figure 1 This is a flowchart of a method for estimating shear wave velocity provided in an exemplary embodiment of this application;

[0030] Figure 2 Based on Figure 1 The flowchart of a method for estimating shear wave velocity provided in the illustrated embodiment is shown.

[0031] Figure 3 This is a flowchart of another method for estimating shear wave velocity provided in an exemplary embodiment of this application;

[0032] Figure 4 This application provides a graph showing the calculation results of kerogen (TOC) content using the Passey formula method, multivariate fitting method, density method, and natural gamma spectroscopy method, respectively.

[0033] Figure 5 This application provides a cross-plot comparing the results calculated using four methods with the measured total kerogen (TOC) content.

[0034] Figure 6 This is a graph showing the calculation results of a rock physics modeling related curve provided in this application;

[0035] Figure 7 This is a cross-plot of brittle mineral content and measured content obtained by an optimized well logging interpretation method provided in this application;

[0036] Figure 8 This application provides a flowchart for rock physics modeling of complex mineral components in shale oil.

[0037] Figure 9 This is a graph showing the results of P-wave velocity, density, and S-wave velocity obtained using the rock physics modeling method for shale oil provided in this application.

[0038] Figure 10 This is a cross-plot of shear wave velocity obtained by using the rock physics modeling method for shale oil provided in this application and measured shear wave velocity;

[0039] Figure 11 This is a structural block diagram of a transverse wave velocity estimation device provided in an exemplary embodiment of this application;

[0040] Figure 12 This is a structural block diagram of a terminal provided in an exemplary embodiment of this application. Detailed Implementation

[0041] To make the objectives, technical solutions, and advantages of this application clearer, the embodiments of this application will be described in further detail below with reference to the accompanying drawings.

[0042] In the following description, when referring to the accompanying drawings, the same numbers in different drawings denote the same or similar elements unless otherwise indicated. The embodiments described in the following exemplary embodiments do not represent all embodiments consistent with this application. Rather, they are merely examples of apparatuses and methods consistent with some aspects of this application as detailed in the appended claims.

[0043] In the description of this application, it should be understood that the terms "first," "second," etc., are used for descriptive purposes only and should not be construed as indicating or implying relative importance. In the description of this application, it should be noted that, unless otherwise explicitly specified and limited, the terms "connected" and "linked" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium. Those skilled in the art can understand the specific meaning of the above terms in this application based on the specific circumstances. Furthermore, in the description of this application, unless otherwise stated, "multiple" refers to two or more. "And / or" describes the relationship between related objects, indicating that three relationships can exist. For example, A and / or B can represent: A existing alone, A and B existing simultaneously, or B existing alone. The character " / " generally indicates that the preceding and following related objects are in an "or" relationship.

[0044] As used herein, the term “if” may optionally be interpreted, depending on the context, as “when,” “in the event of,” “in response to determination,” or “in response to detection.” Similarly, depending on the context, the phrases “if it is determined that…” or “if (the stated condition or event) is detected” or “in response to the detection of (the stated condition or event).”

[0045] In the field of oil and gas reservoir exploration, as easily explored and exploited areas are gradually depleted, unconventional oil and gas reservoirs, which are more complex to explore and extract, have become the main focus. Among them, tight sandstone and shale in unconventional oil and gas reservoirs, as representatives, have gradually become hot research objects in oil and gas exploration and development. Shale oil is a petroleum resource produced in unconventional oil and gas reservoirs studied by the method provided in this application. The characteristics of this shale oil include: medium to high maturity, complex rock composition, organic matter content greater than 2%, porosity between 2% and 10%, permeability between 0.0001 mD and 0.1 mD, and continuous accumulation of source and reservoir. In terms of the storage mode of oil and gas resources, the oil and gas resources are hosted in the nanoporous system of shale in both adsorbed and free states. In terms of rock physics simulation, shale has multiple mineral components and complex pore structure compared with conventional binary sandstone or mudstone. Therefore, this application proposes a scheme for analyzing the storage of shale oil and gas reservoirs based on shale rock physics models, so as to facilitate the exploration and analysis of oil and gas reservoir reserves in shale and improve the efficiency of shale exploration.

[0046] Some shale rock physics modeling schemes include the Self-Consistent (SC) model, the Differential Effective Medium (DEM) model, and Backus theory. Based on the above schemes, a possible implementation scheme is introduced as follows.

[0047] The first step is to use a self-consistent and differentially equivalent (SCA+DEM) model to mix clay and kerogen to obtain kerogen-clay blocks with interconnected properties.

[0048] The second step involves rotating and superimposing a specified number of identical clay-kerogen blocks to simulate shale stratification. The elastic properties of the rotated clay blocks can be calculated using the Bond transformation. Averaging using the Voigt-Reuss-Hill boundary model can be used to calculate the equivalent properties of superimposed clay blocks with different orientations.

[0049] The third step is to use the Voigt-Reuss-Hill boundary model averaging to calculate the equivalent modulus of other brittle minerals besides clay and kerogen.

[0050] The fourth step involves using the equivalent material composed of layered clay-kerogen blocks as the background, and then using a differential equivalent model (DEM) to sequentially add the brittle mixture and pores to the background medium to obtain the final equivalent result.

[0051] The above four-step scheme yields a shale petrophysical model suitable for analyzing oil and gas reservoirs, emphasizing the organic matter within the shale. However, it has the following limitations: First, due to the complex mineral composition and pore structure of shale, determining the various mineral components and pore width-to-length ratios is a crucial aspect of petrophysical modeling, which this method does not address. Second, applying the Voigt-Reuss-Hill boundary model requires assuming homogeneity among the components of the mixture and that the rock is linear and elastic. However, in actual multiphase media, the distribution of stress and strain is unpredictable and non-uniform. Therefore, the Voigt upper limit and Reuss lower limit are insufficient to accurately calculate the equivalent situation of multiphase materials, providing only broad upper and lower limit references. Consequently, the method's use of Voigt-Reuss-Hill averaging to calculate the equivalent modulus of various brittle minerals other than clay and kerogen is not suitable. Third, this model does not address the mixing methods of fluids within the rock. Fourth, as can be seen from the four steps of this modeling method, the process realizes the modeling process of dry rock, but does not mention the fluid displacement model, so it is not considered a complete rock physics modeling method for shale oil.

[0052] Please refer to Figure 1, Figure 1 This is a flowchart illustrating a method for estimating shear wave velocity according to an exemplary embodiment of this application. This method for estimating shear wave velocity can be applied in a terminal. Figure 1 In this context, the methods for estimating the shear wave velocity include:

[0053] Step 110: Calculate the rock mineral composition of the rock sample, which was mined from a shale reservoir. The rock mineral composition is used to indicate the mineral composition of the rock sample.

[0054] During oil and gas exploration, explorers can use drill bits to collect samples from underground rock formations to obtain rock samples. This application can be based on the analysis of the collected rock samples.

[0055] The mineral composition of the collected rock samples is obtained. It should be noted that this application can be applied to determine the shear wave velocity of shale. The following description uses shale samples as an example.

[0056] Shale has a highly complex mineral composition, including more than a dozen minerals such as quartz, feldspar, and dolomite. Determining the content of each mineral individually would be extremely labor-intensive and yield limited returns. Therefore, this application simplifies the complex composition of rock samples into quartz, feldspar, calcite, dolomite, and clay minerals based on the characteristics and abundance of mineral elastic parameters. Simultaneously, this application will also consider the characteristics of shale reservoirs and determine the content of kerogen. That is, in one method of obtaining the mineral composition of a sample rock, this application will determine the content of each of the following minerals in the rock sample: quartz, feldspar, calcite, dolomite, and clay.

[0057] As can be seen from the above introduction, rock mineral composition is used to indicate the content of various minerals in a rock sample.

[0058] In the implementation of step 110, this application also provides four methods for obtaining relevant data, which are described below.

[0059] (1) Determining the dry clay point.

[0060] On the neutron-density cross plot and the acoustic-density cross plot, the three-porosity curve skeleton points of dry clay are determined by the triangle method based on the distribution of data points, including pure quartz points, free water points, and bound water points. These points are used for subsequent well logging component model calculations and modeling parameters.

[0061] (2) Determining the mud content.

[0062] The GR curve is generally used to calculate the clay content. However, due to the complex lithology of shale oil, the GR curve cannot reflect changes in lithology. Therefore, this application uses the neutron-density intersection method to obtain the clay content curve based on the dry clay point.

[0063] (3) Obtaining kerogen.

[0064] There are generally four methods for calculating kerogen content: the Passey formula method, the multivariate fitting method, the density method, and the natural gamma ray spectroscopy method. The Passey formula method works by superimposing the acoustic transit time curve onto the resistivity curve using different coordinate scales on the same coordinate system. In non-source rock strata, the resistivity and porosity curves are parallel and coincident. However, in reservoir or organic-rich source rock strata, there is an amplitude difference between the two curves. The magnitude of this amplitude difference characterizes the amount of kerogen content. The specific formula is as follows:

[0065] ΔlogR=log(R / R 基线 )+K*(Δt-Δt 基线 )

[0066]

[0067] In the above formula, TOC is the kerogen content, R is the resistivity, and RC is the kerogen content. 基线 Here, K is the resistivity baseline, K is the calibration coefficient, and Δt is the acoustic transit time. 基线 R0 is the acoustic time difference baseline, R0 is the vitrinite reflectivity, and B is the TOC value of the non-hydrocarbon source rock layer.

[0068] Based on actual accuracy measurements, the Passey formula method is chosen as one possible approach to calculate kerogen content.

[0069] (4) Finding brittle minerals.

[0070] In the field of oil and gas reservoir exploration, the optimal logging interpretation method aims to obtain a complete compositional model by using logging data sensitive to each component as input for optimization. This method effectively reduces the ambiguity of single data sets and the influence of noise, resulting in the best compositional model. In this application, in addition to using conventional curves, the optimal logging interpretation method also incorporates elemental logging uranium and thorium content curves for calculating brittle minerals.

[0071] Step 120: Calculate the total porosity curve of the rock sample based on the clay content in the rock mineral composition and the first parameter, which includes the acoustic transit time or density curve.

[0072] In this application, based on the determination of clay content, the total porosity is obtained through the Wyllie average equation using either the sonic transit time or density curve. Specifically, this application uses the sonic transit time curve to obtain the total porosity curve. The specific formula is as follows:

[0073]

[0074] In the above formula, v is the velocity of the entire rock sample, v f It is the velocity of the rock matrix, v m Φ is the velocity of the pore fluid, and Φ is the porosity.

[0075] Step 130: Calculate the water saturation curve of the rock sample based on the rock electrical parameters.

[0076] In this application, resistivity and porosity curves are generally used to calculate water saturation using the Archie formula. However, since the Archie formula is a method for interpreting pure rock and does not consider the influence of formation water, two other methods have been derived. The first is the Indonesian equation, which is suitable for formations with low formation water salinity. The second is the Simandoux equation, which is suitable for formations with high formation water salinity.

[0077] Archie's formula: S w =(a*b*R) w / R t *Φ m ) 1 / n

[0078] In the above formula, S w R represents water saturation; a, b, m, and n are electrical parameters of the rock, which are usually constants in a given region. w R is the resistivity of formation water. t Φ represents the true resistivity of the formation, and Φ represents the porosity.

[0079] In one possible application, if the formation water salinity of the rock sample is relatively low, the Indonesian equation can be used to determine the water saturation curve.

[0080] Step 140: Calculate the pore width-to-length ratio curve of the rock sample based on the ratio of the target mineral content to the total mineral content.

[0081] In one possible approach, the pore width-to-length ratio curve can be obtained using theoretical values.

[0082] In another possible approach, this application provides a method for obtaining the pore width-to-length ratio curve that more closely approximates the rock sample. Specifically, this application can calculate the pore width-to-length ratio curve of the rock sample based on the ratio of the target mineral content to the total mineral content.

[0083] Step 150: Based on the equivalent modulus of ductile minerals, equivalent modulus of brittle minerals, equivalent modulus of rock skeleton, equivalent modulus of dry rock, and equivalent modulus of fluid, fluid displacement is performed to establish a rock physics model of the rock sample.

[0084] It should be noted that this application is capable of calculating rock mineral composition curves, total porosity curves, water saturation curves, and pore width-to-length ratio curves, and can establish rock physical models of rock samples based on the above data. This application provides a process for establishing a rock physical model of a rock sample, as described below.

[0085] (1) Plastic mineral equivalent

[0086] Shale typically exhibits good clay stratification, with a wide variety of clay minerals, and the elastic properties of different clay minerals are not entirely the same. Meanwhile, organic matter of varying maturity (such as kerogen) also influences the heterogeneity of shale. Therefore, considering the distribution and interrelationships of clay and organic matter in shale is a necessary factor in establishing shale models. The process of plastic mineral equivalence is explained in two steps below.

[0087] Step (a1): Take clay with an equal amount of kerogen and mix the two using a self-consistent model (SCA).

[0088] In step (a2), using the remaining clay as the background medium and the mixture obtained in step (a1) as the filling material, the two are mixed using a differential equivalent model (DEM) to obtain the plastic mineral equivalent modulus of kerogen-clay with interconnected properties.

[0089] (2) Brittle mineral equivalent

[0090] In one possible approach, if the rock sample contains four brittle minerals: quartz, feldspar, dolomite, and calcite, with quartz, feldspar, and dolomite present in roughly equal amounts, and calcite present in smaller amounts, then the following equivalent method is used to classify the brittle minerals based on their relative amounts.

[0091] Step (b1) involves mixing three brittle minerals with roughly equal amounts of quartz, feldspar, and dolomite using a self-consistent model (SCA) that can simultaneously represent multiphase minerals.

[0092] In step (b2), using the mixture obtained in step (b1) as the background medium and calcite with a small content as the filler, the two are mixed using a differential equivalent model (DEM) to obtain the equivalent modulus of brittle minerals.

[0093] (3) Rock skeleton equivalent

[0094] Using a plastic equivalent material composed of clay and kerogen as the background medium and brittle equivalent materials such as quartz and dolomite as fillers, the two are mixed using a differential equivalent model (DEM) to obtain the equivalent modulus of the rock skeleton.

[0095] (4) Dry rock equivalent

[0096] Using the rock skeleton as the background medium, the pores are added to the background medium using a differential equivalent model (DEM) to obtain the equivalent modulus of dry rock. Here, the pore width-to-length ratio is the pore width-to-length ratio curve calculated above.

[0097] (5) Fluid equivalent

[0098] Fluid properties were calculated using Batzle & Wang et al. based on known temperature, pressure, oil density, formation water salinity, and gas-oil ratio, and fluid mixing was performed using the Brie index method.

[0099] (6) Fluid displacement

[0100] Because shale layers exhibit significant velocity dispersion under oil-saturated conditions, this application selects the full-band Boris fluid displacement model to introduce mixed fluids into dry rock, thereby establishing an equivalent shale model that closely approximates the real situation.

[0101] Based on the above steps, the rock physics model established in this application is analyzed as follows. This application compares and optimizes the calculation methods for rock physics modeling-related curves to ensure the prediction accuracy of these curves, laying a solid data foundation for subsequent rock physics modeling of complex mineral components in shale oil. Previous rock physics modeling methods provided a theoretical constant value for the pore width-to-length ratio of minerals, while this application innovatively calculates the pore width-to-length ratio curve based on the content of each mineral at a depth point. This application uses a self-consistent model (SCA) + differential equivalent model (DEM) for the equivalent of brittle minerals, avoiding the assumptions of the Voigt-Reuss-Hill boundary model that require homogeneous components in the mixture and linear, elastic rocks, making the equivalent of brittle minerals more accurate. This application selects the full-frequency Boris fluid displacement model, which yields more accurate velocities compared to the low-frequency Gassmann fluid displacement model. The rock physics modeling process of the shale reservoir in this application is clear, and the rock physics model selected for each equivalent process is reasonable, representing a complete rock physics modeling method for complex mineral components in shale oil. The shear wave velocity predicted by this application is more accurate. Through a practical application in the test area, the shear wave velocity predicted by existing technology has a 85% agreement rate with the measured shear wave velocity, while the agreement rate of this innovative technology is as high as 92%.

[0102] Step 160: Estimate the transverse wave velocity of the rock sample based on the rock physics model.

[0103] In this application, based on a rock physics model, the shear wave velocity of a rock sample can be estimated. After obtaining the shear wave velocity of the rock sample, the corresponding pre-stack elastic parameters can be calculated. After obtaining the pre-stack elastic parameters, the maximum and minimum horizontal principal stresses can be calculated. Based on the maximum and minimum horizontal principal stresses, the horizontal well fracturing effect, fracturing wellbore stability, fracture propagation direction, morphology, and orientation can be determined, thereby improving the production rate of the horizontal well based on the above data.

[0104] In summary, the shear wave velocity estimation method provided in this application enables the calculation of the pore width-to-length ratio curve of a rock sample after obtaining the sample. Then, it performs equivalence calculations for ductile minerals, brittle minerals, rock skeletons, dry rock, fluids, and fluid displacement to establish a rock physical model of the rock sample. Based on this model, the shear wave velocity of the rock sample can be estimated. Because this application comprehensively establishes a rock physical model of rock samples that closely resembles actual shale reservoirs, the estimation of shear wave velocity is relatively accurate. This lays a methodological foundation for predicting various formation pressures and in-situ stresses using seismic data, and provides strong technical support for subsequent shale oil horizontal well selection and reserve / production enhancement.

[0105] Please refer to Figure 2 , Figure 2 Based on Figure 1 The illustrated embodiment provides a flowchart of a method for estimating shear wave velocity. Figure 2 The execution methods of steps 110 to 130, as well as steps 150 and 160, in the estimation of the provided shear wave velocity are the same as those in the previous steps. Figure 1 The execution method is similar, and will not be repeated here. Figure 2 In this process, step 140 is replaced by steps 141 to 145, as described below.

[0106] Step 141: Determine the sampling depth of the rock sample.

[0107] In this embodiment, rock samples are recorded at the formation depth during collection, i.e., the rock sample collection depth. This application will determine the rock sample collection depth, which will be recorded in the rock sample data.

[0108] Step 142: Obtain the content of each of the n target minerals in the rock sample at the sampling depth, and the theoretical value of the pore width-to-length ratio of each of the n target minerals.

[0109] The rock sample contains n target minerals, where n is a positive integer.

[0110] It should be noted that if the rock sample contains three target minerals, this application requires three sets of data. Each set of data includes the content of the target mineral in that set, as well as the theoretical value of the pore width-to-length ratio of the target mineral in that set.

[0111] Step 143: Determine the total mineral content in the rock sample at the sampling depth.

[0112] In this embodiment, the terminal can determine the total mineral content in a rock sample based on the sampling depth. Different sampling depths will correspond to different total mineral contents.

[0113] Step 144: Calculate the pore width-to-length ratio component of a target mineral based on the total mineral content, the target mineral content, and the theoretical value of the pore width-to-length ratio.

[0114] In this embodiment, the terminal can calculate the pore width-to-length ratio component of a target mineral based on its target mineral content, theoretical pore width-to-length ratio, and total mineral content. For example, if a rock sample contains three target minerals, this step can calculate the pore width-to-length ratio component corresponding to each of the three target minerals.

[0115] In step 144, four different schemes for calculating the pore width-to-length ratio of the target mineral may be included, as described below.

[0116] Option 1 includes steps 1441 and 1442.

[0117] Step 1441: Use the quotient of the target mineral content and the total mineral content as the first intermediate parameter.

[0118] Step 1442: Multiply the first intermediate parameter and the theoretical value of the pore width-to-length ratio to obtain the pore width-to-length ratio component of the target mineral.

[0119] If the pore width-to-length ratio curve of the rock sample is calculated based on Scheme 1, the calculation formula can be as follows.

[0120] Asp=∑((V′ / V T )*asP′)

[0121] Where Asp is the pore width-to-length ratio curve, V′ is the content of a certain mineral, and V T denoted as the total mineral content, and asp′ as the theoretical value of the pore width-to-length ratio of a certain mineral.

[0122] Option 2 includes steps 1441, 1443, 1444, and 1445.

[0123] Step 1441: Use the quotient of the target mineral content and the total mineral content as the first intermediate parameter.

[0124] Step 1443: Multiply the first intermediate parameter by the theoretical value of the pore width-to-length ratio to obtain the second intermediate parameter.

[0125] Step 1444: Obtain the first constant term corresponding to the target mineral.

[0126] Step 1445: The sum of the first constant term and the second intermediate parameter corresponding to the target mineral is used as the pore width-to-length ratio component of the target mineral.

[0127] If the pore width-to-length ratio curve of the rock sample is calculated based on Scheme 2, the calculation formula can be as follows.

[0128] Asp=∑((V′ / V T )*asp′+C1)

[0129] Where Asp is the pore width-to-length ratio curve, V′ is the content of a certain mineral, and V T denoted as the total mineral content, asp′ as the theoretical value of the pore width-to-length ratio of a certain mineral, and C1 as the first constant term.

[0130] Option 3 includes steps 1441, 1446, 1447, and 1448.

[0131] Step 1441: Use the quotient of the target mineral content and the total mineral content as the first intermediate parameter.

[0132] Step 1446: Multiply the first intermediate parameter by the theoretical value of the pore width-to-length ratio to obtain the third intermediate parameter.

[0133] Step 1447: Obtain the first coefficient corresponding to the target mineral.

[0134] Step 1448: The product of the first coefficient and the third intermediate parameter corresponding to the target mineral is used as the pore width-to-length ratio component of the target mineral.

[0135] If the pore width-to-length ratio curve of the rock sample is calculated based on Scheme 3, the calculation formula can be as follows.

[0136] Asp=∑(K1(V′ / V T )*asp′)

[0137] Where Asp is the pore width-to-length ratio curve, V′ is the content of a certain mineral, and V T denoted as the total mineral content, asp′ as the theoretical value of the pore width-to-length ratio of a certain mineral, and K1 as the first coefficient corresponding to the target mineral.

[0138] Option 3 includes steps 1441, 1446, 1447, 14481, 14482, and 14483.

[0139] Step 1441: Use the quotient of the target mineral content and the total mineral content as the first intermediate parameter.

[0140] Step 1446: Multiply the first intermediate parameter by the theoretical value of the pore width-to-length ratio to obtain the third intermediate parameter.

[0141] Step 1447: Obtain the second coefficient corresponding to the target mineral.

[0142] Step 14481: The product of the second coefficient and the third intermediate parameter of the target mineral is used as the fourth intermediate parameter.

[0143] Step 14482: Obtain the second constant term corresponding to the target mineral.

[0144] Step 14483: The sum of the fourth intermediate parameter and the second constant term corresponding to the target mineral is used as the pore width-to-length ratio component of the target mineral.

[0145] If the pore width-to-length ratio curve of the rock sample is calculated based on Scheme 4, the calculation formula can be as follows.

[0146] Asp=∑(K2(V′ / V T )*asp′+C2)

[0147] Where Asp is the pore width-to-length ratio curve, V′ is the content of a certain mineral, and V T denoted as the total mineral content, asp′ as the theoretical value of the pore width-to-length ratio of a certain mineral, K2 as the second coefficient corresponding to the target mineral, and C2 as the second constant term.

[0148] Step 145: Accumulate the pore width-to-length ratio components of each of the n target minerals to obtain the pore width-to-length ratio curve of the rock sample.

[0149] In this embodiment, the terminal will accumulate the pore width-to-length ratio components corresponding to each target mineral, and use the sum as the pore width-to-length ratio curve of the rock sample.

[0150] In summary, the shear wave velocity estimation method provided in this embodiment can calculate the pore width-to-length ratio, which is usually treated as a constant, as a calculable parameter. The pore width-to-length ratio can be determined through various calculation methods, each providing constant terms or coefficients related to the target mineral, making the pore width-to-length ratio closer to reality. This makes the rock physics model constructed in this application more closely resemble actual formation conditions, facilitating the determination of the true shear wave velocity. This lays the methodological foundation for predicting various formation pressures and in-situ stresses using seismic data, and provides strong technical support for subsequent shale oil horizontal well site selection and reserve / production enhancement.

[0151] Please refer to Figure 3 , Figure 3Based on Figure 1 The illustrated embodiment provides a flowchart of another method for estimating shear wave velocity. This method for estimating shear wave velocity can be applied in a terminal. Figure 3 In this context, the methods for estimating the shear wave velocity include:

[0152] Step 301: Extract rock samples from the shale reservoir and calculate the data required to establish a rock physics model of the rock samples based on the sonic transit time curve, density curve and rock electrical parameters of the rock samples. The required data includes mineral composition curve, total porosity curve and water saturation curve.

[0153] Step 302: Calculate the pore width-to-length ratio curve of the rock sample based on the ratio of the target mineral content to the total mineral content.

[0154] Step 303: Based on the mineral composition of the rock sample, the self-consistent model and the differential equivalent model are mixed to obtain the equivalent modulus of plastic minerals and the equivalent modulus of brittle minerals of the rock sample, respectively.

[0155] Step 304: Based on the equivalent materials of ductile and brittle minerals in the rock sample, a differential equivalent model is used to mix them to obtain the equivalent modulus of the rock skeleton of the rock sample.

[0156] Step 305: Based on the rock skeleton and porosity of the rock sample, a differential equivalent model is used to mix the samples to obtain the dry rock equivalent modulus of the rock sample.

[0157] Step 306: Based on the water saturation of the rock sample, the fluid is mixed using the Brie index method to obtain the fluid equivalent modulus of the rock sample.

[0158] Step 307: Based on the dry rock and mixed fluid of the rock sample, fluid displacement is performed using the Boris fluid displacement model to establish a rock physics model of the rock sample.

[0159] Step 308: Estimate the transverse wave velocity of the rock sample based on the rock physics model.

[0160] In summary, this application enables the calculation of the pore width-to-length ratio curve of rock samples after obtaining them. Then, it performs equivalence calculations for ductile minerals, brittle minerals, rock skeletons, dry rocks, fluids, and fluid displacement to establish a rock physical model of the rock sample. Based on this model, the shear wave velocity of the rock sample can be estimated. Because this application comprehensively establishes a rock physical model of rock samples that closely resembles actual shale reservoirs, the estimation of shear wave velocity is relatively accurate. This lays a methodological foundation for predicting various formation pressures and in-situ stresses using seismic data, and provides strong technical support for subsequent shale oil horizontal well site selection and reservoir enhancement.

[0161] Based on the solution disclosed in the previous embodiment, this application can also run a corresponding program through a terminal to realize the method for estimating transverse wave velocity. One practical embodiment can be referred to below.

[0162] In one possible embodiment of this application, Basin A, Depression B is selected as the rock sample collection area. Specifically, samples are collected from a designated three-dimensional region, and the target layer, the Permian Lucaogou Formation, is buried at a depth of 3000-3500 meters. Due to the low porosity and permeability of the "sweet spot" wells, vertical well production is low, and production is mainly increased through horizontal wells. The distribution of geostress is a key factor in increasing production through horizontal well fracturing, determining the direction, morphology, and orientation of the fractures. Pre-stack elastic parameters are used in the calculation of both the maximum and minimum horizontal principal stresses, and accurate shear wave velocity data is essential for calculating high-precision pre-stack elastic parameters. Although there are various methods for calculating shear wave velocity, a reasonable rock physics model remains the most effective method. Therefore, accurately determining the shear wave velocity is a key factor in accurately predicting the geostress distribution.

[0163] Accurate prediction of shear wave velocity in the study area faces two main challenges that need to be addressed.

[0164] (1) Question 1: Since shale has a complex mineral composition and pore structure, accurate calculation of rock physics modeling curves is the basis of modeling.

[0165] Solution: Compare and analyze multiple methods for calculating each curve to obtain the optimal method suitable for the study area.

[0166] like Figure 4 , Figure 4 This application provides a graph showing the calculation results of kerogen (TOC) content using the Passey formula method, multivariate fitting method, density method, and natural gamma spectroscopy method. Figure 5 This application presents a cross-plot comparing the results calculated using four methods with the measured total kerogen (TOC) content. The plot shows that the TOC content calculated using the Passey formula method agrees best with Inoue's actual measurements. Figure 6 This application presents a graph showing the calculation results of relevant curves for rock physics modeling. Based on the analysis of the relevant algorithms for each curve, this application ultimately uses the neutron-density intersection method to obtain the clay content curve, the optimized well logging interpretation method to obtain the brittle mineral content curve, the Wyllie average equation of the sonic transit time curve to obtain the total porosity curve, the modified Archie formula of the Indonesian equation to obtain the water saturation curve, and the pore width-to-length ratio curve to obtain the pore width-to-length ratio calculation formula of this invention. Figure 7This is a cross-plot of brittle mineral content and measured content obtained by an optimized well logging interpretation method provided in this application. The data points are distributed around a 45-degree line.

[0167] Application results: Through comparative analysis of various curve calculation methods, the predicted results of rock physics modeling curves show the highest degree of agreement with the measured results, laying a solid data foundation for subsequent rock physics modeling of complex mineral components in shale oil.

[0168] (2) Question 2: Although scholars at home and abroad have made some research and achievements in rock physics modeling technology for shale, there is no complete rock physics modeling method for shale oil applicable to this study area.

[0169] Solution: Based on thorough technical research, a rock physical modeling method for shale oil with complex mineral components was developed.

[0170] like Figures 8 to 10 Accurate shear wave velocity data were obtained using a rock physics modeling method for shale oil with complex mineral components. Figure 8 This application provides a flowchart for rock physics modeling of complex mineral components in shale oil. First, the ductile and brittle minerals are mixed using SCA (Self-Consistent Model) + DEM (Differential Equivalent Model) to obtain the equivalent modulus of ductile and brittle minerals, respectively. Using the ductile equivalent material as the background, the brittle mixture and pores are sequentially added to the background medium using the differential equivalent model (DEM) to obtain the equivalent modulus of dry rock. Fluid mixing is performed using the Brie index method based on known temperature, pressure, oil density, formation water salinity, and gas-oil ratio. The mixed fluid is then placed into the dry rock using a full-band Boris fluid displacement model, thereby establishing a shale equivalent model that closely approximates the real situation. Figure 9 This is a graph showing the results of P-wave velocity, density, and S-wave velocity obtained using the rock physics modeling method for shale oil provided in this application. Figure 10 This is a cross-plot of shear wave velocity obtained by using the rock physics modeling method for shale oil provided in this application and the measured shear wave velocity. The data points are distributed around a 45-degree line.

[0171] Application results: By applying the rock physics modeling method for shale oil with complex mineral components, the problem of low accuracy in rock physics modeling of shale oil is solved, and the predicted shear wave velocity matches the measured shear wave velocity by as high as 92%, laying a solid foundation for the study of pre-stack elastic parameters.

[0172] The experimental results of this method demonstrate that the multi-component equivalent rock physics modeling method can effectively characterize the complex lithology and multiple mineral components of shale, and obtain high-precision shear wave velocity data. This lays the methodological foundation for predicting various formation pressures and geostresses using seismic data, and provides strong technical support for subsequent shale oil horizontal well selection and reserve and production enhancement.

[0173] In another practical implementation of this application, the following solution is provided.

[0174] (1) Obtaining relevant curves for rock physics modeling, such as Figures 4 to 7 .

[0175] ① Determination of rock mineral composition

[0176] Shale has a very complex mineral composition, including more than a dozen minerals such as quartz and dolomite. It is impractical to determine the content of each mineral. Therefore, through the analysis of the elastic parameters and content of minerals, this application simplifies the complex components to quartz, feldspar, calcite, dolomite and clay minerals. At the same time, considering the characteristics of shale reservoirs, it is also necessary to determine the content of kerogen.

[0177] a. Determining the location of dry clay points

[0178] On the neutron-density cross plot and the acoustic-density cross plot, the three-porosity curve skeleton points of dry clay are determined by the triangle method based on the distribution of data points, including pure quartz points, free water points, and bound water points. The acoustic transit time, density, and neutron porosity values ​​of the dry clay points in this work area are (97, 2.66, 0.55), which are used for subsequent well logging component model calculations and modeling parameters.

[0179] b. Determination of clay content

[0180] The calculation of clay content is generally done using GR curves. However, since the lithology of shale oil is complex, GR curves cannot reflect changes in lithology. Therefore, this application uses the neutron-density intersection method to obtain the clay content curve based on the dry clay point.

[0181] c. Obtaining kerogen

[0182] There are generally four methods for calculating kerogen content: the Passey formula method, the multivariate fitting method, the density method, and the natural gamma ray spectroscopy method. The Passey formula method works by applying different coordinate scales on the same coordinate system, superimposing the acoustic transit time curve onto the resistivity curve. In non-source rock strata, the resistivity and porosity curves are parallel and coincident. However, in reservoir or organic-rich source rock strata, there is an amplitude difference between the two curves. The magnitude of this difference represents the amount of kerogen. The specific formula is as follows:

[0183] ΔlogR=log(R / R 基线 )+K*(Δt-Δt 基线 )

[0184]

[0185] In the above formula, TOC is the kerogen content, R is the resistivity, and RC is the kerogen content. 基线 Here, K is the resistivity baseline, K is the calibration coefficient, and Δt is the acoustic transit time. 基线 R0 is the acoustic time difference baseline, R0 is the vitrinite reflectivity, and B is the TOC value of the non-hydrocarbon source rock layer.

[0186] The kerogen content was determined using the four methods described above, and the results are as follows: Figure 4 By comparing the results calculated using four methods, this application selects the Passey formula method to calculate the kerogen content as follows: Figure 5 .

[0187] d. Determination of brittle minerals

[0188] The optimal logging interpretation method targets the complete compositional model elements, using logging data sensitive to each composition as input for optimization to obtain a complete rock composition model. This effectively reduces the ambiguity of single data and the influence of noise, resulting in the best compositional model. In this application, in addition to using conventional curves, elemental logging uranium and thorium content curves are introduced to calculate brittle minerals when using the optimal logging interpretation method.

[0189] ② Determination of total porosity curve

[0190] Based on the determination of clay content, the total porosity is obtained from the sonic transit time or density curve using the Wyllie average equation. In this application, the total porosity curve is obtained from the sonic transit time curve. The specific formula is as follows:

[0191]

[0192] In the above formula, v is the velocity of the entire rock sample, v f It is the velocity of the rock matrix, v m Φ is the velocity of the pore fluid, and Φ is the porosity.

[0193] ③ Determination of water saturation curve

[0194] Water saturation is generally calculated using resistivity and porosity curves via the Archie formula. However, since the Archie formula is a method for interpreting pure rock and does not consider the influence of formation water, two other methods have been derived. The Indonesian equation is suitable for formations with low formation water salinity.

[0195] The Simandoux equation is applicable to formations with high formation water salinity.

[0196] Archie's formula: S w =(a*b*R) w / R t *Φ m ) 1 / n

[0197] In the above formula, S w R represents water saturation; a, b, m, and n are electrical parameters of the rock, which are usually constants in a given region. w R is the resistivity of formation water. t Φ represents the true resistivity of the formation, and Φ represents the porosity.

[0198] The formation water salinity in this work area is 12,000 ppm, which is relatively low. Therefore, the Indonesian equation was used to obtain the water saturation curve.

[0199] ④ Determination of pore width-to-length ratio curve

[0200] Previous rock physics modeling methods provided a theoretical constant value for the pore width-to-length ratio, while this application innovatively calculates the pore width-to-length ratio curve based on the content of each mineral at a depth point. The specific formula is as follows:

[0201] Asp=∑((V′ / V T )*asp′)

[0202] In the formula, Asp is the pore width-to-length ratio curve, V′ is the content of a certain mineral, and V T denoted as the total mineral content, and asp′ as the theoretical value of the pore width-to-length ratio of a certain mineral. The six minerals in this work area are quartz, feldspar, calcite, dolomite, clay minerals, and kerogen. The theoretical pore width-to-length ratio of quartz and feldspar is 0.12, that of calcite and dolomite is 0.8, and that of clay minerals and kerogen is 0.05.

[0203] The final rock physics modeling curves are obtained through the algorithms used to calculate the various curves mentioned above, as shown in the figure. Figure 6 Its prediction results have the highest degree of agreement with the actual in-well measurements, such as... Figure 7 .

[0204] (2) Shale oil rock physics modeling process as follows Figures 8 to 10 .

[0205] The process of rock physics modeling for complex mineral composition shale oil is as follows: Figure 8 The specific implementation steps are as follows:

[0206] ① Plastic mineral equivalent

[0207] Shale typically exhibits good clay stratification, with a wide variety of clay minerals, and these different clay minerals possess varying elastic properties. Furthermore, organic matter of varying maturity (such as kerogen) also influences the heterogeneity of shale. Therefore, considering the distribution and interrelationships of clay and organic matter in shale is a crucial factor in establishing shale models.

[0208] a. Take an equal amount of clay as kerogen and mix the two using a self-consistent model (SCA).

[0209] b. Using the remaining clay as the background medium and the mixture obtained in a above as the filling material, the two are mixed using a differential equivalent model (DEM) to obtain the plastic mineral equivalent modulus of kerogen-clay with interconnected properties.

[0210] ② Brittle mineral equivalent

[0211] Of the four brittle minerals studied in this application, quartz, feldspar, and dolomite are present in roughly equal amounts, while calcite is present in relatively small amounts. Therefore, based on the amount of the four brittle minerals, the following equivalent method was adopted for the brittle minerals.

[0212] a. Mix three brittle minerals, including quartz, with roughly equal amounts of each mineral, using a self-consistent model (SCA) that can simultaneously represent multiphase minerals.

[0213] b. Using the mixture obtained in a above as the background medium and calcite with a small content as the filler, the two are mixed using a differential equivalent model (DEM) to obtain the equivalent modulus of the brittle mineral.

[0214] ③ Rock skeleton equivalent

[0215] Using a plastic equivalent material composed of clay and kerogen as the background medium and brittle equivalent materials such as quartz and dolomite as fillers, the two are mixed using a differential equivalent model (DEM) to obtain the equivalent modulus of the rock skeleton.

[0216] ④ Equivalent to dry rock

[0217] Using the rock skeleton as the background medium, the pores are added to the background medium using a differential equivalent model (DEM) to obtain the equivalent modulus of dry rock. Here, the pore width-to-length ratio is the pore width-to-length ratio curve calculated above.

[0218] ⑤ Fluid Equivalence

[0219] Fluid properties were calculated using Batzle & Wang et al. based on known temperature, pressure, oil density, formation water salinity, and gas-oil ratio, and fluid mixing was performed using the Brie index method.

[0220] ⑥ Fluid displacement

[0221] Because shale layers exhibit significant velocity dispersion under oil-saturated conditions, this application selects the full-band Boris fluid displacement model to introduce mixed fluids into dry rock, thereby establishing an equivalent shale model that closely approximates the real situation.

[0222] Through the implementation of the above-mentioned rock physics modeling method for complex mineral components in shale oil, the obtained P-wave velocity, density, and S-wave velocity are as follows: Figure 9 The predicted shear wave velocity matches the measured shear wave velocity with a success rate of up to 92%, such as... Figure 10 .

[0223] The following are embodiments of the apparatus described in this application, which can be used to execute the embodiments of the method described in this application. For details not disclosed in the apparatus embodiments of this application, please refer to the embodiments of the method described in this application.

[0224] Please refer to Figure 11 , Figure 11 This is a structural block diagram of a shear wave velocity estimation device provided in an exemplary embodiment of this application. The shear wave velocity estimation device can be implemented as all or part of a terminal through software, hardware, or a combination of both. The device includes:

[0225] The modeling data calculation module 1010 is used to extract rock samples from shale reservoirs and calculate the data required to establish a rock physical model of the rock samples based on the sonic transit time curve, density curve and rock electrical parameters of the rock samples. The required data includes mineral composition curve, total porosity curve and water saturation curve.

[0226] The pore width-to-length ratio calculation module 1020 is used to calculate the pore width-to-length ratio curve of the rock sample based on the ratio of the target mineral content to the total mineral content in the rock sample.

[0227] The rock matrix equivalent module 1030 is used to obtain the equivalent modulus of plastic minerals and the equivalent modulus of brittle minerals of the rock sample by mixing a self-consistent model and a differential equivalent model based on the mineral composition of the rock sample.

[0228] The rock skeleton equivalent module 1040 is used to mix the plastic mineral equivalent material and the brittle mineral equivalent material of the rock sample using a differential equivalent model to obtain the rock skeleton equivalent modulus of the rock sample.

[0229] Dry rock equivalent module 1050 is used to obtain the dry rock equivalent modulus of the rock sample by mixing based on the rock skeleton and porosity of the rock sample using a differential equivalent model.

[0230] The fluid equivalent module 1060 is used to perform fluid mixing based on the water saturation of the rock sample using the Brie index method to obtain the fluid equivalent modulus of the rock sample.

[0231] The fluid displacement module 1070 is used to perform fluid displacement based on the dry rock and mixed fluid of the rock sample using the Boris fluid displacement model, thereby establishing a rock physical model of the rock sample.

[0232] The shear wave velocity estimation module 1080 is used to estimate the shear wave velocity of the rock sample based on the rock physics model.

[0233] In an optional embodiment, the pore width-to-length ratio calculation module 1020 is used to determine the sampling depth of the rock sample; obtain the content of each of the n target minerals in the rock sample at the sampling depth, and the theoretical value of the pore width-to-length ratio of each of the n target minerals; determine the total mineral content in the rock sample at the sampling depth; calculate the pore width-to-length ratio component of one of the target minerals based on the total mineral content, the target mineral content, and the theoretical value of the pore width-to-length ratio; and sum the pore width-to-length ratio components of each of the n target minerals to obtain the pore width-to-length ratio curve of the rock sample, wherein the rock sample includes n target minerals, and n is a positive integer.

[0234] In an optional embodiment, the pore width-to-length ratio calculation module 1020 is used to take the quotient of the target mineral content and the total mineral content as a first intermediate parameter; and multiply the first intermediate parameter by the theoretical value of the pore width-to-length ratio to obtain the pore width-to-length ratio component.

[0235] In an optional embodiment, the pore width-to-length ratio calculation module 1020 is used to multiply the first intermediate parameter and the theoretical value of the pore width-to-length ratio to obtain a second intermediate parameter; obtain a first constant term corresponding to the target mineral; and use the sum of the first constant term corresponding to the target mineral and the second intermediate parameter as the pore width-to-length ratio component of the target mineral.

[0236] In an optional embodiment, the pore width-to-length ratio calculation module 1020 is used to multiply the first intermediate parameter and the theoretical value of the pore width-to-length ratio to obtain a third intermediate parameter; obtain the first coefficient corresponding to the target mineral; and use the product of the first coefficient corresponding to the target mineral and the third intermediate parameter as the pore width-to-length ratio component of the target mineral.

[0237] In an optional embodiment, the pore width-to-length ratio calculation module 1020 is used to multiply the first intermediate parameter and the theoretical value of the pore width-to-length ratio to obtain a third intermediate parameter; obtain a second coefficient corresponding to the target mineral; use the product of the second coefficient of the target mineral and the third intermediate parameter as a fourth intermediate parameter; obtain a second constant term corresponding to the target mineral; and use the sum of the fourth intermediate parameter and the second constant term corresponding to the target mineral as the pore width-to-length ratio component of the target mineral.

[0238] In summary, the shear wave velocity estimation device provided in this application can calculate the rock mineral composition of a rock sample, and based on the clay content and a first parameter in the rock mineral composition, calculate the total porosity curve of the rock sample. Then, based on the rock electrical parameters, it calculates the water saturation curve of the rock sample. Next, based on the ratio of the target mineral content to the total mineral content, it calculates the pore width-to-length ratio curve of the rock sample. Finally, based on the equivalent modulus of plastic minerals, brittle minerals, rock skeleton, dry rock, and fluid, it performs fluid displacement to establish a rock physics model of the rock sample. Based on this rock physics model, the shear wave velocity of the rock sample can be estimated. Because this application comprehensively establishes a rock physics model of rock samples that closely resembles actual shale reservoirs, the estimation of the shear wave velocity of the rock samples is relatively accurate. This lays a methodological foundation for predicting various formation pressures and geostresses using seismic data, and provides strong technical support for subsequent shale oil horizontal well selection and reserve enhancement.

[0239] Optionally, the shear wave velocity estimation device provided in this application can calculate the pore width-to-length ratio, which is usually treated as a constant, as a calculable parameter. The pore width-to-length ratio can be determined through various calculation methods, each providing constant terms or coefficients related to the target mineral, making the pore width-to-length ratio closer to reality. This makes the rock physics model constructed in this application closer to actual formation conditions, helping to obtain the true shear wave velocity. This lays the methodological foundation for predicting various formation pressures and geostresses using seismic data, and provides strong technical support for subsequent shale oil horizontal well site selection and reserve / production enhancement.

[0240] For example, the transverse wave velocity estimation method shown in the embodiments of this application can be applied to a terminal that has a transverse wave velocity estimation function. The terminal may include devices such as laptops, desktop computers, all-in-one computers, servers, or workstations.

[0241] Please see Figure 12 , Figure 12 This is a structural block diagram of a terminal provided in an exemplary embodiment of this application, such as... Figure 12As shown, the terminal includes a processor 1120 and a memory 1140, wherein the memory 1140 stores at least one instruction, which is loaded and executed by the processor 1120 to implement the transverse wave velocity estimation method as described in the various method embodiments of this application.

[0242] In this application, terminal 1100 extracts rock samples from shale reservoirs. Based on the sonic transit time curve, density curve, and electrical parameters of the rock samples, it calculates the data required to establish a rock physical model of the rock samples. The required data includes mineral composition curves, total porosity curves, and water saturation curves. Based on the ratio of the target mineral content to the total mineral content in the rock samples, it calculates the pore width-to-length ratio curve of the rock samples. Based on the mineral composition of the rock samples, it uses a self-consistent model and a differential equivalent model to obtain the equivalent modulus of ductile minerals and brittle minerals of the rock samples, respectively. Based on the ductile mineral composition of the rock samples... The equivalent modulus of the rock sample's rock skeleton is obtained by mixing the equivalent material of the rock sample and the equivalent material of the brittle mineral using a differential equivalent model. Based on the rock skeleton and porosity of the rock sample, the equivalent modulus of the dry rock is obtained by mixing the materials using a differential equivalent model. Based on the water saturation of the rock sample, the equivalent modulus of the fluid is obtained by mixing the fluids using the Brie index method. Based on the dry rock and the mixed fluid of the rock sample, the Boris fluid displacement model is used to perform fluid displacement, thereby establishing a rock physics model of the rock sample. Based on the rock physics model, the transverse wave velocity of the rock sample is estimated.

[0243] Processor 1120 may include one or more processing cores. Processor 1120 connects to various parts within terminal 1100 via various interfaces and lines, executing instructions, programs, code sets, or instruction sets stored in memory 1140, and calling data stored in memory 1140 to perform various functions and process data of terminal 1100. Optionally, processor 1120 may be implemented using at least one hardware form of Digital Signal Processing (DSP), Field-Programmable Gate Array (FPGA), or Programmable Logic Array (PLA). Processor 1120 may integrate one or a combination of several of the following: Central Processing Unit (CPU), Graphics Processing Unit (GPU), and modem. The CPU primarily handles the operating system, user interface, and applications; the GPU is responsible for rendering and drawing the content required for display; and the modem handles wireless communication. It is understood that the modem may also be implemented as a separate chip without being integrated into processor 1120.

[0244] The memory 1140 may include random access memory (RAM) or read-only memory (ROM). Optionally, the memory 1140 may include a non-transitory computer-readable storage medium. The memory 1140 may be used to store instructions, programs, code, code sets, or instruction sets. The memory 1140 may include a program storage area and a data storage area, wherein the program storage area may store instructions for implementing an operating system, instructions for at least one function (such as touch function, sound playback function, image playback function, etc.), instructions for implementing the various method embodiments described below, etc.; the data storage area may store data involved in the various method embodiments described below, etc.

[0245] This application also provides a computer-readable medium storing at least one instruction, which is loaded and executed by the processor to implement the transverse wave velocity estimation method described in the above embodiments.

[0246] It should be noted that the shear wave velocity estimation device provided in the above embodiments is only illustrated by the division of the functional modules described above when executing the shear wave velocity estimation method. In practical applications, the above functions can be assigned to different functional modules as needed, that is, the internal structure of the device can be divided into different functional modules to complete all or part of the functions described above. In addition, the shear wave velocity estimation device and the shear wave velocity estimation method embodiments provided in the above embodiments belong to the same concept, and the specific implementation process can be found in the method embodiments, which will not be repeated here.

[0247] The sequence numbers of the embodiments in this application are for descriptive purposes only and do not represent the superiority or inferiority of the embodiments.

[0248] Those skilled in the art will understand that all or part of the steps of the above embodiments can be implemented by hardware or by a program instructing related hardware. The program can be stored in a computer-readable storage medium, such as a read-only memory, a disk, or an optical disk.

[0249] The above description is merely an exemplary embodiment that can be implemented in this application and is not intended to limit this application. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this application should be included within the protection scope of this application.

Claims

1. A method for estimating shear wave velocity, characterized in that, The method includes: The rock samples are extracted from the shale reservoir. Based on the sonic transit time curve, density curve and electrical parameters of the rock samples, the data required to build a rock physical model of the rock samples are calculated. The required data includes mineral composition curve, total porosity curve and water saturation curve. The pore width-to-length ratio curve of the rock sample is calculated based on the ratio of the target mineral content to the total mineral content. Based on the mineral composition of the rock sample, the equivalent modulus of plastic minerals and the equivalent modulus of brittle minerals of the rock sample are obtained by mixing a self-consistent model and a differential equivalent model. Based on the equivalent materials of ductile and brittle minerals of the rock sample, a differential equivalent model is used to mix them to obtain the equivalent modulus of the rock skeleton of the rock sample. Based on the rock skeleton and porosity of the rock sample, a differential equivalent model is used to mix the samples to obtain the dry rock equivalent modulus of the rock sample. Based on the water saturation of the rock sample, the fluid mixing was performed using the Brie index method to obtain the fluid equivalent modulus of the rock sample. Based on the dry rock and mixed fluid of the rock sample, the Boris fluid displacement model was used to perform fluid displacement, thereby establishing a rock physics model of the rock sample. Based on the rock physics model, the transverse wave velocity of the rock sample was estimated.

2. The method according to claim 1, characterized in that, The rock sample includes n target minerals, where n is a positive integer. The step of calculating the pore width-to-length ratio curve of the rock sample based on the ratio of the target mineral content to the total mineral content includes: Determine the sampling depth of the rock sample; Obtain the content of each of the n target minerals in the rock sample at the sampling depth, and the theoretical value of the pore width-to-length ratio of each of the n target minerals; Determine the total mineral content in the rock sample at the specified sampling depth; Based on the total mineral content, the target mineral content, and the theoretical value of the pore width-to-length ratio, a pore width-to-length ratio component of the target mineral is calculated. By summing the pore width-to-length ratio components of each of the n target minerals, the pore width-to-length ratio curve of the rock sample is obtained.

3. The method according to claim 2, characterized in that, The step of calculating a pore width-to-length ratio component of the target mineral based on the total mineral content, the target mineral content, and the theoretical value of the pore width-to-length ratio includes: The quotient of the target mineral content and the total mineral content is used as the first intermediate parameter; Multiplying the first intermediate parameter by the theoretical value of the pore width-to-length ratio yields the pore width-to-length ratio component of the target mineral.

4. The method according to claim 3, characterized in that, The step of multiplying the first intermediate parameter and the theoretical value of the pore width-to-length ratio to obtain the pore width-to-length ratio component of the target mineral includes: Multiply the first intermediate parameter by the theoretical value of the pore width-to-length ratio to obtain the second intermediate parameter; Obtain the first constant term corresponding to the target mineral; The sum of the first constant term corresponding to the target mineral and the second intermediate parameter is taken as the pore width-to-length ratio component of the target mineral.

5. The method according to claim 3, characterized in that, The step of multiplying the first intermediate parameter and the theoretical value of the pore width-to-length ratio to obtain the pore width-to-length ratio component of the target mineral includes: Multiply the first intermediate parameter by the theoretical value of the pore width-to-length ratio to obtain the third intermediate parameter; Obtain the first coefficient corresponding to the target mineral; The product of the first coefficient corresponding to the target mineral and the third intermediate parameter is used as the pore width-to-length ratio component of the target mineral.

6. The method according to claim 3, characterized in that, The step of multiplying the first intermediate parameter and the theoretical value of the pore width-to-length ratio to obtain the pore width-to-length ratio component of the target mineral includes: Multiply the first intermediate parameter by the theoretical value of the pore width-to-length ratio to obtain the third intermediate parameter; Obtain the second coefficient corresponding to the target mineral; The product of the second coefficient of the target mineral and the third intermediate parameter is used as the fourth intermediate parameter; Obtain the second constant term corresponding to the target mineral; The sum of the fourth intermediate parameter and the second constant term corresponding to the target mineral is taken as the pore width-to-length ratio component of the target mineral.

7. The method according to claim 1, characterized in that, The method further includes: Take clay with an equal amount of kerogen, and mix the kerogen and the clay using a self-consistent model to obtain a first mixture; The clay remaining after the clay of equal content to that of kerogen is taken is used as the first background medium, and the first mixture is used as the filler. The first background medium and the filler are mixed using the differential equivalent model to obtain the plastic mineral equivalent modulus of the rock sample of kerogen-clay with interconnected properties.

8. The method according to claim 1, characterized in that, The method further includes: A second mixture is obtained by mixing (p-1) brittle minerals in equal amounts using a self-consistent model, where p is a positive integer greater than 1. Using the second mixture as the second background medium, and the brittle minerals other than the (p-1) brittle minerals in the target mineral as fillers, the second background medium and the fillers are mixed using a differential equivalent model to obtain the brittle mineral equivalent modulus of the rock sample.

9. The method according to claim 1, characterized in that, The method further includes: Using the rock skeleton as the third background medium and the pore width-to-length ratio curve as the shape feature of the pores, the pores are added to the third background medium using a differential equivalent model to obtain the dry rock equivalent modulus of the rock sample.

10. A device for estimating transverse wave velocity, characterized in that, The device includes: The modeling data calculation module is used to extract rock samples from shale reservoirs and calculate the data required to establish a rock physical model of the rock samples based on the sonic transit time curve, density curve and rock electrical parameters of the rock samples. The required data includes mineral composition curves, total porosity curves and water saturation curves. The pore width-to-length ratio calculation module is used to calculate the pore width-to-length ratio curve of the rock sample based on the ratio of the target mineral content to the total mineral content in the rock sample. A rock matrix equivalent module is used to obtain the equivalent modulus of plastic minerals and the equivalent modulus of brittle minerals of the rock sample by mixing a self-consistent model and a differential equivalent model based on the mineral composition of the rock. A rock skeleton equivalent module is used to mix the plastic mineral equivalent material and the brittle mineral equivalent material of the rock sample using a differential equivalent model to obtain the rock skeleton equivalent modulus of the rock sample. A dry rock equivalent module is used to obtain the dry rock equivalent modulus of the rock sample by mixing based on the rock skeleton and porosity of the rock sample using a differential equivalent model. A fluid equivalent module is used to perform fluid mixing based on the water saturation of the rock sample using the Brie index method to obtain the fluid equivalent modulus of the rock sample. The fluid displacement module is used to perform fluid displacement based on the dry rock and mixed fluid of the rock sample using the Boris fluid displacement model, thereby establishing a rock physics model of the rock sample. The shear wave velocity estimation module is used to estimate the shear wave velocity of the rock sample based on the rock physics model.

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