Rock physics template establishment method, gas saturation quantitative prediction method and device

Abstract

The present application provides a rock physics template establishing method, a gas saturation quantitative prediction method and device. The rock physics template establishing method comprises: obtaining reservoir rock geology parameters, wherein the reservoir rock geology parameters comprise thickness, porosity and gas saturation; obtaining PG attributes corresponding to different geology parameters by using seismic forward simulation according to the reservoir rock geology parameters; establishing a rock physics template based on PG attributes according to the PG attributes and the reservoir rock geology parameters, and determining the relationship between the PG attributes and the gas saturation through the rock physics template; determining the PG attributes of a to-be-tested reservoir according to prestack gather data of the to-be-tested reservoir; and predicting the gas saturation of the to-be-tested reservoir according to the PG attributes of the to-be-tested reservoir and the relationship between the PG attributes and the gas saturation. The present application realizes quantitative prediction of the gas saturation by establishing a PGT (PG attribute rock physics template), which is convenient for oil and gas development in the later stage.

Description

TECHNICAL FIELD

[0001] The present application belongs to the field of oil and gas geological exploration, and particularly relates to a rock physics template establishing method, a gas saturation quantitative prediction method and device. BACKGROUND

[0002] AVO is the abbreviation of Amplitude Variation with Offset, which is translated as amplitude variation with offset. The theoretical basis of AVO is that when a plane longitudinal wave is non-perpendicular incident on the interface between two media, reflected waves and transmitted waves are generated. On the interface, according to stress continuity and displacement continuity, and by introducing reflection coefficient and transmission coefficient, the displacement amplitude of the corresponding wave satisfies the Zoeppritz equation. Since the equation set is relatively complex, the function relationship between the amplitude of the newly generated wave and the relevant parameters cannot be solved. Shuey (1985) further studied the influence of Poisson's ratio on the reflection coefficient and made a further simplification of the Zoeppritz equation, which is: R(a) = P + G*sin2a, where R is the reflection coefficient, a is the incidence angle, P is the AVO intercept, i.e. the reflection coefficient at zero offset, and G is the AVO slope, i.e. the proportional coefficient of amplitude change with incidence angle. In the field of seismic exploration, when the lithology, physical properties, fluid content, etc. of the underground formation change, a relatively obvious AVO response can be detected on the seismic data. Therefore, prestack AVO technology can be used for reservoir prediction, hydrocarbon detection and fracture prediction, etc.

[0003] Seismic rock physics provides a solid foundation for the development of hydrocarbon detection technology and effectively promotes the development of AVO technology, thereby improving the success rate in lithology and fluid prediction. The key step in its application in seismic exploration is to establish a rock physics template. Rock physics template technology (RPTs) is a tool for establishing various rock physics models, which is a semi-quantitative-quantitative interactive interpretation technology for rock reservoir parameters. It can integrate geological, logging data and seismic elastic inversion results to construct the relationship between rock and fluid properties and elastic parameters in the geological environment, and provide templates and basis for quantitative seismic interpretation.

[0004] However, the elastic parameters used in the conventional rock physics template generally depend on prestack seismic inversion. At present, due to the strong multi-solution of density parameters, the large amount of data of prestack data inversion, and the strong uncertainty of inversion, the template establishment has certain multi-solution, which is not conducive to the prediction of reservoir physical parameters in the process of oil and gas development, such as reservoir gas saturation. Therefore, how to improve the accuracy of quantitative prediction of gas saturation in oil and gas reservoirs through rock physics template is a problem to be solved at present. SUMMARY

[0005] In view of the above problems of the prior art, the purpose of the present document is to provide a rock physics template establishing method and a gas saturation quantitative prediction method and device, so as to improve the accuracy of rock physics template in quantitative prediction of gas saturation in reservoirs.

[0006] In order to solve the above technical problems, the specific technical solutions of the present document are as follows:

[0007] In the first aspect, the present document provides a rock physics template establishing method, and the method comprises:

[0008] Obtaining reservoir rock geology parameters, wherein the reservoir rock geology parameters include thickness, porosity and gas saturation;

[0009] According to the reservoir rock geology parameters, PG attributes corresponding to different geology parameters are obtained by using seismic forward simulation;

[0010] According to the PG attributes and the reservoir rock geology parameters, a rock physics template based on PG attributes is established.

[0011] In the second aspect, the present document provides a gas saturation quantitative prediction method, and the method comprises:

[0012] According to the obtained prestack gather data of the to-be-tested reservoir, PG attributes of the to-be-tested reservoir are determined;

[0013] According to the PG attributes of the to-be-tested reservoir, the rock physics template based on PG attributes established by the above method is used to predict the gas saturation of the to-be-tested reservoir.

[0014] In the third aspect, the present document further provides a gas saturation quantitative prediction device, and the device comprises:

[0015] A to-be-tested reservoir PG attribute obtaining module is configured to determine PG attributes of a to-be-tested reservoir according to obtained prestack gather data of the to-be-tested reservoir;

[0016] A to-be-tested reservoir gas saturation predicting module is configured to predict the gas saturation of the to-be-tested reservoir according to the PG attributes of the to-be-tested reservoir by using the rock physics template based on PG attributes established by the above method.

[0017] In the fourth aspect, the present document further provides a computer device, which comprises a memory, a processor and a computer program stored in the memory and executable on the processor, wherein the processor implements the steps of the rock physics template establishing method and / or the gas saturation quantitative prediction method as described above when executing the computer program.

[0018] In a fifth aspect, the paper also provides a computer readable storage medium storing a computer program, which, when executed by a processor, implements the steps of the rock physics template establishing method and / or the gas saturation quantitative prediction method.

[0019] With the technical solution, the rock physics template establishing method, the gas saturation quantitative prediction method and device can obtain PG attributes corresponding to different geological parameters through seismic forward simulation, establish a rock physics template capable of revealing the relationship between the PG attributes and the gas saturation according to the PG attributes and the reservoir rock geological parameters, and finally accurately and quantitatively predict the gas saturation in other reservoirs based on the relationship between the PG attributes and the gas saturation. The rock physics template can improve the accurate prediction of the gas saturation and facilitate the development of oil and gas in the later stage.

[0020] In order to make the above and other objects, features and advantages of the paper more obvious and easy to understand, the following preferred embodiments are described in detail below, and the accompanying drawings are described as follows. BRIEF DESCRIPTION OF DRAWINGS

[0021] In order to more clearly illustrate the technical solutions in the embodiments or the prior art, the following will briefly introduce the drawings needed to be used in the embodiments or the prior art description. Obviously, the drawings in the following description are only some embodiments of the paper, and those skilled in the art can obtain other drawings according to these drawings without creative labor.

[0022] Figure 1 The step schematic diagram of the rock physics template establishing method in the embodiments of the paper is shown;

[0023] Figure 2 The step schematic diagram of obtaining the PG attributes in the embodiments of the paper is shown;

[0024] Figure 3 The step schematic diagram of the PG attribute correction in the embodiments of the paper is shown;

[0025] Figure 4 The step schematic diagram of the gas saturation quantitative prediction in the embodiments of the paper is shown;

[0026] Figure 5 The step schematic diagram of determining the relationship between the PG attributes and the gas saturation in the embodiments of the paper is shown;

[0027] Figure 6 The relationship diagram between the reservoir rock physical parameters calculated based on the patch saturation model and the water saturation in the embodiments of the paper is shown;

[0028] Figure 7The prestack gathers of reservoirs with different gas saturation and thickness when porosity is 5% in the embodiments of the present application are shown;

[0029] Figure 8 The prestack AVO response characteristics when time is 1571ms when gas saturation is 20% and porosity is 5% in the embodiments of the present application are shown;

[0030] Figure 9 The prestack AVO response characteristics when time is 1571ms when gas saturation is 100% and porosity is 5% in the embodiments of the present application are shown;

[0031] Figure 10 The prestack gathers of reservoirs with different porosity when thickness is 5m and gas saturation is 90% in the embodiments of the present application are shown;

[0032] Figure 11 The prestack AVO response characteristics when time is 1571ms when porosity is 13%, thickness is 5m and gas saturation is 90% in the embodiments of the present application are shown;

[0033] Figure 12 The prestack AVO response characteristics when time is 1571ms when porosity is 3%, thickness is 5m and gas saturation is 90% in the embodiments of the present application are shown;

[0034] Figure 13 The prestack gathers of reservoirs with porosity of 13% in the embodiments of the present application are shown;

[0035] Figure 14 The prestack AVO response characteristics when time is 1573ms when porosity is 13%, gas saturation is 100% in the embodiments of the present application are shown;

[0036] Figure 15 The prestack AVO response characteristics when time is 1573ms when porosity is 13%, gas saturation is 0% in the embodiments of the present application are shown;

[0037] Figure 16 The variable saturation and porosity PG attribute crossplot in the embodiments of the present application is shown;

[0038] Figure 17 The variable saturation and thickness PG attribute crossplot in the embodiments of the present application is shown;

[0039] Figure 18 The comparison between the quantitative prediction of gas saturation and the conventional prediction in the embodiments of the present application is shown;

[0040] Figure 19 The structure diagram of the quantitative prediction device of gas saturation in the embodiments of the present application is shown;

[0041] Figure 20A structural schematic diagram of the computer device in the embodiments is shown.

[0042] List of signs:

[0043] 100, reservoir PG property acquisition module to be measured;

[0044] 200, reservoir gas saturation prediction module to be measured;

[0045] 2002, computer device;

[0046] 2004, processor;

[0047] 2006, memory;

[0048] 2008, driving mechanism;

[0049] 2010, input / output module;

[0050] 2012, input device;

[0051] 2014, output device;

[0052] 2016, presentation device;

[0053] 2018, graphical user interface;

[0054] 2020, network interface;

[0055] 2022, communication link;

[0056] 2024, communication bus. DETAILED DESCRIPTION

[0057] The technical solutions in the embodiments will be described clearly and completely in the embodiments in combination with the drawings in the embodiments. Obviously, the described embodiments are only part of the embodiments, not all the embodiments. Based on the embodiments herein, all other embodiments obtained by those skilled in the art without creative labor are within the scope of protection.

[0058] It should be noted that the terms "first," "second," etc., used in the specification, claims, and accompanying drawings herein are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence. It should be understood that such data can be interchanged where appropriate so that the embodiments described herein can be implemented in orders other than those illustrated or described herein. Furthermore, the terms "comprising" and "having," and any variations thereof, are intended to cover a non-exclusive inclusion; for example, a process, method, apparatus, product, or device that comprises a series of steps or units is not necessarily limited to those steps or units explicitly listed, but may include other steps or units not explicitly listed or inherent to such processes, methods, products, or devices.

[0059] In existing technologies, the elastic parameters used in rock physics templates generally rely on pre-stack seismic inversion. Currently, due to the strong ambiguity of density parameters, the large amount of pre-stack data inversion, and the strong uncertainty of inversion, template establishment has a certain degree of ambiguity, which is not conducive to the prediction of reservoir physical parameters during oil and gas development.

[0060] To address the aforementioned issues, this specification provides a method for establishing rock physics templates, which can improve the accuracy of predicting reservoir physical parameters (especially gas saturation or water saturation). Figure 1 This diagram illustrates the steps of a rock physics template creation method provided in the embodiments of this specification. This specification provides the operational steps of the method described in the embodiments or flowcharts, but based on conventional or non-inventive labor, more or fewer operational steps may be included. The order of steps listed in the embodiments is merely one possible execution order among many and does not represent the only possible execution order. In actual system or device products, the methods shown in the embodiments or drawings can be executed sequentially or in parallel. Specifically, as shown in the attached diagrams... Figure 1 As shown, the method may include:

[0061] S101: Obtain reservoir rock geological parameters, including thickness, porosity, and gas saturation;

[0062] S102: Based on the geological parameters of the reservoir rocks, the PG attributes corresponding to different geological parameters are obtained by seismic forward modeling.

[0063] S103: Based on the PG attribute and the reservoir rock geological parameters, establish a rock physical template based on the PG attribute.

[0064] The embodiment of the present application can obtain the geologic parameters of the reservoir rock, such as thickness, porosity and gas saturation, and obtain the PG attribute corresponding to different geologic parameters by using seismic forward modeling, so as to obtain the rock physical template capable of reflecting the change of the gas saturation of the reservoir. The forward modeling can avoid the multi-solution problem of pre-stack seismic inversion, and improve the accuracy of the rock physical template in the quantitative prediction of the gas saturation.

[0065] It should be noted that, in order to improve the reliability of the rock physical template and the accuracy of the prediction of the gas saturation, a sufficient number of PG attribute parameters are required, that is, a sufficient number of forward modeling data are required. In actual work, the geologic parameters of the reservoir rock in step S101 can include the laboratory physical property test data in the known well logging, and can also include more geologic parameters preset according to the geologic parameters in the known well logging. Specifically, according to the continuity principle of the rock geologic parameters, more geologic parameters are set on the basis of the geologic parameters in the known well logging, so as to perform more forward modeling. For example, the porosity can be selected as 3%, 5%, 7%, 9%, 11% and 13%, and the like; the thickness can be selected as 5m, 10m, 15m, 20m and the like; and the gas saturation can be selected as 0%, 10%, 20%, 30%,..., 100% and the like. By using the known and preset geologic parameters, a sufficient number of data can be obtained for seismic forward modeling, so that a sufficient number of parameter data can be obtained for the analysis of the law and the prediction of the gas saturation when the rock physical template is established.

[0066] The geologic parameters of the reservoir rock can include but are not limited to thickness, porosity and gas saturation. The geologic parameters of the known well logging can be obtained by laboratory core physical property analysis, and the preset geologic parameters can be obtained according to the rock layer change information of the geologic profile, and then the known geologic parameters of the well logging are used for presetting, so that the preset geologic parameters are as close as possible to the true values of the reservoir, and the accuracy of the forward modeling result is improved.

[0067] In the description embodiment, as shown in Figure 2 The step S102 can include:

[0068] S1021: calculating the rock physical parameters of the reservoir according to the geologic parameters of the reservoir rock by using the patch saturation model, wherein the rock physical parameters of the reservoir include the P-wave velocity, the S-wave velocity and the density corresponding to different porosities;

[0069] S1022: obtaining the pre-stack gather of different thicknesses, porosities and gas saturations by using seismic forward modeling according to the rock physical parameters of the reservoir and the geologic parameters of the reservoir rock;

[0070] S1023: obtaining the PG attribute corresponding to different geologic parameters by performing AVO analysis according to the pre-stack gather.

[0071] This can be understood as follows: the patchy saturation model (Patchy theory model) can be used to obtain reservoir rock physical parameters that match seismic data. Specifically, these parameters can include P-wave velocity, S-wave velocity, and density. The Patchy theory model is a conventional method for calculating geophysical parameters, and will not be elaborated upon in the embodiments of this specification. Optionally, the embodiments of this specification can calculate the relationship between P-wave velocity Vp and S-wave velocity Vs and gas saturation Sg (or water saturation Sw) and porosity by selecting the Patchy saturation method of the dual-pore medium theory. At the same time, the relationship between density ρ and gas saturation Sg (or water saturation Sw) and porosity can also be calculated. Then, by combining the specific porosity and gas saturation values, the corresponding P-wave velocity, S-wave velocity, and density can be obtained. Here, gas saturation Sg and water saturation Sw represent the material state inside the same pore. In actual calculations, the sum of gas saturation Sg and water saturation Sw in the same pore is 1.

[0072] like Figure 6 The diagram shown is a schematic of the results calculated based on the patch saturation model. With a porosity of 13%, the relationship between the reservoir rock physical parameters calculated by the patch saturation model and the water saturation can be obtained, such as the relationship between P-wave velocity, S-wave velocity, and density and water saturation.

[0073] In one specific embodiment, the forward modeling parameters are based on wells Longgang 1 and Longgang 2 in the Longgang area of ​​the Sichuan Basin, combined with laboratory physical property test data from known well logging. As shown in Table 1, these are partial data of the seismic forward modeling rock physics parameters calculated using the patch saturation model.

[0074] Table 1. Rock Physical Parameters from Seismic Forward Modeling

[0075]

[0076] In the embodiments of this specification, reservoir rock physical parameters are obtained through the above steps, and combined with reservoir rock geological parameters, pre-stack gathers with different thicknesses, porosities, and gas saturation are obtained through seismic forward modeling.

[0077] In one specific embodiment, the elastic wave forward modeling method can be selected for forward simulation. This method is based on the reflectivity method, which is a way to solve the elastic wave equation under one-dimensional assumptions. Therefore, it can simulate multiple waves and converted waves, and consider the effects of seismic wave loss during propagation. It also boasts high computational accuracy and moderate computational cost, making it highly practical. The solution process is performed in the frequency-slowness domain, and the reflectivity in the frequency-slowness domain is transformed to the spatiotemporal domain or the intercept-time-ray parameter domain using numerical integration.

[0078] According to the reflectivity method, assuming a shot point and multiple detectors are placed on top of the first layer of a horizontally layered medium, the total reflection coefficient R(ω,p) in the frequency-slowness domain can be obtained through the six-element vector w = [w(1),…,w(6)] in the frequency-slowness domain:

[0079] R PP (ω,p)=w0(4) / w0(1)

[0080] R PS (ω,p)=w0(5) / w0(1) (1)

[0081] Where w0 represents the total reflected response received by the ground, and R represents the reflection coefficient. pp Indicates the type of incident wave, R ps Indicates the type of reflected wave, w n This represents the total reflection response below the nth underground interface:

[0082] w n =[Δ -R SP Δ -R SS Δ R PP Δ R PS Δ |R|Δ] T (2)

[0083] Δ represents the scaling factor, and || represents the determinant. Assuming the subsurface medium below the Nth stratum interface is a half-space elastic medium with no reflected waves, the response below the Nth layer is:

[0084] w N =[1 0 0 0 0 0] T (3)

[0085] The reflectivity method starts from the bottom interface and uses the transfer matrix Q n The total reflection response below the top interface is obtained through recursive calculation, thereby calculating the reflection coefficient in the frequency-slowness domain. Then, the product of the reflection coefficient and the wavelet is inversely transformed to obtain the synthetic seismic record in the τ-p domain. The recursive process can be expressed as:

[0086] w0=Q0Q1…Q N-1 w N (4)

[0087]

[0088] The study introduces variable E. n , To represent Q n , where matrix E n This describes the phase change of a seismic wave as it passes through the nth layer of medium. The expression of the influence of the nth layer of medium on the amplitude of seismic wave contains 16 independent components, which are respectively:

[0089]

[0090]

[0091]

[0092] wherein, v p represents the velocity of longitudinal wave, v s represents the velocity of transverse wave, respectively represent the vertical slowness of longitudinal and transverse waves, p = sinθ / v p represents the horizontal slowness, let Γ = 2p 2 -1 / v s 2 , μ = ρv s 2 Δh is the thickness of the nth layer of medium, then the 16 independent components are respectively:

[0093]

[0094]

[0095]

[0096] t 32 = -4ip 2 q p t 33 = -ip(Γ - 2q p q s )

[0097] t 35 = -2iΓq s t 42 = -2iΓq p

[0098]

[0099] t 61 = -μ(Γ 2 + 4p 2 q p q s )

[0100] t 62 = -4μΓpq p

[0101] t 63 = -μ(Γ 2 - 4p 2 qp q s )

[0102] t 65 = -4μΓpq s (9)

[0103] The w0 is calculated according to the formula (4) and the formula (5) by a recursive method, and is substituted into the formula (1) to obtain the reflectivity R(ω, p) in the frequency-slowness domain, and the product of the reflectivity R(ω, p) and the seismic wavelet is inverse transformed to obtain the synthetic seismic record τ-p:

[0104]

[0105] Since the seismic record used in the wave impedance inversion is a stacked section, the Snell law p = sinθ / v p The reflectivity R(θ, ω) in the frequency-angle domain is obtained by resampling the reflectivity R(ω, p) in the frequency-slowness domain, and the product of the reflectivity R(θ, ω) and the seismic wavelet is inverse Fourier transformed to obtain the synthetic seismic record through stacking:

[0106]

[0107] Based on the elastic wave reflection principle provided above and the P-wave and S-wave velocities calculated by the patch saturation model, the P-wave amplitude stacked section in the seismic simulation process, i.e., the pre-stack gather corresponding to different geological parameters, can be obtained, and then the variation characteristics of the P-wave amplitude with the offset are determined through the amplitude versus offset (AVO) analysis, the amplitude variation curve at a specific time point is fitted, and the PG attribute corresponding to different geological parameters is determined in combination with the geological body characteristics (porosity, thickness, and gas saturation, etc.) corresponding to the position of the P-wave amplitude.

[0108] The PG attribute can be calculated by the Shuey (1985) approximation formula in combination with the fitted amplitude variation curve, and the Shuey (1985) approximation formula is R(a) = P + G*sin 2 a, wherein R is the reflectivity, which can be obtained by the reflection characteristics of the P-wave under different geological parameters in the forward process, a is the incidence angle, which is the angle of the P-wave incident to the next interface and can be obtained by the amplitude variation curve, P is the AVO intercept, i.e., the reflectivity at zero offset, and G is the AVO slope, i.e., the proportional coefficient of the amplitude variation with the incidence angle.

[0109] In one specific embodiment, due to the low overall porosity and complex pore structure of dolomite reservoirs, the geological parameters obtained through conventional inversion analysis are prone to multiple solutions and are computationally difficult. Therefore, the forward modeling method provided in this specification can be used for prediction. Specifically, forward analysis can be performed using the elastic wave method provided in GeoView software. The corresponding seismic simulation frequencies are extracted from the target layer in actual 3D seismic data, with a dominant frequency of 25Hz, a high cutoff frequency of 75Hz, and the gas layer (reservoir) starting point at 5800m. The forward model can select 4 groups of 11 saturation and 7 thickness models, totaling 308 models. 616 pairs of PG attribute data are extracted, ensuring sufficient parameter values ​​for the PG attributes. Different geological parameters can yield different pre-stack gathers through forward modeling, such as... Figures 7 to 14 Different pre-stack gathers were obtained for different geological parameters, and PG attributes were obtained through AVO analysis.

[0110] The variation characteristics of PG attributes can also be obtained by analyzing the PG attributes extracted from pre-stack gathers and AVO analysis, such as... Figure 7 The figure shows the state of complete gas saturation when the porosity is 5%. Figure 7 -above) and gas saturation of 20% ( Figure 7 - (below) the pre-stack gather, the thickness interval in the figure is 5 meters, the first gather starts from 0 meters, the 7th gather is 30 meters thick, and the other pre-stack gather models shown below are the same. This forward modeling pre-stack gather shows that with a small amount of gas content (Sg = 20%), the amplitude increases rapidly with the shot-receiver distance, however, as Figure 8 and Figure 9 As shown, the PG attributes extracted by AVO analysis at the same time point under different gas saturation levels are shown. The results indicate that the G attributes are basically consistent, while the P attributes show slight changes.

[0111] like Figure 10 and Figure 12 The image shows pre-stack gathers and AVO analyses for gas layers with a thickness of 5 meters and a gas saturation of 90%, and porosities of 3% and 13%, respectively. From the gathers, the amplitude of the 5-meter gas layer (second layer) with 3% porosity is very weak, and the amplitude increases significantly with increasing offset. However, in the forward modeling results with 13% porosity, strong amplitude is observed, but the amplitude decreases with increasing shot-receiver distance. This contradicts the current understanding that gas layers typically exhibit weak amplitude, which increases with increasing shot-receiver distance. Figure 11 and Figure 12 AVO analysis also yielded PG attribute values ​​with significant differences. Therefore, forward simulation in the embodiments of this specification can provide more accurate characteristics of amplitude variation in the reservoir, offering accurate guidance for subsequent reservoir prediction.

[0112] like Figure 13As shown, it is almost difficult to distinguish the difference between water saturation and gas saturation (Sg=100%) and water saturation (Sg=0%) from the gathers, and there is no obvious difference in amplitude and waveform characteristics, and only in the case of large thickness, the weak change can be revealed by the wavelet side lobe reflection record. However, as shown in Figure 14 and Figure 15 As shown, the difference between the two is still very obvious on the PG attribute extracted by AVO analysis, and the P attribute is increased by 26% in gas saturation than in water saturation, and the change of G attribute is 8%, so the PG attribute obtained by forward modeling can accurately reflect the geological conditions in the reservoir, and can better provide a good index for predicting the geological parameters of the reservoir.

[0113] It should be noted that the pre-stack gathers obtained by the above forward and the PG attribute extracted by AVO analysis are only one specific embodiment of the present application, and in the specific reservoir analysis of the work area, the starting depth of the reservoir and the forward simulation of different reservoir rock geological parameters can be determined according to the actual situation, and the embodiments of the present application are not described.

[0114] Since the reservoir rock geological parameters obtained by the above steps are a collection of actual parameters and preset parameters of known wells, enough forward data parameters can be ensured, so that the PG parameters obtained will have a certain deviation. In order to further improve the accuracy of the PG attribute, the correction of the PG attribute can be included before the establishment of the rock physical template. Specifically, as shown in Figure 3 the following steps can be included:

[0115] S1024: obtaining the reservoir rock geological parameters of the known well and the wellbore rock geological parameters adjacent to the known well;

[0116] S1025: obtaining the pre-stack gathers of the known well and the wellbore pre-stack gathers by using seismic forward simulation according to the reservoir rock geological parameters of the known well and the wellbore rock geological parameters adjacent to the known well;

[0117] S1026: performing AVO analysis on the pre-stack gathers of the known well and the wellbore pre-stack gathers respectively to obtain the PG attribute of the known well and the wellbore PG attribute;

[0118] S1027: judging whether the difference between the wellbore PG attribute and the known well PG attribute is within a preset range;

[0119] S1028: if the difference between the wellbore PG attribute and the known well PG attribute is not within the preset range, correcting the wellbore PG attribute until the difference between the wellbore PG attribute and the known well PG attribute is within the preset range, and then performing the step of establishing the rock physical template based on the PG attribute.

[0120] It can be understood that the thickness, porosity and gas saturation parameters of the target interval (reservoir) in the known well logging are known, and the PG attribute of the known well logging position can be obtained by forward calculation according to these known parameters, and the reservoir position of the preset geological parameter is actually unknown. In order to further judge its accuracy, the well side parameter can be verified. Specifically, since the well side position and the well logging position are very close, the PG attribute has continuity, and the PG attribute extracted from the well side trace set is very close to the PG attribute extracted from the well logging trace set. Therefore, the PG attribute of the known well logging can be used to adjust the geological parameter of the well side, so as to ensure that the forward calculation data is closer to the true value, and correspondingly, the rock physical template obtained is closer to the true value and is more reliable. It should be noted that the well side geological parameter can belong to the reservoir rock geological parameter obtained in step S101 in the embodiments of the present application, so as to increase the reliability of the template.

[0121] In actual extraction, all known wells, including wells producing water, gas or dry layer in the target interval, are continuously extracted at the well side trace, so as to have statistical rules and improve the reliability of the established rock physical template.

[0122] The preset range can be set according to the actual well logging geological environment, such as a certain percentage of the actual PG attribute of well logging, which can be 10%-50%, wherein the P or G single attribute not meeting the requirement of the preset range can be corrected, or the PG attribute value not meeting the requirement of the preset range can be corrected. In some other embodiments, the range obtained by dividing the PG attribute between the adjacent two well logging positions in equal proportion gradient can also be used, and the specific implementation manner and comparison manner of the preset range are not limited in the embodiments of the present application.

[0123] When the difference between the well side PG attribute and the well logging PG attribute is not in the preset range, the specific manner of correcting the well side PG attribute can be:

[0124] Adjusting the well side rock geological parameter, and performing seismic forward calculation, AVO analysis and judgment on whether the difference between the corrected well side PG attribute and the known well logging PG attribute is in the preset range;

[0125] If the difference between the corrected well side PG attribute and the known well logging PG attribute is not in the preset range, return to continue to adjust the well side rock geological parameter and the subsequent steps until the difference between the corrected well side PG attribute and the known well logging PG attribute is in the preset range.

[0126] When the difference between the well side PG attribute and the well logging PG attribute is in the preset range, the step of establishing the rock physical template based on the PG attribute can be performed.

[0127] In the embodiments of the present application, on the basis of having obtained the PG attribute, a rock physics template can be established by using the gas saturation and the PG attribute. Specifically, a rectangular coordinate system is established with the P value as the horizontal coordinate and the G value as the vertical coordinate. The PG attribute values of different points can also reflect different geological parameters (the gas saturation, the thickness and the porosity). The different gas saturations can be represented by the color depth of the coordinate points (circles, triangles and other shapes), so that the variation law of the gas saturation in the rock physics template can be seen. Correspondingly, the variation law of the corresponding PG attribute is found according to the variation law of the gas saturation, and the gas saturation is predicted.

[0128] It should be noted that when the reservoir gas saturation is predicted, the thickness and the porosity should also be considered as the features. For example, in the reservoir with high gas saturation, the thickness and the porosity are small, and the reservoir is not an ideal exploitation reservoir. Therefore, the thickness and the porosity can be used to divide the reservoir geological environment, such as determining the surrounding rock position, delineating the effective reservoir (high gas saturation and large porosity) thickness and the like.

[0129] Therefore, the PG attribute rock physics template related to the thickness or the porosity can also be established on the basis of the simple rock physics template. Figure 16 and Figure 17 as shown, the PG attribute rock physics templates of the variable saturation and the variable porosity and the PG attribute rock physics templates of the variable saturation and the variable thickness are established.

[0130] As shown in Figure 16 , in the established rock physics template, all the PG attribute data points of the porosity from 3% to 13%, the thickness from 5 meters to 30 meters and the water saturation from 0% to 100% are displayed. The change of the water saturation (corresponding to the gas saturation) is represented by different colors (color depth), and the size of the circle point represents the change of the porosity, and the larger the point is, the higher the porosity is. The PG attribute of the gas layer top and bottom reflection picking is basically symmetrical to the origin. The diagonal shadow part (that is, the region clamped by the arc lines AA' and BB') in the second and fourth quadrants in the figure can represent the surrounding rock area. According to the data point distribution of the BB'C'C gas layer top boundary PG attribute area, with the increase of the porosity, the data point moves from the fourth quadrant to the third and second quadrants, and with the change of the gas saturation, the change amplitude of the PG attribute also changes correspondingly.

[0131] As shown in Figure 17As shown, in the established rock physical template, all the PG attribute data points of the reservoirs with the porosity from 3% to 13%, the thickness from 5 meters to 30 meters and the water saturation from 0% to 100% are displayed, the change of the water saturation (corresponding to the gas saturation) is represented by different colors (color depth), and the point size represents the change of the thickness, and the larger the point is, the larger the thickness is. No matter the change of the porosity or the gas saturation, the thinner gas layer is closer to the lower limit line DD' and EE' of the gas layer. When the porosity is small, the increase of the thickness mainly represents the increase of the absolute value of the P attribute; and when the porosity is large, the data point set changes in a spiral shape after the change of the thickness, and it is difficult to distinguish such a gas layer by the PG attribute. Taking the porosity of 9% as an example, the 5-meter gas saturation state has similar PG attribute to the 15-meter water saturation state, but in actual data processing and interpretation, most of the thin gas layers are submerged in the water layer samples, and therefore, the characteristics of the reservoirs with different thicknesses and porosities can be accurately obtained by establishing the rock physical template based on the PG attribute, so as to effectively predict the geological parameters of the reservoirs.

[0132] According to the rock physical template establishing method provided above, the embodiment of the present specification further provides a rock physical template establishing device, and the device comprises:

[0133] a reservoir rock geological parameter obtaining module, configured to obtain reservoir rock geological parameters, wherein the reservoir rock geological parameters comprise thickness, porosity and gas saturation;

[0134] a PG attribute obtaining module, configured to obtain PG attributes corresponding to different geological parameters by using seismic forward modeling according to the reservoir rock geological parameters;

[0135] a template establishing module, configured to establish a rock physical template based on PG attributes according to the PG attributes and the reservoir rock geological parameters.

[0136] According to the rock physical template based on PG attributes established by the above steps, the embodiment of the present specification further provides a gas saturation quantitative prediction method, such as Figure 4 As shown, the method comprises the following steps:

[0137] S201: determining PG attributes of a to-be-measured reservoir according to prestack gather data of the to-be-measured reservoir;

[0138] S202: predicting gas saturation of the to-be-measured reservoir by using the established rock physical template based on PG attributes according to the PG attributes of the to-be-measured reservoir.

[0139] The rock physical template is established through the above steps, and the relationship between the PG attribute and the gas saturation is analyzed to determine the variation law of the gas saturation in the reservoir in the work area, so that the gas saturation of the to-be-measured reservoir can be accurately predicted, the amount of PG attribute calculation is greatly reduced in the embodiments of the present specification, the seismic frequency band rock physical template can be directly established, and the lithology change, the formation thickness change, the porosity physical law and the gas bearing law can be reflected.

[0140] It can be understood that, after the rock physical template is established, the to-be-measured reservoir in the work area can be continuously predicted, and the step of establishing the template before each prediction is avoided, thereby improving the prediction efficiency. In addition, during the development of the reservoir in the work area, as the number of gas wells increases, the real geological parameters of the newly added gas wells can be used to update the rock physical template in real time, thereby increasing the prediction accuracy of the rock physical template. With the increase of the exploitation reserves and the decrease of the remaining storage reserves, the prediction accuracy of the remaining reserves in the work area can be improved by gradually updating the rock physical template, which has guiding significance for the research of the gas reservoir in the later period.

[0141] As shown in the formula (1), the quantitative prediction of the gas saturation of the to-be-measured reservoir by the rock physical template can include: Figure 5

[0142] S2021: determining the relationship between the PG attribute and the gas saturation according to the established rock physical template based on the PG attribute;

[0143] S2022: predicting the gas saturation of the to-be-measured reservoir by using the determined relationship between the PG attribute and the gas saturation according to the PG attribute of the to-be-measured reservoir.

[0144] The relationship between the PG attribute and the gas saturation can be understood as the correlation of the variation laws of the two. In actual prediction, since the PG attribute can be obtained by seismic inversion, after the relationship between the two is determined, the PG attribute obtained by seismic inversion can be used to reflect the variation of the gas saturation.

[0145] Specifically, the step of determining the relationship between the PG attribute and the gas saturation can be:

[0146] determining the variation law of the gas saturation in the rock physical template;

[0147] determining the variation law of the PG attribute according to the variation law of the gas saturation, thereby determining the relationship between the PG attribute and the gas saturation.

[0148] ​It can be understood that firstly, a rock physical template (PGT) based on PG attributes is determined, a variation law of gas saturation is determined in combination with the icon color depth variation law in the template, and then a variation law of the PG attributes (P and / or G) is determined, so that the relationship between the gas saturation and the PG attributes can be determined, which is equivalent to that according to the variation law of the gas saturation, what is the variation law of the PG attributes, so that when the PG attributes are obtained, the law distribution of the gas saturation can be inversely deduced based on the variation law of the PG attributes, and the gas saturation can be accurately predicted.

[0149] As Figure 16 and Figure 17 It can be seen that when the gas saturation changes from small to large, the absolute value of P in the PG attributes also becomes large, and the change trend is relatively obvious, so when the gas saturation is quantitatively predicted, the prestack gather data of the reservoir to be measured can be obtained by emitting seismic frequencies, and the large P attribute value can be determined, so that the area with high gas saturation can be predicted.

[0150] It should be noted that the establishment of the rock physical template based on the PG attributes is based on known and preset parameters, in order to ensure the accuracy of the template prediction, a large number of parameters need to be obtained, that is, there are many preset parameters, so the rock physical template in the embodiments of the present specification is equivalent to a general template, and the template mapping method is not conducive to obtaining accurate prediction values when the gas saturation is quantitatively predicted, and the embodiments of the present specification determine the relationship between the gas saturation and the PG attributes by determining the variation law, which is more direct and more universal.

[0151] In actual work, as Figure 18 shown, it is a profile of reservoir gas saturation predicted by the rock physical template (PGT) based on the PG attributes and the conventional elastic impedance coefficient (EC) technology in the embodiments of the present specification, and is applied to the gas saturation quantitative prediction in Longgang 1 and 2 well areas. It can be considered that the result of EC gas layer identification is only a "gas layer", and the gas layers are relatively developed from the platform edge to the platform, only the thickness changes, and the PGT technology in the embodiments of the present specification further describes the variation of "gas saturation" on the basis of the gas layer, and it can be seen that Figure 18 - the gas property is best near the platform edge in the lower drawing. On the EC profile of Figure 18 , the S point is a relatively low-lying part in structure, and unless the gas reservoir is fully filled with natural gas, the S point should have poor gas property, but the gas property of the S point part predicted by EC is the best, which does not conform to the geological law (the natural gas itself has a smaller density, and will rise to the high part of the structure along the cracks or faults and other structures in the reservoir). After the gas saturation is estimated by the PG attribute rock physical template, the gas property is relatively poor compared with the low part of the structure Figure 18-In the S' region of the figure below, the tectonic structure has a significant controlling effect on the gas reservoir, and the gas saturation profile predicted by PGT is more in line with geological laws.

[0152] Based on the above-described method for quantitatively predicting gas saturation, this specification also provides a device for quantitatively predicting gas saturation, such as... Figure 19 As shown, the device includes:

[0153] The PG attribute acquisition module 100 of the reservoir under test is used to determine the PG attribute of the reservoir under test based on the pre-stack gather data of the reservoir under test acquired.

[0154] The gas saturation prediction module 200 for the reservoir under test is used to quantitatively predict the gas saturation of the reservoir under test based on the PG attribute of the reservoir under test and the rock physical template based on the PG attribute established by the method described above.

[0155] like Figure 20 As shown, the computer device 2002 provided in the embodiments of this specification may include one or more processors 2004, such as one or more central processing units (CPUs), each of which may implement one or more hardware threads. The computer device 2002 may also include any memory 2006 for storing information of any kind, such as code, settings, data, etc. Without limitation, for example, the memory 2006 may include any type of RAM, any type of ROM, flash memory, hard disk, optical disk, etc. More generally, any memory may use any technology to store information. Furthermore, any memory may provide volatile or non-volatile retention of information. Furthermore, any memory may represent a fixed or removable component of the computer device 2002. In one case, when the processor 2004 executes associated instructions stored in any memory or combination of memories, the computer device 2002 may perform any operation of the associated instructions. The computer device 2002 also includes one or more drive mechanisms 2008 for interacting with any memory, such as hard disk drive mechanisms, optical disk drive mechanisms, etc.

[0156] The computer device 2002 can also include an input / output module 2010 (I / O) for receiving input (via input device(s) 2012) and for providing output (via output device(s) 2014). One particular output mechanism can include a presentation device 2016 and associated graphical user interface (GUI) 2018. In other embodiments, the input / output module 2010 (I / O), the input device(s) 2012, and the output device(s) 2014 can not be included, and the computer device 2002 can be used merely as a networked computer device. The computer device 2002 can also include one or more network interfaces 2020 for exchanging data with other devices via one or more communication links 2022. The one or more communication buses 2024 couple the various components in the computer device 2002.

[0157] The communication links 2022 can be implemented in any manner, such as through local area networks, wide area networks (e.g., the Internet), point-to-point connections, etc., or any combination thereof. The communication links 2022 can include any combination of hardwired links, wireless links, routers, gateway functionality, name servers, etc., governed by any protocol or combination of protocols.

[0158] Corresponding to the method in Figures 1-5 The embodiments herein further provide a computer readable storage medium, having stored thereon a computer program, which, when executed by a processor, performs the steps of the above-mentioned method.

[0159] The embodiments herein further provide a computer readable instruction, wherein the program in the computer readable instruction, when executed by a processor, causes the processor to perform the method as shown in Figures 1 to 5

[0160] It should be understood that the size of the serial number of the above-mentioned procedures in the various embodiments herein does not mean the order of execution, and the execution order of the procedures should be determined according to its function and inherent logic, and should not constitute any limitation on the implementation process of the embodiments herein.

[0161] It should also be understood that in the embodiments herein, the term "and / or" is merely a description of the association relationship of the associated objects, which means that there can be three relationships. For example, A and / or B can represent the following three cases: A exists alone, A and B exist together, and B exists alone. In addition, the character " / " in this paper generally represents that the front and rear associated objects are in an "or" relationship.

[0162] ​Those skilled in the art can clearly understand that, for the convenience and brevity of description, the specific working process of the system, device and unit described above can refer to the corresponding process in the foregoing method embodiments, and will not be repeated here.

[0163] Those skilled in the art can clearly understand that, for the convenience and brevity of description, the specific working process of the system, device and unit described above can refer to the corresponding process in the foregoing method embodiments, and will not be repeated here.

[0164] In several embodiments provided herein, it should be understood that the disclosed system, device and method can be implemented in other ways. For example, the device embodiments described above are merely schematic, for example, the division of the units is only a logical function division, and actual implementation can have another division manner, for example, multiple units or components can be combined or integrated into another system, or some features can be ignored or not executed. In addition, the coupling or direct coupling or communication connection between the units shown or discussed can be indirect coupling or communication connection through some interfaces, devices or units, and can also be electrical, mechanical or other form of connection.

[0165] The units described as separate components can or can not be physically separated, and the components shown as units can or can not be physical units, that is, they can be located in one place, or can be distributed on multiple network units. Part or all of the units can be selected according to actual needs to achieve the purpose of the embodiments provided herein.

[0166] In addition, each functional unit in each embodiment herein can be integrated in one processing unit, or each unit can exist physically independently, or two or more units can be integrated in one unit. The integrated unit can be realized in the form of hardware or in the form of a software functional unit.

[0167] The integrated unit, if implemented in the form of a software function unit and sold or used as an independent product, can be stored in a computer readable storage medium. Based on such understanding, the technical solutions herein or the entire or part of the technical solutions that essentially contribute to the prior art can be embodied in the form of a software product. The computer software product is stored in a storage medium, and includes a plurality of instructions for causing a computer device (which can be a personal computer, a server, or a network device, etc.) to execute all or part of the steps of the methods described in various embodiments herein. The aforementioned storage medium includes: a U disk, a mobile hard disk, a read-only memory (ROM, Read-Only Memory), a random access memory (RAM, Random Access Memory), a magnetic disk or an optical disk, and various media that can store program codes.

[0168] The principles and implementation manners of the present application are described herein by using specific embodiments. The above description of the embodiments is only used to help understand the methods and core ideas thereof; meanwhile, for those skilled in the art, the specific implementation manners and application ranges can be changed according to the ideas of the present application. In summary, the content of the present description should not be understood as a limitation of the present application.

Claims

1. A method for establishing a rock physical template, characterized in that, The method comprises: obtaining reservoir rock geology parameters, the reservoir rock geology parameters being wellbore-side rock geology parameters, the reservoir rock geology parameters including thickness, porosity and gas saturation; obtaining reservoir rock geology parameters of a known well log adjacent to the wellbore-side rock geology parameters; obtaining reservoir rock geology parameters of a known well log adjacent to the wellbore-side rock geology parameters; obtaining reservoir rock geology parameters of a known well log adjacent to the wellbore-side rock geology parameters; judging whether a difference between the wellbore-side PG attribute and the known well log PG attribute is within a preset range; if the difference between the wellbore-side PG attribute and the known well log PG attribute is not within the preset range, correcting the wellbore-side PG attribute until the difference between the wellbore-side PG attribute and the known well log PG attribute is within the preset range, and then establishing a rock physics template based on the PG attribute and the reservoir rock geology parameters. The step of obtaining reservoir rock geology parameters further comprises:

2. The method of claim 1, wherein, obtaining reservoir rock physics parameters including P-wave velocity, S-wave velocity and density corresponding to different porosities by using a patch saturation model according to the reservoir rock geology parameters; obtaining pre-stack gathers of different thicknesses, porosities and gas saturations by using seismic forward modeling according to the reservoir rock physics parameters and the reservoir rock geology parameters; obtaining PG attributes corresponding to different geology parameters by performing AVO analysis according to the pre-stack gathers. The step of correcting the wellbore-side PG attribute further comprises:

3. The method of claim 1, wherein, adjusting the wellbore-side rock geology parameters, and performing seismic forward modeling, AVO analysis, and judging whether a difference between the corrected wellbore-side PG attribute and the known well log PG attribute is within a preset range; if the difference between the corrected wellbore-side PG attribute and the known well log PG attribute is not within the preset range, returning to adjust the wellbore-side rock geology parameters and the subsequent steps until the difference between the corrected wellbore-side PG attribute and the known well log PG attribute is within the preset range. if the difference between the wellbore-side PG attribute and the known well log PG attribute is within the preset range, performing the step of establishing a rock physics template based on the PG attribute.

4. The method of claim 1, wherein, The step of establishing a rock physics template based on the PG attribute further comprises:

5. The method of claim 1, wherein, establishing a variable porosity and variable gas saturation PG attribute crossplot according to the PG attribute, porosity and gas saturation; and / or establishing a variable thickness and variable gas saturation PG attribute crossplot according to the PG attribute, thickness and gas saturation. The method comprises:

6. A method for quantitative prediction of gas saturation, characterized by, ​ According to the prestack gather data of the reservoir to be measured, the PG attribute of the reservoir to be measured is determined; According to the PG attribute of the reservoir to be measured, the gas saturation of the reservoir to be measured is predicted by using the PG attribute-based rock physical template established by the method of any one of claims 1 to 5.

7. The method of claim 6, wherein, The method of predicting the gas saturation of the reservoir to be measured according to the PG attribute of the reservoir to be measured by using the PG attribute-based rock physical template established by the method of any one of claims 1 to 5 further comprises: According to the established PG attribute-based rock physical template, the relationship between the PG attribute and the gas saturation is determined; According to the PG attribute of the reservoir to be measured, the gas saturation of the reservoir to be measured is predicted by using the determined relationship between the PG attribute and the gas saturation.

8. The method of claim 7, wherein, The method of determining the relationship between the PG attribute and the gas saturation according to the established PG attribute-based rock physical template further comprises: Determining the variation law of the gas saturation in the rock physical template; According to the variation law of the gas saturation, the variation law of the PG attribute is determined, so as to determine the relationship between the PG attribute and the gas saturation.

9. A device for quantitative prediction of gas saturation, characterized by The device comprises: A reservoir to be measured PG attribute acquisition module, configured to determine the PG attribute of the reservoir to be measured according to the prestack gather data of the reservoir to be measured; A reservoir to be measured gas saturation prediction module, configured to predict the gas saturation of the reservoir to be measured by using the PG attribute-based rock physical template established by the method of any one of claims 1 to 5 according to the PG attribute of the reservoir to be measured.

10. A computer device comprising a memory, a processor, and a computer program stored on the memory and executable on the processor, characterized in that, The processor executes the computer program to realize the steps of the rock physical template establishment method of any one of claims 1 to 5 and / or the gas saturation quantitative prediction method of any one of claims 6 to 8.

11. A computer readable storage medium, characterized in that, The computer readable storage medium stores the computer program, and the computer program is executed by the processor to realize the steps of the rock physical template establishment method of any one of claims 1 to 5 and / or the gas saturation quantitative prediction method of any one of claims 6 to 8.

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