Well-seismic mutual feedback fusion tight sandstone gas reservoir seismic sedimentology characterization method

Abstract

The invention discloses a well-seismic mutual feedback fusion tight sandstone gas reservoir seismic sedimentology characterization method, which belongs to the technical field of seismic sedimentology and reservoir characterization, and comprises the following steps: step 1, analyzing seismic response characteristics of different lithology combinations; 2, analyzing a seismic response formation mechanism and geological meanings of seismic attributes according to the lithological combination; and 3, carrying out seismic sedimentology characterization on the compact thin sandstone reservoir according to the seismic response formation mechanism and the geological meaning of the seismic attribute. Aiming at a compact thin sandstone reservoir, on the basis of analyzing the seismic response characteristics of different lithologic combinations, the seismic response mechanism is explored, the geological meaning of seismic attributes is defined, an isochronous stratigraphic framework with well-seismic consistency is established under the guidance of the mechanism, seismic sedimentology method technology optimization and practical application are carried out, and the method has the advantages that the seismic response mechanism is explored; the multiplicity of the seismic sedimentology research is reduced, and a set of well-seismic mutual feedback fusion compact thin sandstone reservoir seismic sedimentology characterization method is formed.

Description

Technical Field

[0001] The present invention relates to the technical field of seismic sedimentology and reservoir characterization, and particularly relates to a method for seismic sedimentological characterization of tight sandstone gas reservoirs with well-seismic mutual feedback fusion. Background Art

[0002] In recent years, as one of the important types of unconventional oil and gas resources, the exploration and development of tight sandstone gas are in a rapid development stage, and large-scale production has been achieved in basins such as Sichuan, Ordos, Bohai Bay, and Songliao, and it has become the "key area" and "bright spot type" for increasing oil and gas reserves and production in China (Sun Longde et al., 2019; Li Luguang et al., 2020; Cai Xunyu et al., 2020; Jia Ailin et al., 2022; Wu Yugen et al., 2022; Zhang Daowei et al., 2022). In 2020, the output of unconventional natural gas in China was 75.68 billion cubic meters, of which 47 billion cubic meters was tight sandstone gas, accounting for 62.1% of the output of unconventional natural gas and 24.4% of the total national natural gas output (Department of Oil and Gas, National Energy Administration, 2021; Li Luguang, 2021; Yang Zhi et al., 2022).

[0003] Tight sandstone gas reservoirs are characterized by complex sand body superimposition, rapid lateral variation, and thin thickness. A large amount of work has been done by predecessors on seismic prediction of thin sandstones, and the relationship between thin beds less than one-quarter wavelength (λ / 4) and amplitude has been summarized. However, under different surrounding rock conditions, the seismic response of thin beds is complex and diverse. The peak reflection can reflect the top surface of the sand body or the bottom surface of the sand body, and the strong amplitude can be proportional or inversely proportional to the sand body thickness (Widess, 1973; Anstey, 1980; Bedley, 1985; Brown, 2011; Wang Changcheng et al., 2015; Xu et al., 2022). Seismic sedimentology developed in recent years has irreplaceable advantages in the identification and quantitative characterization of thin beds, and can identify thin sand bodies that are difficult to identify by seismic vertical resolution, and describe the morphology and distribution characteristics of thin sand bodies (Zeng Hongliu, 2011; Zeng, 2018; Zhu Xiaomin et al., 2019; Ni Changkuan et al., 2022).

[0004] In the past 20 years, seismic sedimentology has played an increasingly important role in the research of thin sandstone sedimentary systems and sand body prediction at home and abroad. It has achieved remarkable results in aspects such as seismic geomorphological (quantitative) description of thin sandstones (Posamentier et al., 2003; Posamentier, 2005; Wood, 2007; Hernan et al., 2011), sequence stratigraphic framework and sedimentary system analysis (Zeng, 2004; Lin Chengyan et al., 2007; Zhu Hongtao et al., 2011; Zeng Hongliu et al., 2015; Wang Jun et al., 2018; Lutome et al., 2020; Dong Yanlei et al., 2020), and fine characterization of sedimentary microfacies and sand bodies (Zhu Xiaomin et al., 2009; Zhang Xianguo et al., 2011; Liu Hai et al., 2018; Yue et al., 2019; Lou Min et al., 2021; Li Dongwei et al., 2022), playing a unique role in oil and gas exploration and development. However, its application in continental tight thin sandstones in China is relatively few. There are mainly some exploratory studies on the Ordos Basin and Sichuan Basin (Liang Quansheng, 2016; Li Ming, 2019; Xiang Nian, 2020; Lai Shenghua et al., 2020; Sun Shaochuan et al., 2021; Zhou Yadong et al., 2022). The main reason is that continental tight sandstones in China have the characteristics of variable provenances, many lithofacies types, rapid spatio-temporal changes, complex lithologic combinations, and complex lithology-wave impedance relationships. The lithologic interpretation of stratigraphic slices is more ambiguous, and it is usually difficult to calibrate the lithology of 90-degree phase seismic profiles (Zeng Hongliu, 2011; Zhu Xiaomin et al., 2019). There are technical bottlenecks in directly applying mature seismic sedimentology research methods, such as difficulties in establishing an isochronous stratigraphic framework consistent with wells and seismic data, inaccurate lithology calibration of seismic attributes, and strong ambiguity in stratigraphic slices.

[0005] Based on this, the present invention designs a seismic sedimentology characterization method for tight sandstone gas reservoirs with well-seismic mutual feedback and fusion to solve the above problems. Summary of the Invention

[0006] In view of the above-mentioned drawbacks of the prior art, the present invention provides a seismic sedimentology characterization method for tight sandstone gas reservoirs with well-seismic mutual feedback and fusion.

[0007] To achieve the above objectives, the present invention is realized through the following technical solutions: A seismic sedimentology characterization method for tight sandstone gas reservoirs with well-seismic mutual feedback and fusion, comprising the following steps: Step 1: Analyze the seismic response characteristics of different lithologic combinations; Step 2: Analyze the formation mechanism of seismic response and the geological meaning of seismic attributes according to the lithologic combination; Step 3: Conduct seismic sedimentology characterization of tight thin sandstone reservoirs according to the formation mechanism of seismic response and the geological meaning of seismic attributes.

[0008] Furthermore, the specific operations of step 1 are as follows: Step 11: Select field profiles and drilling cores for observation, determine the provenance system, sedimentation pattern and microfacies characteristics, and then divide the sedimentary microfacies of typical wells based on logging, well logging, field profiles and core data; Step 12: Determine the vertical and horizontal contact relationships of the sedimentary microfacies of typical wells according to the division of sedimentary microfacies of typical wells, and list the lithologic combination types one by one; Step 13: Correlate the geological stratification of typical wells with seismic horizons, and then analyze the seismic reflection characteristics in combination with lithologic combinations to determine the seismic response type and waveform characteristics.

[0009] Synthesize a synthetic seismogram and perform calibration, correlate the geological stratification of each typical well with the seismic horizon, analyze the corresponding seismic reflection characteristics under various lithologic combinations, and determine its seismic response type and waveform characteristics.

[0010] Furthermore, the statistical range of lithologic combination types is 0.75 wavelengths above and below the target sand group.

[0011] The lithologic combination types also include gas sandstone and water-bearing sandstone of sedimentary microfacies subtypes.

[0012] Furthermore, the specific operations of step 2 are as follows: Step 21: Establish a discrete reflection coefficient sequence: Divide the macro-layers according to the principle of roughly the same wave impedance for the lithologic combination, determine the reflection interface for the macro-layers, and establish a discrete sequence of reflection coefficients through the reflection interface; Step 22: Make a discrete synthetic seismogram and qualitatively analyze the contribution degree of each wave impedance interface to seismic reflection; Step 23: Perform numerical analysis of the convolution model to quantitatively analyze the contribution degree of each wave impedance interface to seismic reflection; Step 24: Analyze the formation mechanism of seismic response and determine the geological meaning of seismic attributes.

[0013] Furthermore, when dividing the macro-layers, the reflection interfaces formed by secondary reflection waves with a time difference less than 1 / 4 cycle from the main reflection wave are excluded.

[0014] Furthermore, the specific operations of step 22 are as follows: Step 211: Calculate the two-way travel time t(i) of the corresponding macro-layer through the velocity V(i) and thickness h(i) of the macro-layer; (1); Step 212: Accumulate the two-way travel times t(i) of all macro-layers to obtain the two-way travel time T0(i) of the seismic wave from the starting depth to the reflection interface; (2); Step 213: Obtain the reflection coefficient R0(i) of the interface between adjacent macro layers through adjacent macro layers; (3); Step 214: Assign the reflection coefficient R0(i) of the interface of the macro layer to the corresponding position of the discrete time series to obtain the discrete reflection coefficient sequence r(L); (4); In the formula , dt is the discrete time interval.

[0015] Furthermore, the specific operation of Step 22: Step 221: Based on the theoretical model of zero-offset self-excitation and self-reception, the seismic record is the sum of the interference superposition of the reflected waves of each reflection interface in the vertical direction, and the seismic record is a one-dimensional seismic profile: (5); In the formula, X(t) is the seismic record at the t-th moment; S n (t) = r(t) × b(t - t n ), is the reflected wave of the n-th reflection interface at the t-th moment; r(t) is the reflection coefficient sequence at the t-th moment; b(t) is the seismic wavelet sequence at the t-th moment; Step 222: Qualitatively compare the amplitudes and energies of the main lobes and the weak amplitude superposition of the secondary lobes of the seismic record to measure the reflection contribution of each interface in the composite wave.

[0016] Furthermore, the specific operation of Step 23: The seismic record trace can also be expressed by the Robinson convolution model formula, that is: or (6); In the formula, X(t) is the seismic record at the t-th moment; r(t) is the reflection coefficient sequence at the t-th moment; b(t) is the seismic wavelet sequence at the t-th moment; b(t) is calculated as follows: (7); In the formula, f p is the center frequency of the seismic wavelet.

[0017] Robinson convolution model formula: (8); Let t = jΔt, τ = kΔt; Δt is the discrete time interval, then (9); For zero-phase wavelet: (10); Among them, j, k, and h are constants from 1 to m, h = j + (m + 1) / 2, and m is the number of discrete points of the zero-phase wavelet.

[0018] X(j) is the sum of the products of the reflection coefficients r(k) of each interface and the seismic wavelet b(k), and the reflection contribution degree of each lithological interface is quantitatively measured by the ratio of each product term to the total amplitude.

[0019] Furthermore, the specific operation of step 24: According to the reflection contribution degree of each wave impedance interface to the earthquake, analyze the formation process of the seismic reflection characteristics of different lithological combinations, determine the reflection formation mechanism, then analyze the lithological characteristics of the interfering wave impedance interfaces, clarify the geological formation mechanism, correlate the seismic wave with the lithology of underground rocks, and then clarify the geological meaning of seismic attributes.

[0020] Furthermore, the specific steps of step 3 are as follows: Step 31: Establish an isochronous stratigraphic framework through well-seismic interaction and fusion; Calibrate the drilling sand groups on the seismic section through synthetic seismic records, and establish an isochronous stratigraphic framework consistent with well and seismic data with the smallest longitudinally identifiable stratum in the seismic data as the unit according to the seismic reflection characteristics and the formation mechanism of seismic responses of different lithological combinations; Step 32: Use seismic sedimentology methods to depict the planar distribution characteristics of sedimentary microfacies; Based on the isochronous stratigraphic framework, use stratigraphic slicing and waveform clustering analysis to make the reflection interface characteristics and sedimentary systems visually imaged in seismic attributes. Combine with the traditional single-well sedimentary microfacies division, cross-well sedimentary microfacies comparison, and drilling sand body thickness, and combine multi-source data to depict the planar distribution characteristics of sedimentary microfacies; Step 33: With the planar distribution characteristics of sedimentary microfacies as the constraint, depict the sandstone and mudstone distribution characteristics within each sedimentary microfacies through phase conversion, seismic inversion, and spectral decomposition.

[0021] Beneficial effects: The present invention aims at tight thin sandstone reservoirs. Based on the analysis of seismic response characteristics of different lithologic combinations, it explores the seismic response mechanism, clarifies the geological meaning of seismic attributes, and under the guidance of this mechanism, establishes an isochronous stratigraphic framework consistent with wells and seismic data. It conducts optimization and practical application of seismic sedimentology methods and techniques, reduces the ambiguity of seismic sedimentology research, can more accurately identify and predict the distribution of tight thin sandstone reservoirs, optimize well placement, and improve the recovery rate of gas reservoirs. The present invention has scientific significance for promoting the improvement of the seismic sedimentology method and technology system for continental tight sandstones, can effectively guide the development and deployment of tight sandstone gas reservoirs. At the same time, in the exploration of new areas, it can provide a scientific basis for the selection and evaluation of exploration targets, reduce exploration risks, improve exploration success rates, and provide strong scientific and technological support for the stable production and increased production of tight sandstone gas and the exploration of new areas. Description of the Drawings

[0022] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required for use in the description of the embodiments or the prior art. Obviously, the drawings in the following description are only some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can be obtained based on these drawings.

[0023] Figure 1 It is the columnar diagram of sedimentary microfacies of a typical well of the present invention; Figure 2 It is the comparison diagram of sedimentary microfacies between connected wells of the present invention; Figure 3 It is the seismic reflection characteristics of different lithologic combinations of a typical well of the present invention; Figure 4 It is the seismic response characteristics of various lithologic combinations of the present invention; Figure 5 It is the schematic diagram of macroscopic layer division of the present invention; Figure 6 It is the seismic simulation diagram of multi-interface reflection superposition interference of the present invention; Figure 7 It is the numerical analysis diagram of the convolution model of the present invention; Figure 8 is the comparison of the well-seismic interaction and fusion isochronous stratigraphic framework of the present invention; Figure 9 is the schematic diagram of seismic sedimentology of the present invention; Figure 10 It is the planar distribution characteristics of sedimentary microfacies of the present invention; Figure 11 It is the comparison diagram of sand bodies between connected wells of the present invention. Detailed Embodiments

[0024] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are some, but not all, of the embodiments of the present invention. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0025] The present invention will be further described below in conjunction with embodiments.

[0026] Embodiment 1: A seismic sedimentology characterization method for tight sandstone gas reservoirs with well-seismic mutual feedback fusion, comprising the following steps: Step 1: Analyze the seismic response characteristics of different lithologic combinations; Step 2: Analyze the formation mechanism of the seismic response and the geological meaning of seismic attributes according to the lithologic combination; Step 3: Conduct seismic sedimentology characterization on the tight thin sandstone reservoir according to the formation mechanism of the seismic response and the geological meaning of seismic attributes.

[0027] The specific operations of Step 1 are as follows: Step 11: Select field profiles and well cores for observation, determine the provenance system, sedimentary pattern, and microfacies characteristics, and then conduct sedimentary microfacies division of typical wells based on logging, well logging, field profiles, and core data; Step 12: Determine the vertical and horizontal contact relationships of the sedimentary microfacies of the typical wells according to the sedimentary microfacies division of the typical wells, and list the lithologic combination types one by one; Step 13: Correlate the geological stratification of the typical wells with the seismic horizons, and then combine with the lithologic combination to analyze the seismic reflection characteristics, and determine the seismic response type and waveform characteristics.

[0028] Synthesize seismic records and conduct calibration, correlate the geological stratification of each typical well with the seismic horizons, analyze the corresponding seismic reflection characteristics under various lithologic combination conditions, and determine their seismic response types and waveform characteristics.

[0029] The statistical range of the lithologic combination types is 0.75 wavelengths above and below the target sand group.

[0030] The lithologic combination types also include gas sandstone and water-bearing sandstone of sedimentary microfacies subtypes.

[0031] The specific operations of Step 2 are as follows: Step 21: Establish a discrete reflection coefficient sequence: According to the principle of roughly the same wave impedance, divide the macro-layers of the lithologic combination, determine the reflection interface for the macro-layers, and establish a discrete sequence of reflection coefficients through the reflection interface; Step 22: Produce discrete synthetic seismic records and qualitatively analyze the contribution degrees of each wave impedance interface to seismic reflection; Step 23: Numerically analyze the convolution model and quantitatively analyze the contribution degrees of each wave impedance interface to seismic reflection; Step 24: Analyze the formation mechanism of seismic responses and determine the geological meanings of seismic attributes.

[0032] When dividing the macro-layers, remove the reflection interfaces formed by the secondary reflection waves whose time difference from the main reflection wave is less than 1 / 4 period.

[0033] The specific operations of Step 22 are as follows: Step 211: Calculate the two-way travel time t(i) of the corresponding macro-layer through the velocity V(i) and thickness h(i) of the macro-layer; (1); Step 212: Accumulate the two-way travel times t(i) of all macro-layers to obtain the two-way travel time T0(i) of the seismic wave from the starting depth to the reflection interface; (2); Step 213: Obtain the reflection coefficient R0(i) of the interface between adjacent macro-layers through adjacent macro-layers; (3); Step 214: Assign the reflection coefficient R0(i) of the interface of the macro-layer to the corresponding position in the discrete time series to obtain the discrete sequence r(L) of the reflection coefficient; (4); In the formula , dt is the discrete time interval.

[0034] The specific operations of Step 22: Step 221: Based on the theoretical model of zero offset self-excitation and self-reception, the seismic record is the sum of the interference superposition of the reflected waves of each longitudinal reflection interface, and the seismic record is a one-dimensional seismic profile: (5); In the formula, X(t) is the seismic record at the t-th moment; S n (t)=r(t)×b(t - t n ), is the reflected wave of the n-th reflection interface at the t-th moment; r(t) is the reflection coefficient sequence at the t-th moment; b(t) is the seismic wavelet sequence at the t-th moment; Step 222: Qualitatively compare the main lobe amplitude and energy dominance of the seismic record with the weak amplitude superposition of the secondary lobes to measure the reflection contribution degrees of each interface in the composite wave.

[0035] Specific operations in Step 23: The seismic record trace can also be expressed by the Robinson convolution model formula, i.e.: or (6); In the formula, X(t) is the seismic record at the t-th moment; r(t) is the reflection coefficient sequence at the t-th moment; b(t) is the seismic wavelet sequence at the t-th moment; The calculation of b(t) is as follows: (7); In the formula, f p is the central frequency of the seismic wavelet.

[0036] Robinson convolution model formula: (8); Let t = jΔt, τ = kΔt; Δt is the discrete time interval, then (9); For a zero-phase wavelet: (10); where j, k, h are constants from 1 to m, h = j + (m + 1) / 2, and m is the number of discrete points of the zero-phase wavelet.

[0037] X(j) is the sum of the products of the reflection coefficients r(k) of each interface and the seismic wavelet b(k), and the contribution degree of each reflection of each lithologic interface is quantitatively measured by the ratio of each product term to the total amplitude.

[0038] Specific operations in Step 24: According to the contribution degree of each wave impedance interface to the seismic reflection, analyze the formation process of the seismic reflection characteristics of different lithologic combinations, determine the reflection formation mechanism, then analyze the lithologic characteristics of the wave impedance interfaces participating in the interference, clarify the geological formation mechanism, correlate the seismic wave with the lithology of the underground rock, and further clarify the geological meaning of the seismic attributes.

[0039] The specific steps of Step 3 are as follows: Step 31: Establish an isochronous stratigraphic framework through well-seismic interaction and fusion; Calibrate the drilling sand groups on the seismic section through synthetic seismic records, and establish an isochronous stratigraphic framework consistent with the well and seismic data with the smallest longitudinally identifiable stratum in the seismic data as the unit according to the seismic reflection characteristics and the formation mechanism of seismic responses of different lithologic combinations; Step 32: Use seismic sedimentology methods to depict the planar distribution characteristics of sedimentary microfacies; Based on the isochronous stratigraphic framework, using stratigraphic slicing and waveform clustering analysis, the characteristics of reflection interfaces and sedimentary systems are visually imaged on seismic attributes. Combining with the traditional division of sedimentary microfacies in single wells, the comparison of sedimentary microfacies between connected wells, and the thickness of drilling sand bodies, multi-source data is used to depict the planar distribution characteristics of sedimentary microfacies; Step 33: Constrained by the planar distribution characteristics of sedimentary microfacies, through phase conversion, seismic inversion, and spectral decomposition, the distribution characteristics of sandstone and mudstone within each sedimentary microfacies are depicted.

[0040] The present invention aims at tight thin sandstone reservoirs. Based on the analysis of the seismic response characteristics of different lithologic combinations, the seismic response mechanism is explored, the geological meaning of seismic attributes is clarified, and an isochronous stratigraphic framework consistent with wells and seismic is established under the guidance of this mechanism. The seismic sedimentology method technology is optimized and practically applied to reduce the multi-solution of seismic sedimentology research, more accurately identify and predict the distribution of tight thin sandstone reservoirs, optimize well placement, and improve the recovery rate of gas reservoirs. The present invention has scientific significance for promoting the improvement of the seismic sedimentology method technology system of continental tight sandstone, can effectively guide the development and deployment of tight sandstone gas reservoirs. At the same time, in the exploration of new areas, it can provide a scientific basis for the selection and evaluation of exploration targets, reduce exploration risks, improve exploration success rates, and provide strong scientific and technological support for the stable production and increased production of tight sandstone gas and the exploration of new areas.

[0041] Specific case: Taking Luodai Gas Field in Western Sichuan as an example, it includes the following steps: S1: According to logging, well logging, field profiles, and core data, combined with previous studies, the sedimentary microfacies of typical wells in the study area are divided ( Figure 1 ). The vertical and horizontal contact relationships of sedimentary microfacies of typical wells are statistically analyzed ( Figure 2 ), and the lithologic combination types of different sedimentary microfacies are clarified. Fine calibration of synthetic seismic records of typical wells is carried out, the geological stratification of each typical well is corresponded to seismic horizons, and the corresponding seismic reflection characteristics under various lithologic combination conditions are analyzed ( Figure 3 ), and the seismic response types and waveform characteristics are summarized ( Figure 4 ); S2: For each type of lithologic combination, macroscopic layers are divided ( Figure 5 ), the discrete sequence of reflection coefficients r(t) is obtained, the wavelet is modulated by the reflection coefficient, the discrete reflection waves of each impedance interface are drawn, and their vector superposition is carried out to obtain the synthetic seismic record of the lithologic profile ( Figure 6 ). On this figure, the contribution degree of each impedance interface to seismic reflection can be qualitatively analyzed. Such as Figure 6The strong wave trough at the top of the synthetic seismogram is a composite wave formed by the superposition and interference of reflected waves 1 - 10. Although it is a composite wave, it is mainly formed by the main lobe of interface 1 and the side lobes of interfaces 2 and 3. This shows that the main contribution to the formation of the strong wave trough comes from interface 1. The secondary lobes of other interfaces participating in the interference have smaller amplitudes and weaker energies, and have little impact on the composite wave. Conduct numerical analysis of the convolution model. According to step 23, obtain the numerical analysis diagram of the convolution model ( Figure 7 ), and quantitatively analyze the contribution degree of each wave impedance interface to seismic reflection. Among them, the strong wave peak reflection of X(6) with an amplitude value of X(6) = r(6) • b(6) indicates that this strong wave peak is a reflection formed by interface r(6) and has nothing to do with other interfaces. Another example is the weak wave trough reflection of X(25) with an amplitude value of X(25) = r(28) • b(3) + r(21) • b(10), indicating that this weak wave trough is formed by the superposition and interference of reflections from interfaces r(21) and r(28). The contribution degree values of each to the amplitude are r(21) • b(10) / X(25) and r(28) • b(3) / X(25). According to the contribution degree of each wave impedance interface to seismic reflection, analyze the formation process of seismic reflection characteristics of different lithologic combinations and determine its reflection formation mechanism; Then analyze the lithologic characteristics of the wave impedance interfaces participating in the interference, clarify the geological formation mechanism, and correlate the amplitude of seismic waves with the lithology of underground rocks. As shown in the seismic wave impedance - amplitude attribute overlay map in Figure 8, through the above analysis, it can be determined that the main sand bodies of the J2S3 2 sub - layer in Luodai Gas Field are located at the peak and trough positions of the seismic wave, thus clarifying the geological meaning of seismic attributes.

[0042] S3: Based on the seismic reflection characteristics and seismic response formation mechanism of different lithologic combinations, establish an isochronous stratigraphic framework of well - seismic interaction and fusion with the tuned thickness, which is the smallest resolvable stratigraphic unit vertically recognizable by seismic, as the benchmark (Figure 8), and carry out research on stratigraphic slicing and waveform clustering (Figure 9). Combine the division of single - well sedimentary microfacies, the comparison of sedimentary microfacies between adjacent wells, and the description of the thickness of drilling sand bodies to depict the planar distribution characteristics of sedimentary microfacies ( Figure 10 ); Constrained by the planar distribution of sedimentary microfacies, carry out technical optimization and selection of methods such as phase conversion, seismic inversion, and spectral decomposition (Figure 9) to depict the distribution characteristics of sandstone and mudstone within each sedimentary microfacies ( Figure 11 ).

[0043] The above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it; although the present invention has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that they can still modify the technical solutions recorded in the foregoing embodiments, or perform equivalent replacements for some of the technical features; and these modifications or replacements will not make the essence of the corresponding technical solutions deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A seismic sedimentology characterization method for tight sandstone gas reservoirs with well-seismic mutual feedback fusion, characterized in that: The following steps are involved: Step 1: Analyze the seismic response characteristics of different lithology combinations; Step 2: Analyze the formation mechanism of seismic response and the geological meaning of seismic attributes based on lithologic combinations; Step 3: Conduct seismic sedimentological characterization of the tight thin sandstone reservoir based on the seismic response formation mechanism and the geological meaning of the seismic attributes.

2. The method for seismic sedimentological characterization of tight sandstone gas reservoirs with well-seismic mutual feedback fusion according to claim 1, characterized in that Step 1: Step 11: Select field sections and drill cores for observation to determine provenance systems, sedimentary patterns, and microfacies characteristics. Then, perform sedimentary microfacies division of typical wells based on well logging, field sections, and core data. Step 12: Determine the vertical and horizontal contact relationships of the sedimentary microfacies of the typical wells based on the sedimentary microfacies division, and list the lithologic combination types one by one; Step 13: Match the geological stratification of typical wells with the seismic horizons, and then analyze the seismic reflection characteristics in combination with the lithologic combination to determine the seismic response type and waveform characteristics.

3. The method for seismic sedimentological characterization of tight sandstone gas reservoirs with well-seismic mutual feedback fusion according to claim 3, wherein The statistical range of lithologic combination types is 0.75 wavelengths above and below the target sand group.

4. The method for seismic sedimentological characterization of tight sandstone gas reservoirs with well-seismic mutual feedback fusion according to claim 3, wherein, Step 2: Step 21: Establish a discrete reflection coefficient sequence: Based on the principle of roughly the same wave impedance, the lithologic combination is divided into macroscopic layers. The macroscopic layers determine the reflection interface, and a discrete reflection coefficient sequence is established through the reflection interface. Step 22: Create discrete synthetic seismic records and qualitatively analyze the contribution of each wave impedance interface to seismic reflection; Step 23: Numerical analysis of the convolution model to quantitatively analyze the contribution of each wave impedance interface to seismic reflection; Step 24: Analyze the formation mechanism of the seismic response and determine the geological meaning of the seismic attributes.

5. The method for seismic sedimentological characterization of tight sandstone gas reservoirs with well-seismic mutual feedback fusion according to claim 4, characterized in that When dividing the macroscopic layer, the reflection interface formed by the secondary reflection wave whose time difference with the main reflection wave is less than 1 / 4 period is eliminated.

6. The method for seismic sedimentological characterization of tight sandstone gas reservoirs with well-seismic mutual feedback fusion according to claim 5, characterized in that The specific operations of step 22 are as follows: Step 211: Calculate the round-trip travel time t(i) of the corresponding macro-layer using the velocity V(i) and thickness h(i) of the macro-layer; (1)； Step 212: Accumulate the two-way travel time t(i) of all macro layers to obtain the two-way travel time T0(i) of the seismic wave from the starting depth to the reflection interface; (2)； Step 213: obtaining the reflection coefficient R0(i) of the interface between adjacent macro layers through the adjacent macro layers; (3)； Step 214: Assign the reflection coefficient R0(i) of the interface of the macro layer to the corresponding position of the discrete time series to obtain the discrete series of reflection coefficients r(L); (4)； where , dt is the discrete time interval.

7. The method for seismic sedimentological characterization of tight sandstone gas reservoirs with well-seismic mutual feedback fusion according to claim 5, characterized in that Step 22 Specific operations: Step 221: Based on the theoretical model of zero-offset self-excitation and self-reception, the seismic record is the sum of interference superposition of reflection waves from each longitudinal reflection interface, and the seismic record is a one-dimensional seismic profile: (5)； where X(t) is the seismic record at the t-th moment; S n (t)=r(t)×b(t - t n ), which is the reflected wave of the n-th reflection interface at the t-th moment; r(t) is the reflection coefficient sequence at the t-th moment; b(t) is the seismic wavelet sequence at the t-th moment; Step 222: Qualitatively compare the main lobe amplitude and the energy-dominant, secondary lobe weak amplitude superposition of the seismic record to measure the reflection contribution of each interface in the composite wave.

8. The method for seismic sedimentological characterization of tight sandstone gas reservoirs with well-seismic mutual feedback fusion according to claim 7, characterized in that Step 23: Specific operation: Seismic traces can also be expressed using the Robinson convolution model formula, namely: or (6); Where X(t) is the earthquake record at time t; r(t) is the reflection coefficient sequence at time t; b(t) is the earthquake wavelet sequence at time t; b(t) is calculated as follows: (7)； where f p is the central frequency of the seismic wavelet; Robinson convolution model formula: (8)； Let t = jΔt, τ = kΔt; Δt is a discrete time interval, then (9)； For zero-phase wavelets: (10)； Among them, j, k, and h are constants from 1 to m, h = j + (m + 1) / 2, and m is the discrete number of points of the zero-phase wavelet. X(j) is the sum of the products of the reflection coefficients r(k) of each interface and the seismic wavelet b(k), and the reflection contribution of each lithologic interface is quantitatively measured by the ratio of each product term to the total amplitude.

9. The method for seismic sedimentological characterization of tight sandstone gas reservoirs with well-seismic mutual feedback fusion according to claim 7, wherein: The specific operations of step 24 are as follows: According to the contribution degree of each wave impedance interface to the seismic reflection, analyze the formation process of the seismic reflection characteristics of different lithology combinations, determine the reflection formation mechanism, then analyze the lithology characteristics of the wave impedance interfaces participating in the interference, clarify the geological formation mechanism, correlate the seismic waves with the underground rock lithology, and further clarify the geological meaning of the seismic attributes.

10. The method for seismic sedimentological characterization of tight sandstone gas reservoirs with well-seismic mutual feedback fusion according to claim 8, wherein: The specific steps of step 3 are as follows: Step 31: Establish an isochronous stratigraphic framework through well-seismic interaction and fusion. Step 32: Use seismic sedimentology methods to depict the planar distribution characteristics of sedimentary microfacies. Step 33: Taking the planar distribution characteristics of sedimentary microfacies as a constraint, depict the sandstone and mudstone distribution characteristics within each sedimentary microfacies through phase conversion, seismic inversion, and spectral decomposition.

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