The piedmont of the complex mountain in southwestern Tarim Basin, located at the intersection of the West Kunlun orogenic belt and the Tianshan orogenic belt, is one of the scarce extremely-challenging exploration areas in China. The high-dip angle and fragmentized underground structures induced by strong compression of the two orogenic belts and the complex and varying near-surface seismic geological conditions jointly lead to extremely low signal-to-noise ratio(SNR) of raw seismic data, bringing difficulty to the imaging of the underground structures. For this reason, there has been no substantial breakthroughs in oil and gas exploration in this area. In recent years, great efforts have been devoted to seismic exploration. In view of seismic acquisition, near-surface seismic survey is strengthened, the shooting and receiving parameters are optimized, the geometry design is updated, and the beam seismic and high-density wide-azimuth 3D seismic techniques are upgraded. In view of seismic processing, some attempts are made in constrained first arrival tomography inversion, strong energy noise suppression at "black triangle belt" of the seismic records, true surface velocity modeling, and depth migration imaging. By virtue of these efforts, the quality of seismic data has been continuously improved, and many drilling targets have been discovered. Two major breakthroughs have been made in the Jurassic sandstone and the Carboniferous-Permian carbonate rocks for the first time, opening up a new stage of oil and gas exploration in the piedmont in southwestern Tarim Basin.

Three-D high-density seismic techniques evolving from 3D seismic techniques and 3D high-precision seismic techniques are still not sufficient for hydrocarbon exploration and development in complicated surface, tectonic, and reservoir conditions.To achieve high-precision imaging in complicated surface and subsurface conditions, we present a new idea of "ultra-high-density seismic techniques" based on the development of high-density seismic techniques, computer technology, and geophysical equipment.Field experiments with small group intervals and forward modeling with small grids show improved near-surface velocity modeling, static correction, and imaging of deep-seated steeply dipping fractures by ultra-high-density seismic acquisition.The strategy of "variable group interval+interpolation" is combined with supporting techniques relevant to instruments, storage, and computation to address the issues of acquisition instruments, mass data, and economic feasibility.Nodal seismograph with the level of 10×10⁴ channels and mass data storage and computation are the foundation of utilizing ultra-high-density seismic techniques; key techniques include high-density acquisition with "small trace distance, small bin, wide azimuth, wide band, high coverage, high shot and trace density", prestack reverse-time depth migration with a "small smooth surface", and compressed sensing or 5D interpolation.To further improve the precision of imaging, seismic acquisition with the shot channel density over 200×10⁴ should be developed; associated equipment and techniques to be developed include large-scale single-point nodal seismograph, devices for mass data storage and computation, and interpolation with variable group interval.Field seismic acquisition should also be propelled.

This study reviewed the history of petroleum and gas exploration in the Sinopec region in the Tarim Basin, summarized the experience and lessons, and identified three significant petroleum and gas exploration achievements.We also outlined the exploration difficulties of different exploration areas and different types of oil and gas reservoirs in the Tarim Basin and the progress and application results of major geophysical exploration techniques.The practice of oil and gas exploration has shown that discovering large oil and gas fields is inseparable from theoretical innovations and technological progress, especially three-dimensional high-precision seismic exploration technology.In the face of deeper, smaller, and more concealed geological exploration targets, we proposed to consolidate the research foundation of the development mechanism of seismic wave fields, develop high-precision seismic acquisition technology in ultra-deep and low signal-to-noise ratio areas, address the processing technology of low-sequence faults and small-scale fracture-cavity targets, and ascertain the technology of the structure under the condition of a complex velocity field in a foremountain.Artificial intelligence technology and pre-stack and post-stack combined application technology were applied in the prediction and hydrocarbon detection of highly heterogeneous carbonate fracture-cavity reservoirs.

Seismic exploration of oil and gas has entered the stage of complex surface, complex structure, complex reservoir, and deep target, and the "wide azimuth, wide broadband, and high density" seismic data acquisition has become the consensus of the industry.The piedmont zone exploration areas of various oil and gas basins in western China have become strategic replacement areas for oil and gas resources, and have achieved good exploration results.However, this does not mean that we have completely broken through the core technical problems of seismic exploration in the "dual-complex" exploration area.This study first defines the fundamental problem of seismic data imaging processing in the piedmont zone as the establishment of a velocity model that meets the requirements of migration imaging based on a highly variable inter-channel time difference and low signal-to-noise ratio data.Then this study comprehensively analyzed the methods and technical process of imaging of seismic data from the following aspects: the exploration seismic medium system is linear and the essence of seismic wave imaging is to realize the in-phase superposition of the reflection wavelet at different offsets at the same underground reflection point; the inter-channel time difference can destroy the linear phase characteristics of the local linear event; the dividing point between time-domain imaging processing and depth-domain imaging processing is that after static correction based on the velocity model above the bottom of the weathered layer, whether the events of the CMP gathers meet the hypothesis of a hyperbolic time-distance relationship; the current linearized tomographic velocity inversion can only estimate the smooth velocity model; and the linearized migration imaging is based only on the smooth velocity model.Based on the analyses, this study pointed out that data preprocessing based on inter-channel time difference elimination, small smooth datum, and full-depth domain seismic wave migration imaging were the effective technical routes to solve solve the problem of seismic imaging processing in the piedmont zone.

Digital cores can be used for the fine characterizations of rock microstructures.Currently, this technology is crucial for analyzing rock microstructures and rock physical properties.Generally, the methods of modeling digital cores can be divided into physical experimental methods, numerical reconstruction methods, and combination fusion methods.In this study, a digital core and digital wellbore are introduced from the aspects of model building and well logging applications.The digital core model building methods for single-and double-pore medium systems, multiporous structures, and multiscale fusion are summarized.The applications of digital core modeling in electrical, acoustic, seepage, and nuclear magnetic resonance properties are discussed.Because the modeling and numerical simulations utilized in the digital core technology are mostly concentrated at the micro or even nano level, exploring the petrophysical properties at the microscale cannot effectively explain the influence of macro factors(rock structure, stratigraphy, fractures, etc.) on the petrophysical properties.Notably, the digital wellbore modeling technology is an emerging technology adopted to construct three-dimensional digital wellbores based on multiscale digital cores combined with electrical imaging, conventional logging, and other information.This technology, combined with nuclear magnetic technology, mercury pressure, conventional logging, and other information, can reflect continuous changes of well periporosity on a large scale.Moreover, it can be applied to the simulations of electrical, elastic, and seepage characteristics and provide virtual logging for well seismic combinations, which can be used to explain the influence of various micro and macro factors on the petrophysical properties of the formation.It is also expected to serve as the main auxiliary tool for the processing and interpretation of three-dimensional logging data in the future.

As an inter-disciplinary technology which integrates a variety of geophysical data and dynamic and static information of reservoirs into detailed characterization and dynamic monitoring of complicated reservoirs, reservoir geophysics is of great significance to improved reserve utilization and recovery efficiency and thus is an important direction of geophysical technologies. We give an overall review of reservoir geophysics in Sinopec in the past two decades and a series of geophysical techniques, including technical innovations and their application from the perspectives of fundamental geophysical research, borehole geophysics, multi-scale joint inversion, geophysically constrained deterministic modelling, time-lapse seismology for remaining oil and gas prediction, seismology-geology-engineering integration, and microseismic monitoring. In the context of petroleum exploration and development in deep water and deep zones, unconventional reservoir exploration and development, enhanced oil recovery in mature fields, and challenges of integrated, intelligent, and green technologies in China, there are still bright prospects for reservoir geophysics in petroleum industry. It is suggested continuing innovations in reservoir geophysics, integration of well, seismic, dynamic, and modelling data, and artificial intelligence application and establishing high-level solutions to exploration-development integration and geology-engineering integration to support life-span reservoir construction.

High-precision 3D seismic acquisition has achieved considerable success.However, for complex geological bodies, it is important to develop full-wave field seismic acquisition methods that can adapt to both continuous interface reflection and random medium scattering.There are two difficulties in seismic acquisition.First, there is no single seismic layout that satisfies both the reflection of large dip interfaces and the scattering of small-scale media; thus, the existing field arrays cannot adequately sample the scattered waves.Second, for the scattering of seismic waves generated by small-scale media, existing observation systems cannot satisfy both the lateral resolution and spatial sampling requirements of the minimum medium size; thus, it is impossible to completely sample small-scale media.According to the concept of quantum mechanics, the propagation of underground heterogeneous bodies and seismic waves is considered to constitute a quantum system, and scattered waves are considered probability waves, so that the spatial sampling density is no longer limited.Full-wave field seismic acquisition is a process of obtaining multi-state seismic waves in a balanced manner.Because probability waves cannot be obtained through sparse and regular sampling, probability-wave acquisition must satisfy the ergodicity requirement.It is advisable to adopt common-midpoint gather discretization technology, which is achieved through multiple observation system design and bin subdivision controlled by the trace density.Owing to the weak seismic scattered wave signal and the characteristics of localization and uncertainty, acquisition parameters should be selected, such as a small bin, a small trace spacing, a small spread, high coverage at near-offset, and a local random layout of the shot and receiver.The full-wave field seismic acquisition method is more flexible and can support simultaneous acquisition, multi-phase embedded acquisition, or well site continuous acquisition.The data have richer effective signals, less background noise, and wider frequency bands.This technology is economically acceptable and physically achievable.

Seismic data denoising is an important processing step to improve data quality. The key to the denoising method is to retain effective signals as much as possible while suppressing the noise. Currently, denoising methods based on deep learning primarily use fixed-scale convolutional kernels to extract local features, which may result in incomplete events. Therefore, we proposed a denoising method based on Dense Dilated Convolutional Residual Network (DDCRN). In this method, multiple dense dilated convolutional feature fusion blocks (DDCFFB) cascade to form a deep network, thereby increasing the information reception range of DDCRN. DDCFFB is mainly composed of two parts that extracted features in parallel. The first part was a dense block that connected different convolutional layers to learn features. Complex information could be extracted efficiently by propagation and reusing of local features. The other part was multi-scale dilation convolution that could access a wide range of information windows. Dilated convolution provided a more comprehensive range of information. The fusion structure combined the features extracted from the two parts. The residual structure accelerated the network training convergence and avoided network degradation by skipping the connection channel. We evaluated the k-singular value decomposition (KSVD), f-x deconvolution (f-x decon), denoising convolutional neural network (DnCNN), u-shaped convolutional neural network (Unet), and DDCRN denoising methods, on the synthetic and real seismic data. The results show that the DDCRN effectively suppresses random noise while preserving the continuity of events compared to the other method.

Optical fiber sensing has been applied to surface, marine, and borehole seismic acquisition and joint borehole-surface seismic acquisition in the latest years. Surface or marine seismic and VSP seismic exploration could be combined to achieve 3D prospecting. Using 3D DAS-VSP data, we could obtain accurate time-depth relationship, interval velocity, deconvolution operator, compensation factor of spherical spreading, absorption attenuation factor, anisotropy parameters, and high-resolution structure imaging around the well bore; above parameters could be used to enhance 3D well-driven land or marine seismic data processing. In this work we performed 3D DAS-VSP data processing and imaging. The 3D DAS-VSP survey was acquired using a downhole armored optical cable with simultaneous OBN data acquisition in the East China Sea. The routine workflow of 3D DAS-VSP data processing includes geometry definition, preprocessing, first break picking, static correction, amplitude compensation, deconvolution, wave field separation, velocity analysis and modeling, and structure imaging using upgoing waves. A new technique of downgoing multiple reflection imaging is developed to enlarge the migration aperture and imaging area of upgoing reflected waves and obtain better quality of imaging. Compared with 3D vintage OBC data imaging, 3D DAS-VSP downgoing multiple imaging yields better results within a large area around the well bore; OBN and 3D DAS-VSP imaging yields better results for high-resolution structure interpretation and fluid detection. Owing to high efficiency and low cost of joint borehole-marine acquisition, it is possible to accomplish fast 3D DAS-VSP imaging and enhanced well-driven resolution processing of 3D marine seismic data. Besides, 3D OBN or OBC data and 3D DAS-VSP data could be processed together for joint borehole-surface or borehole-marine migration to significantly improve the imaging quality of 3D marine seismic data.

The air-water interface is a strong reflector.Therefore, the downward reflection of acoustic waves at the water surface forms a well-known ghost effect in marine seismic waves.In marine surveys, ghost notches on the frequency spectrum reduce the frequency bandwidth and resolution of seismic records, distort waveforms, obscure the identification of events, and increase the difficulty of inversion and interpretation of seismic data.Deghosting seismic data is a longstanding challenge and has become appealing to researchers studying seismic imaging.Berkhout proposed a deghosting method based on echo-deblending, highlighting the similarities between deghosting and deblending, and suggested implementing a technique similar to deblending in simultaneous source seismic waves to separate ghost waves.In marine 3D data acquisition, undersampling seismic data reduces the effectiveness of the present deghosting methods.For 3D marine seismic data, the challenges of deghosting comprise two phases involving handling the wavefield undersampling issue, followed by actual ghost signal removal.To address the undersampling problem of 3D seismic data, Berkhout suggested interpolating seismic data before applying echo deblending to suppress ghosts.In this study, we proposed a 3D-deghosting algorithm for undersampling seismic data based on Berkhout's research.Our algorithm simultaneously addressed the undersampling and deghosting problems.The deghosting method for 3D seismic data based on densely sampled wavefield reconstruction did not use prior interpolation but extended the Berkhout method to establish a dense ghost wavefield on the water surface.It used Lasso regression to solve the problem of sparse extrapolation of the dense wavefield.Our algorithm first reconstructed the dense seismic wavefield at a specified surface by extrapolating the original sparse seismic wavefield.The dense ghost wave field at the water level was calculated using the dense wave fields and the echo-deblending approach.The sparse ghost wave field at the original acquisition position was then obtained.The ghost waves were subtracted from the original data using the least-squares method to resolve the deghosting problem.The goal was to minimize the difference between the actual data and the simulated wavefield, solve the uncertainty of this problem, achieve deghosting, and improve the characteristics of the seismic data.Synthetic data testing and real data processing showed that the deghosting of 3D seismic data based on dense field reconstruction could effectively separate ghost waves, improve wave field characteristics, and improve the resolution of the seismic data.

Reservoirs in deep water and deep zones are becoming the targets of offshore oil and gas exploration, and there is an urgent need for the development of offshore seismic prospecting techniques owing to subsurface tectonic complexities (severe lateral variations), reservoir complexities (changing from structural reservoirs to structural, stratigraphic, and lithologic reservoirs), and seabed topographic and lithologic complexities. The primary issue in improving the efficiency of offshore exploration is to develop advanced techniques for seismic data acquisition and high-precision seismic imaging. Wide-azimuth wide-band high-density acquisition and seismic imaging represented by full waveform inversion (FWI)/least squares reverse time migration (LS_RTM) are characteristic leading techniques in offshore and onshore seismic exploration. In offshore seismic exploration, OBN acquisition is generally accepted to be the most feasible way to accomplish wide-azimuth wide-band high-density acquisition. Compared with streamer data acquisition, ocean bottom node (OBN) data acquisition features wide-azimuth illumination, high signal-to-noise ratio, no detection-end ghosts, measured (at least first-order free surface related) downgoing wave field, and four-component observations, especially wide-azimuth illumination and at least first-order free surface related downgoing wave field, which make it possible to achieve high-precision imaging of complicated middle and deep structures and near-seabed media. Our efforts focus on the requirements of high-precision imaging for seismic data acquisition, the necessity of OBN acquisition in offshore exploration, the characteristics of OBN seismic wave field, and the basic logic and corresponding key techniques for OBN data imaging. The particularities of marine data processing are supposed to be mainly caused by characteristic reflectors, which include seawater surface, seabed, and subsurface strong reflecting horizons. We propose a technical solution to the prediction and suppression of multiples related to characteristic reflectors based on model-driven wave theory and compare some basic theories for multiples prediction. The linearized imaging operator-based prestack data domain and prestack imaging domain are supposed to be equivalent. Centering on the post processing of imaging gathers, expected imaging gathers are defined, and weak side lobes and quantitative reflection coefficients are taken as the targets of high-fidelity high-resolution imaging to achieve in-phase stacking of the wavelets from the same subsurface reflection (diffraction/scattering) point and different offsets in two domains and obtain imaging results of band-limited reflection coefficients with high fidelity and high resolution. It is suggested performing band-limited reflection coefficient imaging for broad-band impedance imaging. Based on the characteristics of OBN data, we present a basic workflow and key techniques of OBN data imaging. With respect to four-component OBN observations, the disagreements between wave phenomena in observed multi-component seismic wave field (mainly P_SV waves) and wave propagation and simulation theory lead to unsatisfactory multi-wave imaging. It is recommended focusing on the physical origin of the disagreements between wave phenomena in observed multi-component seismic wave field and wave propagation and simulation theory instead of more advanced vector wave imaging algorithms. We hope that our ideas may promote further application of OBN data to offshore seismic exploration.

Geological target-oriented imaging technology aims to improve the imaging of deep target layers and special geological formations, such as highly steep structures, sub-salt structures, and small-scale structures, by selecting local areas as the imaging target.We summarized the research progress in seismic migration imaging methods for geological targets.Geological target-oriented migration methods can be classified into data and model selection methods.Data-selection imaging methods use characteristic seismic waves to image special geological structures, including data-selected prismatic wave imaging, multiple imaging, diffracted wave imaging, and diving wave imaging methods.The model-selection imaging methods, which mainly include data datum reconstruction methods, target-oriented CFP imaging methods, local target imaging methods, acoustic-elastic coupled wavefield continuation methods, and least-squares migration in the imaging domain, selected local target regions for accurate imaging, which substantially improved the computational efficiency.The general trend in geological target-oriented seismic migration technology ranges from migration-based imaging to inversion-based imaging and integrating model selection and data selection types with artificial intelligence technology to achieve seismic target imaging for geological targets.

Full waveform inversion is a powerful imaging tool in geophysics.However, it suffers from local minimum issues owing to inaccurate starting models, the absence of low-frequency data, and inaccurate physical simulation.Convex objective functions have been studied for several decades.Over the past few years, geophysicists have achieved remarkable success with optimal transport functions, which has motivated the geophysics community to explore new formulations for optimal transport functions.In this study, five optimal transport functions, namely W2, BFM, KR-OT, GS-1D, and GS-2D(including 1D and 2D algorithms), were reviewed, and their convexities were compared and analyzed through synthetic tests.These full waveform inversion tests demonstrated that the 2D optimal transport function was superior to that of the 1D algorithm.Specifically, the BFM function was better than the W2 function and the GS-2D function was better than the GS-1D function.

The decomposition of elastic wavefields is key to anisotropic elastic reverse-time migration(ERTM).Because the P- and S-waves in anisotropic materials are not polarized parallel and perpendicular to the wave vectors, respectively, the wavefield decoupling method based on Helmholtz decomposition and that based on isotropy in the time-space domain are not suitable for anisotropic media.This unsuitability is because their use results in crosstalk of P- and S-waves after decoupling, and ultimately affects the imaging quality.The anisotropic wavefield decoupling methods in the wavenumber domain are computationally expensive owing to the Fourier transform at each period.In this study, we propose a time-space domain wavefield decomposition method, which first decomposes the elastic parameter in transversely isotropic(VTI) media into the P- and S-wave constants, and then substitutes them into the elastic wave equation to obtain the decomposed P- and S-elastic equations.According to this process, we can obtain the vector P- and S-waves.This method is simple and does not require amplitude or phase correction, which will promote the industrialization of elastic reverse-time migration in VTI media.A simple model was used to test the separation effect of the elastic wavefield, which revealed that little crosstalk still exists after this process.Moreover, a single trace was used to analyze the crosstalk of the decomposed vector wavefield.A standard model was used to test the elastic reverse-time migration.The imaging results show that the interface information is consistent, has a high signal-to-noise ratio, and can clearly describe complex structures, such as faults and folds.Additionally, no imaging artifacts or depth inconsistencies are present.The model test demonstrates the adaptability of the proposed method.

Under complex geological conditions, effectively improving the fracturing results of shale gas wells is important to increase the production and efficiency of shale gas wells. Seismic fracturing simulation before fracturing in shale gas wells is a key measure for guiding fracturing engineering. In general, the finite element method is used for numerical fracturing simulations. However, this method has grid distortion problems in areas with strong formation deformations and enrichment fault fractures, resulting in inconsistencies between the simulation and actual fracturing results. This reduces the shale gas development efficiency. The seismic, geological, and engineering-integrated fracturing simulation technology proposed in this study can effectively avoid these problems using the material point method (MPM) for numerical simulation calculations. First, this technique uses seismic imaging logging data to construct the fracture surface curve, which reflects the fracture situation. Second, we used fuzzy mathematics to optimize the sensitive attribute of the fracture. Third, we used a fuzzy neural network to construct the natural fracture model. Finally, the MPM was used to obtain the results of the fracturing simulation. These four steps were the main methods for predicting the fracturing simulation around a well and eventually obtaining a favorable fracturing zone. This study applied seismic fracturing technology to the J study area and the seismic fracturing simulation of Well J1 and Well J2. This result was consistent with the actual fracturing effect. This technique is a seismic fracturing simulation technique used before the actual fracturing of shale gas wells and can provide design guidance for fracturing operations, which is of great practical significance for shale gas development to reduce costs.

Pre-stack depth migration is widely used in seismic data processing, and the result of such pre-stack migration is an important factor in seismic geometry evaluations.Generally, quantitative evaluations of the seismic geometry based on the resolution of migration imaging can guarantee optimal imaging results when designing seismic acquisition.At present, the seismic geometry evaluation method based on migration imaging resolution is primarily based on double-focus analysis, which requires wave field continuation in the realization, resulting in a low calculation efficiency.In this study, an improved Gaussian beam method is used to enhance the calculation efficiency of the conventional double-focus analysis.This method includes the following steps: a.using Gaussian beam propagation based on Snell's law with a limited frequency and a viscoelastic medium model to generate a CFP gather of a target point; b.implementing double-focus calculation in the plane centered on the target point according to the ray tracing result; and c.using the width of the main energy as the migration imaging resolution to evaluate the geometry.In this method, the effect of Fresnel zones is considered during ray tracing, and the effect of the Q factor is included in dynamic tracing, with a consideration of the frequency changing of wavelets; these improvements enhance the reliability of the calculation results.The principle of this method is consistent with pre-stack depth migration.Model application results indicate that this method can efficiently and reliably realize quantitative evaluations of the seismic geometry based on migration imaging resolution for a certain target point or target layer underground.Hence, this method presents high feasibility for the design of 3D seismic surveys of complex geological targets.

Carbonate reservoirs, including fractured-vuggy reservoirs, fractured reservoirs, and fractured and fractured-vuggy reservoirs, are an important reservoir type in the Tarim Basin.Fractured-vuggy units, which are much smaller than seismic wavelength, mainly cause diffracted waves, and how to preserve and enhance diffracted waves is a ticklish problem in seismic acquisition.Since more and more large fractured-vuggy reservoirs have been recovered, small reservoirs become exploration targets.As per the study of reservoir models with small dissolved cavities and fractures, seismic responses feature low energy, low apparent velocity, and positive correlation between energy intensity and the dominant frequency of source wavelet.Theoretical study and field tests of shooting and receiving conditions in Tahe area show that a small quantity of dynamite may excite the source wavelet with high dominant frequency, which is favorable for diffraction enhancement for small geologic units.The quantities of 4 and 6kg used in 2D tests perform better than 10kg in high-frequency enhancement to improve imaging resolution.An array length larger than 20m may lead to a considerable loss of diffracted waves with low apparent velocities and thus impair focusing energy in migration to image fractured-vuggy units.The array length not greater than 12m is a good choice to balance imaging quality of small reservoirs and signal-to-noise ratio.For equal geometry parameters, the combination of small array length and small dynamite quantity is favorable for detecting weathering-crust fractured-vuggy reservoirs, as indicated by 30% more bead-like reflections identified.

Gas hydrates are an important type of mineral resources in geologic and resource surveys, but there are many challenges, e.g.unestablished seismic responses and mechanical and electrical properties, in hydrate exploration and development.Without appropriate ambient temperatures and pressures needed for gas hydrate occurrence, these solid compounds may decompose and then trigger marine environmental change and geologic hazards.An effective way to understand complicated rock physics of gas hydrates is lab tests.We review the synthetic methods including cooling and icing, THF solution, excess water, excess gas, temperature, and ice powder blending and the factors that may influence hydrate synthesis, e.g.temperature, gas pressure, particle size, mineral composition, water content, surfactant, salt content, and formation skeleton.We also discuss the progress in acoustics, mechanics, and electricity related to hydrate rock physical experiments and future efforts focusing on rock physical experiments.

In the past few decades of exploration and development in the Tarim Basin, the development of Ordovician carbonate fracture-cavity reservoirs in the northern region of the Tarim has moved from the early large-scale fracture-cavity reservoirs to small-scale reservoirs. Fracture-cavity reservoir contour description, internal structure prediction. and small-scale cave detection have become the key points for reserve and production growth. Based on high frequency-division pre-stack time migration data volume, we used the perigram, root mean square amplitude attribute, and 3D visualization to finely characterize the spatial distribution of different scale fractures and caves. This technology has been widely applied in the Tahe Oilfield with a work area of 80km². Compared with the identification results of fracture-cavity based on conventional pre-stack time migration data volume, this technology can improve the accuracy of fracture-cavity reservoir contour description and also distinguish the internal structure of fracture-cavity combinations. More importantly, it can considerably improve the precision with which small-scale fracture-cavity reservoirs are identified. The research results reported here have broad applicability and importance regarding future hydrocarbon development and production, as well deployment in the northern region of the Tarim Basin.

The productivity prediction of tight sand is critical for oil and gas exploration in China.Owing to the complex structure and limited number of vertical wells in the study area of the Ordos Basin, it is difficult to characterize "sweet spots" of productivity using single traditional prediction methods.We proposed a method that combines seismic attributes and deep learning results to calculate "sweet spot" productivity using seismic data.In this study, a convolutional neural network was used to characterize the sedimentary microfacies of sandy debris flows in the study area by combining geological, logging, and seismic data to obtain the dominant facies distribution.Considering the impact of the local structure on the study area, the three-dimensional distribution of productivity "sweet spots" was obtained by integrating the curvature properties and sandy debris flow microfacies.This method was used to extract and optimize productivity-sensitive attributes from the seismic data.Simultaneously, deep learning was used to predict the reservoir properties and sedimentary facies from seismic data.Finally, the productivity "sweet spot" distribution was obtained by integrating the sensitive attributes and projected sedimentary microfacies.The application results showed that the productivity "sweet spot" distribution obtained by the above fusion was significantly improved and correlated well with the production data.The "sweet spot" area was consistent with the drilled horizontal well results.These results provide a reference for the future deployment of high-yield well locations and more effective exploitation of tight sand reservoirs.

The Maokou Formation in the Longhuichang-Longmen area, northeastern Sichuan, is located in the sedimentary high-energy facies belt and is a part of the paleogeomorphology, having favorable conditions to form facies-controlled karst reservoirs.Wells drilled in the Maokou Formation of the study area commonly show good oil and gas contents, indicating considerable exploration potential.However, the Maokou Formation has strong reservoir heterogeneity, low thickness, and unclear reservoir distribution patterns and seismic response characteristics.This has failed to form an effective reservoir seismic prediction model.Given these problems, this study summarized the seismic response of the reservoir and established an effective seismic prediction method for the Maokou Formation reservoir based on the seismic geological data, single-well characteristics of the Maokou Formation reservoir, and forward modeling.Based on the detailed geological background, single-well characteristics, and seismic prediction, the impact of paleogeomorphology and high-and low-angle faults on reservoir development were analyzed to establish a detailed seismic identification model for the Maokou Formation reservoirs in Northeast Sichuan.This study has shown that the shoal facies and karst paleogeomorphology of high-energy deposition are the basis for forming reservoirs in the Maokou Formation.Low-and high-angle faults can further expand and transform the reservoir, and high-angle faults are the links between the Maokou Formation and Silurian to Ordovician source rocks.Therefore, the favorable facies belt, the high part of the paleogeomorphology, and the high-low angle fault development area were the most favorable areas for exploration.A combination of seismic facies and attributes should be used for reservoir prediction under the constraints of the aforementioned geological information.Syncline areas that meet the prediction model also have considerable potential for exploration.

Green, low-carbon development has become a contemporary theme that profoundly affects the direction and route of global economic and social development.The development of green geophysical technologies is an important task in the geophysical industry.The connotations and characteristics, hierarchy and composition, and future development directions of green geophysical technology are expounded.The geophysical industry should enhance its technological advantages in terms of green energy, technology, systems, and services.Moreover, it should innovate its technological systems, service content, and application scenarios, enhance the level and competitiveness of green and low-carbon application services, optimize traditional application services, explore emerging application service fields, and contribute to global sustainable development.Green geophysical technologies can be divided into two levels: basic and general.Basic green geophysical technology refers to environmentally sound geophysical technology that has no negative impact on or damage to natural ecological and human survival environments.General green geophysical technology refers to any geophysical technology that benefits from protecting the Earth's ecological environment, applying it to protect the Earth's ecological environment, and serving green and low-carbon fields.Green geophysical technology generally has key characteristics such as environmental friendliness, strong environmental adaptability, high security, low energy consumption, low resource consumption, high efficiency, low cost, and non-destructivity.Environmentally sound geophysical technology includes green equipment, acquisition technology, computing technology, analysis technology, and systems.The important development directions of green geophysical technology include passive geophysics, green sources, nodal seismic, multiphysical nodes, satellite remote sensing, unmanned aerial vehicle geophysical measurements, fast calculation and green computing, automated data processing and intelligent data analysis, DAS-based permanent monitoring systems, and low-cost geophysical technologies.

Petrological analysis has shown that the low-permeability genesis of Oilfield B mainly includes primary sedimentation, strong compaction, and strong cementation in late diagenesis.However, sedimentary microfacies primarily control the relatively high-permeability dessert layers developed locally in low-permeability reservoirs.In this oilfield, the petrophysical characteristics of the local dessert layers are slightly different from those of tight reservoirs.Therefore, high permeability dessert layers are difficult to distinguish using conventional geophysical methods.Based on the different geneses of sand bodies, this study first summarized the vertical superposition mode of dessert layers in a tight reservoir, established representative models with varying thicknesses of reservoir, dessert thicknesses, dessert locations, and dessert heterogeneity changes, and conducted forward modeling.Theoretical seismic attributes that were relatively sensitive to different superimposed geological models were selected, and a multi-sensitive attribute combination chart was constructed according to the different reflection characteristics.Finally, the superposition pattern of the dessert layers in the tight reservoir was identified by matching the "multi-sensitive attribute combination" chart with the actual seismic attribute.In this way, the dessert layers of Oilfield B were predicted, and the results were in accordance with the drilling.This method improved the accuracy of dessert prediction using seismic attributes and provided a new method for evaluating and developing low-permeability tight oil.

The curvelet transform method for seismic data denoising with a hard threshold is prone to weak event blurring when used to denoise seismic data because of the discontinuity at the threshold. This study proposed a method for removing random noise based on curvelet transform-joint bilateral filtering. First, the curvelet transform was applied to the original seismic data, and the scale information of the original curvelet coefficients was analyzed. Coarse-scale signals primarily characterize seismic data structures. To process the coarse-scale curvelet coefficients, the proposed method used bilateral filtering. Intermediate-scale signals typically contain a large amount of weak event information. Joint bilateral filtering was performed on the intermediate-scale curvelet coefficients. The curvelet transform handles multi-directional linear changes more effectively, and joint bilateral filtering has a guide map that can repair the key features of effective information and improve the continuity of weak events. Fine-scale signals typically contain noise. The hard-thresholding method was applied to deal with fine-scale curvelet coefficients. The processed coarse-, intermediate-, and fine-scale curvelet coefficients were then used to compose new curvelet coefficient sets. The denoised seismic data was obtained by performing an inverse curvelet transform on the new curvelet coefficient sets. Simulated and real pre- and post-stack seismic data were used to verify the effectiveness of the proposed method. When compared with the curvelet transform method with a hard threshold and the wavelet transform method, the proposed method can remove random noise and obtain a higher signal-to-noise ratio and peak signal-to-noise ratio. The energy of weak events was enhanced, and their continuity was improved. The curvelet transform-joint bilateral filtering method can be extended to seismic data with low signal-to-noise ratios to provide high-quality seismic data to modeling and interpretation engineers.

Moving coil geophone and piezoelectric sensor (including piezoelectric pressure hydrophones used in water and piezoelectric accelerometers used on land, LP) are the two most widely employed types of sensors in geophysical prospecting. A table consisting of the physical structures, mathematical models, and transfer functions of these two sensor types is established for comparison. Theoretical analysis and field experiment data showed that the velocity measured by moving coil geophone and the acceleration by LP accelerometer are equivalent across the major frequency bands in terms of representing ground movement. Regarding hydrophone, it is essential to understand that it is pressure-type detector, not an accelerometer. Based on the fundamentals of seismic wave dynamics and practical application, output of pressure-type hydrophone is proportional to the velocity of water particles for the up-going wave field and a -180° phase difference is exhibited for the down-going wave field. This relationship forms the basic principles for dual-sensor summation technology. This technology relies on several assumptions, such as a plane wave field, the sensor being very close to the seafloor but without direct contact (avoiding sensor-ground coupling effects), and without involvement of the sensing system. The author questions these assumptions and argues that more effective attenuation of water column reverberation by this technology requires additional efforts theoretically, experimentally and operationally. Meanwhile, the main function of sensor is simply to follow the movement of the ground faithfully, circuit-based enhancement of high frequencies in the field may reduce the S/N ratio and resolution and should not be promoted. Finally, the classification of sensors based on different standards has been clarified, contributing to a more thorough understanding of the nature of sensors and also its output data.

The Shaximiao Formation, located in the central-western Sichuan, is a tight sandstone gas reservoir with a complex rock composition, low porosity, and complex structure. Due to tectonic movements, multiple pressure systems coexist, resulting in significant variation in the formation pressure between different sand bodies vertically and horizontally. A classification formation pressure prediction method was proposed to address this issue. According to the measured formation pressure data, the vertical pressure unit was divided based on the Shaker division and we used parameters such as vertical depth, resistivity, porosity, three-porosity ratio, and gas saturation to analyze the correlation between each parameter and the formation pressure coefficient. Based on this classification, a comprehensive pressure index chart was constructed to predict the formation pressure. There are two types of charts: ultra-low-pressure charts and normal- and low-pressure charts. An ultra-low-pressure chart established by the comprehensive pressure index and vertical depth was used to determine whether the pressure type was ultralow, and the model established by the water absorption principle of the underlying mudstone was used to predict ultralow pressure. The pressure of this type is predicted according to the Eaton method, selected after comparing and predicting normal and low pressures using the Eaton, Fillippone logging, and effective stress methods. The model was based on the principle of water absorption of the underlying mudstone for predicting the ultralow pressure. The coincidence rate of chart classification reached 85%, and the overall prediction result of the formation pressure coefficient was as high as 96.15%. This outcome is consistent with the measured results and provides a calibration basis for the vertical divisional classification calculation of the formation pressure of the Shaximiao Formation and the prediction of seismic formation pressure.

In the process of seismic imaging, the accuracy of prestack migration imaging depends on the migration velocity model; therefore, migration velocity analysis is crucial for high-precision imaging. Based on the inverse scattering imaging condition under a high-frequency approximation, this paper proposes a converted phase elastic wave equation migration velocity analysis method. First, based on the inverse scattering imaging condition under a high-frequency approximation, the converted S-wave scattering potential was estimated by reverse time migration. The upward-converted S-wave was then reconstructed by combining the incident P-wave and the converted S-wave scattering potential. Finally, the gradient of the objective functional with respect to velocity was derived using the adjoint state method. The inverse scattering imaging condition effectively ensured a stable solution for the migration velocity analysis of the gradient elastic wave equation. A numerical experiment demonstrated that the proposed method produced a high-quality gradient. According to the preliminary experimental results, the inverted S-wave velocity effectively flattened the common image gathers and improved imaging quality. In addition, the intelligent recognition technology for the curvature of the residual moveout simplifies the intermediate processes, and the proposed intelligent velocity analysis framework likely improves the computational efficiency.

There has been a breakthrough in the study of the Middle Permian Qixia Formation in the Jingyan area of the Sichuan Basin. However, the highly diverse and heterogeneous reservoirs, and the unclear seismic response characteristics and plane distribution rules of the different dolomite and dolomitic limestone reservoirs, restrict the direction of oil and gas exploration in this area. Based on the regional geological research background, two forward models of dolomite and dolomitic limestone reservoirs of different types, thicknesses, and development positions were established and simulated using drilling, logging, and seismic data. The main factors affecting the variation of seismic reflection characteristics in the Qixia Formation were summarized, and the identification modes for different types of reservoirs were established. The plane change of the sedimentary environment was determined by combining drilling lithology, logging facies, and seismic facies, while the favorable position of dolomite reservoir development was determined by the fluctuation of paleogeomorphology. In the existing seismic data, the seismic response characteristics of the thin-layer dolomite, dolomitic limestone, and calcareous dolomite thin-interbedded reservoirs were not significantly different. Using waveform decomposition and reconstruction technologies, the study statistically classified seismic waveforms with different energies. Based on the reservoir fine calibration, the waveform components representing the response characteristics of the dolomite, dolomitic limestone, and calcareous dolomite reservoirs were optimized. This allowed for qualitative determination of the plane distribution of different types of reservoirs, while the spatial distribution was quantitatively determined using color filter impedance inversion technology. Combined with the sedimentation, structure, reservoir, and hydrocarbon sources, favorable areas for reservoir development in the Qixia Formation were delineated, and favorable exploration targets were defined. The results of this study show that the Jingyan area is located on the southern margin of the central Sichuan Paleo-uplift and the different types of reservoirs in the Qixia Formation are controlled by paleogeomorphology. A higher paleogeomorphology indicates higher degree of dolomitization. Thick and large dolomite reservoirs are mainly distributed in the northwest of the study area, while thin dolomite, dolomitic limestone, and calcareous dolomite reservoirs are mainly distributed in the south and northeast. Favorable reservoir development areas and superimposed areas with structural and dissolution fractures are favorable for further oil and gas exploration.

The static elastic modulus of rocks is an important mechanical property for oil and gas exploration and development.However, the number of direct experimental measurements is relatively small and expensive, and the original method of realizing dynamic and static modulus conversion through empirical formulas has an unclear physical meaning and low precision.This means it cannot meet the requirements of drilling, fracturing, and other projects.Therefore, a prediction method based on a rock physical model was proposed.A pore-fracture rock physical model was constructed using logging data to calculate the dynamic modulus.Based on the dynamic modulus, the elastic modulus of low-frequency drying of rock was obtained by considering the frequency dispersion effect and drainage effect, considering the difference in strain amplitude between the dynamic and static moduli, simulating the process of rock static deformation, and realizing the prediction from the dynamic to static modulus.This method considered the micro-factors of dynamic and static modulus conversion and was theoretically more rigorous.Finally, the static modulus was predicted using the experimental data from the actual working area.The predicted results are in line with the experimental data.The error in the dynamic elastic Young's modulus was 4%, and the error in the static Young's modulus was 8%, demonstrating the method's applicability.

Fluvial reservoir discontinuities caused by channel migration and truncation are unfavorable for fluid flow and remaining oil and gas recovery, and seismic resolution is usually not high enough to detect these discontinuities.Based on model tests, we develop a computational method of phase spectrum to increase frequency resolution for identifying thin interbedded fluvial sands.A Fourier transform of seismic data, which are padded with zeros at the end of the time window to make the fundamental period longer and improve robustness, is executed to obtain unwrapped phase spectrum and integration-based unwrapped phase.Based on typical fluvial sandstone stacking configuration, we establish two groups of superimposed sandstone models with different heights to analyze their phase responses.Owing to the qualitative relationship between phase anomalies and discontinuous interbedded sandstone thickness, it is feasible to use integration-based unwrapped phase to identify sandstone discontinuities, particularly when the signal-to-noise ratio is larger than 5∶1.We apply this method to a survey in the southern Bohai Sea and identify two areas with superimposed sands, which agree with log interpretation.The method of padding with zeros and integration-based unwrapped phase is demonstrated to be stable and effective in discontinuity detection for superimposed sandstones.

Permian igneous rocks are widely developed in the Shunbei oil and gas field, and the strong transverse heterogeneity of fracture-controlled fracture-cavity reservoirs makes accurate velocity modeling and imaging difficult.Wide-azimuth seismic acquisition results in consistent underground observation energy and all wave fields required for accurate imaging of underground targets, which facilitates anisotropy analysis and utilization.The CIP gathers generated by the traditional OVT seismic processing technology exhibit poor performance in lateral velocity mutations and cannot obtain true underground angle information.To ensure the efficient application of wide-azimuth seismic data, full-azimuth local angle domain migration imaging technology can achieve accurate azimuth and dip imaging in complex structural areas.The residual delay of the full-azimuth gathers was analyzed using the full-azimuth mesh tomography velocity modeling technology, and a tomographic imaging matrix was established to realize accurate velocity modeling of the anisotropic field.To improve the recognition of deep small-scale geological bodies, full-azimuth local angle decomposition and imaging technology were used, and the full-azimuth gathers were processed for inclination gather stacking, scattering, and image enhancement.Full-azimuth local angle domain decomposition imaging technology can perform ray-tracing and imaging decomposition of seismic data in the underground local angle domain, obtain inclination and reflection gathers simultaneously, and then perform weighted superposition imaging of the reflection and diffraction wave fields according to imaging requirements.Scatter data were obtained using the characteristics of the inclination gathers, and the energy of the underground fracture-cavity reservoir was obtained.By using the characteristics of the reflection wave fields to perform mirror-energy imaging, stack data with a higher signal-to-noise ratio and clearer details were obtained, and the fault distribution was clearly depicted.This provides basic data for the prediction of fracture-cavity reservoirs and small-scale geological bodies in the Shunbei oil and gas fields, and provides a technical reference for the prediction of fracture-cavity geological anomalies in other areas.Compared with the conventional Kirchhoff migration technology, the full-azimuth local angle domain migration technology retains the local orientation information of wave field imaging in different propagation directions and can reflect the information of underground imaging points more accurately.This technology has achieved a good application effect in the Shunbei area, where the imaging accuracy was improved, the energy reflected by the beads was highlighted, and the lateral resolution of the faults was increased.

When reservoirs contain oil and gas, the amplitude and frequency of seismic data change, thereby laying a foundation for oil and gas identification through seismic data. Because the CEEMD algorithm can adaptively separate the local feature information of a complex signal, this study adopted this algorithm to extract hydrocarbon information from seismic data. By adopting EMD, EEMD, and CEEMD algorithms to decompose Marmousi Ⅱ model synthetic records with different dominant frequencies and phases and actual logging data synthetic records, it was revealed that there is no obvious correspondence between the IMF components based on EMD and oil and gas. Among the IMF components obtained based on EEMD and CEEMD, the IMF1 component can highlight the seismic response of oil and gas reservoirs and suppress the seismic response of non-oil and gas reservoirs. However, when the number of integrations is small, the MF1 component based on EEMD is significantly affected by white noise. Compared with EMD and EEMD, the IMF1 component based on the CEEMD algorithm can accurately depict the distribution range of hydrocarbons with fewer computations. Finally, the method was applied to the Bohai A oilfield, and the results showed that A2 well is deployed to implement oil-water contact. The A2 well has a 0.9m drilled oil layer, 1.3m oil-water layer, and 6.1m water layer. The pre-drilling prediction results were consistent with the actual drilling results, which confirmed the feasibility and effectiveness of the method proposed in this study.

The beneficial exploration and development of deep shale gas requires seismic technology to implement the "sweet spot" area, in which it fractures easily for high production and has targeted the special demands for the imaging quality and information abundance of seismic data.First, high-quality imaging of faults, fault depressions, and low-order faults that are closely related to the structural preservation and evaluation of shale gas must be achieved.Second, high-quality, high-precision, and high information abundance pre-stack 5D seismic imaging data for the "sweet-spot" prediction of deep shale gas fracturing must be achieved.Driven by the key requirements of seismic data for the benefit exploration of deep shale gas in the Sichuan Basin, this study focused on seismic technology progress, including the design of geological target-oriented 3D geometry, processing of prestack full-azimuth information preservation, and its application in the DX target region of the Qijiang high-steep structural belt.Geological target-oriented 3D geometry utilizes multidimensional lighting and seismic data degradation processing to design an optimal observation system that meets the needs of geological target detection based on 3D surface and subsurface geological and seismic forward modeling.The prestack full-azimuth information preservation process integrates mountain seismic data regularization and image correction for time differences during the prestack migration processing to obtain prestack 5D seismic imaging data that fully retain offset and azimuth information based on the division of data with an offset vector tile (OVT).In the DX target area, 3D high-precision seismic acquisition of wide azimuth (full azimuth), high fold, and strong coupling with symmetrical and uniform sampling of shot and receiving points and OVT full-azimuth processing were applied, which can realize the full acquisition and retention of prestack azimuth-offset seismic information of deep shale gas geological targets to provide seismic imaging data with high quality, accuracy, and information abundance for structural preservation evaluation, design, and control of horizontal well trajectory, and fracturing prediction of deep shale gas.

In a desert area with rolling sand dunes, dynamite-excited ringing tends to occur as non-linear noises in common-shot gathers with the amplitude varying with dune height.On 3D stacked sections, ringing noises are weak in the direction parallel to receiver lines and strong in the direction perpendicular to receiver lines.Thus, ringing noises may be neglected in seismic data processing because of their indistinct responses in shot gathers and in inline direction.We use the near-surface velocity model derived from tomographic static correction for numerical simulation based on the wave equation and obtain synthetic ringing noises, which are consistent with field records and show as linear noises in common-receiver gathers.Ringing noises, which correspond to sand dunes at the wavefront on synthetic wave field snapshots, are oscillatory refracted waves between land surface and the phreatic water table.Ringing cycle is equal to the travel time of seismic waves in the sand layer; this means that ringing noises are linear in common-receiver gathers and thus could be easily suppressed after sorting common-shot gathers into common-receiver gathers.

Due to the influence of complicated near-surface conditions and huge sand dunes, desert seismic data generally suffer from the problems of low quality and weak signals in the zones of interest.In addition, with the existence of subsurface strong reflectors, the internal multiples are extensively developed and they are difficult to predicted and attenuated using existing demultiple methods, especially for the data-driven demultiple methods which require higher data quality.To solve these problems, we propose a new strategy by combining the useful and effective demultiple methods with a horizion-constrained inverse scattering series algorithm as the key component.Field data in western China tests show that the new strategy improves the signal-to-noise ratio and resolution of seismic data by effectively suppressing internal multiples and protecting primaries in the target zone.Thus, it improves the imaging quality of faults and reservoirs, and provides a solid data foundation for subsequent interpretation and evaluation.

Karst anomalies of the Maokou Formation in southeastern Sichuan are associated with faults and have a small scale, and their seismic reflection characteristics are not obvious. It is also limited by the overlaying of strong event shielding, resulting in a low resolution of seismic data, difficulty in identification, and a lack of prediction accuracy. In view of the above problems, this study explored a karst anomaly identification method based on seismic waveform decomposition technology. Compared to the traditional method, which has the problems of complex basis function selection and signal aliasing, the variational mode decomposition(VMD) method has the advantages of high resolution and complete decomposition of seismic information. Based on the optimization of basis pursuit, the VMD method was used to decompose the seismic data in the entire frequency band to obtain the mode components with different waveform characteristics. The correlation coefficient method was applied to classify these components and the largest component was removed to reduce the energy influence of the strong signal at the bottom of the Longtan Formation. Simultaneously, components that could characterize abnormal features were selected for reconstruction. The seismic data processed using the VMD method can effectively weaken the shielding effect of the strong reflection layer, highlight the lateral anomalies of the karst in the lower part of the events, and further improve the identification accuracy of faults and thin layers. Additionally, seismic attributes were extracted from the reconstructed data to comprehensively identify karst anomalies in the study area. The practical application results show that seismically weak signal information can be enhanced to a certain extent after the strong shielding layer is weakened. The verification was performed in combination with drilling data, which has achieved favorable results. This indicates that the proposed method is significant as a reference for the follow-up prediction of karst reservoirs in the southeastern Sichuan area.

For wide-azimuth seismic data, trace interval in gathers at far offsets is much smaller than the theoretical value; the spatial sampling rate tends to be more heterogeneous and trace interval varies quickly at large crossline offsets.Consequently, the time-distance curves of such linear coherent noises as surface waves and reverberation vary hyperbolically with crossline offset; thus, it is difficult to suppress such noises using routine methods.To address this issue, we develop a mean value-weighted approach based on cone filtering to reduce coherent noises in cross spread.The noise model is obtained through cone filtering, followed by mean value-weighted processing, for the separation of signals and noises to improve signal-to-noise ratio.Our approach is validated to be feasible and credible by field data processing as coherent noises in wide-azimuth seismic data could be effectively reduced without impairing signals and thus the signal-to-noise ratio is improved.

Recently, well JT1 and others in the Central Sichuan Basin have drilled multiple sets of thick beach facies reservoirs in the Sinian Paleozoic, and basement fractures have developed in the seismic section beside the well.Oil and gas discoveries were obtained in a multilayer system test of this well, demonstrating the three-dimensional exploration potential in Central Sichuan.Based on the latest high-quality two-and three-dimensional seismic, gravity, and magnetic, time-frequency electromagnetic, drilling, and logging data, the characteristics of basement faults in the Jianyang-Zhongjiang area in the Central Sichuan Basin and their control over the Sinian-Paleozoic stratigraphic sedimentation and hydrocarbon accumulation formation were analyzed in this study.Many NW-and NE-trending basement faults have developed in the Jianyang-Zhongjiang area.Basement faults developed in the pre-Sinian rift boundary and uplifted the sag transition zone within the rift.The basement fault controls the pre-sedimentary uplift and depression pattern of the Dengying Formation, generates fault horsts and grabens in different degrees(dominant and recessive) during the Xingkai rift, Caledonian movement, and Emei rift, and longitudinally controls the distribution of a large area of the Sinian-Paleozoic superimposed favorable facies belt The uplift area of the Dengying Formation is located in the high geomorphic part of the pre-Sinian uplift and is distributed along the NW and NE basement faults.The beach body of the Permian Maokou Formation developed in the Horst highland fault and is distributed along NW basement faults.The volcanic rocks of the Permian explosive facies are mainly distributed along the basement fault(volcanic channel) of the Horst graben transition zone, and the beach body of the Changxing Formation is deposited above the volcanic cone formed after the volcanic rock eruption and is distributed along the NW basement faults.The basement fault in the Jianyang-Zhongjiang area controls the distribution of Cambrian high-quality hydrocarbon sources in the Deyang-Anyue rift trough and the vertical multi-layer beach deposition and paleokarst to form high-quality reservoirs and control the distribution of dense shielding zones between reservoirs.As a guide, the basement fault formed a good "source reservoir configuration." The Sinian-Paleozoic has good hydrocarbon accumulation-forming conditions and great potential for three-dimensional exploration.

A strong reflection often exists in seismic data, such as high-velocity layer reflection formed by ash composition or mudstone dehydration and coal measure stratum reflection. These strong reflections shield the effective reflection information of the reservoir and weaken the reflection of the target layer, thereby affecting the reservoir prediction. To eliminate the influence of strong seismic reflection energy on the reflection characteristics of surrounding rocks, a matching pursuit method with the Ricker wavelet as the basis function is typically adopted. Because of the existence of side lobes in this wavelet, the side axis was disturbed during dereflection. Therefore, a strong shielding separation method based on Gaussian wavelet matching pursuit was proposed. As a side-lobe-free wavelet, the Gaussian wavelet has the advantages of fewer control parameters and concentrated energy and will not affect the paraxial while removing strong reflection. In this method, the Gaussian wavelet was used as the basic atom to establish a dynamic wavelet library, and the positions of the peak and trough of the strong reflection in-phase axis were obtained using the layer information. The peaks and troughs of the strong reflection in-phase axis were then decomposed and reconstructed, respectively. The number of iterations was controlled by setting the residual threshold, and the component most related to the strong seismic reflection component was removed during each reconstruction to reduce the strong reflection shield. One-dimensional and two-dimensional strong-reflection shielding models were designed to verify the adaptability of the method. The theoretical model and practical data application show that the method can effectively reduce strong reflection shielding, highlight the weak reflection information around the strong reflection, and exhibit less residual energy decomposition and does not affect the paraxial.

It is difficult to construct an accurate model for static correction and seismic imaging owing to heterogeneous wave absorption related to loess thickness change at the surface of the loess tableland, the southern Ordos Basin, and discontinuous seismic reflections were once supposed to be caused by poor data quality acquired.North China Oil and Gas Company performed extensive 3D seismic surveys in this region in the 12th five-year plan, but it is hard to interpret lithologic traps and low-relief structures due to chaotic and discontinuous reflections.According to the geologic model established after regional geologic research, regional strike-slip faults, instead of seismic acquisition, are supposed to be an important contributor to poor data quality and complicated reflections because these faults break stratal continuity and geobody integrity.Seismic interpretation using reprocessed data with significantly improved imaging quality shows well-developed strike-slip faults of different grades and associated fracture system generated by the Yanshan movement, which dominated tight oil accumulation and enrichment in the Mesozoic Erathem, especially in the Triassic System, in the south marginal basin.The geologic model lays the foundation for the integrated study of geology and geophysics in the loess tableland.We use seismic responses of fractures and seismic attributes for 3D characterization of fractured units, including their style, association, responses, period, and boundary.Based on the methodology and workflow of seismic data processing and interpretation in the surface conditions of loess tableland, high-yield tight oil accumulations were discovered, which opened new ground for hydrocarbon exploration by Sinopec in the loess tableland, the southern Ordos Basin.