Seismic Resolution Research Articles

Application of frequency extension processing technology in logging constrained inversion

The resolution of seismic data affects the accuracy of sand body identification. Generally, the higher the resolution of seismic data, the higher the accuracy of sand body identification. Aiming at the problem of low seismic resolution in block X, this paper attempts to increase the effective signal bandwidth of the original seismic data by using the frequency extension method, maximize the resolution on the premise of ensuring that the seismic data are not distorted, and then use the waveform indication inversion technology to predict the reservoir after the frequency extension. Compared with the drilled wells, it is found that the combination of frequency extension and waveform indication inversion can not only improve the vertical resolution of seismic data, but also maintain the lateral continuity of seismic data, which conforms to the distribution characteristics of sand body and has higher prediction accuracy. The method of frequency extension + waveform indication inversion has a good application prospect, which provides a new idea for the next step of sand body characterization and well location deployment.

A 3D complexity-adaptive approach to explore sparsity in elastic wave propagation

We have developed an adaptive approach for seismic modeling by which the computational cost of a 3D simulation can be reduced while retaining the resolution and accuracy. This azimuthal complexity adaptation (ACA) approach relies upon the inherent smoothness of wavefields around the azimuth of a source-centered cylindrical coordinate system. Azimuthal oversampling is thereby detected and eliminated. The ACA method has recently been introduced as part of AxiSEM3D, an open-source solver for global seismology. We use a generalization of this solver that can handle local-scale Cartesian models and that features a combination of an absorbing boundary condition and a sponge boundary with automated parameter tuning. The ACA method is benchmarked against an established 3D method using a model featuring bathymetry and a salt body. We obtain a close fit when the models are implemented equally in both solvers and an expectedly poor fit otherwise, with the ACA method running an order of magnitude faster than the classic 3D method. Furthermore, we evaluate maps of maximum azimuthal wavenumbers that are created to facilitate ACA. We determine how these maps can be interpreted in terms of the 3D complexity of the wavefield and in terms of seismic resolution. The expected performance limits of the ACA method for complex 3D structures are tested on the SEG/EAGE salt model. In this case, ACA still reduces the overall degrees of freedom by 92% compared with a complexity-blind AxiSEM3D simulation. In comparison to the reference 3D method, we again find a close fit and a speedup of a factor of 7. We explore how the performance of ACA is affected by model smoothness by subjecting the SEG/EAGE salt model to Gaussian smoothing. This results in a doubling of the speedup. Thus, ACA represents a convergent, versatile, and efficient method for a variety of complex settings and scales.

Impacts of seismic resolution on fault interpretation: Insights from seismic modelling

Seismic mapping of subsurface faults is hampered by factors such as seismic resolution, velocity control for depth conversion and human bias. Here, we explore the challenges and pitfalls related to interpreting normal faults by comparing objective and subjective uncertainties. A panel of 20 interpreters, with different geoscientific backgrounds, interpreted faults in modern conventional (dominant frequency 40 Hz) and high-resolution P-Cable (dominant frequency 150 Hz) 3D seismic data from the Hoop area, SW Barents Sea. The interpretations created by the test-panel were sorted into 10 scenarios characterized by different fault geometries. These scenarios were explored with 2(3)D point-spread function based convolution seismic modelling to investigate the potential of seismic data to image detailed fault architectures. The results reveal that: (1) Statistical analysis shows considerable variations between manually picked faults. (2) Identifying the location of fault tips is challenging and smaller antithetic faults are rarely recognizable. (3) Uncertainties arise from masking of closely spaced fault segments even where displacement values are large, showing distorted reflection signatures of apparent extensional fault tip monoclines. The distortion is larger for conventional versus high-resolution data. (4) In the conventional and high-resolution seismic data the vertical resolution of closely spaced reflections and small offset faults is 20 m and 5 m, respectively. (5) The utilisation of high-resolution seismic data, combined with seismic modelling, add confidence to interpretation of conventional seismic data in the same area. We conclude that subsurface fault mapping with seismic data requires insight in objective uncertainties associated with the data. Automatic machine-learning fault interpretation is void of subjective bias but still hampered by objective limitations. Further, a risking workflow requires acknowledgement of uncertainties that are transferred to seismic based fault analysis techniques such as juxtaposition analysis, quantitative fault seal analysis, and fault stability analysis.

Revisit seismic attenuation attributes: Influences of the spectral balancing operation on seismic attenuation analysis

Seismic attenuation analysis is important for seismic processing and quantitative interpretation. Nevertheless, classic quality factor estimation methods make certain assumptions that may be invalid for a given geologic target and seismic volume. For this reason, seismic attenuation attribute analysis, which reduces some of the theoretical assumptions, can serve as a practical alternative in apparent attenuation characterization. Unfortunately, most of the published literature defines seismic attenuation attributes based on a specific source wavelet assumption, such as the Ricker wavelet, rather than wavelets that exhibit the relatively flat spectrum produced by modern data processing workflows. One of the most common processing steps is to spectrally balance the data either explicitly in the frequency domain or implicitly through wavelet shaping deconvolution. If the poststack seismic data have gone through spectral balancing/whitening to improve their seismic resolution, the wavelet would exhibit a flat spectrum instead of a Ricker or Gaussian shape. We have addressed the influence of spectral balancing on seismic attenuation analysis. Our mathematical analysis shows that attenuation attributes are still effective for poststack seismic data after certain types of spectral balancing. More importantly, this analysis explains why seismic attenuation attributes work for real seismic applications with common seismic processing procedures. Synthetic and field data examples validate our conclusions.

The transition from salt diapir to weld and thrust: Examples from the Northern Flinders Ranges in South Australia

AbstractThe interactions between salt diapirs, thrust welds and thrusts in contractional belts are poorly understood due to, first, the inability of seismic data to distinguish between thrusts and welds or resolve associated sub‐resolution deformation, and second, the paucity of good field examples. The Warraweena area in the Northern Flinders Ranges of South Australia contains examples of Neoproterozoic to Early Cambrian squeezed diapirs linked by steep reverse faults formed during the Delamerian Orogeny. Benefiting from good field exposures, we use geological mapping, cross‐section construction and conceptual structural models to assess the three‐dimensional geometry and evolution of the structures, the lateral transition from diapirs to linking faults and the variability of associated meso‐ and small‐scale deformation. Three discrete diapirs consist of narrow outcrops of Callanna Group megabreccia (Willouran in age) up to 5‐km long. Their diapiric origin is confirmed by local development of caprock, steepening of flanking strata in composite halokinetic sequences and reworked diapir and roof debris in adjacent strata. The surrounding rocks display only background levels of small‐scale deformation. In contrast, the linking faults show no evidence of precursor diapirism, have fault‐related anticlines up to 100s of m in wavelength in their hanging walls, and an associated increase in small‐scale deformation (i.e. millimetre to metre scale folds, fractures and shear fabrics). The transitions from diapirs to faults occur within less than 200 m as short thrust welds at the diapir terminations. The exposed structures are analogous to those found on the subsurface of other salt basins such as the Gulf of Mexico and the South Atlantic conjugate margins. The results of this work can aid geoscientists evaluating three‐way traps against squeezed diapirs, welds or faults, and can help them to predict the style and abundance of both halokinetic and small‐scale structures that are below seismic resolution.

Fluvial reservoir architecture interpretation below the seismic resolution in an offshore oilfield

Reservoir discontinuity is a practical representation of reservoir heterogeneity, which leads to the nonuniform flow of hydrocarbons during production and increases the difficulties of producing the remaining oil in clastic reservoirs. For offshore oilfields, reservoir discontinuity analysis will have to rely on seismic data due to their sparse well distribution. However, traditional discontinuity detection methods are restricted to large-scale discontinuities (such as faults). It is difficult to detect small-scale discontinuities in seismic data such as interfaces of sands. To interpret small-scale discontinuities below the seismic resolution, we have adopted a direction-adaptive mathematical morphology gradient algorithm that can detect the boundaries of reservoir architectures in different directions on horizon-based seismic attributes. We elaborated a hierarchy of fluvial reservoir architectures and classified compound sandstones as different architectural elements according to the deposition period. Forward models were designed to analyze the seismic responses of the architectures. The results demonstrate that amplitude-related seismic attributes could be sensitive to different reservoir architectures below the seismic resolution. The amplitude-related seismic attributes can be extracted through a time window guided by the horizons. The horizon-based attributes can be treated as digital images, which may contain the information of compound sandstones with hidden discontinuity boundaries. Then, our algorithm is applied to detect discontinuity boundaries based on this extracted attribute. The application to field data in the Bohai Bay demonstrates that our algorithm can detect the discontinuity boundaries inside the compound sandstone, which is less than the seismic resolution. This method could enhance our capability to visualize and understand the complexity of reservoir heterogeneity.

Model of Seismic Wave Field Excited by Horizontally Distributed Charge

The amplitude-frequency characteristics of seismic wave field excited by an explosive source can directly affect the accuracy of seismic prospecting. To reveal the laws by which the horizontally distributed charge excites the amplitude-frequency characteristics, a method to calculate seismic wave field excited by horizontally distributed charge was studied in this paper. By taking the spherical cavity source model as the basis, the superposition method was applied to obtain the approach of calculating seismic wave field excited by horizontally distributed charge. Compared with numerical simulation, the error of this method was controlled under 7%. As a matter of fact, the distributive charge can effectively reduce the impact on ground vibration and increase the downward seismic wave energy. The charges that are horizontally distributed with 1 m interval can enhance the seismic wave resolution excited by explosive source. The research shows that the established theoretical model can correctly describe the amplitude-frequency characteristics of the seismic wave field excited by horizontally distributed charges.

Seismic Lithofacies Distribution Modeling Using the Single Normal Equation Simulation (SNESIM) Algorithm of Multiple-Point Geostatistics in Upper Assam Basin, India

Recently, multiple-point geostatistical simulation gained much attention for its role in spatial reservoir characterization/modeling in geosciences. Accurate lithofacies modeling is a critical step in the characterization of complex geological reservoirs. In this study, multiple-point facies geostatistics based on the SNESIM algorithm integrated with the seismic modeling technique is used as an efficient reservoir modeling approach for lithofacies modeling of the fluvial Tipam formation in the Upper Assam Basin, India. The Tipam formation acts as a potential reservoir rock in the Upper Assam Basin, India. Due to the basin geological complexity and limitation in seismic resolution, many discontinuities in depositional channels in this fluvial depositional environment have been identified using conventional lithofacies mapping. This study combines three techniques to reproduce continuity of the lithofacies for better reservoir modeling. The first is simultaneous prestack inversion for inverting prestack gathers with angle-dependent wavelets into seismic attributes. A cross-plot of P-impedance and VP/VS ratio from well-log data was used to classify the different reservoir lithofacies such as hydrocarbon sand, brine sand, and shale. The second is the Bayesian approach that incorporates probability density functions (PDFs) of non -parametric statistical classification with seismic attributes for converting the seismic attributes into lithofacies volume and the probability volumes of each type lithofacies. The third technique is multiple-point geostatistical simulation (MPS) using the Single Normal equation Simulation (SNESIM) algorithm applied to training images and probability volumes as constraints for a better lithofacies model. These integrated study results proved that MPS could improve reservoir lithofacies characterization.

Inversion-based non-stationary normal moveout correction along with prestack high-resolution processing

Seismic wave propagated in viscoelastic media always suffers from amplitude attenuation and velocity dispersion. It not only reduces seismic resolution, but also affects the quality of traditional stationary normal moveout (NMO) correction by distorting wavelets. To address both issues of attenuation and the wavelet stretch simultaneously, we present a non-stationary NMO correction method along with prestack high-resolution processing. Instead of invariant wavelets, spatiotemporal variant wavelets are adopted via an inversion scheme for implementing NMO correction and removing the attenuation effect. In the inversion, two goal-oriented constraints including the temporal sparsity and horizontal coherence of prestack reflectivity are combined into a structural sparsity constraint to impose on the data misfit between the synthetic non-stationary common-midpoint (CMP) gather and the observed one. Both constraints approximately represented by a convex l2,1 norm limit the optimal solution to structural sparsest reflectivity, contributing to construct the flattened corrected gather with invariant wavelets. Synthetic and field data examples illustrate performances of the inversion-based non-stationary NMO correction. Moreover, we compared the corrected gathers obtained by the improved approach with those by the traditional and inversion-based stationary NMO correction approaches, and took the gabor spectrum as a quality control. The proposed method produces more flatten events without stretch and gives consistent frequency components, thus improving prestack seismic resolution.

Use of spectral decomposition technique for mapping geologic features of ‘Reigh’ field, Onshore Niger Delta

Spectral Decomposition Technique based on Short-Window Discrete Fourier Transform (SWDFT) was applied to threedimensional (3D) seismic data obtained from ‘Reigh’ field, onshore Niger Delta with a view to enhancing stratigraphic interpretation for geological features which are beyond seismic resolution. Two sands units from the study area were studied to produce spectrally decomposedsurfaces. The result of the study revealed thin bed layer at the centre of the field on sand unit ‘A’. Sand-filled meandering channel wasdetected and highlighted in the northern part of sand unit ‘B’ based on Red-Green-Blue frequency modulation of spectral decomposition. The study has enhanced geologic understanding of the field by improving thin bed resolution, highlighting geologic features and displaying bed thickness variation of studied sand units in the study area.
 Keywords: geologic features, Niger Delta, seismic data, spectral decomposition

Unsupervised machine learning using 3D seismic data applied to reservoir evaluation and rock type identification

Net reservoir discrimination and rock type identification play vital roles in determining reservoir quality, distribution, and identification of stratigraphic baffles for optimizing drilling plans and economic petroleum recovery. Although it is challenging to discriminate small changes in reservoir properties or identify thin stratigraphic barriers below seismic resolution from conventional seismic amplitude data, we have found that seismic attributes aid in defining the reservoir architecture, properties, and stratigraphic baffles. However, analyzing numerous individual attributes is a time-consuming process and may have limitations for revealing small petrophysical changes within a reservoir. Using the Maui 3D seismic data acquired in offshore Taranaki Basin, New Zealand, we generate typical instantaneous and spectral decomposition seismic attributes that are sensitive to lithologic variations and changes in reservoir properties. Using the most common petrophysical and rock typing classification methods, the rock quality and heterogeneity of the C1 Sand reservoir are studied for four wells located within the 3D seismic volume. We find that integrating the geologic content of a combination of eight spectral instantaneous attribute volumes using an unsupervised machine-learning algorithm (self-organizing maps [SOMs]) results in a classification volume that can highlight reservoir distribution and identify stratigraphic baffles by correlating the SOM clusters with discrete net reservoir and flow-unit logs. We find that SOM classification of natural clusters of multiattribute samples in the attribute space is sensitive to subtle changes within the reservoir’s petrophysical properties. We find that SOM clusters appear to be more sensitive to porosity variations compared with lithologic changes within the reservoir. Thus, this method helps us to understand reservoir quality and heterogeneity in addition to illuminating thin reservoirs and stratigraphic baffles.

Spatial delineation of rock types in the Meramec Formation by integrating core and seismic measurements, Loyal area, Kingfisher County, Anadarko Basin

The Mississippian-age Sooner Trend Anadarko Canadian Kingfisher (STACK) area of Oklahoma is one of the more important new resource plays in North America. It consists of multilevel drilling targets, including mudrock, siltstone, and carbonate reservoirs, some of which are self-sourced and all of which require hydraulic fracturing to produce commercial quantities of oil. The efficacy of the fracturing relies on whether the created fracture network drains from producible rock types. We have integrated data at core and seismic resolution scales to map the rock types’ spatially exhaustive lateral and vertical variation for this new play. We measured porosity, permeability, saturated compressional wave (P-wave) and shear wave (S-wave) velocity, and density in the laboratory at 2 ft intervals on the cores. We defined rock types corresponding to engineering flow units based on porosity and permeability measurements. We mapped these rock types against alternative elastic property crossplots, including P-impedance, S-impedance, Poisson’s ratio, lambda-rho, and mu-rho. P- and S- impedance are the only two independent elastic properties measured on the core samples, and other elastic properties are calculated from these. Hence, the rock types showed equal sensitivity to all of the elastic property pairs. We observe a 30% difference between the core and seismic elastic values, attributed to dispersion and effective media effects. We managed this discrepancy between the core and surface seismic elastic values by simple linear scaling. We found that the P-impedance and Poisson’s ratio core measurements were easier to scale linearly to the corresponding seismic frequency measurements. Once scaled, we used Bayesian classification to map the P-impedance and Poisson’s ratio rock type template defined by the core measurements to the same elastic parameters measured by prestack seismic inversion. As we move away from the six cored wells deeper into the basin and more distal from the shelf, we encounter P-impedance/Poisson’s ratio pairs not seen in the core, resulting in areas where the rock type is “unknown.” The seismically predicted rock types show an excellent correlation at the well locations and provided stratigraphically reasonable images away from the wells, suggesting that as more wells are cored, these unknown rock types can be classified.

Deep learning for multitrace sparse-spike deconvolution

Sparse-spike deconvolution (SSD) is an important method for seismic resolution enhancement. With the wavelet given, many trace-by-trace SSD methods have been proposed for extracting an estimate of the reflection-coefficient series from stacked traces. The main drawbacks of trace-by-trace methods are that they neither use the information from the adjacent seismograms nor do they take full advantage of the inherent spatial continuity of the seismic data. Although several multitrace methods have been consequently proposed, these methods generally rely on different assumptions and theories and require different parameter settings for different data applications. Therefore, traditional methods demand intensive human-computer interaction. This requirement undoubtedly does not fit the current dominant trend of intelligent seismic exploration. Therefore, we have developed a deep learning (DL)-based multitrace SSD approach. The approach transforms the input 2D/3D seismic data into the corresponding SSD result by training end-to-end encoder-decoder-style 2D/3D convolutional neural networks (CNN). Our key motivations are that DL is effective for mining complicated relations from data, the 2D/3D CNN can take multitrace information into account naturally, the additional information contributes to the SSD result with better spatial continuity, and parameter tuning is not necessary for CNN predictions. We determine the significance of the learning rate for the training process’s convergence. Benchmarking tests on the field 2D/3D seismic data confirm that the approach yields accurate high-resolution results that are mostly in agreement with the well logs, the DL-based multitrace SSD results generated by the 2D/3D CNNs are better than the trace-by-trace SSD results, and the 3D CNN outperforms the 2D CNN for 3D data application.

Flow pathways in multiple-direction fold hinges: Implications for fractured and karstified carbonate reservoirs

Caves developed in carbonate units have a significant role in fluid flow, but most of these subsurface voids are below seismic resolution. We concentrated our study on four caves to determine the roles of fractures and folds in the development of karst conduits that may form flow pathways in carbonate reservoirs. We performed structural field investigations, petrographic analyses, and geometric characterization using Light Detection and Ranging (LIDAR) for caves in Neoproterozoic carbonates of the Salitre Formation, central part of the São Francisco Craton, Brazil. We found that the conduit shape, usually with an ellipsoidal cross-section, reflects the tectonic features and textural variations. Carbonate layers containing pyrite and low detritic mineral contents are generally karstified and appear to act as favorable flow pathways. Our results indicate that the development of the karst system is related to fracture corridors formed along parallel and orthogonal sets of fold hinges, which provide preferential pathways for fluid flow and contribute to the development of super-K zones. This study provides insights into the prediction of subseismic-scale voids in carbonate reservoirs, with direct application for the hydrocarbon and hydrogeology flow and storage.

The magneto-seismic method in geoscience

Key concepts and potential applications associated with a phenomenon hitherto unexplored by the geoscience community, which we have named the magneto-seismic effect, are introduced. The method is based on the simple principle that when an electric charge moves in the presence of an external magnetic field, the charge carrier experiences an instantaneous force, which is equal to the vector cross product of the current it carries and the magnetic field that is present. This “Lorentz force” can create both compressional and shear sound waves in electrical conductors by passing an alternating current through them via an electromagnetic source. In laboratory settings, this magneto-seismic effect can produce readily detectable rock frame displacements. This opens up the possibility of developing new experimental methods to interrogate elastic and poroelastic response of rocks in a broad frequency range from subhertz to megahertz, potentially closing the frequency gap between traditional ultrasonic characterization and properties of interest in the seismic frequency band. In exploration settings, electric current dipole/bipole sources, or novel rotating magnetic dipole sources, can be used to generate electric currents at depth. These currents produce seismic waves at interfaces (or boundaries) where conductivity abruptly changes. The amplitude and propagation directions of these generated seismic waves depend on the relative orientation of the interfaces (or boundaries) with respect to the earth's magnetic field. These seismic waves can then be recorded by receivers at the surface and, in principle, might be processed to yield a resistivity map with seismic resolution. It is shown that processing to obtain a signal from deep targets is significantly limited by seismic background noise. However, an acceptable signal-to-noise ratio might be achieved for shallower targets. The difference between the magneto-seismic response and the previously well-studied electro-seismic response will be discussed.

Discussion on the applicability of 90° phase conversion technique in seismic sedimentology

Since 1998, domestic and foreign scholars have conducted more systematic research on the theory and application technology of seismic sedimentology, and 90° phase conversion has been proposed as one of the core technologies of seismic sedimentology. But in actual research and application, the technology has not achieved the expected results. The 90° phase conversion intends to give the meaning of the seismic reflection event representing the stratum interface to the lithologic strata by means of phase shift. Due to the complexity and change of the underground strata, there are usually multiple lithology frequent thin interbeds. Therefore, the event axis in the seismic profile is the combined effect of multiple sets of thin interbeds. The seismic data after 90° phase conversion cannot convert the original seismic data from interface seismic profile to lithologic stratigraphic profile, and lacks clear geological meaning. Its application ability in seismic structure interpretation and seismic lithology interpretation is very limited. Therefore, it is difficult to become an applied technology of seismic sedimentology. Therefore, it is not appropriate to use the 90° phase conversion technology as the core technology of seismic sedimentology. This technology neither improves the seismic data resolution capability nor accurately converts the seismic profile into a lithological profile.

SEISMIC ATTRIBUTES AIDED DETECTION OF NW-SE TRENDING FAULTS DEVELOPED ON AN ISOLATED CARBONATE PLATFORM IN THE NW SIRTE BASIN, NORTH CENTRAL LIBYA

The lower and upper Paleocene reservoir formations, the primary producing formations in the northwest Sirte Basin, north-central Libya have complex structures which have an impact on the performance of the reservoirs. It is extremely crucial to understand the complex relationships between the fault networks and stratigraphy of the area for future field development. However, delineating faults particularly subtle faults is not an easy process due to the low signal-to-noise ratio in the post stack seismic data despite the effort and careful process of the pre-stack data. Seismic attributes are critical tools in detecting and enhancing major and minor fault interpretation beyond the seismic resolution of the conventional seismic dataset. This study utilizes variance, root mean square, and curvature attributes computed from the post-stack 3D seismic data acquired in the northwest Sirte Basin to detect major and minor faults along an isolated carbonate platform. A spectral whitening and median filter were applied to improve the quality of the data and remove random noise resulted from data acquisition and processing steps. Those methods were utilized to provide high-resolution seismic data and better show edges and structural features. Numerous faults have been detected in the study area. Most major faults in the lower and upper Paleocene reservoir formations are located along the margins of the isolated carbonate platform and have a NW-SE trend. Data conditioning and seismic attribute analyses applied on the 3-D seismic dataset effectively enhanced our understanding of the reservoir complexity and improve the detection of the major and minor faults and fracture zones in the study area.

Submarine channel and lobe hidden inside mass-transport deposits in the northern Gulf of Mexico

Despite numerous subsurface studies of mass-transport deposits (MTDs) using seismic data, internal characters of MTDs at the seismic scale are still not well understood, largely because of the limitation of seismic resolution. This study investigates Miocene-Pliocene MTDs in an understudied, hydrocarbon-rich region of the northern Gulf of Mexico. With the help of quantitative seismic geomorphology techniques, we utilized a high-quality 3D seismic dataset. We document sinuous channel and lobe features hidden within individual MTDs. This provides evidence for considering a seismically-defined MTD unit as amalgamated deposits of multiple events with different flow types (e.g., turbidity currents and cohesive flows), rather than an en masse deposit of a singular event. Additionally, we document an unshielded erosional remnant, which is generated by the bifurcation of a megascour marking the base of an MTD unit. Remnant strata are interpreted as sandy sediment waves. Channel, lobe, and erosional remnant features examined in this study demonstrate the presence of reservoir-prone facies encased within MTD units, forming stratigraphic traps. This research enhances our understanding of the intermingling nature of MTDs and other typical deep-water deposits, and the reservoir potential of MTDs and associated strata.

Seismic resolution enhancement by the Curvelet transform

Zone A in Nanpu Sag of Bohai Bay has the characteristics of multiple provenances, multiple sedimentary systems, fast phase transition, many faults, a short fault distance, thin reservoirs and rapid lateral changes. At present, due to the low resolution of seismic data and thin sand layer of the target formation, it is difficult to depict the channel sand body, and it is also difficult to meet the requirements of accurately implementing low amplitude structures, reservoir prediction and well location deployment. When a seismic wave propagates in the stratum, it has the characteristics of multi-scale, multi-resolution and multi-directionality, while the Curvelet transform has the advantage of expressing these characteristics. In this paper, according to the geological characteristics and seismic response characteristics of continental thin interbedded strata in zone A, the seismic data are first transformed to the Curvelet domain. Then, the formation absorption and seismic wave attenuation are compensated in the Curvelet domain. Lastly, the data mentioned above are inversely transformed into the time–space domain. This paper presents the method and process of using the Curvelet transform to enhance the resolution of seismic data in thin interbedded strata. The application of a theoretical model and field data show that this method can effectively enhance the resolution of seismic data while maintaining a high signal-to-noise ratio. The innovative use of this method in zone A lays the foundation for the follow-up work of this structure.

A robust approach to estimate Q from surface seismic data and inverse Q filtering for resolution enhancement

Accurate estimation of seismic quality factor (Q) is important in seismic data processing to correct for the velocity dispersion effects and to compensate for absorption losses through inverse Q filtering. To estimate it, often logarithmic spectral ratios of the non-stationary seismic signal between two depth levels are linearly inverted. As these ratios are usually derived from the standard Fourier transform (FT) which has a poor time-frequency resolution, this can lead to biased Q estimation. We have calculated spectral ratios from the high-resolution time-frequency spectrum using the Stockwell transform (ST). We then non-linearly inverted these improved spectral ratios to estimate Q using the Levenberg-Marquardt (LM) method. For a synthetic wedge model, results demonstrate a reasonable improvement in the accuracy of Q estimation with the combined ST-LM approach. Application on a real P-wave reflection seismic dataset revealed an anomalous attenuation zone of very low Q (29–75) values. Inverse Q filtering using the estimated Q profile has enhanced the seismic resolution below it and minimized the differential viscous losses. Frequency slice filtering on Q compensated data has improved the S/N ratio and hence the amplitude fidelity of reflectors.