Prestack Depth Imaging Research Articles

Reflection seismic imaging of subsurface geologic structures in the Bayan Obo mining area, China

A dense 2D seismic reflection survey was conducted at the Bayan Obo rare-earth-elements-Nb-Fe deposit in China to explore its geologic features and mineral endowment. A composite processing workflow was established for prestack depth imaging of this data set, which involved static correction to compensate for shifts caused by lateral inhomogeneities in near-surface layers and rugged topography. Standard methods were used to attenuate different types of noise and improve the signal-to-noise ratio of the data. A velocity model in the depth domain was obtained from refraction tomography and velocity analysis, and then used in migration. The preliminary interpretation of the final image revealed the mapping of mineralization at its true position in depth, indicating a relatively deep extension (approximately1.5 km). The results demonstrate the potential of seismic imaging as a complementary exploration tool to gravity and electromagnetic methods for mineral exploration purposes in the Bayan Obo mining area, providing a high-resolution seismic image and allowing for depth characterization of the mineral deposits. In addition, the images provide important information for guiding the selection of drilling borehole locations for deep exploration.

Pre-Stack Imaging for the Messinian Sub Salt Sequences in the Levantine Basin of the East Mediterranean: A Case Study, Offshore Lebanon

The Mediterranean Sea has a progressive geological significance; it is considered a vast extensive promising basin for gas exploration. Herodotus and Levantine basins are the main basins in the eastern Mediterranean basin, which are similar in their evolution stages and accommodate similar sedimentary sequences. The recent geophysical and petrophysical studies proved that Herodotus and Levantine basins are promising for gas with possible great reserves exceeding 2,000 bcm. Recent discoveries and increased exploration activities including seismic acquisition and offshore drilling made the Eastern Mediterranean a hot area for gas exploration, especially after the discovery of Zohr gas Field in 2015, offshore Egypt. However, the regional extension of the complex Messinian salt beds and domes make the exploration of high risk. The subsalt seismic imaging in a time domain and the resolution of the underlying carbonate/clastic reservoirs' primary reflections are a big challenge in this area. Therefore, the main objective of the present study is to improve sub-salt imaging with much more accurate interval velocity estimation. In the study area, offshore Lebanon, the delineated structures in the sub-salt imaging after the Pre-stack Depth Imaging were more significant compared to the Pre-Stack Time Imaging which provided optimum sub-salt imaging and enabled the accurate interpretation of the main geologic features which may increase the certainty level of the hydrocarbon exploration and discoveries.

Seismic Imaging of Mineral Exploration Targets: Evaluation of Ray- vs. Wave-Equation-Based Pre-Stack Depth Migrations for Crooked 2D Profiles

Seismic imaging is now a well-established method in mineral exploration with many successful case studies. Seismic data are usually imaged in the time domain (post-stack or pre-stack time migration), but recently pre-stack depth imaging has shown clear advantages for irregular/sparse acquisitions and very complex targets. Here, we evaluate the effectiveness of both ray-based and wave-equation-based pre-stack depth imaging methodologies applied to crooked-line 2D seismic reflection profiles. Seismic data were acquired in the Kylylahti mining area in eastern Finland over severely folded, faulted and subvertical Kylylahti structure, and associated mineralization. We performed 3D ray-based imaging, i.e., industry-standard Kirchhoff migration and its improved version (coherency migration, CM), and wave-equation-based migration, i.e., reverse time migration (RTM) using a velocity model built from first-arrival traveltime tomography. Upon comparing the three different migrations against available geological data and models, it appeared that CM provided the least noisy and well-focused image, but failed to image the internal reflectivity of the Kylylahti formation. RTM was the only method that produced geologically plausible reflections inside the Kylylahti formation including a direct image of the previously known shallow massive sulfide mineralization.

Sensitivity analysis to near-surface velocity errors of the Kirchhoff single-stack redatuming of multi-coverage seismic data

We present a study of a Kirchhoff-type redatuming approach for irregular multi-coverage land seismic data to remove the disturbing influence of rugged topography and a considerable near-surface velocity inhomogeneity, like a thick weathering layer, on the subsurface reflections. The redatuming method is physically more justified than the commonly used field-static correction methods that provide - in the indicated situation - non-physical temporal adjustments (field statics) by shifting traces in time, which lead to sub-optimal imaging and inversion of the reflections. The redatuming procedure studied here is different: It transforms the multi-coverage seismic reflection data on the irregular measurement surface to a regular measurement configuration on a pre-specified datum, below the inhomogeneous velocity overburden. This is done by stacking/summing the input traces with certain operators or traveltime curves which are calculated by ray tracing. In this way, incoherent subsurface reflections in the input data become coherent and thus recognizable in the output data. To have this happen, the redatuming operation requires a good approximation of the overburden velocity model and a reasonable one of the sub-burden homogeneous velocity model (below the datum). Then the multi-coverage output data on the new flat datum can be imaged and inverted much better than with standard data processing, i.e., with field-static correction. This work is dedicated to explaining the single-stack Kirchhoff-type redatuming approach kinematically using a synthetic model and data based on a real geological situation. However, our main aim is to study the sensitivity of this redatuming method to errors of the overburden velocity model, which is determined from multi-coverage seismic data using first arrivals traveltime tomography commonly used in the oil industry. We apply the redatuming process to a multi-coverage synthetic seismic dataset generated from the models that represent the real geological situation with irregular measurement surfaces and inhomogeneous overburden or near-surface velocity. To assess accuracy, the redatumed data was migrated in depth-domain and the results showed the correct positioning of the reflectors. The results revealed that this redatuming method produces reliable and accurate redatumed data even using approximate velocity models, which can be useful for prestack time and depth imaging.

Detection of point scatterers using diffraction imaging and deep learning

ABSTRACTDiffracted waves carry high‐resolution information that can help interpreting fine structural details at a scale smaller than the seismic wavelength. However, the diffraction energy tends to be weak compared to the reflected energy and is also sensitive to inaccuracies in the migration velocity, making the identification of its signal challenging. In this work, we present an innovative workflow to automatically detect scattering points in the migration dip angle domain using deep learning. By taking advantage of the different kinematic properties of reflected and diffracted waves, we separate the two types of signals by migrating the seismic amplitudes to dip angle gathers using prestack depth imaging in the local angle domain. Convolutional neural networks are a class of deep learning algorithms able to learn to extract spatial information about the data in order to identify its characteristics. They have now become the method of choice to solve supervised pattern recognition problems. In this work, we use wave equation modelling to create a large and diversified dataset of synthetic examples to train a network into identifying the probable position of scattering objects in the subsurface. After giving an intuitive introduction to diffraction imaging and deep learning and discussing some of the pitfalls of the methods, we evaluate the trained network on field data and demonstrate the validity and good generalization performance of our algorithm. We successfully identify with a high‐accuracy and high‐resolution diffraction points, including those which have a low signal to noise and reflection ratio. We also show how our method allows us to quickly scan through high dimensional data consisting of several versions of a dataset migrated with a range of velocities to overcome the strong effect of incorrect migration velocity on the diffraction signal.

An integrated seismic study of a shale reservoir in the Sichuan Basin, onshore China

We describe an integrated seismic evaluation for the Longmaxi shale gas potential in the central part of the Sichuan Basin, onshore China, which benefits from innovations in high-density 3D seismic, borehole-based vertical seismic profiling (VSP), and passive seismic recording for microseismic monitoring. The geology of the basin has a complex history that creates several geophysical challenges, including strong multiple contamination and the requirement for high-resolution data to enable detailed structural and stratigraphic mapping. For the 3D surveys, we adopted a new wide-azimuth and high-density acquisition design. A large part of the processing was devoted to noise removal, optimizing surface-consistent processes including deconvolution, and thorough testing of data-driven internal multiple attenuation. Prestack depth imaging is important for accurate geosteering of long horizontal trajectories within a narrow target window, and our resulting images in depth provide a more planar target structure than with (more routine) time imaging. The more planar true structure was confirmed by drilling. For the borehole seismic calibration, vibroseis was used as the VSP source in preference to the standard use of explosives. This resulted in greater consistency of the waveforms and better amplitude and timing of events with which to constrain the 3D seismic processing and imaging. Surface microseismic monitoring of the stimulation was achieved using a new and bespoke design. The detected microseismic activity helped support and optimize the real-time fracture operations, mitigate casing deformation, obtain in-situ stress fields, and understand the control of preexisting geologic features. The innovations in surface seismic, VSP, and microseismic, along with the integration of other disciplines, contributed to the project's overall success.

Revealing new hydrocarbon potential through Q-compensated prestack depth imaging at Wenchang Field, South China Sea

Wenchang Field in the South China Sea contains a well-developed fault system, resulting in complex subsurface geology. Imaging the complex fault system plays an important role in hydrocarbon exploration in this area since the fault system forms a link between the source rocks and reservoirs. However, it is difficult to obtain a high-quality depth image of the fault system due to the effects of complex velocity and seismic absorption. Inaccurate depth velocities lead to fault shadows and structure distortions at the target zone. Absorption effects further deteriorate seismic imaging as they cause amplitude attenuation, phase distortion, and resolution reduction. We demonstrate how a combination of high-resolution depth velocity modeling and Q imaging work together to resolve these challenges. This workflow provides a step change in image quality of the complex fault system and targeted source rocks at Wenchang Field, significantly enhancing structure interpretation and reservoir delineation. A couple of commercial discoveries have been made, and several other potential hydrocarbon reservoirs have been identified based on the reprocessed data, which reveal new hydrocarbon potential in this region.

Cost-Effective Seismic Exploration: 2D Reflection Imaging at the Kylylahti Massive Sulfide Deposit, Finland

We show that by using an advanced pre-stack depth imaging algorithm it is possible to retrieve meaningful and robust seismic images with sparse shot points, using only 3–4 source points per kilometer along a seismic profile. Our results encourage the use of 2D seismic reflection profiling as a reconnaissance tool for mineral exploration in areas with limited access for active seismic surveys. We used the seismic data acquired within the COGITO-MIN project comprising two approximately 6 km long seismic reflection profiles at the polymetallic Kylylahti massive sulfide mine site in eastern Finland. The 2D seismic data acquisition utilized both Vibroseis and dynamite sources with 20 m spacing and wireless receivers spaced every 10 m. For both source types, the recorded data show clear first breaks over all offsets and reflectors in the raw shot gathers. The Kylylahti area is characterized by folded and faulted, steeply dipping geological contacts and structures. We discuss post-stack and pre-stack data processing and compare time and depth imaging techniques in this geologically complex Precambrian hardrock area. The seismic reflection profiles show prominent reflectors at 4.5–8 km depth utilizing different migration routines. In the shallow subsurface, steep reflectors are imaged, and within and underneath the known Kylylahti ultramafic body reflectivity is prominent but discontinuous.

Seismic depth imaging of sequence boundaries beneath the New Jersey shelf

Numerical modelling of fluid flow and transport processes relies on a well-constrained geological model, which is usually provided by seismic reflection surveys. In the New Jersey shelf area a large number of 2D seismic profiles provide an extensive database for constructing a reliable geological model. However, for the purpose of modelling groundwater flow, the seismic data need to be depth-converted which is usually accomplished using complementary data from borehole logs. Due to the limited availability of such data in the New Jersey shelf, we propose a two-stage processing strategy with particular emphasis on reflection tomography and pre-stack depth imaging. We apply this workflow to a seismic section crossing the entire New Jersey shelf. Due to the tomography-based velocity modelling, the processing flow does not depend on the availability of borehole logging data. Nonetheless, we validate our results by comparing the migrated depths of selected geological horizons to borehole core data from the IODP expedition 313 drill sites, located at three positions along our seismic line. The comparison yields that in the top 450 m of the migrated section, most of the selected reflectors were positioned with an accuracy close to the seismic resolution limit (≈ 4 m) for that data. For deeper layers the accuracy still remains within one seismic wavelength for the majority of the tested horizons. These results demonstrate that the processed seismic data provide a reliable basis for constructing a hydrogeological model. Furthermore, the proposed workflow can be applied to other seismic profiles in the New Jersey shelf, which will lead to an even better constrained model.

Prestack imaging of seismic data using Lp iterative reweighted least-squares wavefield extrapolation filters in the frequency-space domain

A stable explicit depth wavefield extrapolation is obtained using [Formula: see text] iterative reweighted least-squares (IRLS) frequency-space ([Formula: see text]-[Formula: see text]) finite-impulse response digital filters. The problem of designing such filters to obtain stable images of challenging seismic data is formulated as an [Formula: see text] IRLS minimization. Prestack depth imaging of the challenging Marmousi model data set was then performed using the explicit depth wavefield extrapolation with the proposed [Formula: see text] IRLS-based algorithm. Considering the extrapolation filter design accuracy, the [Formula: see text] IRLS minimization method resulted in an image with higher quality when compared with the weighted least-squares method. The method can, therefore, be used to design high-accuracy extrapolation filters.

Enhanced 3D prestack depth imaging of broadband data from the South China Sea: a case study

We present a case study of prestack depth imaging for data from the South China Sea using an enhanced work flow with cutting edge technologies. In the survey area, the presence of complex geologies such as carbonate pinnacles and gas pockets creates challenges for processing and imaging: the complex geometry of carbonates exhibits 3D effect for wave propagation; deriving velocity inside carbonates and gas pockets is difficult and laborious; and localised strong attenuation effect from gas pockets may lead to absorption and dispersion problems. In the course of developing the enhanced work flow to tackle these issues, the following processing steps have the most significant impact on improving the imaging quality: (1) 3D ghost wavefield attenuation, in particular to remove the ghost energy associated with complex structures; (2) 3D surface-related multiple elimination (SRME) to remove multiples, in particular multiples related to complex carbonate structures; (3) full waveform inversion (FWI) and tomography-based velocity model building, to derive a geologically plausible velocity model for imaging; (4) Q-tomography to estimate the Q model which describes the intrinsic attenuation of the subsurface media; (5) de-absorption prestack depth migration (Q-PSDM) to compensate the earth absorption and dispersion effect during imaging especially for the area below gas pockets. The case study with the data from the South China Sea shows that the enhanced work flow consisting of cutting edge technologies is effective when the complex geologies are present.

Constraining a 3D anisotropic tomography inversion with 800 wells – A Canadian oil sands case history

This Canadian oil-sands case history is a very shallow play with a complex geology that includes Quaternary thrusting at surface, sinkholes, and highly karsted Devonian carbonates at the base of the notoriously complex McMurray reservoir. Despite this challenging environment, we were able to demonstrate that Depth Imaging brought significant improvements as compared to the routinely used time imaging. Recent developments in Anisotropic Pre-Stack Depth Imaging technologies provided a better focused and better positioned 3D subsurface image that accurately tied several hundreds of wells. These results were achieved using steering filters, solver bounds and simultaneous multi-parameter tomography inversion while constraining the tomography updates with the well top picks from over 800 wells. Surveys of different vintages, geometries, orientations and shooting directions were regularized using 5D interpolation and merged together. Besides a better imaging of the subsurface, one of main objective of the project was the characterization of the McMurray reservoir. To that aim, the Anisotropic Pre-Stack Depth Migration (APSDM) generated better conditioned Offset Vector Tile gathers for subsequent pre-stack inversion work. The Alberta oil sands are one of the largest bituminous hydrocarbon reserves in the world (Alberta Energy Regulator, 2015). At reservoir temperature, the bitumen is so viscous that it can almost be considered as a solid. In situ thermal recovery processes such as steam-assisted gravity drainage (SAGD) that lower viscosity and increase mobility are required to extract the bitumen from the reservoir. SAGD operations consist of horizontal well pairs that are drilled into the base of the reservoir. In each pair, one well is drilled about 5 m directly above the other well. The top well is injected with steam to melt the bitumen. The bitumen seeps down towards the bottom producing well, which pumps the bitumen to the surface. The well pairs are generally configured to about ten parallel horizontal well pairs that are around 100 m apart horizontally and are 1000 m long, which constitute a 1-km2 pad.

Time-Lapse Seismic for Reservoir Management: Case Studies From Offshore Niger Delta, Nigeria

Summary This paper presents case studies focused on the interpretation and integration of seismic reservoir monitoring from several fields in conventional offshore and deepwater Niger Delta. The fields are characterized by different geological settings and development-maturity stages. We show different applications varying from qualitative to quantitative use of time-lapse (4D) seismic information. In the first case study, which is in shallow water, the field has specific reservoir-development challenges, simple geology, and is in phased development. On this field, 4D seismic, which was acquired several years ago, is characterized by poor seismic repeatability. Nevertheless, we show that because of improvements from seismic reprocessing, 4D seismic makes qualitative contributions to the ongoing field development. In the second case study, the field is characterized by complex geological settings. The 4D seismic is affected by overburden with strong lateral variations in velocity and steeply dipping structure (up to 40°). Prestack-depth-imaging (PSDM) 4D seismic is used in a more-qualitative manner to monitor gas injection, validate the geologic/reservoir models, optimize infill injector placement, and consequently, enhance field-development economics. The third case study presents a deep offshore field characterized by a complex depositional system for some reservoirs. In this example, good 4D-seismic repeatability (sum of source- and receiver-placement differences between surveys, dS+dR) is achieved, leading to an increased quantitative use of 4D monitoring for the assessment of sand/sand communication, mapping of oil/water (OWC) front, pressure evolution, and dynamic calibration of petro-elastic model (PEM), and also as a seismic-based production-logging tool. In addition, 4D seismic is used to update seismic interpretation, provide a better understanding of internal architecture of the reservoirs units, and, thereby, yield a more-robust reservoir model. The 4D seismic in this field is a key tool for field-development optimization and reservoir management. The last case study illustrates the need for seismic-feasibility studies to detect 4D responses related to production. In addition to assessing the impact of the field environment on the 4D- seismic signal, these studies also help in choosing the optimum seismic-survey type, design, and acquisition parameters. These studies would possibly lead to the adoption of new technologies such as broad-band streamer or nodes acquisition in the near future.

Amplitude-preserving reverse time migration: From reflectivity to velocity and impedance inversion

Conventional methods of prestack depth imaging aim at producing a structural image that delineates the interfaces of the geologic variations or the reflectivity of the earth. However, it is the underlying impedance and velocity changes that generate this reflectivity that are of more interest for characterizing the reservoir. Indeed, the need to generate a better product for geologic interpretation leads to the subsequent application of traditional seismic-inversion techniques to the reflectivity sections that come from typical depth-imaging processes. The drawback here is that these seismic-inversion techniques use additional information, e.g., from well logs or velocity models, to fill the low frequencies missing in traditional seismic data due to the free-surface ghost in marine acquisition. We found that with the help of broadband acquisition and processing techniques, the bandwidth gap between the depth-imaging world and seismic inversion world is reducing. We outlined a theory that shows how angle-domain common-image gathers produced by an amplitude-preserving reverse time migration can estimate impedance and velocity perturbations. The near-angle stacked image provides the impedance perturbation estimate whereas the far-angle image can be used to estimate the velocity perturbation. In the context of marine acquisition and exploration, our method can, together with a ghost compensation technique, be a useful tool for seismic inversion, and it is also adaptable to a full-waveform inversion framework. We developed synthetic and real data examples to test that the method is reliable and provides additional information for interpreting geologic structures and rock properties.

A Fourier integral algorithm and its GPU/CPU collaborative implementation for one-way wave equation migration

Pre-stack one-way wave equation (OWE) is a useful tool for seismic imaging and modeling. Since the idea of OWE appeared in the 1970s, geophysicists have made great effort to improve the accuracy of the one-way wave equation extrapolators. In this paper, we present the idea of solving OWE using the Fourier integral method, which represents OWE as a Fourier integral equation and solves it in dual spaces (both space and wave-number domains). By doing this, we can propagate wave-fields up to nearly 90° angle from the vertical direction in the presence of lateral velocity variations. The proposed method is stable, does not suffer from the numerical dispersion, and overcomes the azimuthal anisotropy problem when extended to three dimensions. The computation cost of the Fourier integral method is too high and was considered impractical for a conventional computer. In this paper, we take advantages of the Graphic Processing Unit (GPU) and use the matrix multiplication technique to accelerate the algorithm. The speedup ratio we obtained is tens of hundreds times so that the method can be applied to a real project for pre-stack depth imaging.

Enhanced prestack depth imaging of wide-azimuth data from the Gulf of Mexico: A case history

We present a case study of enhanced imaging of wide-azimuth data from the Gulf of Mexico utilizing recent technologies; and we discuss the resulting improvements in image quality, especially in subsalt areas, relative to previous results. The input seismic data sets are taken from many large-scale wide-azimuth surveys and conventional narrow-azimuth surveys located in the Mississippi Canyon and Atwater Valley areas. In the course of developing the enhanced wide azimuth processing flow, the following three key steps are found to have the most impact on improving subsalt imaging: (1) 3D true azimuth surface-related multiple elimination (SRME) to remove multiple energy, in particular, complex multiples beneath salt; (2) reverse-time migration (RTM) based delayed imaging time (DIT) scans to update the complex subsalt velocity model; and (3) tilted transverse isotropic (TTI) RTM to improve image quality. Our research focuses on the depth imaging aspects of the project, with particular emphasis on the application of the DIT scanning technique. The DIT-scan technique further improves the accuracy of the subsalt velocity model after conventional ray-based subsalt tomography has been performed. We also demonstrate the uplift obtained by acquiring a wide-azimuth data set relative to a standard narrow-azimuth data set, and how orthogonal wide-azimuth is able to enhance the subsalt illumination.

A case study for azimuthally anisotropic prestack depth imaging of an onshore Alaska prospect

In a study of the Sterling-Triangle area of Alaska, U.S.A., we initiated prestack depth migration (PSDM) to improve imaging on a prospect initially identified on a prestack time-migrated (PSTM) volume. Under the isotropic media assumption, the first few iterations of the reflection tomography had difficulty in converging to the proper velocity model. Upon further investigation, a very-high-velocity conglomerate layer was identified in the middle of the section across the whole survey area. We adopted the salt-flood practice, routine in depth-imaging salt provinces such as the Gulf of Mexico. The strategy was to focus on the shallow section above the conglomerate first, followed by a constant-velocity flood for picking the conglomerate base. The finalisotropic PSDM result showed that significant residual moveout differences existed on gathers along different azimuths. The net anisotropic effect on the isotropic PSDM was a degraded final PSDM volume. In the subsequent anisotropic PSDM work, azimuthally variant horizontal velocities were allowed in the model building. Common-image-point (CIP) gathers were created along different azimuths using sectored input gathers. Residuals picked on the sectored CIP gathers were used in joint tomography to invert different horizontal velocities. Incorporating significant well information, we built an anisotropic velocity model such that the azimuthal moveout on the butterfly gathers was essentially flat. The resulting anisotropic PSDM was consistent with well data and could be interpreted with much higher confidence.

New methods of improving seismic data to aid understanding of passive margin evolution: a series of case histories from offshore west of Ireland

Abstract Deepwater sedimentary basins are attracting increased attention from the hydrocarbon industry and academia as they remain one of the last geological frontiers still to be fully explored and understood. As part of a regional project to understand basin development offshore Ireland, we have developed and tested new ways of improving seismic images, and of incorporating these improvements into geological interpretations. Here we illustrate this methodology using three case histories from the Porcupine, Slyne and Erris Basins. In each case, the first stage of the workflow consists of reprocessing a selection of key seismic data. Processing includes relative amplitude preservation and advanced demultiple and interpretation-driven pre-stack depth imaging. Interpretation of the data is assisted by incorporating products such as multiple models, pre-stack gathers, velocity models and attributes. Finally, we show how a velocity model can be inverted to exhumation estimates. The results and approach developed here can be applied to other deepwater exploration areas.

Prestack depth imaging of ocean-bottom node data

Ocean-bottom node acquisitions provide high-quality data but usually have large distances between the nodes because of cost. This makes the use of conventional processing difficult and has led to relatively little interest in such data for industrial purposes. We have considered a three-step workflow specifically designed for prestack depth imaging of P-waves recorded by ocean-bottom nodes. It consists of multiple attenuation, velocity model estimation, and prestack depth migration. Whereas multiple attenuation and tomography use data in the common-receiver domain, migration is performed in the common-angle domain. One of the main features is the handling of the sparse receiver geometry during velocity model estimation: the reciprocity of the PP-Green’s functions is used to obtain the required tomographic input using only the common-receiver gathers. The tomographic method also provides an estimate of the geologic dip, which is used to limit the migration operator. This provides migrated images free of migration smiles. The workflow contains no additional assumptions compared to those used to process ocean-bottom cable data. We validate the workflow on a 2D line extracted from a 3D real data set acquired in the North Sea. The results show that it is possible to use ocean-bottom data efficiently for prestack depth imaging.

3‐D Seismic Interpretation

This volume is a brief introduction aimed at those who wish to gain a basic and relatively quick understanding of the interpretation of three‐dimensional (3‐D) seismic reflection data. The book is well written, clearly illustrated, and easy to follow. Enough elementary mathematics are presented for a basic understanding of seismic methods, but more complex mathematical derivations are avoided. References are listed for readers interested in more advanced explanations. After a brief introduction, the book logically begins with a succinct chapter on modern 3‐D seismic data acquisition and processing. Standard 3‐D acquisition methods are presented, and an appendix expands on more recent acquisition techniques, such as multiple‐azimuth and wide‐azimuth acquisition. Although this chapter covers the basics of standard time processing quite well, there is only a single sentence about prestack depth imaging, and anisotropic processing is not mentioned at all, even though both techniques are now becoming standard.