Mapping Seismic Data Research Articles

Migration and controls of Shenhu submarine canyons in the upper continental slope of northern South China Sea: Insights from three‐dimensional seismic data mapping

AbstractSubmarine canyons, prominent features on continental margins, hold significant scientific and engineering implications. Despite extensive research on various types of submarine canyons, current understanding of those canyons developed on the upper continental slope, recognized as the most common type globally, remains limited. The Shenhu Canyons on the upper continental slope of the northern South China Sea, comprising over 19 subparallel features persistently developed from the Late Miocene to Quaternary, offer an excellent opportunity for in‐depth study. Previous assumptions suggested a unidirectional eastward migration of these canyons parallel to the host margin, primarily based on observations from two‐dimensional transverse seismic profiles. However, this study's analysis using three‐dimensional seismic data mapping reveals that not all canyons have migrated eastward; 28% display an opposite or a zigzag patterned migration, challenging previous assumptions. The eastward migration of the Shenhu Canyons on the eastern slope of the palaeo‐Pearl River shelf‐edge delta can be linked to the south‐east–southward progradation of the host margin and the palaeo‐shelf‐edge delta. However, the overall eastward migration pattern is complicated by submarine landslides and turbidity current processes. Landslides can influence the direction and magnitude of canyon migration through four mechanisms: turbidity current diversion; retrogressive development of canyon‐wall landslides; retrogressive landslides on surrounding open slopes; and emplacement of landslides in canyon thalwegs. These mechanisms may result in widening, bifurcation, confluence or obstruction of canyons, contributing to canyon migration. Erosion by turbidity currents can trigger canyon‐wall failures, which in turn promote the lateral migration of the canyons. If overspilled turbidity currents lead to the growth of levées in the lower reaches, canyon confinement increases, suppressing lateral migration. The inherited high‐gradient Palaeogene syn‐rift tectonic slope, combined with the depositional delta‐front slope of the palaeo‐shelf‐edge delta, creates favourable conditions for the initiation and persistent development of the straight Shenhu Canyons. This comprehensive analysis provides valuable insights into the complex dynamics and factors influencing the migration of upper continental slope submarine canyons.

Seismic Inversion Based on 2D-CNNs and Domain Adaption

Deep learning has been applied to tackle the seismic inversion problem, bringing more efficiency and accuracy. However, bad spatial continuity and poor generalizability limit the practical application. To solve these problems, we propose a 2D end-to-end seismic inversion method based on domain adaption. Firstly, the proposed 2D network learns the inversion mapping of seismic data under the constraint of domain adaption layer, which can reduce the difference between the features of real seismic data and synthetic seismic data, improving the generalization ability on real seismic data. Then, the trained model is finetuned with well logging data. In the first process, the spatial continuity of the inversion result is guaranteed by the 2D training scheme. Meanwhile, due to the constraint of the domain adaption layer, our model not only performs well on the synthetic data but also has good generalization ability on the real seismic data. And we carefully discuss the mechanism of domain adaption layer. In the second process, finetuning introduces well logging information, which can further improve the ability to invert details. Moreover, in order to improve the inversion accuracy on real seismic data, we develop a new training data generation method that can generate the synthetic samples close to the real samples, and a 2.5D training strategy is adopted to improve the continuity of the 3D data. The experiments on both synthetic and real seismic data show that our method performs better than both the recursive inversion method and the 1D closed-loop CNN methods.

Characterizing Concealed Fault Systems by Integrating Field Data Mapping and Laboratory Experiments: A Case Study of the Huawa Area in East China

Concealed faults can be important for understanding the regional structural geology and the subsurface fluid distribution. However, such faults are usually difficult to identify and characterize because of their small size and complex mechanism. To address this issue, we present an integrated approach of three-dimensional seismic data mapping and physical modeling experiments to examine the geometrical and kinematic characteristics of concealed faults and their relationship with the main faults in the Huawa area, east China. Three series of experiments were designed to characterize the differences in the scale of concealed faults and main faults, which also allowed us to examine how the concealed faults grow with the main faults in the area. Through this integrated study, we have demonstrated that: 1) NE-SW-striking concealed faults are below the resolution of the available seismic datasets and not easily recognized in seismic sections and that most of them grew later than the E-W-striking main faults, with some of them having grown at the same time; 2) pre-existing faults, rather than asymmetry of the basin structure, affect the faults that develop during subsequent episodes of extension; 3) E-W-striking pre-existing faults under a NW-SE stress direction of extension are most likely the formation mechanism of concealed faults. This study is of reference value in the interpretation of concealed faults in other regions.

Oriented prestack time migration using local slopes and predictive painting in the common-source domain for planar reflectors

Seismic imaging techniques often require an input velocity model. Velocity analysis is one of the most critical stages in seismic data processing. Standard ways to find the velocity model from seismic data in the time domain are constant velocity stack and semblance velocity analysis that may be time consuming and labor intensive. Oriented/velocity-less imaging using local event slopes is an alternative to the conventional imaging techniques. In some previous oriented techniques, seismic data must be sorted in two different domains, whereas seismic data are not always available in both domains and the use of interpolation is inevitable in such cases. Other methods are developed in terms of the higher order derivatives of traveltime with respect to offset, whereas estimation of the higher order derivatives is difficult to achieve with the required accuracy. We addressed the limitations by developing an oriented local slope based prestack time migration technique in only one domain: the common-source domain. The migration technique is developed for reflectors with small curvature. In the proposed approach, the need for the estimation of higher order derivatives is replaced by a point-to-point mapping of seismic data using the predictive painting technique. The theoretical contents of the proposed technique are tested on a simple synthetic data example and applied to a field data set.

SPS to Seismic Data Mapping: An AWK Script for Merging Field Geometry with Seismic Data

SPS (Shell Processing Support) files contain vital acquisition information and are standard input for merging field geometry with seismic data. These files are interrelated and must conform one another and the data as well for some of the prime fields. But on many occasions, it does not hold and requires user's massive efforts to rectify this correspondence. The best way to circumvent this problem is to automate the procedure through coding a script. With this concept, an AWK script is coded, which replenishes processing geophysicist's inventory with data mapped SPS files which can straight away be input for updating trace headers of seismic data.

Impact of 3D Seismic Technologies on Sedimentology Study

Progress of 3D seismic technologies has played a vital role in the developments of sedimentology in terms of analytical methodology and concepts. High-density and high-resolution 3D seismic data can be used to reconstruct 3D views of sedimentary paleo-evironment by direct imaging of depositional elements and can also be used to analyze sedimentary paleo-evironment evolution in 3D detail by mapping facies variability at a specific geologic time by slicing though it. And such data connected with well logging data can be used for predictions of rock properties distribution to delineate sedimentologic heterogeneity. High resolution of 3D seismic data mapping can also be used to image the geometry of diagenesis front to a resolution of a few meters over thousands of square kilometers, which is a new approach to the study of diagenesis process in basin scale. The potential for future developments in this field is considerable. Relative methods and examples of such Studies on the aspects mentioned above are presented.

Potential Eocene and Oligocene stratigraphic traps of the Rockall Plateau, NE Atlantic Margin

Abstract Following thermal uplift during the late Paleocene to early Eocene, the denudation of the subaerial hinterland provided a massive sediment supply that led to the development of a number of large, prograding sedimentary wedge systems flanking the Hatton and Rockall basins. Regional seismic data mapping and borehole data indicate that the wedges are Eocene in age and have a high percentage of coarse clastic material typical of high-energy, fluvial or near-shore marine environments. The prograding wedges have been mapped and can be viewed as large, clastic fairways within which trapping at a number of scales exists. Seismic interpretation suggests that the wedges are present at various stratigraphic levels within the Eocene and are locally separated by unconformities. However, all pre-date the margin-wide late Eocene unconformity (C30), which resulted in subsidence and deepening of the Rockall and Hatton basins. A marine transgression inundated most former land areas, and a marked change occurred in basinal facies; a change from fluvial/near-shore clastic sedimentation to deep-water mud and ooze deposition influenced by bottom-currents. These conditions persisted throughout most of the Oligocene and Neogene and hence provided a seal for potential hydrocarbon-bearing sand-prone Eocene reservoirs internal to the wedge-systems. Additional sealing potential may be provided by shale layers internal to the wedges. Buried Eocene pinchout lobes, submarine fans at the base of basalt scarp faces and Oligocene slump deposits also provide potential trapping mechanisms. High, and probably unacceptable, risks include biodegradation and poor seal development due to the typically shallow depth of burial of the wedges. However, the majority of the wedges should be treated as analogues, with some of the deeper examples providing some scope for consideration as exploration targets. The scale of the prograding wedge play fairway is massive, with volumes measured in tens of cubic kilometres.

SEISMIC EVIDENCE FOR REVERSE AND WRENCH FAULT TECTONICS—CLIFF HEAD OIL FIELD, PERTH BASIN

Seismic interpretation of the Cliff Head oil field has shown it to be structurally complex with reverse faults, wrench faults and listric faults mapped at both field and reservoir scale within the Permo-Triassic section.The Cliff Head field overlies the Abrolhos Transfer Zone and has strong similarity to the progressive evolution, internal structure and rhomboid map geometry in experimental models of restraining stepovers in strikeslip systems. It is concluded that the Cliff Head oil field is a pop-up structure formed during the Permian and early Cretaceous within a restrained convergent wrench system—the result of sinistral transpression.A similar style of faulting could be applied when mapping seismic data in other offshore areas and especially the onshore Perth Basin with its poorer seismic data quality.Interpretation of prospects with a strong reverse or wrench component has implications for the timing of hydrocarbon emplacement and the potential for seal breach and leakage. Furthermore, paleo-structural style will determine fracture density and orientation and may be critical in determining optimum design of producer and injection wells during field development.It is recommended that interpreters of seismic data in the Perth Basin treat the fault patterns and structural trends of the Permian and early Cretaceous as different structural packages. The two should only be linked when it is very clear that there is a strong early Cretaceous overprint.

Seismic data mapping and reconstruction

Seismic data mapping uses data at source and receiver locations one actually has to create or simulate data at the locations one desires to have. The process is similar to seismic migration, though less demanding in that only data relatively near to the desired output point need be employed. Basic data mapping adjusts phase and amplitude of the data to conform to the geometry at the output location under the assumption that reflectivity does not change with angle of incidence. Full seismic data reconstruction goes beyond basic data mapping by also allowing reflection coefficients to change with incident angle. In the straight‐raypath approximation, both data mapping and full data reconstruction are Kirchhoff‐like operations of small integration aperture, with data mapping the simpler of the two. Operating on moveout‐corrected data, they are (up to a point) velocity independent. The operators can map or continue data from one offset to another [dip moveout (DMO) being a special case of data mapping] or from one source or receiver location to another. Both 2‐D and 3‐D versions of the operators can be constructed. The 2‐D mapping and reconstruction operators apply when input and output offset azimuths are aligned. The 3‐D operators are equivalent, at least in principle, to two passes of the corresponding 2‐D operators: the first pass a DMO to zero offset, the second an inverse DMO to the desired location. Potential uses for data mapping and reconstruction include filling in missing data, regularizing a data set, consolidating to a smaller data set, removing acquisition footprints, and so on.

The Mesozoic and early tertiary tectonic evolution of the Socotra area, eastern Gulf of Aden, Yemen

Recent interpretation and mapping of seismic data covering the area to the south and west of the Island of Socotra have enhanced the understanding of the Mesozoic and Early Tertiary tectonic history of the Socotran Platform.Lineament orientations, after restoration to account for Oligo-Miocene Gulf of Aden rifting, indicate:o1.The most significant basin forming lineament has a 140° orientation. Basin initiation, based on onshore Yemen analogues, occurred in the Late Jurassic-Early Cretaceous (Oxfordian to Hauterivian) and is believed to be associated with Neo-Tethys rifting between the Afro-Arabian and Laurasian Plates;2.The presence of a 45° lineament orientation associated with the extension and subsequent opening of the North Somali Basin. Separation of the Indian Plate from the African Plate during Callovian-Oxfordian times resulted in the opening of a number of en-echelon rift basins (Mozambique, West Somali and North Somali Basins) offset by major north-south orientated fracture zones (Davie Ridge and A.R.S.-V.L.C.C. Fracture Zones);3.Cretaceous post-rift carbonate platform development in the study area was followed by several phases of later structural evolution. These have characteristic translational aspects to their movements and occurred in the Late Cretaceous-Palaeocene, further modifying the structural geometry of the Socotran sub-basins. The majority of the translational features and faults evident on seismic data, and mapped at late Cretaceous and Palaeocene time horizons, suggest an 80° Principal Displacement Zone (PDZ) orientation; seismically derived isochrons indicate that movement along this zone was intermittent.

Phase Correction and Vertical Resolution Enhancement of Seismic Data Utilizing Post Stack Wavelet Extraction from Well Data

The method of post-stack wavelet extraction utilizing well log data has been described by Ramsden and Hobson (1987) and Danielson and Karlson (1984). This paper presents the results of the application of this method to two vintages of vibroseis data from the Eromanga Basin, Queensland, Australia. A perennial problem in the mapping of seismic data, recorded over the same locality, is the character and timing mismatch often found between different vintages of data. Utilizing well logs a post stack wavelet is extracted from each vintage of seismic data, and used to deconvolve each vintage's wavelets to zero phase. In the area of interest it is found that the wavelets on the two datasets are out of phase by approximately 70 degrees. A wavelet deconvolution operator is designed to correct the data to zero phase. This improves the character and timing misties between the different vintages of data and also improves the vertical resolution of the seismic data. The stability of the seismic wavelet over the survey area is demonstrated by extracting the wavelet from the two wells which are separated by approximately 50 kilometres.

Direct mapping of seismic data to the domain of intercept time and ray parameter—A plane‐wave decomposition

Marine seismic data recorded as a function of source‐receiver offset and traveltime are mapped directly to the domain of intercept or vertical delay time and horizontal ray parameter. This is a plane‐wave decomposition based on beam forming of wide‐aperture seismic array data to determine automatically the loci of coherent seismic reflection and refraction events. In this computation, semblance, in addition to the required slowness or horizontal ray parameter stack, is found for linear X — T trajectories across subarrays. Subsequently, semblance is used to derive a windowing filter that is applied to the slowness stack to determine the points of stationary phase and eliminate aliasing. The resulting filtered slowness stacks for multiple subarrays can then be linearly transformed and combined according to ray parameter, range, and time. The resulting function of intercept time and horizontal ray parameter offers significant computational and interpretational advantages for the case of horizontal homogeneous layers and leads directly to the derivation of a detailed velocity‐depth function.