Rhyl Field: developing a new structural model by integrating basic geological principles with advanced seismic imaging in the Irish Sea

2016 ◽  
Vol 8 (1) ◽  
pp. 355-371 ◽  
Author(s):  
Gavin Ward ◽  
Dean Baker
Keyword(s):  
Structural Model ◽  
Seismic Imaging ◽  
Critical Factor ◽  
Integrated Approach ◽  
Velocity Model ◽  
Irish Sea ◽  
Depth Migration ◽  
Processing Power ◽  
And Migration ◽  
Automated Quality Control

AbstractA new model of compression in the Upper Triassic overlying the Rhyl Field has been developed for the Keys Basin, Irish Sea. This paper highlights the significance of the overburden velocity model in revealing the true structure of the field. The advent of 3D seismic and pre-stack depth migration has improved the interpreter's knowledge of complex velocity fields, such as shallow channels, salt bodies and volcanic intrusions. The huge leaps in processing power and migration algorithms have advanced the understanding of many anomalous features, but at a price: seismic imaging has always been a balance of quality against time and cost. As surveys get bigger and velocity analyses become more automated, quality control of the basic geological assumptions becomes an even more critical factor in the processing of seismic data and in the interpretation of structure. However, without knowledge of both regional and local geology, many features in the subsurface can be processed out of the seismic by relying too heavily on processing algorithms to image the structural model. Regrettably, without an integrated approach, this sometimes results in basic geological principles taking second place to technology and has contributed to hiding the structure of the Rhyl Field until recently.

Kinematic interpretation in the prestack depth‐migrated domain

Geophysics ◽  
1997 ◽  
Vol 62 (4) ◽  
pp. 1226-1237 ◽  
Author(s):  
Irina Apostoiu‐Marin ◽  
Andreas Ehinger
Keyword(s):  
Signal To Noise Ratio ◽  
Velocity Model ◽  
Point Of View ◽  
Prestack Depth Migration ◽  
Depth Migration ◽  
Velocity Models ◽  
Time Domain Data ◽  
And Migration ◽  
Point To Point ◽  
Homogeneous Media

Prestack depth migration can be used in the velocity model estimation process if one succeeds in interpreting depth events obtained with erroneous velocity models. The interpretational difficulty arises from the fact that migration with erroneous velocity does not yield the geologically correct reflector geometries and that individual migrated images suffer from poor signal‐to‐noise ratio. Moreover, migrated events may be of considerable complexity and thus hard to identify. In this paper, we examine the influence of wrong velocity models on the output of prestack depth migration in the case of straight reflector and point diffractor data in homogeneous media. To avoid obscuring migration results by artifacts (“smiles”), we use a geometrical technique for modeling and migration yielding a point‐to‐point map from time‐domain data to depth‐domain data. We discover that strong deformation of migrated events may occur even in situations of simple structures and small velocity errors. From a kinematical point of view, we compare the results of common‐shot and common‐offset migration. and we find that common‐offset migration with erroneous velocity models yields less severe image distortion than common‐shot migration. However, for any kind of migration, it is important to use the entire cube of migrated data to consistently interpret in the prestack depth‐migrated domain.

The isochron ray in seismic modeling and imaging

Geophysics ◽  
2004 ◽  
Vol 69 (4) ◽  
pp. 1053-1070 ◽  
Author(s):  
Einar Iversen
Keyword(s):  
Seismic Imaging ◽  
Model Updating ◽  
Velocity Model ◽  
Seismic Modeling ◽  
Prestack Depth Migration ◽  
Depth Migration ◽  
Geometric Spreading ◽  
Model Independent ◽  
Map Migration ◽  
Upper Level

The isochron, the name given to a surface of equal two‐way time, has a profound position in seismic imaging. In this paper, I introduce a framework for construction of isochrons for a given velocity model. The basic idea is to let trajectories called isochron rays be associated with iso chrons in an way analogous to the association of conventional rays with wavefronts. In the context of prestack depth migration, an isochron ray based on conventional ray theory represents a simultaneous downward continuation from both source and receiver. The isochron ray is a generalization of the normal ray for poststack map migration. I have organized the process with systems of ordinary differential equations appearing on two levels. The upper level is model‐independent, and the lower level consists of conventional one‐way ray tracing. An advantage of the new method is that interpolation in a ray domain using isochron rays is able to treat triplications (multiarrivals) accurately, as opposed to interpolation in the depth domain based on one‐way traveltime tables. Another nice property is that the Beylkin determinant, an important correction factor in amplitude‐preserving seismic imaging, is closely related to the geometric spreading of isochron rays. For these reasons, the isochron ray has the potential to become a core part of future implementations of prestack depth migration. In addition, isochron rays can be applied in many contexts of forward and inverse seismic modeling, e.g., generation of Fresnel volumes, map migration of prestack traveltime events, and generation of a depth‐domain–based cost function for velocity model updating.

3D PRE-STACK DEPTH MIGRATION: A TOOL FOR REDUCING EXPLORATION RISK IN THE SWAN GRABEN, TIMOR SEA

2005 ◽  
Vol 45 (1) ◽  
pp. 421
Author(s):  
P. Bocca ◽  
L. Fava ◽  
E. Stolf
Keyword(s):  
Seismic Data ◽  
Integrated Approach ◽  
Velocity Model ◽  
Fault Reactivation ◽  
Depth Image ◽  
Substantial Contribution ◽  
Surface Geometry ◽  
Depth Migration ◽  
Imaging Tool ◽  
Seismic Image

3D pre-stack depth migration (PSDM) reprocessing was conducted in 2003 on a portion of the Onnia 3D seismic cube, located in exploration permit AC/P-21, Timor Sea.The main objective of the reprocessing was to obtain the best seismic depth image and the most realistic structural reconstruction of the sub-surface to mitigate the risk factors associated with trap definition (trap retention and trap efficiency). This represents one of the main challenges for oil exploration in the area.The 3D PSDM methodology was chosen as the most appropriate imaging tool to define the correct sub-surface geometry and fault imaging through the use of an appropriate velocity field. An integrated approach to building the final velocity model was adopted, with a substantial contribution from the regional geological model.Several examples are given to demonstrate that the 3D PSDM reprocessing significantly improved the seismic image and thus the confidence in the interpretation, contributing strongly to the definition of the exploration targets.The interpretation of the new seismic data has resulted in a new structural picture in which higher confidence in seismic imaging has improved fault correlation. This has enabled better structural definition at the Middle Jurassic Plover Formation level that has reduced the complexity of the large Vesta Prospect, in the centre of the Swan Graben to the northwest of East Swan–1. Improved understanding of the fault reactivation mechanism and the structural elements of the trap (trap integrity) were eventually incorporated in the prospect risking.In the Swan Graben 3D PSDM has proved to be a very powerful instrument capable of producing significant impact on the exploration even in an area with a complex geological setting and a fairly poor seismic data quality.

Novel strategies for complex foothills seismic imaging — Part 1: Mega-near-surface velocity estimation

2020 ◽  
Vol 8 (3) ◽  
pp. T651-T665
Author(s):  
Yalin Li ◽  
Xianhuai Zhu ◽  
Gengxin Peng ◽  
Liansheng Liu ◽  
Wensheng Duan
Keyword(s):  
Seismic Imaging ◽  
Velocity Model ◽  
Velocity Estimation ◽  
Innovative Approach ◽  
Surface Velocity ◽  
Near Surface ◽  
Depth Migration ◽  
Static Corrections ◽  
Over Time

Seismic imaging in foothills areas is challenging because of the complexity of the near-surface and subsurface structures. Single seismic surveys often are not adequate in a foothill-exploration area, and multiple phases with different acquisition designs within the same block are required over time to get desired sampling in space and azimuths for optimizing noise attenuation, velocity estimation, and migration. This is partly because of economic concerns, and it is partly because technology is progressing over time, creating the need for unified criteria in processing workflows and parameters at different blocks in a study area. Each block is defined as a function of not only location but also the acquisition and processing phase. An innovative idea for complex foothills seismic imaging is presented to solve a matrix of blocks and tasks. For each task, such as near-surface velocity estimation and static corrections, signal processing, prestack time migration, velocity-model building, and prestack depth migration, one or two best service companies are selected to work on all blocks. We have implemented streamlined processing efficiently so that Task-1 to Task-n progressed with good coordination. Application of this innovative approach to a mega-project containing 16 3D surveys covering more than [Formula: see text] in the Kelasu foothills, northwestern China, has demonstrated that this innovative approach is a current best practice in complex foothills imaging. To date, this is the largest foothills imaging project in the world. The case study in Kelasu successfully has delivered near-surface velocity models using first arrivals picked up to 3500 m offset for static corrections and 9000 m offset for prestack depth migration from topography. Most importantly, the present megaproject is a merge of several 3D surveys, with the merge performed in a coordinated, systematic fashion in contrast to most land megaprojects. The benefits of this approach and the strategies used in processing data from the various subsurveys are significant. The main achievement from the case study is that the depth images, after the application of the near-surface velocity model estimated from the megasurveys, are more continuous and geologically plausible, leading to more accurate seismic interpretation.

Integrated gravity and seismic interpretation in the Norman Range, Northwest Territories, Canada

Geophysics ◽  
2007 ◽  
Vol 72 (5) ◽  
pp. B107-B112 ◽  
Author(s):  
Donald C. Lawton ◽  
J. Helen Isaac
Keyword(s):  
Northwest Territories ◽  
Structural Model ◽  
Gravity Data ◽  
Velocity Model ◽  
Data Interpretation ◽  
Deformation Model ◽  
Geologic Mapping ◽  
Seismic Line ◽  
Depth Migration ◽  
Reflection Seismic

We integrate the interpretation of gravity data acquired across the Norman Range near Norman Wells, Northwest Territories, Canada, with geologic mapping and the processing and interpretation of a 2D reflection seismic line. Our purpose is to determine which of two contrasting structural models of deformation is supported by both gravity and seismic data. Interpretation of the gravity data implies that the more likely structural model is that of thin-skinned deformation with a low-angle thrust fault having a décollement within Upper Cambrian evaporites. We use this structural model to guide the development of a velocity model for prestack depth migration of the seismic line. Interpretation of the processed seismic line supports the thin-skinned deformation model.

Seismic imaging beyond depth migration

Geophysics ◽  
2001 ◽  
Vol 66 (6) ◽  
pp. 1895-1912 ◽  
Author(s):  
A. J. Berkhout ◽  
D. J. Verschuur
Keyword(s):  
Seismic Imaging ◽  
Time Lapse ◽  
Velocity Model ◽  
Surface Layers ◽  
Near Surface ◽  
Depth Migration ◽  
New Type ◽  
Complex Propagation ◽  
The Common ◽  
Focus Point

If seismic imaging is formulated in terms of two focusing steps—focusing in emission and focusing in detection (or vice versa)—the output of the first focusing step yields a new type of seismic gather, the common‐focus‐point (CFP) gather, which is available for data analysis and information extraction. One important consequence of this novel option is that the involved focusing operators can be updated without updating the underlying velocity model. Introducing the concept of “dynamic focusing,” it is proposed to verify the validity of focusing operators by comparing the “gather of focus‐point responses” with the “gather of focusing operators.” Compared with velocity‐driven time and depth migration, operator‐driven CFP migration can be considered as the most general approach to seismic imaging: it does not require a velocity model, and it automatically takes into account unknown complex propagation effects such as conversion, anisotropy, and dispersion. In addition, in CFP migration, the second focusing step can be extended to produce both angle‐averaged reflection information and angle‐dependent reflection information. The CFP approach to seismic migration allows new solutions in the situation of complex near‐surface layers, subsalt targets, multicomponent processing, and time lapse analysis.

scholarly journals Advanced Seismic Data Interpretation for Carbonate Targets Based on Optimized Processing Techniques

GeoArabia ◽  
1996 ◽  
Vol 1 (2) ◽  
pp. 285-296
Author(s):  
Klaus C. Fischer ◽  
Ulrich Möller ◽  
Roland Marschall
Keyword(s):  
Seismic Data ◽  
Velocity Model ◽  
Data Interpretation ◽  
Second Phase ◽  
Shelf Area ◽  
Depth Migration ◽  
Amplitude Versus Offset ◽  
And Migration ◽  
Processing Techniques ◽  
Seismic Anomalies

ABSTRACT Seismic data from the shelf area of the Cretaceous Shu’aiba Formation in Abu Dhabi is used to investigate stratigraphic and structural seismic anomalies. The data consists of a 2-D grid of seismic lines, acquired in the late 1980s and 1993. The data was reprocessed in several phases. The first phase consists of standard time domain processing upto final Dip Move Out stack and migration. In the second phase, a macro-velocity model for post-stack depth migration is generated and tested by the interpreters. The third phase is the interpretation of the pre-stack depth migration stack. Due to the structural irregularity of the Shu’aiba Formation, the pre-stack depth migrated data is considered the most reliable for Amplitude Versus Offset analysis. Further steps are L-1 deconvolution followed by Born Inversion. These last steps are required before the lithology can be modeled with high-resolution. The final lithological model is verified by applying forward modeling. The lithological model forms the basis for reservoir and geostatistical evaluations which account for heterogeneities.

Integrated Approach to Coastal Zone Management in Puerto Galera, Oriental Mindoro, Philippines

1984 ◽  
Vol 16 (3-4) ◽  
pp. 433-440
Author(s):  
O C A Iriberri
Keyword(s):  
Coastal Zone ◽  
Coastal Zone Management ◽  
Integrated Approach ◽  
Physical Parameters ◽  
Ecological Studies ◽  
Continuous Increase ◽  
Zone Management ◽  
Single Fragment ◽  
Human Attitude ◽  
And Migration

Coastal zone management requires an understanding of the complex milieu of interactions and activities taking place in an environmental system. Man is beginning to recognize that the old method of dealing with individual issues and problems as single fragment of a whole ecosystem is not enough. This paper tries to deal with the integrated manner in carrying out effectively the management of the coastal zone in Puerto Galera, Oriental Mindoro by the Man and the Biosphere Interagency Committee on Ecological Studies. To attain the objective of the project, the different agencies monitor, identify, observe, investigate various natural and physical parameters contributing to the ecological balance and study the rational use of the resources along the coastal zone. Result of the study showed that although such factors as land use practices of shifting cultivation (kaingin), human attitude towards forest and its resources, and continuous increase in population and migration of people were observed, such pressure on lands has not greatly affected the Puerto Galera coastal zone resources.

Sign in / Sign up

Export Citation Format

Share Document