Dynamic time corrections and their application to seismic data over sea floor canyons in the Gippsland Basin

Seismic reflection events beneath marked lateral velocity variations are distorted by complex ray paths. This can result in a stacked section with events that show poor continuity and are affected by 'pull up' or 'push down'. Where the velocity anomaly is not near the surface, conventional statics often fail to produce an adequate result.A pre-stack solution based on ray tracing is presented, which applies dynamic time corrections that vary with offset and travel time. The method was applied to a grid of data in the Gippsland Basin, affected by deep erosional canyons on the sea floor. The resulting sections generally showed significant improvement to the continuity of events thus enabling depth maps of greater accuracy to be constructed. We conclude that the method is more suitable in the study area than other pre-stack techniques given the absence of steep dips beneath the canyons and the exploration objectives. Other applications of the method are also mentioned.

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Structural Interpretation of Yamama and Naokelekan Formations in Tuba Oil Field Using 2D Seismic Data

Iraqi Geological Journal ◽

10.46717/igj.54.2b.5ms-2021-08-25 ◽

2021 ◽

Vol 54 (2B) ◽

pp. 55-64

Author(s):

Belal M. Odeh

Keyword(s):

Seismic Data ◽

Seismic Reflection ◽

Synthetic Seismogram ◽

Oil Field ◽

Well Log ◽

Seismic Reflection Data ◽

Depth Maps ◽

Reflection Data ◽

Interpretation Process ◽

Southern Iraq

This research includes structure interpretation of the Yamama Formation (Lower Cretaceous) and the Naokelekan Formation (Jurassic) using 2D seismic reflection data of the Tuba oil field region, Basrah, southern Iraq. The two reflectors (Yamama and Naokelekan) were defined and picked as peak and tough depending on the 2D seismic reflection interpretation process, based on the synthetic seismogram and well log data. In order to obtain structural settings, these horizons were followed over all the regions. Two-way travel-time maps, depth maps, and velocity maps have been produced for top Yamama and top Naokelekan formations. The study concluded that certain longitudinal enclosures reflect anticlines in the east and west of the study area representing Zubair and Rumaila fold confined between them a fold consist of two domes represents Tuba fold with the same trending of Zubair and Rumaila structures. The study confirmed the importance of this field as a reservoir of the accumulation of hydrocarbons.

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Approximating subsurface structure in areas of severe subsea erosion—A nonprocessing technique

Geophysics ◽

10.1190/1.1442603 ◽

1989 ◽

Vol 54 (11) ◽

pp. 1397-1409

Author(s):

Fred W. Lishman ◽

Michael N. Christos

Keyword(s):

Seismic Data ◽

Seismic Reflection ◽

Velocity Model ◽

Subsurface Structure ◽

Submarine Canyons ◽

Arrival Times ◽

Sea Floor ◽

Static Corrections ◽

Map Migration ◽

Made In

Severe subsea erosion distorts seismic reflection times and velocity analyses and makes determining subsurface structure difficult. Although data reprocessing is the logical solution for removing these distortions, reprocessing can be expensive. We present a case history describing a nonprocessing depth‐conversion technique using a geologic erosional model. A grid of common‐midpoint seismic data located in and around several submarine canyons was used for this study. Establishing a geologic erosional model requires an accurate representation of the sea floor, which we obtain by map migration of the sea‐floor reflection. A velocity model was developed using only those analyses not adversely affected by sea‐floor erosion. To remove the effects of erosion from the arrival times of a mapped horizon, static corrections (velocity replacement and compaction) were developed. We replaced the water velocity in the eroded section with depth‐equivalent rock velocities from the velocity model. The compaction correction, which was derived empirically, is based on the assumption that porosity restoration occurred in the sediments beneath the canyons when erosion reduced the overlying pressure. Compaction correction in conjunction with velocity replacement produced structure maps (time and depth) that exhibit only minor effects of erosion. These results were further improved by applying dynamic corrections obtained by ray tracing a subsurface model to determine the traveltime through the water for the reflection from the mapped horizon. Our final structure maps demonstrate that a geologically reasonable structural interpretation in depth can be made in areas of severe subsea erosion without reprocessing the data.

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2D Seismic Structural and Stratigraphic Study of Kirkuk Group Formation in Amara Oil Field- Southeastern Iraq

Iraqi Journal of Science ◽

10.24996/ijs.2021.62.11.15 ◽

2021 ◽

pp. 3942-3951

Author(s):

Ali K. Jaheed ◽

Hussein H. Karim

Keyword(s):

Seismic Data ◽

Seismic Reflection ◽

Sedimentary Basin ◽

Group Formation ◽

Structural Features ◽

Field Structure ◽

Synthetic Seismograms ◽

Oil Field ◽

Well Logs ◽

Depth Maps

The Amarah Oil field structure was studied and interpreted by using 2-D seismic data obtained from the Oil Exploration company. The study is concerned with Maysan Group Formation (Kirkuk Group) which is located in southeastern Iraq and belongs to the Tertiary Age. Two reflectors were detected based on synthetic seismograms and well logs (top and bottom Missan Group). Structural maps were derived from seismic reflection interpretations to obtain the location and direction of the sedimentary basin. Two-way time and depth maps were conducted depending on the structural interpretation of the picked reflectors to show several structural features. These included three types of closures, namely two anticlines extended in the directions of S-SW and NE, one nose structure (anticline) in the middle of the study area, and structural faults in the northeastern part of the area, which is consistent with the general fault pattern. The seismic interpretation showed the presence of some stratigraphic features. Stratigraphic trap at the eastern part of the field, along with other phenomena, such as flatspot (mound), lenses, onlap, and toplap, were detected as indications of potential hydrocarbon accumulation in the region.

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Seismic reflection test on the granite of the Skye Tertiary igneous centre

Geological Magazine ◽

10.1017/s0016756800021804 ◽

1992 ◽

Vol 129 (5) ◽

pp. 633-636 ◽

Cited By ~ 7

Author(s):

N. R. Goulty ◽

M. Leggett ◽

T. Douglas ◽

C. H. Emeleus

Keyword(s):

Seismic Data ◽

Seismic Reflection ◽

Intrusive Complex ◽

Gravity Modelling ◽

Test Location ◽

Basic Rocks

AbstractWe have conducted a seismic reflection test over a short profile on the granite of the Skye Tertiary central intrusive complex. From previous gravity modelling work it had been inferred that the granite is approximately 1.5 km thick and overlies basic rocks. The seismic data indicate that the granite is at least 2 km thick at the test location. Reflection events of alternating polarity between depths of 2.1 and 2.4 km suggest that basic and acidic sheets are interlayered at the base of the granitic mass.

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Pitfalls and limitations in seismic attribute interpretation of tectonic features

Interpretation ◽

10.1190/int-2014-0122.1 ◽

2015 ◽

Vol 3 (1) ◽

pp. SB5-SB15 ◽

Cited By ~ 64

Author(s):

Kurt J. Marfurt ◽

Tiago M. Alves

Keyword(s):

Seismic Data ◽

Seismic Attributes ◽

Seismic Attribute ◽

3D Data ◽

Amplitude Data ◽

Seismic Sections ◽

Push Down ◽

Data Coherence ◽

Level Of Experience ◽

Tectonic Features

Seismic attributes are routinely used to accelerate and quantify the interpretation of tectonic features in 3D seismic data. Coherence (or variance) cubes delineate the edges of megablocks and faulted strata, curvature delineates folds and flexures, while spectral components delineate lateral changes in thickness and lithology. Seismic attributes are at their best in extracting subtle and easy to overlook features on high-quality seismic data. However, seismic attributes can also exacerbate otherwise subtle effects such as acquisition footprint and velocity pull-up/push-down, as well as small processing and velocity errors in seismic imaging. As a result, the chance that an interpreter will suffer a pitfall is inversely proportional to his or her experience. Interpreters with a history of making conventional maps from vertical seismic sections will have previously encountered problems associated with acquisition, processing, and imaging. Because they know that attributes are a direct measure of the seismic amplitude data, they are not surprised that such attributes “accurately” represent these familiar errors. Less experienced interpreters may encounter these errors for the first time. Regardless of their level of experience, all interpreters are faced with increasingly larger seismic data volumes in which seismic attributes become valuable tools that aid in mapping and communicating geologic features of interest to their colleagues. In terms of attributes, structural pitfalls fall into two general categories: false structures due to seismic noise and processing errors including velocity pull-up/push-down due to lateral variations in the overburden and errors made in attribute computation by not accounting for structural dip. We evaluate these errors using 3D data volumes and find areas where present-day attributes do not provide the images we want.

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A method of ground‐roll elimination

Geophysics ◽

10.1190/1.1442526 ◽

1988 ◽

Vol 53 (7) ◽

pp. 894-902 ◽

Cited By ~ 39

Author(s):

Ruhi Saatçilar ◽

Nezihi Canitez

Keyword(s):

Seismic Data ◽

Seismic Reflection ◽

Wave Motion ◽

Frequency Interval ◽

Vertical Resolution ◽

Matched Filters ◽

One Dimensional ◽

Frequency Bands ◽

Ground Roll ◽

Seismic Reflections

Amplitude‐ and frequency‐modulated wave motion constitute the ground‐roll noise in seismic reflection prospecting. Hence, it is possible to eliminate ground roll by applying one‐dimensional, linear frequency‐modulated matched filters. These filters effectively attenuate the ground‐roll energy without damaging the signal wavelet inside or outside the ground roll’s frequency interval. When the frequency bands of seismic reflections and ground roll overlap, the new filters eliminate the ground roll more effectively than conventional frequency and multichannel filters without affecting the vertical resolution of the seismic data.

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LONG-PERIOD SURFACE-RELATED MULTIPLE SUPPRESSION IN 2D MARINE SEISMIC DATA USING PREDICTIVE DECONVOLUTION AND COMBINATION OF SURFACE-RELATED MULTIPLE ELIMINATION AND PARABOLIC RADON FILTERING

10.32008/geolinks2021/b1/v3/30 ◽

2021 ◽

Author(s):

Pimpawee Sittipan ◽

Pisanu Wongpornchai

Keyword(s):

Seismic Data ◽

Seismic Reflection ◽

Petroleum Reservoirs ◽

The United States ◽

Multiple Reflections ◽

Long Period ◽

Predictive Deconvolution ◽

Short Period ◽

Marine Seismic ◽

Multiple Elimination

Some of the important petroleum reservoirs accumulate beneath the seas and oceans. Marine seismic reflection method is the most efficient method and is widely used in the petroleum industry to map and interpret the potential of petroleum reservoirs. Multiple reflections are a particular problem in marine seismic reflection investigation, as they often obscure the target reflectors in seismic profiles. Multiple reflections can be categorized by considering the shallowest interface on which the bounces take place into two types: internal multiples and surface-related multiples. Besides, the multiples can be categorized on the interfaces where the bounces take place, a difference between long-period and short-period multiples can be considered. The long-period surface-related multiples on 2D marine seismic data of the East Coast of the United States-Southern Atlantic Margin were focused on this research. The seismic profile demonstrates the effectiveness of the results from predictive deconvolution and the combination of surface-related multiple eliminations (SRME) and parabolic Radon filtering. First, predictive deconvolution applied on conventional processing is the method of multiple suppression. The other, SRME is a model-based and data-driven surface-related multiple elimination method which does not need any assumptions. And the last, parabolic Radon filtering is a moveout-based method for residual multiple reflections based on velocity discrimination between primary and multiple reflections, thus velocity model and normal-moveout correction are required for this method. The predictive deconvolution is ineffective for long-period surface-related multiple removals. However, the combination of SRME and parabolic Radon filtering can attenuate almost long-period surface-related multiple reflections and provide a high-quality seismic images of marine seismic data.

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Interpretation of seismic reflection profiling data for the structure of the San Andreas fault zone

Bulletin of the Seismological Society of America ◽

10.1785/bssa07306a1701 ◽

1983 ◽

Vol 73 (6A) ◽

pp. 1701-1720

Author(s):

R. Feng ◽

T. V. McEvilly

Keyword(s):

Fault Zone ◽

Seismic Reflection ◽

San Andreas Fault ◽

Velocity Model ◽

Seismic Reflection Profile ◽

Lateral Velocity ◽

Zone Structure ◽

Ray Method ◽

Velocity Change ◽

San Andreas

Abstract A seismic reflection profile crossing the San Andreas fault zone in central California was conducted in 1978. Results are complicated by the extreme lateral heterogeneity and low velocities in the fault zone. Other evidence for severe lateral velocity change across the fault zone lies in hypocenter bias and nodal plane distortion for earthquakes on the fault. Conventional interpretation and processing methods for reflection data are hard-pressed in this situation. Using the inverse ray method of May and Covey (1981), with an initial model derived from a variety of data and the impedance contrasts inferred from the preserved amplitude stacked section, an iterative inversion process yields a velocity model which, while clearly nonunique, is consistent with the various lines of evidence on the fault zone structure.

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