Western Geophysical Research Articles

Industrial Ionising Radiation Activity: A Case Study of Western Geophysical Industry in Port Harcourt, Nigeria

Industrial Ionising Radiation Activity: A Case Study of Western Geophysical Industry in Port Harcourt, Nigeria

Reflections on elastic impedance

The story goes back to 1986 when I was first hooked on AVO after reading an SEG expanded abstract called “Seismic lithologic modeling of amplitude versus offset data” by Gelfand et al. of Western Geophysical. That in turn led me to Shuey's paper. I spent the next couple of years experimenting with AVO processing, analysis, and modeling. I concluded that any attribute with heavy dependency on the gradient term would be unreliable given the errors inherent in estimating the gradient (at least on 1980s vintage 2D data). Furthermore, the value of forward modeling gathers was limited because it was a step removed from the prime benefit provided by seismic—the image. I felt that producing constant angles stacks to image the AVO anomaly was the way to go.

Saturation Mapping From 4D Seismic Data in the Statfjord Field

This article is a synopsis of paper OTC 12100, "Saturation Mapping From 4D Seismic Data in the Statfjord Field," by P.M. Doyen, D.E. Psaila and D. Astratti, Western Geophysical, and L.B. Kvamme and N.F. Al- Najjar, Statoil A/S, originally presented at the 2000 Offshore Technology Conference, Houston, 1-4 May.

Evolution of a seismic acquisition methodology through integrated testing - onshore Abu Dhabi, United Arab Emirates, 1996-2000

Summary For onshore seismic data the resolution at the exploration target level depends on the complex interaction of many factors. These include the survey environment, geology, acquisition configuration and data processing procedures. When designing seismic surveys we wish to achieve the required target level resolution while minimising both cost and risk. For Vibroseis surveys, the time expended recording each source point, called the sweep effort/VP, can be a key cost factor. Uncertainty about the impact of differing options for the acquisition geometry and source point sweep effort on the target level resolution represents a risk factor. A 3D seismic exploration methodology driven by the resolution at the target level has been implemented for onshore Abu Dhabi, United Arab Emirates, by the Abu Dhabi Company for Onshore Operations (ADCO), in co-operation with Western Geophysical. Techniques originally developed for the on-crew processing of 2D acquisition parameter tests have been extended to 3D. Integrated data acquisition and processing tests provide fully processed, 3D migrated data volumes. Test analysis is based on the interpreted resolution at the target level, allowing direct judgements on key parameters affecting data cost and quality. The spatial distribution of source energy, improving the trace offset distribution and increasing the CMP fold is seen as significantly more important than the sweep effort/VP. Close co-operation between ADCO and Western's Geophysical Abu Dhabi data acquisition and processing staff ensure that complex data manipulation issues are handled in a timely manner, allowing the results of the testing to influence an ongoing 3D project. Use of this methodology has so far provided both improvements in data quality to levels not seen before for Abu Dhabi onshore data while simultaneously reducing the cost and risk of data acquisition. This paper summarises results from some of the key events in the development of the acquisition testing methodology: (A) 1996 – 2D testing for 2D acquisition. (B) 1997 – 2D testing for 3D acquisition. (C) 1998 – Simultaneous downhole acquisition. (D) 1999 – 3D testing for 3D acquisition.

Interpretation and Modeling of Legacy Time-Lapse Seismic Data

This article is a synopsis of paper OTC 12132, "Interpretation and Modeling of Time-Lapse-Seismic Data: Lena Field, Gulf of Mexico," by D.H. Johnston, J.J. Shyeh, SPE, and J.E. Eastwood, ExxonMobil Upstream Research Co.; and M. Khan, SPE, and L.R. Stanley, Western Geophysical, originally presented at the 2000 Offshore Technology Conference, Houston, 1-4 May.

Improved satellite transmission speeds challenge conventionalwisdom on processing marine seismic data

Western Geophysical is testing a new satellite system for high speed transmission of data which could transform the way contractors transfer and process marine seismic acquisition data. At the very least it will trigger debate on the logistics and costs of the supercomputer processing facilities on board today's 3D seismic vessels. Andrew McBarnet reports.

Positioning Ocean-Bottom Seismic Cables

This article is a synopsis of paper OTC 10871, "Positioning Ocean- Bottom Seismic Cables," by Simon Partridge, Sonardyne Intl., and Noel Zinn, Western Geophysical, originally presented at the 1999 Offshore Technology Conference, Houston, 3-6 May.

Displacement of migrating bowhead whales by sounds from seismic surveys in shallow waters of the Beaufort Sea

Seismic surveys for subsea oil deposits were conducted each summer, 1996–98, mainly in water <20 m deep. Airgun arrays were used, with 6–16 airguns and total volumes 560–1500 cu.in. Low-frequency sound pulses were created at intervals of 8–20 s. Effective source levels for horizontal propagation were lower than nominal source levels, but pulses were often detectable to 50+ km offshore. Westward autumn migration of bowhead whales near and offshore of the exploration area was monitored by aerial surveys flown daily, weather permitting, during the three seasons. Aerial survey data from days with and without airgun operations were compared. Most bowheads avoided the area within 20 km of the operating airguns; bowheads were common there on days without airgun operations. In 1998, numbers sighted 20–30 km away were also significantly reduced during airgun operations. Conversely, sighting rates just beyond the avoidance zone were higher on days with airgun operations. Broadband received levels of airgun pulses at 20 km were typically 120–130 dB re: 1 μPa (rms over pulse duration), lower than those previously demonstrated to cause avoidance by bowheads. Many migrating bowheads 20 to 50+ km offshore were exposed to weaker but presumably detectable pulses. [Work supported by Western Geophysical and BP Exploration (Alaska), Inc.]

Monitoring and education help seismic crew protect environment in transition‐zone survey

A program based on active monitoring and education helped Western Geophysical late last year complete a large speculative 3-D seismic survey in a sensitive Louisiana transition zone without creating the need for environmental remediation. Environmental authorities praised the program for, among other things, enabling Western Geophysical to discover a rookery of the endangered mottled duck and avoid disturbing it. The company has decided to use the program in all transition‐zone surveys in the southeastern United States.

The influence of seismic survey sounds on bowhead whale calling rates

During September in 1996–98, airgun arrays operated close to the coast of the Alaskan Beaufort Sea. It was of interest to know if the airgun pulse sounds affected migrating whales. Autonomous seafloor acoustic recorders were installed at various distances from shore and from the airguns. They recorded continuously for up to 22 days. Both the bowhead calls and the airgun pulses were clustered in time, requiring a greater quantity of data to isolate an influence than would be the case with nonclustered data. The consistent results from the three years were: (1) bowhead whales called frequently during their migration through the study area; (2) calling continued, although possibly at different rates, when the whales were exposed to airgun pulses; and (3) call detection rates at some locations differed significantly when airgun pulses were detectable versus not detectable. At least in 1996, patterns of call detection rates were consistent with aerial survey evidence that most bowheads were displaced from the area near the operating airguns. However, there was no significant tendency for call detection rates to change consistently at times when airgun operations started or stopped. [Work supported by BP Exploration (Alaska) and by Western Geophysical.]

Lessons Learned from 4D Projects

This article is a synopsis of paper SPE 49144, "Lessons Learned from 4D Projects," by J.R. Waggoner, SPE, Western Geophysical, prepared for the 1998 SPE Annual Technical Conference and Exhibition, New Orleans, 27-30 September.

Time-Lapse-Seismic Processing and Analysis

This article is a synopsis of paper OTC 10743, "Time-Lapse-Seismic Processing and Analysis: Gulf of Mexico Example, Lena Field," by John Eastwood, David H. Johnston, SPE, and Jane Shyeh, SPE, Exxon Production Research Co., and Xuri Huang, Ken Craft*, Robert Vauthrin, and Ricky Workman, SPE, Western Geophysical (*now with Energy Innovations Inc.), originally presented at the 1999 Offshore Technology Conference, Houston, 3-6 May.

4-C/4-D at Teal South

In late 1996, Texaco and Input/Output embarked on a novel experiment to test a low‐cost 4-C/4-D permanent reservoir monitoring system (PRMS). Western Geophysical and Digicourse were brought into the project to provide data acquisition and positioning services. In July and August 1997, four‐component (4-C) data acquisition was performed over 9 km2 in Eugene Island Block 354 (Teal South), using a dense shot grid (25×25 m). In late 1997, Texaco turned control of the project over to the Energy Research Clearing House and invited industry participation. The consortium remains open to new members.

Reservoir Characterization by Integrating Time-Lapse-Seismic and Production Data

This article is a synopsis of paper SPE 38695, "Reservoir Characterization by Integration of Time-Lapse-Seismic and Production Data," by Xuri Huang, SPE, Laurent Meister, and Rick Workman, SPE, Western Geophysical, originally presented at the 1997 SPE Annual Technical Conference and Exhibition, San Antonio, Texas, 5-8 October.

Repeatability of 3D Ocean-Bottom-Cable Seismic Surveys

This article is a synopsis of paper OTC 8310, "Repeatability of 3D Ocean-Bottom-Cable Seismic Surveys," by Craig J. Beasley, Ron E. Chambers, Ricky L. Workman, Kenneth L. Craft, and Laurent J. Meister, Western Geophysical, originally presented at the 1997 Offshore Technology Conference, Houston, 5-8 May.

Richard White, president, Western geophysical

Richard White, president, Western geophysical

Richard White, president, Western geophysical

Richard White, president, Western geophysical

Section Activities

PreviousNext You have accessThe Leading EdgeVolume 12, Issue 11Section Activitieshttps://doi.org/10.1190/tle12111132.1 SectionsAboutPDF/ePub ToolsAdd to favoritesDownload CitationsTrack CitationsPermissions ShareFacebookTwitterLinked InRedditEmail Section officers for 1993–94Permian Basin – President Steve Jumper (Dawson Geophysical); 1st Vice-President Sam Dobbs (Western Geophysical); 2nd Vice-President James Flis (Chevron USA); Treasurer Carroll Shearer (Seismic Advantage); Secretary Mark Fortuna (Marathon Oil).FiguresReferencesRelatedDetails Volume 12Issue 11Nov 1993Pages: 1062-1139ISSN (print):1070-485X ISSN (online):1938-3789 publication data© 1993 © 1993 by The Society of Exploration GeophysicistsPublisher:Society of Exploration Geophysicists HistoryPublished: 13 Jul 2017Published in print: 01 Nov 1993 CITATION INFORMATION (1993), "Section Activities," The Leading Edge 12: 1132-1132. https://doi.org/10.1190/tle12111132.1 Plain-Language Summary PDF Download Metrics Loading ...

To: “Seismic amplitude anomalies and AVO analyses at Mestena Grande Field, Jim Hogg Co., Texas” by R. C. Burnett (August 1990 GEOPHYSICS, 55, 1015–1025).

On p. 1019, right hand column, fifth paragraph, the sentence, “The AVO response of the Queen City interval was modelled by Western Geophysical using Sierra Geophysics’ SOLID program” should read”ellip; Sierra Geophysics’ VESPA program.”

The relationship of pre-stack apparent velocity filtering to the symmetry of the CMP stack response

Wearing my processing geophysicist's hat, I, like others, often ask questions to which there appear to be no answers readily available. One such question that had re-occurred to me was 'what is the relationship between pre-stack apparent velocity filtering and the common midpoint (CMP) stack response?' The elements of any answer were roughly -potential reduction in spatial resolution; -reduction in coherent noise; -apparent velocity in common source or geophone space is twice that observed on the CMP stack. During the summer of 1983 Walt Lynn presented some material at Western Geophysical's London office (as part of a week long 'Wave Equation Update School' lecture course given by Jon F. C1aerbout) entitled 'Dip filtering for noise suppression'. Part of this graphical material demonstrated how apparent velocity filtering could be viewed in source-geophone space as removing ciearly definable parts of a pre-stack diffraction. Upon this basis the following text is an attempt to answer my question by doing three things: • Setting down the necessary equations. • Showing how certain symmetry conditions affect the CMP stack. • Computing synthetic examples. The text will consider a point scatterer in the subsurface, how it responds to the CMP method and what happens when pre-stack apparent velocity filtering is included. The most important conclusion will be that certain apparent velocity filter symmetry conditions are necessary if the CMP stack is to respond similarly to positive and negative dips. The analysis will commence by describing the prestack traveltime surface that is associated with the point scatterer, which is sometimes called Cheop's Pyramid. Equations for apparent velocity on the commonly used axes of Cheop's Pyramid will be derived which show how certain areas of the surface are rejected by apparent velocity discrimination. The idea of symmetry will be described and a set of rules will be presented in order to test whether the pre-stack apparent velocity filter will prejudice dip direction on the CMP stack. Some computed examples will be presented along with a brief description of the computational method used. Finally a potential problem with 'marine' three-dimensional (3D) surveys that can be caused by pre-stack apparent velocity filtering will be briefly discussed.