Jack Bouska

Advantages of wide-patch, wide-azimuth ocean-bottom seismic reservoir surveillance

A dramatic advance in seabed seismic quality is imminent. Recent application of wide-patch, wide-azimuth, 3D ocean-bottom seismic technology (OBS and OBC) over several BP fields (including Azeri, Gunashli, Clair, Bruce, and Valhall) has improved data quality compared to towed-streamer 3D data. The “wide-azimuth” aspect of this technology is, in particular, opening new breakthroughs in processing, imaging, and interpretation that are simply not achievable using conventional narrow-azimuth OBC or towed-streamer acquisition.

The first 3D/4-C ocean bottom seismic surveys in the Caspian Sea: Acquisition design and processing strategy

Bubbling mud volcanoes create havoc for conventional seismic images over the crest of the Azeri-Chirag-Gunashli (ACG) structure in the Caspian Sea. Layers of trapped gas and shallow mud flows in the overburden sediments leave areas of severely degraded data quality at the crest of the reservoir structure. Fortunately, in 2002, the application of the first 3D four-component (3D/4-C) seismic in the Caspian has helped lift the veil of mud and gas attenuation which previously obscured the details of the subsurface reservoir.

Reducing Structural Uncertainty On the Azeri Field Using Ocean Bottom Seismic: Offshore Azerbaijan

The interpretation of 3D Ocean Bottom Seismic survey over part of the Azeri field, offshore Azerbaijan has delivered significant reduction in structural uncertainty. The crest and South/Central flank of the field was poorly imaged on towed streamer data; this led to “no data areas” with large depth uncertainty and a poorly resolved structural model. The depth migrated PZ products from the OBS survey have facilitated a choice between alternative structural interpretations and provided improvements in depth prediction for development drilling.

Acquisition Design of the First Four Component 3D Ocean Bottom Seismic in the Caspian

Summary The signal to noise problems inherent in towe d streamer data associated with mud volcanoes, subsurface heterogeneities and gas in the Azeri, and Gunashli structures of the Caspian sea prompted the use of three dimensional four component ocean bottom seismic (3D/4C OBS) to improve imaging. The introduction of several innovative enhancements to the traditional ocean bottom cable technique, when applied cohesively across both acquisition and processing, resulted in cost savings compared to traditional OBS acquisition and improved final data quality compared to towed streamer seismic.

Foinaven 4D :Processing and analysis of two designer 4Ds.

Summary Seismic reservoir monitoring over part of the Foinaven field began in 1995 (1) with the goals of comparing different technologies for seismic reservoir monitoring and of assisting the asset team in managing the reservoir. A permanent seabed array was installed for maximum repeatability on the receiver side, while TRISOR (4) source control was used to monitor shot-by-shot changes in source output. The baseline 3D surveys, one seabed survey and one towed streamer survey, were acquired in 1995 before any production. Both surveys were repeated in 1998, about 10 months after start of production, with all controllable parameters kept the same. The observed time-lapse effects on the two types of surveys were clear and comparable (2,3). This paper discusses the 4D processing, analysis and matching applied to the data from the time-lapse surveys into the seabed array and from towed streamer surveys.

Depth Imaging of 3D, 4C OBS Surveys In the Caspian Sea

The 3D ocean-bottom seismic (OBS) surveys acquired by BP over the Azeri-Chirag-Gunashli (ACG) structure in the southern Caspian Sea prompted the development of new techniques for velocity model building, tomography, anisotropy estimation and event matching, to generate prestack depth-migrated datasets of both pressure-wave (PZ) and mode-converted shear-wave (PS). The OBS data are better able to resolve previously poorly imaged mud volcano features, reducing structural uncertainty particularly over the crest of the anticline, and provide a greater degree of confidence in well positioning. Subsequent drilling in the area has verified the viability of the techniques developed.

Azeri field: new frontiers for 3D4C and borehole‐seismic integration

Reliable structural interpretation and subsurface model building for the giant Azeri oilfield in the Caspian Sea is vital for optimal reservoir development. The area presents major challenges to defining such a model, including steep geologic dips, strong and rapid lateral and vertical velocity variations, strong velocity anisotropy and the consequential impact of these factors on 3D seismic imaging. BP, WesternGeco and Schlumberger conducted a comprehensive program of 3D4C seismic acquisition, borehole seismic acquisition, borehole geophysical logging, and borehole-integrated seismic data processing to establish a consistent structural model for field development. This paper describes the integration of borehole geophysical data with 3D P-wave and C-wave prestack depth migration to yield 3D seismic volumes that have reduced structural uncertainty, identified a circular depression feature on the flank of the Azeri field, and have improved depth predictions for development drilling.

The Acambuco 3-D Challenge And Response: Application of Technical Limit Concepts

In 1999, Pan American Energy (PAE), as operator of the UTE Acambuco (PAE, YPF S.A., O&G a Shell-Capsa subsidiary, Apco-NW), was faced with the challenge of acquiring a large heliportable 3-D seismic survey and minimizing its environmental impact. This is the largest 3-D/3-C ever shot in any thrust belt in the world and represents the largest effort to date in terms of the number of live recording channels on land (4000+). The challenges involved designing a cost-effective 3-D, minimizing the impact to the environment, and optimizing field operations in this remote area. The response revolved around the application of the concepts of technical limits to all phases of the 3-D.

From Elephant Gun to Vacuum Cleaner: The Evolving Role of SPARSE 3-D In Efficient Extraction of Remaining Resource In a Mature Basin.

Summary An illustrated case history depicting the spectacular growth in the use of 3-D seismic for exploration and production within Amoco Canada. Emerging from the early limited mindset of using 3-D strictly as a post-discovery technique, for known features (which had relegated virtually all land based 3-D seismic exclusively to the role of an expensive exploitation tool), we expose how the introduction of the SPARSE 3-D technique (Bouska, 1997); employing wide patch, line and channel spacing, with attendant rock bottom price per square kilometer, and previously unheard of areal extents, has sparked dramatic shifts in business practice.