Petroleum Traps in Deepwater Settings
Published:January 01, 2006
Renaud Bouroullec, Gabor Tari, 2006. "Petroleum Traps in Deepwater Settings", Introduction to the Petroleum Geology of Deepwater Setting, Paul Weimer, Roger M. Slatt, Renaud Bouroullec, Richard Fillon, Henry Pettingill, Matthew Pranter, Gabor Tari
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A trap is any geometric arrangement of rock—regardless of its origin—that permits a significant subsurface accumulation of oil or gas, or both (Biddle and Wielchowsky, 1994). Deepwater reservoirs produce petroleum from a wide variety of traps. As we note in Chapter 2, about 25% of the giant deepwater fields produce from structural traps that have four-way closure, approximately 9% produce from purely stratigraphic traps, and most deep-water fields (66%) produce from combined structural-stratigraphic traps (Figure 15-1).
Many deepwater settings are characterized by syndepositional tectonics, such that the creation of structural traps is inextricably linked with the evolution of the other elements of the petroleum systems. The lapout or truncation of the reservoir elements against the flank of contemporaneously active structures helps create many of the combined structural-stratigraphic traps (Figure 15-2). In addition, the continued deformation in many settings constantly changes other local elements of the petroleum systems, including the local and regional pressure systems and migration pathways.
The subject of traps in deepwater settings is extremely broad, because most deepwater sedimentary basins have multiple trapping styles. In this chapter, we begin by looking at four types of deepwater settings: (1) basins with mobile substrates (salt or shale), (2) basins with nonmobile substrates (i.e., basement blocks, wrench tectonics), (3) unconfined basins, and (4) shallow to continental reservoirs that now rest in deep water (Figure 15-3; see also Chapter 2 of this book) (Worrall et al., 2001). Within
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Introduction to the Petroleum Geology of Deepwater Setting
This publication is intended to provide the working geologist, geophysicist, and petroleum engineer with a broad overview of the petroleum systems of deepwater settings. Deepwater depositional systems are the one type of reservoir system that cannot be easily reached, observed, and studied in the modern environment, in contrast to other siliciclastic and carbonate reservoir systems. The study of deepwater systems requires many different remote observation techniques, each of which can only provide information on one part of the entire depositional system. As a consequence, the study and understanding of deepwater depositional systems as reservoirs has lagged behind that of the other reservoir systems, whose modern processes are more easily observed and documented. For this reason, geoscientists use an integrated approach, working in interdisciplinary teams with multiple data types. The types of data used in the study of deepwater deposits include: outcrop studies, 2D and 3D seismic-reflection data (both for shallow and deep resolution), cores, conventional and specialized log suites, biostratigraphy, and well test and production information. These data sets are routinely incorporated into computer reservoir modeling programs for production performance simulation and forecasting. Technologies for deepwater exploration and development are improving rapidly. The intent of this publication is to provide information that will be usable even as the technologies advance beyond what we present here.