Exploration and production in deep water (500-2000 m) and ultradeep water (>2000 m) have expanded greatly during the past 15 years, to the point that they are now major components of the petroleum industry's annual upstream budget. Most E&P activity has concentrated in only three deepwater areas of the world—the northern Gulf of Mexico, Brazil, and West Africa. Globally, deep water remains an immature frontier, with many deepwater sedimentary basins being explored only lightly.
Deepwater discoveries account for less than 5% of the current worldwide total oil-equivalent resources1, although this amount is increasing rapidly. These resources are predominantly oil and are concentrated in non-OPEC countries. Thus, deep water represents an important component of the world's future oil equation. Gas exploration in deep water is extremely immature, reflecting current infrastructure and economic limitations, but it is also destined to become a major focus in the future.
Although the global deepwater play was initially restricted to a few large major companies, progressively smaller companies have become involved throughout time. Presently, even large- or medium-size companies must understand the geologic, engineering, and economic characteristics of the deepwater play. Generally, smaller companies are exploring in areas where (1) major infrastructure already exists, and consequently where they are able to operate, and/or (2) they can be a partner with a limited working interest, thus limiting their financial risk while still exposing themselves to potentially high rewards.
This chapter presents an overview of exploration and development in deepwater settings. The first part addresses the
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This course provides the working geophysicist with a broad overview of the petroleum systems of deepwater settings. The six main elements of petroleum systems will be covered: reservoirs, traps, seals, source rocks, generation, migration, and timing. The course is designed to teach students approximately 80% of what is important. For those interested in further study of a specific topic, each chapter has extensive references for the current literature. About 10% of the current cutting-edge information remains proprietary and cannot be included.
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 sili-ciclastic and carbonate reservoir systems. The study of deepwater systems requires many remote-observation systems, each of which can provide only one view of the entire depositional system. As a consequence, the study and understanding of deepwater depositional systems as reservoirs have lagged behind those 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 (Figure 1-1). The types of data used in the study of deep-water deposits include detailed outcrop studies, 2D and 3D seismic-reflection data (both for shallow and deep resolution), cores, log suites, and biostratigraphy. These data sets are routinely incorporated into computer reservoir modeling and simulation (Figure 1-1).
The following chapters integrate all of these data types and disciplines to characterize the many facets of deepwater systems. Technologies for deepwater exploration and development are improving rapidly. The intent of the course is to provide information that will be usable even as the technologies advance beyond what we present here.
With that in mind, this chapter introduces basic deepwater terminology and concepts for deepwater systems that will be used throughout this book.
Geoscientists routinely use several terms to describe the sedimentary processes and characteristics of deepwater settings and deposits. For the sake of consistency in this book, we define these terms as follows.
The term deep water is used informally in industry in two ways. First, deep water refers to sediments deposited in water depths considered to be “deep,” i.e., those under gravity-flow processes and located somewhere in the upper- to middle-slope region of a basin. Sediment gravity-flow processes are operative in lakes in relatively shallow water and in cratonic basins where water depths may be less than 300 m. Thus, unless stated otherwise, we use the term deepwater systems to refer to marine-sediment gravity-flow processes, environments, and deposits.