Sediment-Gravity Flows and Their Processes
Published:January 01, 2006
2006. "Sediment-Gravity Flows and Their Processes", 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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How are sediments transported to, and deposited in, deepwater environments? This question has been the subject of discussion and debate since the 1870s and researched since the 1950s (see Shanmugam, 2000, for a comprehensive review). Collectively, the primary processes that transport sediment into deep water environments are called “sediment gravity flows” (Middleton and Hampton, 1973). Sediment gravity flows range from mass movements (rock falls) and cohesive debris flows at one end of the spectrum to fully turbulent flows at the other end of the spectrum (Fig. 4-1). Although the term “turbidity current” is often used to describe deep water transport processes, it is only one of several types of flows that transport sediment into deep water, and rework them once deposited.
Unfortunately, transport and depositional processes are only rarely observed or measured in deep marine and lacustrine environments. Thus, to understand sediment gravity flows, we must combine data sets from outcrops, subsurface well logs and cores, seismic reflection profiles, modern sea floor images and samples, laboratory flume experiments, and mathematical models. Fortunately, rapidly evolving imaging, measurement, and computing technologies— mainly driven by petroleum exploration and development—are providing new data and insights that are leading to improved understanding of the complexities of sediment gravity flows and their deposits.
This chapter summarizes our current state of knowledge by combining key historical concepts with more recent observations and analyses. The chapter is organized to discuss the initiation of sediment gravity flows, followed by the spectrum of processes
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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.