Modern outcrops and subsurface data sets provide a mapping opportunity to characterize deep- water depositional systems from shelf edge to basin plain. This includes observations of the grain- to basin-scale framework and key stratigraphic surfaces that subdivide the basin-fill.
Analysis from recent mapping campaigns (2009-2019) from over 20 stratigraphic intervals in the Americas, Europe, Asia and New Zealand yields the following insights. (1) The range and variability in deep-water siliciclastic conventional petroleum reservoirs includes deposits resulting from transport and deposition via fluid turbulence, matrix strength and a combination of those two mechanisms. (2) Sediment distribution patterns in the deep sea are controlled by several key factors including various aspects of grain size and sediment volume, gradient, accommodation and overall basin type. (3) Sub-bed-scale, semi-quantitative analysis of sedimentary fabric ratios commonly gleaned from core and image logs reveals critical information on bulk rock volume, net:gross and porosity to help determine stock tank original oil in place (STOOIP). (4) Sedimentary provenance and source-to-sink routing systems are intimately linked to overall reservoir presence and reservoir quality in fine-grained turbidite reservoirs. (5) Downslope sediment gravity flow behavior can be used to calibrate and understand the predictive attributes in deep-water reservoir type from canyon head to basin plain.
The results of these mapping campaigns reveal new observations on sediment gravity flows, their processes of transport and sedimentation, and their bearing on oil and gas exploration and development in deep-water depositional systems. This presentation incorporates observations from passive margins including faulted slopes and ponded mini-basins, and active margins including foreland, forearc, back-arc, strike-slip, intracratonic and hybrid basins.
FIGURE 1. The main processes in deep-water regions include pelagic and hemi-pelagic sedimentation, mass movements, ocean currents, tides, waves and biological processes. Some of the main deposits that function as petroleum reservoirs include deposits from turbidity currents (A, B, C), debris flows (D), and flows that experience both fluid turbulence and matrix strength, such as slurry flow deposits, hybrid event beds, transitional flow deposits or argillaceous sandstone beds.
Jon R. Rotzien is President of Basin Dynamics, a US based consulting company providing innovative geoscience and reservoir characterization solutions. He has published peer-reviewed research papers and scientific conference proceedings pertaining to petroleum geology, reservoir quality, reservoir characterization, sequence stratigraphy, process sedimentology, basin analysis and geophysics, and he teaches petroleum reservoir courses in North America, South America, Europe, Asia and New Zealand. He is a Distinguished Service Award winner of GCSSEPM (2018), associate editor of the Bulletin of Canadian Petroleum Geology and co-founder of the Houston Explorers Club. Mr. Rotzien received a Ph.D. in Geological Sciences from Stanford University and a B.A. degree in Geology from Colorado College.
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