Recent Advances in Deepwater Slope Valley Depositional Models: Implications of Channel-Fill Percent and Stacking Patterns from Reservoir Architecture and Producibility

Morgan D. Sullivan¹, Michael J. Pyrcz¹, Henry W. Posamentier¹, Timothy McHargue², Andrea Fildani², Nicholas Drinkwater¹, and Julian Clark^2
1Chevron Energy Technology Company, Houston, TX
²Chevron Energy Technology Company, San Ramon, CA

Based on detailed analysis of deepwater slope valleys distinct relationships have been observed relating variations in overbank aggradation rate and the degree to which channels are filled to channel stacking patterns and reservoir connectivity. Rate of overbank aggradation contribute to channel relief and thus impact the likely degree of channel-fill. High aggradation rate favor under-filled channels and low aggradation rate tend to produce channels with a high degree of fill. Individual channel elements that have a low channel-fill percent exhibit a sharp base and overall upward-fining character. Low channel-fill elements typically display organized stacking patterns at the complex scale with lateral offset of elements in a down-flow direction. High channel-fill elements exhibit sharp bases and tops and complexes display disorganized map patterns. Overbank aggradation rate also strongly influence the stacking pattern of successive elements and complexes. In situations characterized by low aggradation rate, lateral shifting is common and a greater degree of amalgamation occurs. This is in contrast to those situations where the aggradation rate is high and successive elements and complexes are characterized by significant vertical stacking and a lesser degree of channel amalgamation. Consequently low aggradation rate tends to favor better channel amalgamation. Channel amalgamation, however, is not always directly related to connectivity. In low aggradation situations, organized lateral stacking leads to preferential erosion of high quality channel axis facies and preservation of poorer quality channel margin facies which produces a poorly connected reservoir. In high aggradation settings, however, organized stacking of channels favors well connected elements. Together, channel-fill percent integrated with rate of overbank aggradation constitute the major controls on stratigraphic architecture and connectivity of deepwater channel elements and complexes.

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