Understanding Compartmentalization of Deepwater Reservoirs

Abstract

Abstract Objective/Scope The high cost of deepwater developments and the limited reach from offshore platforms requires operators to have a good understanding of the expected reservoir compartmentalization in the field before the first well is drilled. Deepwater reservoirs can be compartmentalized both structurally and stratigraphically. This paper will briefly address the structural compartmentalization and discuss the stratigraphic baffling that occurs in deepwater depositional settings. Methods, Procedures, Process The distribution of reservoir facies within deepwater depositional settings is well-understood from outcrop studies, seismic facies mapping, and exploration and development drilling. This understanding can be used to predict where stratigraphic compartmentalization is likely to occur. Results Observations and Conclusions Channel levee complexes and crevasse splays are deposited principally on the slope. Deposits are typically characteristic of a meandering river. Fluid flow in channel levee complexes occurs principally along the channel thalweg. Small-scale slumps within the channel levee complex may baffle flow from the levee into the channel thalweg. Crevasse splays are deposited when there has been a breach in the levee. The reservoir distribution in a crevasse splay deposit is characteristic of a river-dominated delta. Fluid flow in a crevasse splay will be generally toward the channel breach. Submarine fans are deposited in structurally restricted basins on the slope or on the basin floor. Interbedded shales baffle vertical fluid flow, with lower or distal lobe deposits more vertically baffled than upper lobe deposits. Lateral baffling of fluid flow in lower fan deposits is generally caused by small faults. In the middle to upper fan lateral erosional channels as well as small faults can baffle lateral fluid flow. Gorges or canyons are incisional events. They can occur anywhere on the system but are more common and more deeply incised in the upper fan and slope. The reservoir facies that fill the gorge are typically sand-prone, with sand more prevalent in the lower gorge-fill. Debris flows and slumps can occur anywhere in the system. Since reservoir connectivity within the debris flow is minimal, these should not be targeted for development.