Chapter 7 - Reservoir Quality—Global Examples

Abstract

Measured porosity and permeability values of SMTDs and BCRS from global case studies demonstrate that there should no longer be any doubt about their reservoir quality to serve as important petroleum reservoirs. In the Krishna–Godavari Basin in the Bay of Bengal, the Pliocene canyon-fill facies are characterized by the close association of sandy debrites and tidalites. Reservoir sands, composed mostly of amalgamated units of sandy debrites, are thick (up to 32 m), and low in mud matrix (less than 1% by volume). The best reservoir facies is composed of sandy debrites. This facies exhibits high values of measured porosities (35–40%) and permeabilities (850–18,700 mD). Sandy tidalites and related bottom-current reworked facies exhibit moderate porosity (31–40%) and permeability (525–6,930 mD). Muddy tidalites are poor reservoirs. Muddy slumps and debrites and hemipelagites are considered to be nonreservoirs. Postdepositional sandy injectites, closely associated with sandy debrites, also exhibit high values of porosity (34–35%) and permeability (8,680–11,760 mD). Sandy debrites on the upper-slope settings develop not only sheet-like geometries in the intercanyon areas but also exhibit high porosities and permeabilities because of low mud matrix. Because upper-slope sandy debrites mimic base-of-slope turbidite channels and lobes in planform geometries, use of conventional submarine fan models as a template to predict the distribution of deepwater sand is dubious.