How stratigraphy influences oil recovery: A comparative reservoir database study concentrating on deepwater reservoirs

The degree to which the depositional environment influences recovery from a reservoir is a topic of some importance, but one that has not been thoroughly addressed. One of the most widely known and cited examples relating stratigraphy to recovery efficiency is the study of Tyler and others (1984; Tyler, 1988, updated in 1991 by Tyler and Finley). In this study, 450 major Texas petroleum reservoirs were evaluated (Galloway et al., 1983). They showed that average recovery efficiency could be closely tied to depositional environment and drive mechanism (Figure 1). Reservoirs composed of fluvial rocks with water drive, or solution gas drive, or gas cap expansion may have recovery efficiencies of 35–50%, whereas barrier strand-plain reservoirs with gas-cap expansion may be characterized by recovery efficiencies of 50–70%. However, because they plot recovery efficiency against drive mechanism and depositional system, it is still unclear which of these factors has more important influence on recovery efficiency....