Architectural Styles and Reservoir Performance--A Predictive Tool

Noel Tyler, Robert J. Finley

Reservoir architecture--the internal fabric of reservoirs--exerts a fundamental control on hydrocarbon recovery efficiency. Wave-dominated deltaic and shore-zone systems are characterized by high mobile oil recoveries; channelized systems display much lower recovery efficiencies. This predictable trend reflects the level of heterogeneity in the reservoir. For example, wave-dominated depositional systems are internally less complex and variable than those in which channels form major framework components.

Much attention has been focused on scales of heterogeneity. At scales of micrometers to a few meters, pore structure and sedimentary structure control capillarity, saturation characteristics, and local flow pathways around the well perforations. However, style of heterogeneity at scale of a few meters to 1 km is more important in controlling paths of fluid flow and sites of remaining mobile oil, residual oil, and gas saturations. Heterogeneity style, the geometric component of reservoir compartmentalization, is a product of depositional processes and is thus predictable. Aggradational reservoirs are typically bottom flooding or have multiple flood fingers and poor vertical conformance. Laterally, the flood front is confined to paleochannels, and it bypasses hydrocarbons in adjacent li hofacies. Progradational reservoirs are typically top flooding and recovery efficient; however, boundaries between accretion wedges can provide flow baffles in low-permeability reservoirs. Lateral accretion in fluvial or tidal sands can produce such flow baffles. Detailed knowledge of variations in style and scale of reservoir heterogeneity will foster more efficient exploitation of remaining mobile oil and improved implementation of projects for residual oil recovery.

AAPG Search and Discovery Article #91022©1989 AAPG Annual Convention, April 23-26, 1989, San Antonio, Texas.