Reservoir Characterization of Devonian Deposits in the Salem Field

Abstract

Reservoir characterization and the prediction of reservoir heterogeneities have a significant role in reducing risks and uncertainties for future enhanced oil recovery projects in the Salem Field. The Salem is a giant oil field with multiple petroleum reservoirs in southern Illinois. The field has produced over 400 million barrels of oil since 1939, mostly from the Mississippian and Middle Devonian strata related to the Kaskaskia sequence. The focus of this study was on characterization of the Middle Devonian Grand Tower carbonate reservoirs. A combination of geophysical logs, core samples, and well cuttings from the field were used to characterize the reservoir rocks and evaluate their potential.

Porosity trends and well-to-well correlation using wireline logs have revealed that the Middle Devonian reservoirs are vertically and laterally heterogeneous. In the central and southern parts of the field, two reservoir zones have been identified in the Grand Tower Formation, separated by an intervening dense limestone, which serves as a barrier to flow. The barrier zone pinches out in the northern part of the field, and the two reservoir units coalesce, forming a single, thick reservoir. Core examination indicates that the primary controls on reservoir heterogeneities are dolomitization and dissolution, which had a significant influence on reservoir quality. A combination of dolomite intercrystalline and vuggy porosities resulted in an interconnected pore network. Initial production and porosity maps of the reservoir units indicate that the production rate of each individual well corresponds closely to the porosity trends of the reservoirs.

AAPG Datapages/Search and Discovery Article #90218 © 2015 Eastern Section Meeting, Indianapolis, Indiana, September 20-22, 2015