CHARACTERIZATION OF BEREA SANDSTONE PETROLEUM RESERVOIRS IN SOUTHWESTERN WEST VIRGINIA

Six cores of the Berea Sandstone from Lincoln and Boone counties, West Virginia, are described using lithology, petrographic characteristics, and gamma-ray and porosity profiles to determine the sequence stratigraphy and its relation to petroleum production. The Berea in the study area is recognized as a shallow, marine shelf sand with fluvial influence from the Gay-Fink and Cabin Creek trends. An overall coarsening upward sequence observed in lithology and gamma-ray and porosity logs indicates a regressive depositional environment.

The Berea Sandstone is a light-gray, very fine-grained, argillaceous sandstone. Bedding structures observed include thin flaser laminations, less distinct microboxwork, and very thin cross laminations. Pebble-size rip-up clasts observed are mostly clay and shale, but also include some quartz grains. Quartz pebble conglomerates are seen in most cores and contain some clay or shale clasts.

Three transgressive parasequences are recognized. The basal sequence (Sequence I) consists of mostly massive sandstone with rip-up clasts at the base and is capped by laminated sandstone. Sequence II represents a more extensive regression and is composed of fine to very fine sandstone with cross-laminations and rip-up clasts in the base, a massive to thinly laminated interval capped by another interval of cross-laminated sandstone with rip-up clasts. There is then a gradational contact with the conglomeritic unit that represents the base of Sequence III. The final transgressive parasequence is believed to be the most proximal to the fluvial source.

Each parasequence is characterized by a peak in porosity/bulk density as well as a drop in radioactivity. Sequence II has the greatest porosity peak at 12 percent in each core observed, while Sequence I and II have peaks of 10 and 8 percent, respectively. The reduced porosity correlates with an increase in authigenic carbonate at the base of each parasequence.

Two pay zones of oil with gas within the Berea previously have been identified in the Griffithsville Field of Lincoln County, West Virginia. These two zones correlate with the pays in Sequences I and II of the Lincoln County wells in this study. The gas wells of Boone County do not show a correlation between production and the parasequences observed.