Stratigraphy and Petroleum Potential of Berea Sandstone in Larkin and Williams Fields, Midland and Bay Counties, Michigan: ABSTRACT

Abstract

The Berea is an Early Mississippian deltaic sandstone confined to the eastern side of the Michigan basin. The Berea Sandstone consists of three members: upper, middle, and lower. Only the upper and middle members are present in the Larkin and Williams area. The middle member is the main reservoir, and scanning electron microscope studies indicate that the sand has primary, interparticle porosity with some secondary leaching of interstitial clays and feldspathic grains. Over the past 5 years, wells have been drilled 2500 ft into the Berea along a structure between Midland and Bay Counties. The structure is a northwest-southeast-trending anticline that plunges northwest into the basin. A review of the wells drilled along this anticline reveals a progression of structural-stratigraphic traps within the middle Berea member. At the southeast end of each reservoir (the updip end), a stratigraphic pinchout cuts across the middle Berea member creating a barrier to oil migrating updip along the northwest-southeast structural trend. These pinch-outs are narrow with a north-northeast orientation and are considered to be abandoned, mud-filled channels cutting across an apron sheet sand, which is interpreted to be a beach-strand-plain complex. Because the middle Berea member has excellent porosity and permeability, many wells inmore » the field have flowed oil with initial production ranging between 75 and 350 BOPD. The original oil in place is estimated to be more than 23 million bbl of oil; only 1.4 million bbl of oil has been produced.« less