Outcrop Analogs and Sequence Stratigraphic Context of the First Cow Run Sandstone,  (Late Pennsylvanian, Missourian), St. Mary’s  and Newell Run  Oilfields, West Virginia and Ohio

Martino, Ronald L. and Wehrle, Donny

Marshall University, Huntington, WV

The First Cow Run sand has been the most productive reservoir in the Conemaugh Group in southeastern Ohio. The discovery well was drilled in 1861 on Cow Run in Washington County. The sandstone has a maximum thickness of 14 m and  a porosity and permeability as high as 23.8% and 1770 md.  A linear, northwest-trending area of production 1.6-3.2 km wide and at least 32 km in length extends through the Newell Run field southeastward into West Virginia near the town of St. Mary’s.  A second linear Cow Run trend in this area strikes west-northwest, is  1-3 km wide and at least 45 km in length and includes the Chesterhill (Ohio) and Boaz  (West Virginia) Oilfields.

Sequence stratigraphic analysis of  87 outcrops of the Glenshaw Fm (Lower Conemaugh Group) 130-150 km southwest of the oilfields indicates the presence of nine

glacioeustatically controlled, fifth order sequences. Incised-valley fills from 20-35 m thick are occupied by LST/TST fluvio-estuarine strata, with individual channel-fills from 6 to 10 m thick.  Well-developed paleosols formed on interfluves during sea level lowstands and facilitate recognition of sequence boundaries. They are readily distinguishable on caliper logs as cave or washout zones.  Geophysical logs  were correlated through the oilfields and paleoenvironments interpreted based on log patterns and comparison with outcrops.   

It is suggested that the First Cow Run trends near St. Mary’s formed as alluvial and possibly estuarine channel deposits that filled valleys cut by northwest-flowing, coastal plain rivers during  one or possibly two glacioeustatic lowstands.