RECENT DEEP DRILLING TO THE UPPER ORDOVICIAN TRENTON/BLACK RIVER IN WEST VIRGINIA AND PENNSYLVANIA, U.S.A

The total number of wells drilled into the Upper Ordovician Trenton and Black River carbonates in West Virginia has nearly doubled since 1999. This activity was spurred by the success of wells drilled into rocks of similar age in the Finger Lakes region of New York. Drilling began in West Virginia after a high-volume, high pressure well was completed in April, 1999 in Roane County. To date, over 270 wells have been permitted in WV; fewer than 10% of these have actually been drilled. It should be noted that the reservoir in WV is fractured limestone as opposed to fractured dolomite in NY.

Trenton wells are about 10,000 feet deep in WV; in NY, depths range from 6,000 to 10,000 feet. Production from these new wells in WV totals 5.1 billion cubic feet (Bcf) of gas from 1999 to 2001. The discovery well has produced about 3 Bcf; eight other wells have contributed the remaining 2.1 Bcf of gas.

In Pennsylvania, where the Trenton/Black River is at greater depths than in WV or NY, a few recent wells have been drilled to about 11,000 feet. All of these wells reportedly were dry in the Trenton/Black River. The wells were deviated or horizontal wells designed to penetrate the most highly fractured carbonates, but there was no dolomitization association with those fractures. Basement structure seems to be important in locating the fractures necessary to provide a reservoir. Producing wells in WV are located along the southeast margin of the Rome Trough, a major basement structural feature, and wells in Pennsylvania have thus far unsuccessfully been targeted along the trough and intersecting basement wrench faults. The Rome Trough has been recognized as a reactivated Cambrian rift zone that contains an abnormally thick sequence of Cambrian sediments.