Douglas G. Patchen

West Virginia Geological Survey, Morgantown, WV 26508-8079

The current Trenton-Black River gas play began when Columbia Natural Resources (CNR) drilled the discovery well for the Glodes Corners Road field in Steuben County, New York in 1985. However, it was not until a full decade later, in 1995, that CNR drilled a confirmation well, and 1996 before the first wells went on line. The play then developed rapidly in New York, attracting national interest as more discoveries were made and large open flows and annual production were reported. By 1999, four fields had been discovered in New York, and the play had moved into Ohio and West Virginia with the discovery of York and Cottontree fields, respectively. This same year, the Appalachian Region of PTTC began to host a series of workshops on the play, which led to the creation of an industry-government-funded Trenton-Black River Research Consortium. The main goal of the Consortium was to compile all available information into one basinwide playbook, complete with analyses and interpretations made from a multidisciplinary, integrated study of the data. Three additional objectives were defined: to develop a resource assessment model for this complex, unconventional play; to develop a model to explain the origin of dolomite reservoirs; and to define possible fairways within which to concentrate further exploration.

The gas resource contained in these reservoirs is significant. To assess this resource, the Trenton-Black River assessment area was divided into two separate plays, a hydrothermal dolomite play in the shallower, western side of the basin, and a fractured limestone play immediately adjacent to the east. The boundary between these plays approximates the western edge of the Rome trough and the eastern, fault-controlled edge of the former Black River ramp.

The method used to estimate gas resources in each play area required that team members estimate the number and size of undiscovered fields in the assessment area, fields that can be expected to be discovered within the next 30 years. The number and sizes of undiscovered fields were estimated at three levels of probability - 90%, 50% and 10% - and resource numbers were calculated for each probability level for both plays. The final assessment numbers for the entire assessment area are as follows: there is a 90% probability that at least 2.7 Tcf of gas will be discovered; a 50% chance that at least 6.0 Tcf will be discovered; and a 10% chance that as much as 11.0 Tcf will be discovered. These numbers are quite comparable to estimates made during an independent assessment by the Potential Gas Committee in 2004. The corresponding PGC estimates were 2.5, 5.4 and 8.5 Tcf at the same levels of probability.

AAPG Search and Discovery Article #90059©2006 AAPG Eastern Section Meeting, Buffalo, New York