Independent oil and gas companies such as Beiden and Blake continue to search for new sources of hydrocarbon reserves. In many instances this has resulted in a re-evaluation of reservoirs that were considered depleted or of higher risk. The Trenton Limestone reservoir, located in the northwestern part of Ohio, is a case study of such an occurrence.
Through an extensive three-year evaluation of this area, both geologically and from an active drilling program, it was found that the area still contains vast amounts of hydrocarbons located in various types of geologic traps. While large amounts of oil and gas exist in this reservoir, ultimate production is sensitive to well completion and production practices. More specifically in the case of natural gas, pressure transient tests were conducted to determine whether gas reserves were sufficient to consider pipeline construction. Results of the reservoir tests verified the Trenton formation to be of low permeability in the range of one millidarcy, and porosity between 2 and 4 percent. An economic evaluation was then performed to determine what reservoir flow capacities, well spacing and economic criteria were required for successful engineering and economic development.
Conclusions of the case study showed (1) the need for high grading the well site selection through geological interpretation in order to expand the "sweet spots," (2) a need for stimulation treatments designed to enhance production, (3) a marginal return on investment with current economics, and (4) that gas pipeline construction should be delayed until larger reserves are found or until a more favorable gas marketing climate develops.