ABSTRACT
An analysis and evaluation of the Devonian Shale oil production's rapid decline rates and future potential were performed. Various analysis techniques were employed to evaluate the performance of oil wells completed in the Lower Huron Member of the Devonian Shale in a seven-county area of western West Virginia and southeast Ohio. The analyses included material balance, and analysis of production data by a transient method and numerical simulation, together with statistical methods. Results of the evaluation showed that the coexistence of natural fractures and matrix permeability and porosity are necessary for oil production from the Lower Huron in this area. Matrix permeability and porosity created by the inclusion of silt in the shales are necessary for oil accumulation and production. Because the matrix permeability is extremely low, fractures are necessary to transmit the matrix production to the well bore. Although the cumulative oil volume is quite low, the recovery efficiency within the well drainage volume is significantly higher than expected for solution gas drive. A proposed explanation is that a mechanism of gas trapping is responsible for the high oil recovery efficiency. Another major finding of the study was that the methods of completion and stimulation had no effect on productivity. No major production problems except possible fracture closures were determined.
The study also showed that the combination of the geologic features necessary for oil production from shale is unique to this area but is by no means consistent over the entire area. In fact, the probability of locating the geological conditions necessary for economic oil production is only about 4 percent with current methods. Although unlikely, even if the technology for finding and producing oil from the Devonian Shale is greatly improved, few opportunities for commercial wells remain since the area is already densely drilled. Also, restimulation of old wells does not appear promising because wells are usually too close to abandonment pressure for additional oil production.
