Recovery Efficiency Aspects of Horizontal Well Drilling in Devonian Shale

Abstract

ABSTRACT This study is part of the Department of Energy's Eastern Gas Shales research whose primary objective is to increase the gas reserves for the Devonian shales in the Appalachian, Illinois, and Michigan Basins. The study simulated the effect of using horizontal wells to increase the recovery efficiency of shale gas from two specific sites: Wayne County, West Virginia, where vertical well gas production has been historically high and no permeability anisotropy is thought to exist, and Meigs County, Ohio, an area with a history of moderate gas production and a calculated permeability anisotropy of approximately 8:1. In this study, a three-dimensional, dual-porosity reservoir simulator was used to characterize the study areas after sensitivity analyses were made to determine those parameters significant in determining gas production profiles. Once the study areas were characterized, the 20-year production profile for a 2,000- foot (610-meter) horizontal well was simulated for three well locations in Wayne County and one location in Meigs County. The performances for several vertical wells were also simulated and compared with those for their corresponding horizontal wells in Wayne County. Results of the simulation showed that a horizontal well could produce seven to ten times more gas than a vertical well placed at the same location for the Wayne County site. In the Meigs County area, the study showed that permeability anisotropy is an important factor in determining the orientation that a horizontal well should be drilled. Furthermore, the study concluded that horizontal wells are more efficient than vertical wells in producing Devonian shale gas from a fixed volume of rock.