Columbia Natural Resources, Inc. a subsidiary of the Columbia Gas System, and United States Department of Energy(DOE drilled and completed a horizontalwell in the Devonian Shale, in Martin County, Kentucky, USA, in 1990. The wellwas drilled both on air and foam. It reached a measured depth of 6,263 feet, with a true vertical depth (TVD) of 3,754 feet and a horizontal displacement of2,812 feet in the direction of N10°W. Six zones were completed with a combinedopenflow of 3.1 MMcfd. The well has been on production for 24 months.Production performance from the well is compared with the surrounding 27vertical wells. Efforts have also been made to compare its productionperformance with three other horizontal wells drilled in the Devonian Shale indifferent parts of the Appalachian Basin.
SITE SELECTION AND DRILLING DIRECTION
The well is located in southeastern Martin County, Kentucky, which is partof the Big Sandy Field (Figure 1). The Big Sandy is a large gas field, whichcovers several counties in eastern Kentucky and western West Virginia. The Big Sandy has been a prolific producer of gas since the turn of the century. Theprimary producing horizon in the Big Sandy Field is Devonian Shale; secondarytargets are Mississippian sandstones and carbonates. The Devonian Shale of the Eastern U.S. is characterized as unconventional reservoir with low porosity andlow permeability. Production is dependent upon the presence of naturalfractures.
The Martin County, Kentucky, site was selected after careful considerationof regional geology, reservoir quality, availability of undeveloped acreage andproximity to existing production properties. The preferred drilling directionof N10°W was determined from analysis of induced and natural fractured azimuthsobtained from nearby oriented core production trends and surfacelineaments.
The Devonian shale in the Big Sandy Field is naturally fractured and as aresult is an ideal target for horizontal drilling. The Devonian Shale insoutheastern Martin County has also been fractured by more than one tectonicevent. Three basement related events the Rome Trough (part of a Paleozoic riftsystem), the Warfield Fault and Anticline and the Pike County, Kentucky Upliftand one non-basement related feature the Pine Mt. Thrust (part of the easternoverthrust belt) have fractured the shale during geologic time.