Recent drilling and completion operations have demonstrated the technical and economical successes of horizontal wells over that of vertical wells. The need for horizontal wells was established as a vital production enhancement technique for wells production enhancement technique for wells producing from economically marginal, low producing from economically marginal, low permeable gas formations in the Appalachian Basin permeable gas formations in the Appalachian Basin exhibiting strong permeability anisotropy.
As part of a U.S. Department of Energy (U.S.DOE) funded research project, several horizontal wells were drilled and completed to the Devonian Shale strata in the Appalachian Basin. Production from these wells exhibited high improvement ratios to that from vertical wells; however, to enhance the economics of the horizontal wells, stimulation was indicated. The success of the stimulation techniques and the measure of improvements were determined from production results and/or pressure analyses.
This paper exhibits and summarizes the results of production and pressure buildup data analyses for the production and pressure buildup data analyses for the different horizontal wells. Based on pre- and post-stimulation production and pressure data, various post-stimulation production and pressure data, various well test analysis techniques such as type curves for horizontal gas wells, reservoir simulation, Homer's method, and other applicable techniques are utilized.
Finally, the correlation of production and pressure analysis results helped in the assessment and evaluation of the stimulation techniques.
Horizontal wells have effectively demonstrated the improvements in field development, increase in production and reserves, and the potential for production and reserves, and the potential for positive economic results in comparison to that of positive economic results in comparison to that of vertical wells. At the present time, the field histories tend to indicate that the recovery factors from horizontal wells are, in general, 2-5% higher than those for vertical wells. Most of the horizontal drilling to date has targeted oil-bearing formations, although interest is increasing in the use of horizontal wellbores to improve the economics of gas plays. plays. Horizontal gas wells are highly beneficial in areally anisotropic tight reservoirs and are used to enhance drainage volume per well in a given time period, such is the case with the highly fractured, mostly anisotropic, tight Devonian Shale reservoirs which underlies southwestern West Virginia.