Analysis of Eastern Devonian Gas Shales Production Data
Authors: Gatens J.M. , Lee W.J. , Lane H.S. , Watson A.T. , Stanley D.K. , Lancaster D.E. 
Published: December 2007

Summary
Production data from more than 800 Devonian shale wells have been analyzed. Permeability-thickness product and gas in place estimated from production data have been found to correlate with well performance . Empirical performance equations, production type curves, and an analytical dual-porosity model with automatic history-matching scheme were developed for the Devonian shale.

Introduction
Thousands of wells have been completed in the Devonian gas shales Of the Appalachian basin. Although a wealth of historical production data exists for these wells, these data have never been studied systematically on a large scale. The purpose of our work was to gather and to analyze as many of these data as possible with the following objectives in mind:to analyze Devonian shale production data to reservoir characteristics,to identify those reservoir characteristics that correlate with superior well quality, andto develop analytical tools for the practicing engineer to use in analyzing and predicting production in the Devonian shales.
Production data and other pertinent well information have been gathered for more than 1,500 Devonian shale wells in Kentucky, Ohio, and West Virginia. We first conducted a pilot data-analysis study on wells located. in southwestern West Virginia and eastern Kentucky (Area 1 in Fig. 1) to ensure that Devonian shale production data could be analyzed logically and systematically. Upon successful completion of the pilot study, we selected four areas (Fig. 1) for study.
During the course of this work, we developed an analytical dualporosity reservoir model for analyzing and predicting Devonian shale production; analyzed flow test and/or production data on more than 1,000 wells; correlated permeability thickness product and gas in place with observed well performance; developed a family of type curves for analyzing and producing Devonian shale production; and developed empirical equations for predicting Devonian shale production.
In the next section, we discuss the data gathered for this study. We then discuss the analytical dual-porosity model and history-matching scheme used to analyze the available production data. The analysis of initial-open-flow (IOF) data and the development of type curves for analyzing production data are also briefly outlined. We then present a statistical analysis of the results of our production data analysis. Finally, we discuss the application of our results to predicting future gas-well performance.

Data Acquisition
Data have been gathered from four areas in Kentucky, Ohio, and West Virginia (Fig. 1). Area 1, often referred to as the Big Sandy area, contains a large number of wells with long producing This area includes most of the best shale gas wells and produces chiefly dry gas. Area 2, in central West Virginia, contains many wells of average quality that produce mainly dry gas. Area 3 is in southeastern Ohio and generally has poorer-quality wells that produce dry gas, except near Area 4. Area 4, or the Burning Springs area, includes a large number of recently completed wells that produce gas and liquids.