Abstract

The discovery of new oil production (with associated gas) from the Devonian shales in western West Virginia in 1979 led to a tremendous increase in Devonian shale exploration and development in that area. The records of the West Virginia Geological and Economic Survey indicate that over 40% of drilling permits issued in 1982 were for various zones in the Devonian shales. With the decline in the gas market, the number of Devonian shale gas wells has declined in 1983. Nevertheless, activity in Ritchie, Pleasants, and Wood counties has remained very high. That activity is a source of considerable practical information on Devonian shale exploration and development. In fact, that play has provided an active testing ground for a variety of theories and techniques. The information presented in this paper is derived largely from the experience of one operator, Rendova Oil Company of Midland, Texas. That organization has been active in West Virginia since 1980 and, through the end of 1983, has drilled over 40 Devonian shale wells. That effort has been a continuous learning process in all phases of exploration and development. This paper will attempt to share that experience by describing the methods and techniques that have been tried as well as Rendova's current practices. The discussion will include exploration rationale, drilling methods, and completion and production practices. In addition, we will discuss what we see as the major problems that remain in developing oil and gas reserves in the Devonian shales.

Introduction

In the last ten years, considerable R and D effort has been directed towards producing gas from the Devonian Shales. The Federal government, state governments, and private organizations have all contributed to this research effort. The Devonian shales are extensive in the Eastern United States (Figure 1), and the research results have been impressive. We have a much better understanding of the geology of the Devonian Shales and, in particular, the properties that affect its productive particular, the properties that affect its productive potential. There are a variety of new tools and potential. There are a variety of new tools and techniques available for assessing the shales. And there have been considerable improvements in completion and stimulation techniques. Ultimately, the measure of success of a research effort of this type is its commercial application. Do operators in the field use the newly developed techniques and methods? Is the research answering the questions that the operators need answered?

The field application of the new tools, methods, and techniques has been hindered in the last couple of years by the reduced demand and oversupply of natural gas. The major pipeline companies have been forced to curtail purchases and gas that did find a market brought a relatively low price to the producer in spite of government price to the producer in spite of government regulations which allow higher prices for Devonian Shale gas, All these factors have contributed to a reduction in gas well drilling in the Appalachians and particularly in the Devonian shales.

One area in which activity has remained high is in the western part of the state of West Virginia, including parts of Ritchie, Pleasants, Wood, and Tyler counties. In this area, many Devonian shale wells produce oil as well as gas. There have been reports of small amounts of oil encountered in the Devonian shales in this region since the mid-1960's. It was not until 1979 that reports of substantial amounts of oil caused a rapid increase in activity. The chart in Figure 2 shows the surge of activity in drilling for Devonian shale wells as compared to total completions. Since 1979, there have been several reports of wells with initial flows of greater than 300 BOPD. One report in 1981 indicated a well with initial flow of over 1800 BOPD and 4.4 MMCF. These production rates certainly add significant economic incentive. That economic incentive has also led to considerable willingness on the part of operators to quickly accept technical advances which might improve the probabilities of successfully completing wells in probabilities of successfully completing wells in the Ritchie county area.

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