American Institute of Mining, Metallurgical, and Petroleum Engineers, Inc.

Abstract

A numerical model was used to simulate a portion of the Bradshaw Gas Reservoir and to portion of the Bradshaw Gas Reservoir and to evaluate the effect of well spacing and gathering-system pressure on production. A model study of the entire reservoir was not warranted because of limited data. After selecting a portion of the reservoir for which production data were available, an acceptable production data were available, an acceptable history match was obtained and performance prediction runs made to simulate the reservoir prediction runs made to simulate the reservoir under different future operating conditions.

Following the reservoir study the effect of well spacing on economics was determined. Production forecasts were obtained for well Production forecasts were obtained for well spacings ranging from 150 to 400-acres and for formation thicknesses of 20 and 25 feet. For each case, the economics of a typical well were determined for four gas price levels, including the current price. The results show that while the profitability index increases as well spacing increases, the present worth value calculate at a ten percent discount rate exhibits a maximum within the range of well spacings investigated. The maximum value depends on the gas price and the formation thickness.

Introduction

The Bradshaw Gas Field is located in McDowell County, West Virginia. The reservoir is a tight, relatively low-pressure Berea sand at an average depth of approximately 4000 feet, with first production established in the middle 1960's. Development of the reservoir was based on 150-acre to 300-acre spacing depending on the operator. Cities Service Oil has been producing its wells since 1966 on 300-acre spacing. producing its wells since 1966 on 300-acre spacing. This investigation was initiated to answer several questions concerning the development of the reservoir. Of particular interest was the optimum well spacing because portions of the reservoir still remained to be developed. Also, infill drilling could be initiated at several locations provided 150-acre or 200-acre spacing proved to be more economically attractive than proved to be more economically attractive than 300-acre spacing. Another objective of the investigation was to determine the effect of lowering the gathering-system pressure on production. At the time the study was production. At the time the study was undertaken, Cities Service Oil was delivering gas at a line pressure of 250–300 psig, while outside operators were producing into a line pressure of about 150 psig. In addition, other pressure of about 150 psig. In addition, other operators had drilled several wells and planned to drill several more on small leases along a railroad right-of-way which goes through some of Cities Service Oil leases.

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