A Study of Reservoir Parameters Affecting Gas Well Spacing in West Virginia

Abstract

Abstract Well spacing has a significant effect on gas reservoir deliverability optimization. A single well seldom provides the desired rate of production from a given reservoir. Generally, the total rate of gas production increases with the number of the wells production increases with the number of the wells completed in the gas reservoir. At the same time, inter-well interference tends to reduce this increase in total rate of production as the number of producing wells are increased. Consequently, there producing wells are increased. Consequently, there must exist a well-spacing which will result in the most efficient recovery from a natural gas reservoir. This optimum well spacing depends upon the producing formation characteristics as well as economics of field development. The overall objective of this paper is to provide a general guideline based on reservoir provide a general guideline based on reservoir engineering principals for efficient well spacing pertaining to gas producing formations in West pertaining to gas producing formations in West Virginia. The objective was achieved by developing a general reservoir model which simulates the flow of gas in a reservoir containing several wells. The model was then used to study the parameters which affect well interference and spacing. The model has the advantage of also accounting for the inertial component of pressure drop in gas flow through porous media, a factor which was found to affect porous media, a factor which was found to affect well interference. Reservoir data pertaining to Big Injun and Benson formations were collected and interpreted. The interpreted data were statistically analyzed and the results were utilized in conjunction with the model to provide general guidelines pertaining to spacing for gas wells producing from these two horizons in West Virginia. Introduction As more and more of the natural gas reserves are depleted, more efficient methods of extraction/ recovery must be used to insure a reliable supply of natural gas in the future. Generally, a single well seldom provides sufficient withdrawal capacity for a whole reservoir. Total production can be increased by drilling and producing additional wells, but inter-well interference tends to diminish the increase in total rate of production as the number of producing wells are increased. Consequently, there must exist an optimum number of wells and an optimum spacing pattern which will result in the most efficient recovery of natural gas from a reservoir. The optimum well spacing is defined by Van Winegen as "The density of wells that will result in the greatest ultimate profit to operator". Defined in these terms, it implies that the evaluation of different development programs will be controlled by such economic factors as drilling and completion cost, net price of hydrocarbons, interest rate, and operating life. The optimum number of wells that are identical in their geometry as well as production capacity in a reservoir can be estimated when the reservoir is substantially uniform throughout. If, however, the reservoir is highly heterogeneous or contains numerous faults, no known general model lends itself to a realistic estimate of optimum well spacing. In order to determine the optimum well spacing in a gas reservoir, it is necessary to identify and study the reservoir and well parameters which control the reservoir deliverability and interference. The objective of this study is to determine general guidelines for optimum well spacing for efficient recovery of natural gas in West Virginia. The result of this study can be used as a technical basis for evaluating state-wide gas well spacing regulations or to determine the most efficient gas field development method by the individual operator. P. 251