Abstract

Research presently underway at the Pennsylvania State U. is concerned with the Pennsylvania State U. is concerned with the study of the mechanical stability of underground gas storage reservoirs. This research involves a number of phases including a laboratory model study which will be outlined in the present paper. paper. In these studies small scale models containing reservoir cavities of simple geometry were first loaded under typical in-situ stresses then pressurized internally until failure occurred. Microseismic techniques were utilized to detect reservoir failure.

A description of the experimental facilities and the model fabrication techniques are included along with a review of results obtained from tests on a number of differently shaped reservoir cavities. A discussion, relative to the effect of reservoir geometry and depth below surface, on the optimum storage pressure is included. In general, the results of the model study indicate that optimum storage pressures may be considerably higher than those based on the discovery pressure or the average hydrostatic gradient.

Introduction

The natural gas industry today is faced with the problem of locating and developing sufficient underground storage reservoir capacity to meet peak seasonal demands. Since it is economically desirable to store the gas at the mammon possible pressure, an accurate value for the optimum pressure, namely the maximum pressure to which a reservoir could be pressure to which a reservoir could be pressurized and still remain mechanically stable, is pressurized and still remain mechanically stable, is of great importance.

Natural gas is stored underground in former gas and oil reservoirs, aquifers and man-made cavities. As the demand for natural gas increases the necessity for storing larger and larger volumes of gas underground during periods of low demand has increased markedly. In 19701 a total of 325 storage reservoirs were reported in the U. S. The majority of underground storage was located in former gas and oil reservoirs with a lesser number in aquifers and relatively few in man-made cavities.

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