(eBook version)Need: One of the most pressing problems of the Natural Gas Industry today is that of locating and developing sufficient underground storage reservoir capacity to meet peak seasonal demands. In these reservoirs, the gas is stored under pressure in the pore spaces with in the rock that originally contained gas, oil or water. Since it is economically desirable to store the gas at the maximum possible pressure, an accurate value for the optimum pressure, namely the maximum pressure to which the reservoir could be pressurized and still remain mechanically stable, is of great importance.
Result: This report presents the results of a five-year study established to investigate the stability of underground gas storage reservoirs. The main object of this study was the evaluation of a suitable criterion for optimum pressurization based on the principles of rock mechanics. Basically the research program was oriented along two parallel lines of approach consisting of laboratory studies of reservoir models and associated analytical studies. Both approaches have innate defects due to necessary simplifications; however, by carrying out both studies simultaneously and comparing the results, it was possible to draw a number of meaningful conclusions from the overall study.
Benefit: Detailed discussions and conclusions associated with various stages of laboratory and analytical study have been included at the appropriate location throughout this report. Based on the results of the study described in this report, it is concluded that optimum storage pressures in underground gas storage reservoirs could be, at least, of the order of those defined by the geostatic gradient, namely 1.0 psi per foot of cover, with no mechanical rock failure (plastic deformation or fracturing) of the reservoir or cap rock.
