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Rock compressibility and failure as reservoir mechanisms in geopressured gas reservoirs

Journal Article · · J. Pet. Technol.; (United States)
DOI:https://doi.org/10.2118/2500-PA· OSTI ID:5594569
Rock compressibility has long been recognized as an important factor in material-balance calculations of oil in place for closed reservoirs producing above bubble-point pressure. For example, if the pore volume compressibility of the reservoir rock is half of the compressibility of the undersaturated oil, neglect of the rock-compressibility term results in about a 50% overestimation of oil in place. In general, it may be stated that in material-balance calculations on closed reservoirs, consideration of rock compressibility becomes increasingly important as the fluid compressibility decreases. A study of the N. Ossun field, Louisiana, reveals that as reservoir pressure is depleted, the increase in net overburden pressure initially causes rock failure, and as the failure continues with decreasing pore pressure, rock compressibility decreases until eventually it reaches a normal value. The N. Ossun field is a geopressured gas reservoir with an initial pore pressure of 8,921 psia at 12,500 ft subsea depth, or a gradient of 0.725 psi/ft. Tabular data give pertinent information on this reservoir. Good geologic control is indicated by a structure map.
Research Organization:
Phillips Petroleum Co; Louisiana State Univ
OSTI ID:
5594569
Journal Information:
J. Pet. Technol.; (United States), Journal Name: J. Pet. Technol.; (United States) Vol. 21; ISSN JPTJA
Country of Publication:
United States
Language:
English