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Title: Control of reservoir porosity and permeability by original depositional fabric

The Emma San Andres field exhibits many of the classic signs of a depleted reservoir including declining annual production rates and high water cuts. By the end of 1986, oil production from the Emma reservoir, more than 19 million bbl, totaled nearly 100% of the estimated ultimate recovery. Recent studies, however, indicate that as much as 25 million bbl of recoverable mobile oil still remain in the reservoir. These studies also indicate that the observed poor recovery efficiency (32%, typical for San Andres/Grayburg reservoirs) is due to reservoir heterogeneity caused primarily by variations in original depositional fabric. Two distinct porosity intervals are recognized in the Emma reservoir. The lower interval is composed of fusulinid packstone/wackestone that contains moldic and intercrystalline porosity and low (average 2 md) permeabilities. These deposits are continuous and relatively uniform throughout the area; net pay in this zone is controlled primarily by the field structure, a low-relief northwest-trending anticline. Comparison of production data with faces mapping suggests that most oil production has been controlled by the distribution of skeletal grainstone and not by structure. Effective exploitation of this remaining mobile oil must include selective completion and injection programs based on variations in the distribution of skeletalmore » grainstone. The absence of significant production from local grainstone thicks, for example, points to inefficient drainage in several parts of the field.« less
Authors:
Publication Date:
OSTI Identifier:
6776087
Report Number(s):
CONF-880301-
Resource Type:
Conference
Resource Relation:
Conference: Annual meeting of the American Association of Petroleum Geologists, Houston, TX, USA, 20 Mar 1988
Publisher:
American Association of Petroleum Geologists,Tulsa, OK
Country of Publication:
United States
Language:
English
Subject:
02 PETROLEUM; OIL WELLS; PRODUCTION; PETROLEUM DEPOSITS; GEOPHYSICS; RESERVOIR ROCK; SEDIMENTATION; TEXAS; EXPLORATION; PERMEABILITY; PETROGENESIS; PETROLEUM GEOLOGY; POROSITY; RESERVOIR ENGINEERING; SANDSTONES; ENGINEERING; FEDERAL REGION VI; GEOLOGIC DEPOSITS; GEOLOGY; MINERAL RESOURCES; NORTH AMERICA; RESOURCES; ROCKS; SEDIMENTARY ROCKS; USA; WELLS 020200* -- Petroleum-- Reserves, Geology, & Exploration; 020300 -- Petroleum-- Drilling & Production