--> Abstract: Modeling and Simulation of a Vuggy Carbonate Reservoir, by K. Dehghani, P. M. Harris, K. A. Edwards, and W. T. Dees; #90942 (1997).
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Abstract: Modeling and Simulation of a Vuggy Carbonate Reservoir

DEHGHANI, KAVEH and PAUL M. HARRIS, KELLY A. EDWARDS and WILLIAM T. DEES

McElroy field (Permian Grayburg formation, West Texas) produces approximately 17,000 BOPD from a mature waterflood. The approximately 24-m thick main pay zone is primarily peloidal dolograinstones/packstones containing interparticle/intercrystalline porosities. But thin high porosity-permeability vuggy zones in the central portion of the field lessen the effectiveness of waterflood leaving a major portion of oil bypassed in the lower permeability matrix.

The primary and waterflood phases in a 15 well, 100 acre vuggy portion of the field were modeled, and then successfully history matched: (1) A detailed one million cell geostatistical distribution of total porosity was derived using the well log data from 67 wells; permeability was assigned using a cloud transform of core data from 10 wells; (2) Two vuggy zone distribution cubes were generated geostatistically using different vug correlation lengths; sonic (matrix) porosity calculated using the Wyllie Previous HitTimeNext Hit-Previous HitAverageNext Hit Previous HitEquationTop was subtracted from transform total porosity to yield secondary porosity, and significant differences in matrix and total porosity were considered to represent vugular intervals; (3) Each vug distribution cube was superimposed on the main permeability cube generated in the first step, and an exceptionally high permeability value (e.g., 4 Darcy) was assigned to the vuggy zones; and (4) The generated detailed permeability models were scaled-up to 12,000 cell models for simulation studies.

The models developed considering vuggy zone distributions showed a far superior history match of primary and waterflood process than those scaled-up directly from step one. A good quality history match was seen even on an individual well basis! Modeling shows that primary recovery produced 14% of OOIP and waterflood added 12% incremental recovery.

AAPG Search and Discovery Article #90942©1997 AAPG International Conference and Exhibition, Vienna, Austria