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ABSTRACT: Developmental Sequence, Necessity of High Deliverability and Volumetrics--South Lake Arthur Field

Mike Barnes

Thirty-one wells have been drilled in and near the productive area of South Lake Arthur field, Jefferson Davis and Vermilion Parishes, Louisiana, since its discovery in November 1979. Three reservoirs exist within the field from a depth of 16,600 ft to 17,500+ ft. They are, in relative economic importance, the middle, lower, and upper depositional sequence of an isolated deeply buried overpressured delta. Average field reserves in the Oligocene Miogypsinoides series (24 MYBP) productive trend prior to discovery range from 100 to 200 BCFG. This discovery, prior to 1985, was not suspected to be an order of magnitude (five to ten times) greater than the trend norm. The earliest recognition of the field's larger reserve potential was predictable with data from two key wells d illed eight months apart. The wells combined had 386 ft of productive sand and dip-meter logs recorded approximately 11 degrees of south-southwest dip. At this point a geologist could have recognized that structural advantage existed in a north and easterly direction.

Ten wells were drilled in the first six years of the field's life, by five operators. Twenty-one wells were drilled in the next four years by eight operators. The intense competition to control and extract reserves has resulted in a capital expenditure of approximately $300 million. The need for high deliverability wells, which cost $8 million to drill and complete, is a critical economic factor in well design and planning. Two basic well completion designs have resulted in sustained daily deliverabilities of 12 to 20 MMCFG. Reservoir thickness and aerial extent coupled with the need for competitive production capacity within common reservoirs has had a significant influence on completion practices. The major portion of the reserves is in the northeast quadrant of the anticlinal struc ure, owing to stacking of distributary mouth

bars of the lower and middle Miogypsinoides sand bodies. The zones appear (because of pressure similarities) to be in communication. There are, however, numerous examples of water-bearing zones above the bottom water field limit. There is a high probability of isolated sub-reservoirs that require perforation of the entire sand interval to ensure maximum competitive recovery.

AAPG Search and Discovery Article #90999©1990 GCAGS and Gulf Coast Section SEPM Meeting, Lafayette, Louisiana, October 17-19, 1990