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ABSTRACT: West Chalkley Field: A Significant Discovery in a Mature Area

Richard J. Powell, John R. Bedingfield, Forrest E. Hand, Gregory L. Jones, Erick C. Nefe, Joel E. Matek

In August 1989 the Exxon 1 Sweet Lake flowing at a rate of 21.9 mmcf per day with 384 bbl of condensate per day and ushered in a significant discovery in the Oligocene Frio Miogyp sand of south Louisiana. The West Chalkley discovery is located within the Miogyp Embayment of south Louisiana, 20 mi west of nearest equivalent production at South Lake Arthur field. The trap is a buried lowside rollover anticline downthrown to the embayment fault. The Miogyp sequence is an expanded lowstand deltaic system with porosities averaging 17-20% and permeabilities up to several hundred millidarcies. The test was from a 66-ft interval at the base of this deltaic system in an overall pay section between 14,000 ft and 14,860 ft. Development drilling in West Chalkley field began in late 1 89.

The Miogyp Embayment exemplifies the nature of exploration in a mature basin where new, deeper resolution seismic is imaging high-potential buried structures. West Chalkley Field is located beneath the 400 bcf of gas Chalkley field discovered in 1938, where five tests had unsuccessfully attempted to explore deeper targets. Until recently, seismic data in the West Chalkley field area was not of high enough resolution to adequately image structures at the depths drilled by the 1 Sweet Lake.

This deep (14,000-20,000 ft) trend has become very active over the last two years, fueled not only by the 1980 discovery of South Lake Arthur but also by numerous speculative seismic surveys which sparked a fast-paced lease play for large Miogyp structures. The West Chalkley discovery illustrates how the use of sequence stratigraphic concepts, combined with detailed log correlations and modern seismic data, can still lead to significant discoveries even in mature areas such as south Louisiana.

AAPG Search and Discovery Article #91003©1990 AAPG Annual Convention, San Francisco, California, June 3-6, 1990