Abstract: Permian Karst and Caves in Yates Field

Scott W. Tinker, M. D. Brondos, M. J. Parsley, J. R. Ehrets

Yates field was discovered in 1926, and has produced approximately 1.2 billion barrels of oil from estimated 4 billion BOIP, In large part from a single Permian (Guadalupian) dolomite reservoIr. By 1929, many wells had tested at rates in excess of 10,000 BOPD, ranging upward to nearly 200,000 BOPD. The remarkable flow rates, along with numerous bit drops encountered during early field development, and sedimentologic features observed in whole cores recovered during development drilling programs provide evidence of an extensive fracture and karst system within the San Andres Formation.

Yates field is characterized by a modern log database from nearly 1800 wells, generally drilled on 10-acre spacing, along with a core database totaling approximately 23,000 aggregate feet cut in 118 wells. This database provides an opportunity to document in detail the distribution of karst features within Yates field. However, relatively little evidence of caves is preserved in core. Conversely, distinguishing post-San Andres karst on logs is difficult, emphasizing the need to integrate all of the log, core and production data In order to characterize the karst system accurately.

This paper discusses the formation and distribution of karst related to (1) near-surface solution breccias and altered fabrics associated with the post-San Andres Permian unconformity; (2) highly altered sedimentary fabrics, infiltrated sediments, cements and open voids associated with the extensive network of caves formed beneath an emergent post-San Andres island complex; and (3) a deeper cave system possibly related to an earlier San Andres exposure event.

AAPG Search and Discovery Article #90986©1994 AAPG Annual Convention, Denver, Colorado, June 12-15, 1994