ABSTRACT: Anomalous Porosity Development, Northeastern Lisburne Field Area, North Slope, Alaska

Leta K. Smith

Wells drilled in the northeastern portion of the Lisburne field, where anomalously high porosity was found, were originally anticipated to have correspondingly high production. But an evaluation of the porosity type shows that the high porosity portion of the field is dominated by microporosity and poorly connected moldic pores that cause very poor permeability. Spacial relationships of this porosity development to adjacant structures indicate that it is related to both the Lower Cretaceous unconformity, which defines the eastern limits of the field, and the Niakuk fault which defines the northern limits of the field.

Evidence for the porosity types came from two sources. Petrographic observations were not entirely conclusive because only drill cuttings existed from wells in the high porosity area. Production data supported the conclusion suggested by the petrography by demonstrating that different productivity trends are associated with different porosity types. This technique of correlating production data with porosity type my prove useful in similar reservoirs where different facies are represented by different porosity types and where the productivity is less than expected for the amount of porosity present.

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