DONALDSON, ALAN, XIANGDONG ZOU, KURT DONALDSON, MILTON HEALD, JAMES BRITTON, LI ZHENG, and THOMAS WILSON, West Virginia University, Morgantown, WV

ABSTRACT: Seals, Barriers and Compartments of Fluvial-Deltaic Reservoir: Granny Creek Field, West Virginia

Initial and cumulative oil production maps, reflecting primary development of the Granny Creek field, show northwest trending belts of elliptical areas of higher production separated by a belt of lower production in northern part of field, whereas the belt of highest oil production in southern part is oriented approximately north-south. Oil is trapped in Granny Creek field in Price/Pocono Big Injun sandstone, on the flank of an anticline, between the gas cap updip and the pre-Greenbrier unconformity downdip. Principal pay zone is the fine-grained sandstone (C member) of marine-influenced proximal distributary-mouth bar subfacies, where chlorite coatings on grains minimized cementation and maximized the porosity and permeability. The seal is quartz-cemented coarse sandstone and conglom rate (B member) of fluvial channel fill, where illitic laminae produced pressure solution and abundant cementation on previously uncoated grains. Two thin tabular porositv barriers occur within pay zone and compartmentalize the proximal mouth-bar subfacies: 1) at boundaries separating C1, C2, and C3 tongues, concordant with bedding; and 2) diagenetic zone, discordant to bedding. Overprinting northwest aligned narrow belts of differential oil production are: 1) porosity barriers trending north to north-northwest, 2) southwest oriented narrow belts where pre-Greenbrier unconformity has removed B member seal, and 3) northeast trending faults/fracture zones. Compartments, bounded by seals and barriers, range from 1000-3000 x 1000-1500 feet, exhibit differential initial and cumulative oil pro uction, and rock pressures. Secondary recovery records northeast communication of wells when overstimuiation of wells, necessitating different strategies for optimum oil recovery.

AAPG Search and Discovery Article #90987©1993 AAPG Annual Convention, New Orleans, Louisiana, April 25-28, 1993.