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The AAPG/Datapages Combined Publications Database

Williston Basin Symposium

Abstract

SKGS-AAPG

Sixth International Williston Basin Symposium, October 7, 1991 (SP11)

Pages 161 - 164

SEDIMENTOLOGY AND PETROLEUM GEOLOGY OF A TRIASSIC SPEARFISH SANDSTONE RESERVOIR, SOUTH STARBUCK FIELD, BOTTINEAU COUNTY, NORTH DAKOTA

CHRIS A. OGLESBY, Bass Enterprises Production Company, 201 Main Street, Suite 2900, Fort Worth, Texas 76109
DAVID W. FISCHER, Exploration Geologist, 1016 Cherry Street, Grand Forks, North Dakota 58201

ABSTRACT

The South Starbuck field (Township 160N, Range 78W) produces from a Triassic Spearfish Formation point bar sandstone that rests unconformably upon evaporites and carbonates of the Mississippian Charles Formation or is in erosional contact with Spearfish bioturbated mudstones/siltstones. The facies progression from base to top is as follows: coarse-grained Previous HitlagTop deposits of the thalweg; medium to fine-grained, festoon cross-stratified sandstone; fine-grained, planar-bedded sandstone; fine to very fine-grained, current ripple-laminated sandstone; and abandonment fill (sparsely burrowed siltstones with occasional climbing ripples). The thalweg deposits are well cemented resulting in non-reservoir rock. Early cementation occurred in the most permeable facies prior to oil migration. The lower energy facies, which were less permeable, were not affected by this phase of cementation.

Oil migration into the Spearfish is postulated to be secondary, from a breached Mississippian trap in the Starbuck Southwest field to the west, where the point bar sandstone is in contact with the underlying Charles Formation (Berentson Member) reservoir.

Lack of an active water drive has resulted in relatively low recoveries (40,000 bbl/well). Similar facies are productive in the Russell field (Township 160N, Range 79W) where recoveries are much higher (110,000 bbl/well), due to the presence of an excellent edge-water drive.

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