--> ABSTRACT: Reservoir Heterogeneity in Red River Formation, Horse Creek and South Horse Creek Fields, Bowman County, North Dakota, by Mark W. Longman, Thomas G. Fertal, James R. Stell; #91002 (1990).

Datapages, Inc.Print this page

ABSTRACT: Reservoir Heterogeneity in Red River Formation, Horse Creek and South Horse Creek Fields, Bowman County, North Dakota

Mark W. Longman, Thomas G. Fertal, James R. Stell

The contiguous Horse Creek and South Horse Creek fields produce oil from the Ordovician Red River Formation's "C" Burrowed Member. The fields are in an area of gentle (<1°) northeast regional dip and each consists of two parts: a small (<1 mi) structural closure to the east and an elongate north-trending stratigraphically trapped reservoir to the west. Each structural closure covers less than 640 ac and is drained by up to 3 wells; the stratigraphic trap covers more than 3000 ac with 15 productive wells flanked by 8 dry holes.

Reservoir rocks are highly burrowed dolomitized carbonate mudstones and wackestones deposited in open to restricted shelf environments. Increasing restriction above the reservoir culminated in deposition of the widespread Red River "C" Anhydrite. Downwardseeping brines generated during anhydrite deposition caused the dolomitization and porosity generation in the reservoir rocks. The best reservoirs occur where both the burrow fills and adjacent carbonate matrix were completely dolomitized.

Production rates in the two fields vary greatly depending on degree and thickness of dolomitization. Up to 20% porosity is present in intercrystalline and vuggy pores in the best reservoirs. Permeability, which rarely exceeds 30 md, is limited by dolomite crystal size (generally <100 microns). Interbedding of porous and relatively tight (partly dolomitized) layers gives the reservoir marked vertical heterogeneity. Ultimate production in the structures is about 640 MBO/well with increasing watercut; the stratigraphic pool will average about 240 MBO/well (including several poor wells) with little increase in watercut.

AAPG Search and Discovery Article #91002©1990 AAPG Rocky Mountain Section Meeting, Denver, Colorado, September 16-19, 1990