Abstract: Evidence for Fractured Reservoirs in Shallow Gas Fields near Cedar Creek Anticline in the Northern Great Plains

SHURR, GEORGE W.

Several lines of evidence for fractured reservoirs are displayed by shallow natural gas fields on and near Cedar Creek Anticline. The reservoirs are low-resistivity, fine-grained clastic rocks of the Cretaceous Judith River and Eagle Formations. These units were deposited in an outer shelf setting and were subsequently deformed by Laramide movements on basement blocks.

Production patterns are similar to patterns of published surface faults in three fields in eastern Montana: Gaslight (Eagle), Plevna (Judith River), and Cedar Creek north of Baker (Judith River). Production patterns parallel structure contours, linear features on air photos, and surface drainages in southwestern North Dakota at the Little Missouri Field (Eagle) and in northwestern South Dakota at the West Short Pine Hills (Eagle) and Cady Creek (Eagle) Fields.

In and around West Short Pine Hills Field in Harding County, SD, there are several additional indications of fractured reservoirs. A fault plane is preserved as a striated displacement surface in core taken from the Eagle Formation. Two areas of high cumulative production, separated by an intervening area of lower production, are elongate north and south. Fractures measured in outcrops of Tertiary sandstones within the field have a north-south mode that is well defined and on trend with the production patterns.

AAPG Search and Discovery Article #90946©1997 AAPG Rocky Mountain Section Meeting, Denver, Colorado