Datapages, Inc.Print this page

Abstract: The Powder River Basin - A Classic Area of Basement Control on Oil & Gas Fields, Including a Number of "Purely Stratigraphic Traps"


In the Powder River Basin most of the prolific oil producing formations were laid down during the Cretaceous period contemporaneously with the Laramide orogeny. This powerful EW or ENE-directed compressional event strongly affected depositional patterns in the strata and created many of the traps and/or reservoirs into which oil migrated.

Given the fault block nature of basement and the occurrences of weakness zones bounding these blocks - the subject of previous presentations by the author - it is not difficult to imagine that there should be basement control of individual oil fields. The basement fault block pattern has not been mappable under thick sedimentary cover in the past with any of the common geological or geophysical techniques, but it is possible to map these blocks using properly acquired, processed, and interpreted aeromagnetic data. Comparisons of this type of mapping with well known traps and reservoirs in the basin have shown many one-on-one correlations, indicating the following types of basement control have taken place:

(1) Frontier-Dakota formations - asymmetric folds created during Laramide compression by high angle reverse faults over basement weakness zones,

(2) Muddy formation - channels following low topography in the underlying shale resulting from erosion of more highly jointed areas located over basement faults, and

(3) Shannon Sussex Ferguson, Tecla, Teapot sands - sand bars that apparently formed from the winnowing action of bottom currents flowing over sea floor highs resulting from high angle reverse faults at basement level.

I will show examples of about 20 individual oil fields that fall in the above categories, including Poison Draw, Hartzog Draw, Dead Horse-Barber Creek, Salt Creek, Big Muddy, Bell Creek, Fiddler Creek, and Clareton.

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