Cretaceous System Stratigraphy and Shallow Gas Resources on the Fort Peck Reservation, Northeastern Montana

Abstract

ABSTRACT Four upper Cretaceous formations have been identified as shallow gas exploration targets on the Fort Peck Reservation in northeastern Montana. Gas shows are documented and sandy intervals correlated with Canadian equivalents. Progradational, regressive, depositional environments vary from inner shelf, sand ridge complexes to outer shelf, shaly, sheet sands. The Judith River, Eagle, Niobrara and Greenhorn Formations present suitable horizons for further investigation. Stratigraphic thinning in upper Cretaceous rocks generally occurs where these sands are better developed over the prominent structural feature known as the Wolf Creek nose. Conventional drilling for deeper oil zones has not properly tested the shallow gas zones. Shows, net pay maps, and reservoir quality determinations will guide exploration and development along structural trends.