Abstract

The Upper Cretaceous Niobrara Formation is the latest in a series of fractured plays at the forefront of exploration activity within the Rocky Mountain region. Prolific oil and gas production has been achieved through the use of modern exploration methods followed by advanced horizontal and vertical drilling and completion techniques.

Regional historical 2-D seismic data as well as older single fold seismic data is used to target attractive exploration areas within the mature Denver Basin of eastern Colorado, southeastern Wyoming, and western Nebraska. The use of these reconnaissance data is followed by modern high-resolution 3-D seismic surveys that identify Niobrara faults along with their orientation and throw.

McElvain Oil & Gas Properties, Inc. acquired a series of three proprietary 3-D surveys in Yuma County, Colorado, which were merged into one contiguous 54.5 mi² 3-D survey through data reprocessing. Subsequent interpretation techniques, including volume curvature, were used to identify Niobrara fault trends, patterns, and fault displacements and reveal attractive structural exploration targets in the Niobrara Formation. These techniques led to the discovery of two new Niobrara fields within the Mildred combined 3-D survey area. Two additional 3-D surveys, the 4.2 mi² Krieger 3-D in Weld County, Colorado and the 14.6 mi² Cedar Creek 3-D in Cheyenne County, Nebraska are shown to illustrate Niobrara faulting signatures in other portions of the Denver Basin. These surveys reveal that fault patterns within the Niobrara Formation may be influenced by both Laramide reactivation of basement shear zones and post-Cretaceous dissolution of Permian salt beds.