ABSTRACT

A plate tectonic model is introduced to explain thermal maturation and fracturing of the Bakken Formation in the central Williston basin. Subduction-driven clockwise rotation of the Phanerozoic cover can explain the asymmetry of some Williston basin structures. Notable are east-verging anticlines in the north (Antelope) and west-verging structures in the south (Cedar Creek Anticline). Punctuated diagenesis, rather than burial diagenesis, is an important mechanism for expulsion of hydrocarbons and fracturing the Bakken. This occurred during the Late Cretaceous and Paleocene, and gradually died out by mid-Eocene. Wrench faulting was important in opening major zones of tension fractures. Combining Laramide plate tectonics with punctuated diagenesis, creates a useful model for exploring for fractured Bakken hydrocarbon reservoirs. Important fracture zones can often be found by studying Landsat data.

Landsat TM imagery and digital data provide an inexpensive yet very effective tool to aid exploration in tight oil reservoirs such as the Bakken. Careful basin-wide analysis of multispectral data, particularly false color infrared photographic imagery, isolates fracture trends, fault zones, structural offsets and bright spots. In many cases previously undetected fracture zones, particularly along wrench faults, and other tectonic features are found. Follow-up work with digital multispectral data may be done using simple software on a personal computer. Township-sized data areas are available from Eosat on floppy disk at reasonable prices. Software allows the imaging and manipulation of this data on the PC screen. Histogram manipulation, stretching, band ratioing and various enhancements may be accomplished on the PC to locate or substantiate anomalies. These anomalies, then, may be field checked to determine ground truth. Various geologic signatures are susceptible to band ratioing; several common types are discussed. Application to Bakken exploration is stressed.