thumbnail

Organic metamorphism in the Lower Mississippian-Upper Devonian Bakken shales. Part 1: Rock-Eval pyrolysis and vitrinite reflectance.

Journal of Petroleum Geology

By:
, ,

Links

  • The Publications Warehouse does not have links to digital versions of this publication at this time

Abstract

The Williston basin is an intracratonic basin extending across parts of several states, principally North Dakota, on the US/Canadian frontier. A sequence of up to 16 000 ft of Phanerozoic rocks exists in the basin; the Bakken formation is a relatively thin clastic unit composed of three members, of which the middle one is a black shale. Both core chip and cutting chip samples from a series of widely-distributed well locations were taken for laboratory analysis. Pyrolysis data showed 'wide variations' in maturity indices in samples from equivalent depths at different well locations. This suggests that a number of different palaeoheat-flow regimes have existed in the basin, resulting in the optimization of hydrocarbon formation processes at varying depths at different localities. The vitrinite reflectance profiles presented illustrate the expected trend of linearly-increasing maturity with depth to around 6500 ft. Between 6700 and 10 000 ft, however, this trend is interrupted by two 'reversals'. It is suggested that these reversals are due to suppression of the vitrinite reflectance values in samples with high concentrations of H-rich organic matter, and that they may therefore be associated with transitions from 'terrestrial-derived' to marine-depositional conditions. Consequently, the precise identification of the thresholds of intense hydrocarbon generation within the basin is problematic.-J.M.H.

Additional Publication Details

Publication type:
Article
Publication Subtype:
Journal Article
Title:
Organic metamorphism in the Lower Mississippian-Upper Devonian Bakken shales. Part 1: Rock-Eval pyrolysis and vitrinite reflectance.
Series title:
Journal of Petroleum Geology
Volume
9
Issue:
2
Year Published:
1986
Language:
English
Larger Work Type:
Article
Larger Work Subtype:
Journal Article
First page:
125
Last page:
162
Number of Pages:
38