--> --> The Bakken Formation, New Light Through Old Windows: Implications on the Origin and Formation of Organic Matter and Hydrocarbon Generation

International Conference & Exhibition

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The Bakken Formation, New Light Through Old Windows: Implications on the Origin and Formation of Organic Matter and Hydrocarbon Generation

Abstract

Both the Lower and Upper Bakken shale have generated and retained vast amounts of oil, particularly within the USA portion of the subcrop, with estimates range from 271 to 500 billion bbl oil (4.3 to 8.0 × 1010 m3). However, despite advances in technology, the exploration and production of the Bakken remains a high-risk venture due, in part to assessments founded on the classical theory of oil generation and the basin-wide assessment of production and source potential derived from drill cuttings, limited core sample or wire-line logs. This paper presents the findings of a integrated and comprehensive assessment of the oil generative potential for the Lower and Upper Bakken within the northern portion of the Williston Basin (Canada), using the high resolution sampling of over 40 borehole core, the resultant data base (750+ samples) of integrated geochemical and petrographic analyses is augmented by fully calibrated 1D, 2D and 3D basin models. Using the concept of Organic Facies, the organic-rich shale within both the Upper and Lower Bakken have been successfully subdivided into both major and minor correlatable organic facies across the basin by identifying a number of key petrographic components, particularly the amorphous Biuminite. Integrated geochemical analysis, (e.g., RockEval pyrolysis, pyrolysis-gas chromatography-mass spectrometry, organic sulphur analysis), with the organic petrography were used as inputs into Petrel and BasinMod. Using Organic Facie specific kinetic parameters a number of ‘micro-kitchens’ within the northern part of the Williston Basin were identified, when using standard kinetic parameters, the Bakken essentially remains immature in those same areas. Biomarker analysis has also shed significant light on the type of precursor organisms present during the formation of primary organic matter with the identification of the presence of Bacterivorous Ciliates within the euxinic water column. The presence of bacteriovores, within the water column, is interpreted as the main mechanism for the formation of the amorphous kerogen identified geochemically as Type II (IIs) and petrographically as Bituminte.