Application of the pyrolysis-carbon isotope method for determining the maturity of kerogen in the Bakken shale

A maturity indexing procedure based on the isotopic difference between the total accumulated methane produced by exhaustive pyrolysis and the kerogen (Δ¹³C) and the mole ratio of methane to kerogen carbon (CMR), has been tested by applying a standardized technique, i.e. exhaustive pyrolysis (600°C for 120 hr) of extracted-powdered samples and measurement of the amounts and isotopic composition of the methane and kerogen carbon, on a suite of 15 Bakken shale samples.A linear relation was found between the carbon mole ratio of pyrolysis-derived methane and total organic carbon and the δ¹³C difference between the pyrolysis-derived methane and total organic carbon (r = −0.79); and between the amount of CH₄ generated from exhaustive pyrolysis and H/C atomic ratios (r = +0.91).