--> Modified Method and Interpretation of Source Rock Pyrolysis for an Unconventional World

AAPG Annual Convention and Exhibition

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Modified Method and Interpretation of Source Rock Pyrolysis for an Unconventional World

Abstract

Our understanding of unconventional reservoirs is evolving daily and never at a greater rate than the past 15 years. However, programmed pyrolysis methods developed in the 1970s are still used today to assess the present day organic matter quality and quantity of potential source rocks. More importantly the interpretive guidelines for unconventional reservoirs developed for the Barnett Shale int eh 80s and 90s are still being used to characterize organic matter quality and maturity of nearly all prospective unconventional plays new and old. Recent advancements in pyrolysis technology, manufacturing, training and communications have paved the way for organic screening via pyrolysis on larger numbers of samples with faster turnaround times. The results are now available for critical time sensitive decisions such as where to land a lateral and how to apply customized completions, but also feed development of more models and trend mapping. Investigation of pyrograms which now span a much larger range of organic matter types and maturities has exposed multiple caveats in the traditional pyrolysis method and the interpretive guidelines being applied to liquids rich source rocks. The most problematic of which are attributed to heavy hydrocarbon carryover from S1 to S2 which can complicate kerogen quality assessment, maturity determination and production quantity/quality estimate resulting in potential inconsistencies between maps/models and production. Pyrograms and comparative results from parallel samples run through different pyrolysis methods will be presented for discussion. Modified initial isotherm temperatures designed to volatize a larger range of hydrocarbon without cracking kerogen provide a possible solution to the heavy hydrocarbon carryover issues. Pyrograms generated from both a traditional temperature ramp and a more rapid pyrolysis temperature ramp are presented to fully investigate the effects on the S2 peak geometry/quantification as well as Tmax assessment. Furthermore we attempt to properly address maturity as a function of kerogen quality with several new concepts better using the raw data generated from our modified source rock pyrolysis method.