Model-assisted Rock-Eval data interpretation for source rock evaluation: Examples from producing and potential shale gas resource plays

Rock-Eval pyrolysis has been widely accepted by the petroleum industry as a useful technique for a quick, easy and cost effective source rock evaluation. However, there are misconceptions and misuse of some of the existing Rock-Eval parameters due to implicit underlying assumptions or poor understanding of the limitations, which could lead to erroneous conclusions. Data interpretation from a perspective of hydrocarbon generation kinetics may facilitate better interpretation of the hydrocarbon generation capacity of a source rock from its thermal stability and transformational behaviors. We present a model-assisted approach for data interpretation, from which data scatters can be viewed not only for the remaining petroleum generation potential of individual samples, but also for data specific thermal decomposition path as a whole to verify whether the data come from a single kerogen population with similar kinetics and associated generation potentials. Moreover, we propose a concept of dimensionless TOC and S2 variables that effectively removes the thermal maturity overprint in the traditional TOC vs. S2 plot used for the determination of the kerogen type. The dimensionless variables are defined by rescaling the parameters against their original values before thermal decomposition. On a dimensionless plot, data points from the same genetic population of source rocks align on a single line regardless of their thermal maturation levels. This article demonstrates the methods and the proposed approaches for studying oil generation kinetics and resource potential using traditional Rock-Eval data through examples from selected producing and potential shale gas plays in Canadian sedimentary basins and elsewhere.