Conclusions

For thorough characterization of a CBM or gas shale reservoir, and to assess its gas recovery and/or CO2 storage potential, a detailed assessment of its organic and mineral matter characteristics, sorption properties, and flow attributes through its pore-fracture system is of paramount importance. Generating reliable geochemical data in the laboratory is one of the first requisites for prospect or play appraisals. While analysing subsurface shales and coals, often the Rock–Eval technique is used, as the data provides important insights viz. thermal maturity stage, kerogen type, organic richness, and free hydrocarbons present within the samples. Although the overall process is simple and the results produce are easily interpreted, different factors influence the results. Particle crush-size and amount of sample used for analysis affect the results, and analysts should cross-check the nature of the resultant curves generated from analysis for improving the accuracy of the dataset generated. FID detector response (saturated or undersaturated or reliable), nature of S2 curves (asymmetrical or Gaussian-shaped or spiky), nature of S3 (whether CO2 during pyrolysis is generated from decomposition of organic matter or if there’s any influence of carbonate minerals) and S4 (whether entire area is calculated for TOC; also, especially significant for low-TOC or overmatured samples) curves, all provide critical insights about the unconventional play being targeted. Thorough and careful consideration of the above-mentioned factors, not only allows generation of precise data, but helps is predicting the nature of the sample being studied.