Assessment of any shale gas potential is normally made using original S 2 value calculated from the present day S 2 values of the rock-eval analysis. The present day S 2 itself has got technical limitation and to get the original S 2 it is necessary to evaluate the original TOC which is also bound by many limitations. The technical limitation of S 2 suggests available hydrocarbons above C 24 composition cannot come as S1 thus increasing amount of S2 although the cracked S2 amount may not be

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... high. Calculation of the original TOC value is also made by different methods. Based on the previous works it is accepted that type-1 kerogen loose TOC up to 80% , to 20% to generate petroleum. Original TOC is calculated as equal to Present day TOC / (1-%converted). Calculation of the converted percentage should be very definite to conclude the percentage of original TOC. Jarvy has shown a calculation method using iso-decomposition and iso-original HI profiles. This method is limited to the fact that original HI can only be known once the original TOC is known. In this work attempt has been made to develop a mathematical equation using vitrinite reflectance (Vro) to calculate the original TOC. This method is also limited to the correct measure of Vro data and the equation is valid only based on the assumption that the cracking of kerogen to generate petroleum is same. www.iosrjournals.org 69 |Page V. Conclusions Calculations above show reasonable assessments of generated hydrocarbons in the study area. Limitation of the evaluation of generated hydrocarbons mainly depends on the calculation of original TOC. Assessment of the unconventional resource is limited to the generation potential and effective primary migration. Re-calculation of the available published data suggests sample 2, 6 and 7 remained in oil window are sweet spots for shale oil. Sample 2 is near the end of oil window and may have some more associated gas also compared to sample 6 and 7. Sample 3, 4, 5 and 8 are sweet spots of shale gas and expected potential is nearly 298 scf/tonne of the rock. This research is mainly focused on technology but the values in wells may not relevant because all calculations are made based on same pressure of 3772.96psi which is not correct. However well-wise pressure data, lithology, porosity, density may upgrade the work for dependable values.