Evaluation of Organic Matters, Hydrocarbon Potential and Thermal Maturity of Source Rocks Based on Geochemical and Statistical Methods: Case Study Miocene of the Seblat and Lemau Formation, Bengkulu Basin

Abstract

32 rock samples have been studied by means of geochemical and statistical analyses for evaluating source rocks. The geochemical analysis includes pyrolysis data. The results show that the Miocene Source rock are fair to excellent hydrocarbon potential level, with kerogen contained is included into Type II that have the capability of generating oil and limited gas. The analyzed data were treated statistically to find some factors, clusters, and relations concerning the evaluation of source rocks. These factors analysis can be classified into two factors. (1) Variables S2, TOC%, S1, and HI which determine the organic richness, hydrocarbon potentiality and the type of organic matter. (2) Variables PI, HI, and Tmax which determine the thermal maturity. In addition, cluster analysis separated the source rocks in the study area into two major groups. (1) Source rocks characterized by HI <400 (mg/g), TOC from 0, 22 to 11, 53%, S1 from 0.00 to 1.05(mg/g) and S2 from 0.04 to 23.64 (mg/g) ) indicating fair to good source rocks with kerogen of type II and III capable of generating oil and gas. (2) Source rocks characterized by HI 350 - <703 (mg/g), TOC from 5.39 to 23.58%, S1 from 0.24 to 0.88 (mg/g) and S2 from 29.62 to 84.48 (mg/g) indicating good to excellent source rocks with kerogen of type II capable of generating oil and limited gas. Moreover, Pearson’s correlation coefficient shows a strong positive correlation between TOC and SI, S2 and positive correlation between TOC and HI, and negative correlation between TOC and Tmax.