| dc.description.abstract | This research discussed the relationship of organic material characteristics and thermal maturity versus hydrocarbon potential from the viewpoint of applied organic geochemistry. The purpose is to establish the reliable indices of synthetic assessment of organic matter in the evaluation of petroleum potential. Therefore, the scope is focused on maceral composition analysis, vitrinite reflectance measurement, Rock-Eval pyrolysis, elements analysis, and multivariate statistical analysis. In addition, it is to present new guidelines for improved assessment of the kerogen type, generative potential and thermal maturity using Rock-Eval parameters.
The analytic results indicate that petroleum generation potential is completely exhausted at a vitrinite reflectance of 2.00-2.20% or a Tmax of 510-520°C. A decline in BI signifies the start of the oil expulsion window and occurs within the vitrinite reflectance range 0.75-1.05% or a Tmax of 440-455 oC. The petroleum potential can be divided into four different parts based on the cross-plot of HI vs. %Ro. The area with the highest petroleum potential is located in section B with %Ro=0.60-1.00%, and HI>100. The start of the oil expulsion window occurs within the %Ro range of ~ 0.75–1.05%Ro or the Tmax range ~ 440-455°C and the total oil window extends to %Ro = ~ 1.25-1.95 or Tmax = ~ 465-525°C.
The H/C ratio, as well as the HI, S1, and S2, generally decreases with the maturity increasing. The H/C ratio decreases slightly from 1.1 to 0.7 with the maturity increasing from Ro 0.55% to 0.85%. Samples with H/C ratio in this range show significant change in certain other geochemical parameters (eg. HI, S1, S2, S1+S2, S1/(S1+S2), S1/TOC, (S1+S2)/TOC, Tmax). The (S1+S2)/TOC ratio (defined as QI) was used as an indicator of the hydrocarbon potential. The QI, HI and H/C ratio show a certain correlation, all increasing accordingly. The QI of the samples analyzed in this study is approximately 100 to 380 (mgHC/gTOC), similar to that of most humic coals for oil and gas generation. Samples with Ro value lower than 0.55% always show significant variation in their HI, ranging from 80mgHC/gTOC to 520mgHC/gTOC. It is inferred that hydrocarbon potential started from Ro 0.55% and atomic H/C ratio 1.1 in this study.
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