One of the widely used hydrocarbon maturity parameter was vitrinite reflectance (Ro). The effectiveness of this technique had been proven good if it was :used for coal sample. But, its effectiveness was relatively declining if it was used for determining source rock, especially if that source rock contained relatively high hydrogen. In this case, the value of gained vitrinite reflectance was usually lower than the regional value. The existence of this deviation can cause a miss interpretation on the determination of source rock maturity in a certain district. From the result of maturity analysis, it was shown that there was a vitrinite reflectance suppression on Brown Shale Formation, and the existence of this suppression was affected by the hydrogen content. The result of the maturity analysis using Ro (MVR or Measured Vitrinite Reflectance) data showed that there was an oil window at a deeper depth compared with using Tmax analysis and CVR (Corrected Vitrinite Reflectance). The determination of oil window point using MVR data, Tmax, and CVR, in fact, showed that the determination of oil window based on the data Tmax had equal result with the use of CVR data.
Authors : M. Syaifudin & Bambang Triwibowo