Publications

Geochemical analysis of the crude oils from various wells in Rantau, Aru and Langkat-Medan block, North Sumatra, characterises them as light hydrocarbons, considered to be condensates. Analysis of the GC-MS data, C1 - C31 whole oil, C12+ Saturate gas-liquid chromatography and Pr/Ph ratios, indicate that the crudes are very light, quite similar and genetically related, having originated from a common source in a reducing environment. The triangular plot of C4 - C7 gasoline range compounds in normalised percentages of 2-Methylpentane (2MP), 3-Methylpentane (3MP) and Methylcyclopentane (MCP) show one family of samples, however, the cluster is elongated alorrg the MCP axis. This is interpreted to reflect a difference in level of maturity amongst the crudes. The MCP compound is not as stable as the MP compounds, hence the samples with high MCP percentages are believed to be less mature than the samples with low MCP percentages.The results of this study show that Rantau crudes have lower MCP percentages than Aru and Langkat/Medan crudes so that the Rantau crudes are overall more mature than the other crudes. This condition is largely controlled by the high geothermal gradient in the Rantau area.