Spatial – Temporal Variability of Hydrocarbon Distribution in the Lambir Formation, NE Sarawak

Lambir Formation (Mid- Miocene) has produced oil in the past. Recent interest in the SK333 block to explore for oil and gas has generated renewed research interest in this and other related Formations. This formation was studied to evaluate possible spatial-temporal variations in hydrocarbon distribution. Three representative samples were collected and tested using a range of mineralo-chemical analysis. Sample 1, has a E4/E6 ratio of 1.42 with presences of aliphatic CH compound and CH / Aryl-CH / Aryl-H shared peaks at 2945.01cm-1 and 784.97cm-1 respectively. Aliphatic C=C (Olefins) bonds were also detected in a shared peaks with carbonyl compound at 1600.81cm-1. Aromatic compounds were found in all samples from the Lambir Formation at around 400-700cm-1 region. Sample 2 and Sample 3 which showed low E4/E6 values, indicate a dominance of aliphatic components. In sample 2, the low aliphatic values is also reflected in the FTIR spectra with prominent aliphatic group such as the CH and CH / CH2 detected at 1407.94cm-1 / 1620.10cm-1 and 2920.03cm-1 respectively. Similarly in sample 3, the FTIR spectra showed the presence of aliphatic compounds at 1463.87cm-1, 2850.60cm-1 and 2918.10cm-1. All samples showed variations in the UV-vis spectra with values indicating the presence of aliphatic and aromatic compounds at varying proportions. The Fourier Transform Infrared analysis reconfirmed the presence of aliphatic and aromatic compounds in various proportions. The variations in the proportions of aliphatic and aromatic compounds suggest possibly differential migration of hydrocarbons within the Formation. This also indicates that the Lambir Formation may not have been a primary reservoir.