Textural and petrological characteristics of possible reservoir sandstones in the onshore Balingian province, NW Borneo

Textural and petrological characteristics of Tertiary sandstones outcrop in part of the onshore Balingian province, Sarawak Basin were studied with regards to sandstone suitability as petroleum reservoirs. Granulometric analysis and thin section petrography were carried out using standard laboratory procedures on sixteen and twelve samples respectively that were collected during field work. Dominant grain size in the studied sandstone is fine grained. Sorting, skewness and kurtosis in agreement with grain size supports low depositional energy and relatively uniform sediment source. Though quartz is the dominant mineral in all the samples, microscopic study revealed that most of the samples are characterized by muddy matrix supported texture. Occurrence of quartz overgrowth and heamatitic cementation, which are capable of impeding interconnectivity of pore spaces characterized samples with grain supported textures. These evidences of diagenetic alterations in the sandstones are suggestive of high dwindling rate of reservoir energy, which will in turn necessitates the need to use enhance reservoir recovery (EOR), in order to produce such reservoirs.