Publications

Several new Pematang depocentres are now recognised in the Teso and Cenako PSC's, Central Sumatra and include a southern extension to the Bengkalis Trough, a recognized Pematang Depocentre which has been responsible for sourcing numerous oil fields in the area. Seismic data and drilling results show that the Bengkalis Trough extends onto the Kampar Uplift which was previously thought to mark its southern boundary. The southern extension of the Bengkalis Trough is represented by the Cenako halfgraben. Seismic facies analysis of the Cenako half-graben indicated that low velocity, high amplitude reflectors in the axis of the half-graben represent organic rich, lacustrine ",brown shales",.SAR data which supplemented the planning of geological and geophysical field campaigns has resulted in the recognition of an inverted half-graben in the Bukit Susah area, some 20 kilometres South of the Cenako half-graben. A classic Pematang ",type section", is exposed in which all the facets of a Pematang depocentre are represented, from basal redbeds through to coarse, lake-fill clastics. The Pematang section is in turn succeeded by over 200 metres of post-unconformity, reservoir quality sands of the Lower Sihapas Menggala Formation. Subsurface mapping reveals two opposing polarity, half-grabens separated by an accommodation zone which is linked to an E-W mega-linear visible on SAR imagery. Subsequent transpressional wrenching has resulted in the present outcrop configuration.Shallow core data from the Pematang in Bukit Susah has revealed a complex sequence of lacustrine evolution with organic rich, lacustrine mudstones being periodically exposed during tectonically controlled ",low stands",. In contrast, in the Kiliran Pematang depocentre at the western boundary of the Teso PSC thick (18 m), Pematang coals are overlain by a continuous exposure (80 m) of deep lacustrine brown shales which exhibit upward shallowing, but no evidence of lacustrine low stands.