CHRONOSTRATIGRAPHIC RECONSTRUCTION OF MIO - PLIOCENE MAHAKAM DELTA AND ITS CONSEQUENCES FOR PETROLEUM PLAYS: AN ANALOG FLUME TANK EXPERIMENTAL MODEL OF MAHAKAM AREA

摘要

The Miocene sequence of Mahakam Delta has contributed significant hydrocarbon production from several pay zones with substantial thickness up to ± 1600 m. The main reservoirs comprise stacked mouth bar sands, distributary channels, and thin tidal bar sands with slight fluvial influence. The purpose of this experiment is to obtain a better understanding of the stratigraphic architecture and deltaic successions. The experimental variables in this study have been derived from quantitative stratigraphic interpretation of the Mahakam area. The variables serve as constraints for the modeling experiment. The spatial scale of the model, in conjunction with sediment supply rate, replicates 9.2 million years of basin fill processes of four sequences totaling 360 minutes. Assumptions used in this experiment include estimations of sea level change and local basin subsidence due to growth faulting. The results of the experiment demonstrate that growth faulting effected sedimentary successions on both sides of hanging and foot wall blocks, whereas the hanging wall succession is characterized by early transgressive, lowstand and highstand deposits, while the foot wall succession, in contrast, comprises predominantly late transgressive deposits. The significant petroleum plays observed in the modeling are highlighted in each system-tract scale. The reservoir elements derived from coarse grain highstand deposits of Highstand Sytem-Tract (HST) lowstand wedge deposits of Lowstand Sytem-Tract (LST), incised valley and lowstand channel fill of Transgressive System-Tract (TST), while highstand flooding (HST) and Maximum Flooding Surface (MFS) deposits are considered as effective intraformational and regional seals. Possible hydrocarbon traps were found as stratigraphic, structural and their combination. These significances and models need to be tested and validated with subsurface data. Three dimensional seismic geomorphology methods are an alternative that authors suggest.