SEISMIC GEOMORPHOLOGY: A STUDY FROM WEST NATUNA BASIN, INDONESIA

摘要

1. Regarding the complexity of fluvial and fluvial-deltaic process, there are many similarities between meandering river systems and distributary chanel systems during Neogene time in the West Natuna basin with the modern system in the surrounding study area, such as east coast of Malaysia and Sumatera.rn2. Several predictive relationships can be concluded from examination of the morphometrics of the West Natuna Basin fluvial systems that can aid in resolving uncertainty in subsurface reservoir character. These include:rn2.1 Channel widths decrease as sinuosity increases. Small channels (0-400 m) show a very wide range of sinuosity, thus a high uncertainty in predicting channel width from sinuosity. Likewise the widest channels tend to have a predictable low sinuosity.rn2.2 As meander length increases, channel width prediction gets more and more uncertain.rn2.3 Suspended load systems have a much larger range of meander belt widths than any of the other classes, and the meander belt width (B) is nearly always larger than the meander wavelength (Lm). In contrast, in bedload systems, the meander belt width is nearly always smaller than the meander wavelength. This translates into a large uncertainty when trying to predict meander belt width in suspended load systems. However, there are no systems with meander lengths greater than 10 Km that have meander belt width greater than 5 Km, therefore providing an upper limit to the width of meander belts in those systems.rn2.4 Bedload systems historically have provided the highest net gross sand development and therefore the best reservoir opportunities. These data show that bedload systems will not develop meander belts wider than approximately 5,000 meters. However, there fs clearly a population of very low width systems with very larger meander belt lengths (i.e. low sinuosity systems). This population appears to form anastomosing patterns.rn2.5 There is a large uncertainty in predicting radius of curvature within sinuosity classes. However, between sinuosity classes there are consistently higher upper limits to the radius of curvature moving from bed load to mixed load to suspended load systems. Finer-grained, more heterolithic systems develop increasingly large meander radius.rn2.6 The width of the meander belts increasingly larger upper limits as systems progress from bed load to mixed load to suspended load systems. Meander belts widen as the fluvial systems become increasingly fine-grained.