Publications

Drainage network and hinterland analysis typically stops at the coastline and provides information primarily on the location and importance of sediment input points and their evolution (FUGRO ROBERTSON BV, 2010a,b). Knowledge about the geology, geomorphology, hydrology and climate of the hinterland has to be linked with the knowledge of sedimentological evolution of a depositional system in a basin in order to make a valuable contribution to reservoir risk assessment. This approach also requires an evaluation and reconstruction of the offshore settings, including the sediment transport and distribution pathways in to the basin, location of transfer points for sand supply, a regional scale review of stratigraphic architecture, climatic and oceanic current patterns and basin dynamics on the one hand and a morpho-tectonic and palaeo drainage reconstruction on the other hand.Fugro Robertson has developed techniques in Drainage network and Hinterland Analysis based on STRAHLER (1957), PIKE & WILSON (1971) and MARKHAM & REPP (1992) that offer means of predicting the location, character and stratigraphic variation of sediment input points and improving understanding of the hinterland morphotectonic evolution comprehensively. Integrated drainage network studies are evidence-based and depend on the integration of data form various sources. For this purpose all data is maintained in a specifically designed GIS. The data sets required for this study include: DEMs (Digital Elevation Models) of SRTM (Shuttle Radar Topography Mission), a GIS-geology map (Black Gold Energy Indonesia Ltd, 2009), DCW -river network map (Digital Chart of the World, ESRI, 1993), topographic maps and literature covering both the onshore and offshore.In order to reduce exploration risk in the basins offshore Sulawesi (FUGRO ROBERTSON BV, 2010a) and Papua (FUGRO ROBERTSON BV, 2010b) a study (Figure 1) has been undertaken to investigate the distribution and evolution of sand supply and sand composition to the basins offshore Sulawesi (Makassar, Bone, Banggai-Sula and Gorontalo) and Papua (Cendrawasih, Misool, Bintuni and Seram).This study focused on the drainage characteristics and anomalies on Sulawesi and Papua including Birds Head combined with detailed morphotectonic analyses to unravel palaeo drainage pathways and succeeded a pilot study conducted for Black Gold Energy Indonesia Ltd (now NIKO Asia Ltd.) in 2009, which was aimed at finding evidence in drainage and morpho-tectonic characteristics on the Island of Sulawesi to confirm or refute the hypothesis if the Palu drainage basin was captured by the Lariang drainage basin, resulting in sudden increase in sediment supply to the North Makassar Basin and thereby forming the Makassar Fan (Decker et al., 2008). In fact, a complex reorganization of drainage has been reconstructed in Central Sulawesi.The drainage characteristics (interpretations) data set consists of wind gaps, water gaps, canyons, under-fit (oversized) valleys and stream diversions etc. and constitutes the basis of the spatio-temporal drainage network evolution reconstruction. Figure 2 illustrates one of the case studies on morphotectonic activity impact on drainage basins and river networks in the northern part of Birds Head. About 48 km of sinistral strike slip displacement has taken place along the Sorong Fault since the Pliocene. The Koor river outlet shifted in time from 3 (after late Miocene) to 2 to 1 at Present.In Central Sulawesi, a sinistral strike slip displacement of 50 km has been recognized from valley and outcrop off-set along the Palu Fault over the past ~2.5Ma. The GPS velocities that support these reconstructions are retrieved from Bock et al. (2003) and Cloos et al (2005).The morpho-tectonic analysis part of the study provides insight in to the tectonic and denudation evolution of different morpho-tectonic domains that make up Sulawesi and Papua. Figure 3 summarizes the major structures and kinematics. The results are integrated with the drainage analyses to explain the river network reorganizations that have taken place.The impact on sand volume and type changes per drainage basin as a consequence of these morphological events has been reconstructed, illustrating the changes in clastic reservoir quality offshore Papua and Sulawesi for the Miocene to Holocene time slices.The technique consists of integrated structural kinematic analyses including geologicalstratigraphic analyses besides a review of radiometric data (e.g. van Leeuwen et al, 2007).The methodology is unique and has been successfully applied to several regions around the World. It is proven and provides a basis for identifying atypical characteristics of drainage systems and topography, and for building an evidence-based evolutionary model for the system(s) under investigation.