Miocene Sedimentology of Eastern Sabah, Borneo, and Consequent Hydrocarbon Potential in the Adjacent Sulu Sea

Jon Noad
Shell International Exploration and Production, Rijswijk, Netherlands

Five exploration blocks remain open in the onshore and nearshore of eastern Sabah, located on the Northeastern margin of Borneo, and the area is under-explored in terms of hydrocarbons. Potential reservoirs include structural and stratigraphic traps within the sandstones of both Tanjong and Sandakan Formations, and more significantly structural traps in the Ganduman Formation to the South and in the offshore. Extensive fieldwork has been used to build detailed palaeogeographic reconstructions, which have in turn been used to assess the hydrocarbon potential and possible exploration targets in the nearshore Sulu Sea.

The Tanjong Formation is dominated by clastic shelfal deposits, cut by channels feeding sediment to the offshore. The sandy, organic-rich channel deposits may reach 15 metres in thickness, and incise into thick featureless mudstones. The contemporaneous Sandakan Formation is made up of mangrove to shelfal mud-dominated deposits, with sheet-like and rip current channel tempestites making up much of the succession. In contrast the Ganduman Formation is tidally dominated, with stacked tidal channel and estuarine deposits filling incised valleys up to a kilometer in width and 60 metres in depth. All three Formations are interpreted as having significant hydrocarbon potential in the offshore.

AAPG Search and Discovery Article #90039©2005 AAPG Calgary, Alberta, June 16-19, 2005