Abstract

Shell Malaysia Exploration and Production (SM-EP) has been exploring the shallow marine shelf and upper slope area, offshore NW Borneo since the 1950's. In 1992, Shell discovered large volumes of gas in turbidite reservoirs situated beneath the shelf edge, so proving the existence of large deepwater sand-rich fan systems offshore NW Borneo. Since 1995 when SM-EP moved into the true deepwater arena, Shell and partners have amassed a significant deepwater database comprising basin-wide 2D and 3D seismic datasets and 11 exploration and appraisal wells that have been drilled to test a number of plays and fan intervals. This data has enabled SM-EP and its partners to de-risk the NW Borneo deepwater play for reservoir, charge and retention, to understand the complexity of the deepwater fan stratigraphy, to reconstruct the basin-wide palaeogeography through time, and to establish the spatial and temporal controls on deepwater fan deposition in this active margin setting.

Submarine fan deposition across the region has been influenced by tectonic as well as eustatic events. Uplift and erosion across the inboard shelf and mountainous hinterland regions of Sabah have shed large volumes of sediment into the shallow marine domain of the NW Borneo basin. Because of limited accommodation space along a narrow shelf, sands cascaded over the shelf edge through a system of upper slope feeder channels or canyons and were deposited in a system of fan lobes on the deepening floor of the NW Borneo trough. Today these fans have been folded and thrust within the NW Borneo active margin fold belt. Deformation within this fold belt commenced around 9.5 Ma. Prior to this, gravitational delta tectonics was the dominant structuring mechanism in the basin.