Abstract

To aid exploration and appraisal of hydrocarbon discoveries in deepwater deposits of the Kutei Basin, a study of analogous sedimentary architectures in Recent deposits of the same basin has been undertaken. The aim was to develop an understanding of the external and internal geometry of slope to basin floor elements in a structured setting using high quality 3D seismic data. Geological models generated have been used to help constrain geometries, aspect ratios and net to gross variations of deposits in the prospective section.

Images of the seabed and excellent imaging of near surface deposits using 3D seismic data show canyons deflected by toe-thrust anticlines and related mud diapirs. Over slope-steps, gravity flows are laterally confined and the resultant facies belts are narrow. In slope mini-basins, flows are less confined resulting in deposition over a broad area.

The Recent deposits of a single canyon and associated basin floor system illustrate the deepwater depositional elements of the Kutei Basin. On the slope, debrites at the base are followed by a slope channel complex then a channel-levee complex. The succession on the basin floor is similar; debrites, basin floor fan and a channel-levee complex. Slope channel complexes and basin floor fans appear to be sand prone.

These sand prone deposits increase in width:thickness and areal extent from slope-step to slope mini-basin and from the slope to basin floor. Apparent lateral connectivity increases and vertical connectivity decreases from the slope to basin floor. The formation of channel-levee complexes shifts sand prone depocentres. Leveed-channel deposits are poorly developed on the middle slope and well developed on the lower slope and basin floor, where they appear sand prone and are likely to have good connectivity. Basin floor fans that form at the point of downdip levee termination are shifted basinward.