The economic importance of contourites

Abstract

AbstractThe importance of contour currents in shaping and building continental margins has long been accepted. Their economic implications and the stratigraphic framework in which they are developed remain largely unknown. Data retrieved from sidescan sonar images, seismic profiles and their attribute maps, as well as sea-floor coring, boreholes and the few known outcrops around the world, suggest that bottom currents can locally develop large deposits of relatively coarse-grained sediments. Accumulation of coarse-grained deposits under the influence of bottom currents requires sediment availability, a geologically persistent strong circulation regime and a favourable physiographic setting both for enhancing the currents and for hosting the sediments. The hydrocarbon exploration of oceanic depositional systems demands a better understanding of the role of bottom currents and their implications for petroleum systems such as reservoir and sealing rocks. Such understanding implies additional alternatives for the definition of exploration targets and prospect risk reduction. Correlating seismic anomalies from 3D mapping with core and well logging data reveals the depositional geometry and sedimentological characteristics of coarse-grained contourites. Fine-grained drifts can locally and regionally develop large and thick accumulations, which have an important seal potential for trapping hydrocarbon.