Sand injectites: an emerging global play in deep-water clastic environments

Abstract

Although long-recognized features in the geological record, the hydrocarbon reserve potential of sand injectites has only recently become apparent. Advances in the quality and resolution of 3D seismic data allow the definition of a range of trap and reservoir geometries that have, in the past, not been deliberately targeted by exploration wells. Sand injectites form a new trapping style. They are intrusive, occuring as discrete traps and in combination with structural and stratigraphical features. Dykes, sills, emergent sills, scalloped tops and irregular bodies are identified as trapping styles. Reservoir quality is typically homogeneous and good, even when in an overall low net:gross system. The North Sea Palaeogene, in which at least 2.4 × 10 9 BOE reserves are associated with injectite fields, or fields modified by sand injection, is used as an example of sand injectite plays. Statistically, the additional reserve potential for sand injectites in the North Sea Palaeogene is high. Globally, the presence and significance of sand injectites is largely overlooked. As most sand injectite reservoirs of commercial significance develop during early burial and are associated with overpressure, play concepts are developed that combine mechanisms for overpressure development with sedimentology. Recognition of the presence of sand injectites will have a major affect on many deep-water and other plays both in terms of exploration and production.