The company has completed a seismic reservoir characterization study investigating the Early Cretaceous shallow marine play fairway. The goal was to improve understanding of theDarwin reservoir interval, both within and surrounding the discovery and also its projected facies trend along the Aptian shelf.
Analysis was based on 2,500 sq km (965 sq mi) of pre-stack depth migration (PSDM) 3D seismic data.
Initial interpretation confirmed the basic structural mapping but extended knowledge northward away from the discovery. Mapping also highlighted numerous seismic amplitude anomalies, some coincident with previously mapped leads.
One of the main insights was the influence of stratigraphic thinning of reservoirs on regional prospectivity. Potential reservoir intervals in the Early Cretaceous section, including the Darwin reservoir, thin toward the west and northwest.
The next phase of evaluation involved a seismic inversion study using well-to-seismic calibration to help characterize the reservoir and aid prospect definition. It led to identification of new potential reservoir intervals and improved definition of prospects and resource assessments.
Results have highlighted a previously unrecognized reservoir interval extending over part of the Darwin East and Darwin West structures, just above the main reservoir. Although it is poorly developed in the discovery well, it appears to expand to the east and south on the inverted seismic data.
B&S considers this porous interval is considered to be charged and to have a common contact with the main Darwin reservoir. As a result, the company now estimates recoverable gas condensate from Darwin East and Darwin West at 360 MMbbl.
Main near-field prospects targeted by the seismic inversion study include Covington and Morgan, where the chief target is the main Darwin shallow marine reservoir. Assuming both prospects are oil-charged, they could hold total resources of 446 MMbbl.
Target intervals for the Sulivan and Stokes prospects are older and deeper than the main proven Darwin reservoir, within a stratigraphy not penetrated in the discovery well. Based on the amplitude anomalies, there appears to be a stronger chance of gas condensate, with potential resources of 607 MMbbl recoverable.
The Wickham prospect has a target stratigraphically younger than the main Darwin reservoir in a shallow marine sand interval, again not encountered in the discovery well. It is on the downthrown side of the main Darwin fault, with potential for oil (possibly 119 MMbbl recoverable).
B&S’ future sub-surface work will focus on improved understanding of the Early Cretaceous deepwater channel and fan play that includes the previously identified prospects Burgess and Bute.