Technical summary

Borders & Southern has operatorship of five Production Licences in the South Falkland Basin (80 blocks, 19,598 sq km). The basin has had one well test, which was unsuccessful.

The geology of the basin is completely different to that of the North Falkland Basin, where the first commercial field in the Falkland Islands (Sea Lion) has recently been announced. The main difference is that, in the North Falkland Basin, the sediments that comprise reservoir, source and seal were deposited in a lacustrine environment (lakes within a rift valley). In the South Falkland Basin sediments were deposited in a marine environment.

The geology of the basin is similar to the contiguous Malvinas and Magallenes Basins located to the west. The Magallenes Basin has yielded discoveries of approximately six billion barrels of oil equivalent.

The petroleum system comprises Late Jurassic/Early Cretaceous marine source rocks (proven in DSDP wells to the east of the Falkland Islands and in exploration wells in the contiguous basins to the west) along with Cretaceous and Tertiary clastic reservoirs.

Borders & Southern has completed extensive regional and licence specific technical studies. Within its acreage the company has acquired 2,862 km of 2D seismic data and 1,492 sq km of 3D seismic data, significantly exceeding the licence obligations. The company has an outstanding work programme obligation of one exploration well. This needs to be drilled before November 2012.

Schematic cross section illustrating the Stebbing and Darwin prospects.

The 2D seismic data identified an east–west trending foreland fold and thrust belt, within which numerous simple structures were mapped. The 3D seismic data provided greater definition of the structures, an incite in the potential reservoir distribution across the structures and interesting amplitude anomalies, possibly reflecting direct hydrocarbon indicators.

Three main trap types have been evaluated: thrust-cored anticlines; tilted fault blocks; and stratigraphic traps. The most robust and lowest risk features are the anticlines and fault blocks and these have therefore been high graded. Prospect sizes map out up to 150 sq km.

The 3D seismic data revealed numerous amplitude anomalies associated with the structures, including gas hydrates (identified by bottom-simulating reflectors) above the prospects and AVO anomalies associated with potential reservoir intervals. The amplitude anomalies have been used to high grade and rank the
prospect inventory.

Thermal modelling studies of the source rock interval predict that both oil and gas will be generated within the licensed acreage. Those prospects that have access to oil kitchens and migration pathways have been high-graded.

Borders & Southern has compiled an extensive prospect inventory with multi-billion barrel recoverable potential. Two prospects have been selected as the first tests: Darwin; and Stebbing. These prospects are completely independent except that they require the same source rock to be present throughout the area.

Darwin is a tilted fault block. The reservoir is interpreted to be Lower Cretaceous shallow marine sandstone. The prospect has a flat spot, amplitude conformance to structure and an AVO anomaly. The company’s P50 recoverable resource estimates for the amplitude anomaly alone are 300 million barrels. P50 recoverable resource estimates for the entire structure down to the mapped spill point are 760 million barrels.

Stebbing is a thrust-cored anticline. Stacked reservoirs are interpreted to be Upper Cretaceous and Tertiary deep water marine sandstone. The prospect has AVO anomalies in the Tertiary. The company’s P50 recoverable resource estimates for the combined two reservoir intervals are 1,280 million barrels.