Falkland Islands: Past exploration strategies and remaining potential in under-explored deepwater basins

Richards, Phil, British Geological Survey, West Mains Road, Edinburgh, Scotland, UK

Abstract

The Falkland Islands are surrounded by four major sedimentary basins (the Falkland Plateau basin to the east, the South Falkland basin to the south, the Malvinas basin to the west, and the North Falkland basin to the north). The basins underwent complex rifting from the ?Triassic through Valanginian, during fragmentation of Gondwanaland, before being subjected to Cretaceous thermal sag and Cenozoic uplift coincident with Andean compression and the development of overthrusting along the plate boundary to the south.

Only the North Falkland basin has been drilled: six wells spudded back to back by four operators who formed a unique alliance in 1998 to undertake all of the logistics and support work to facilitate a multi-well drilling campaign. Drilling took place in water depths between 250 and 460 metres. Five of the six wells had oil shows, mostly in post-rift sandstones located immediately above the main source rock interval. Live oil was recovered at the surface from one of the Shell wells; significant levels of gas were also recorded in some wells. Although none of the wells encountered commercially viable accumulations, it is possible that up to 60 billion barrels of hydrocarbons could have been expelled in the basin. Post-mortem analyses of the petroleum system have revealed why the wells were non-commercial, and have pointed the way to future commercial success.

As well as the remaining potential of the North Falkland basin, the other large, deep water to ultra-deep water basins around the islands are under-explored, and are covered only by reconnaissance seismic data. Oxfordian to Aptian claystones encountered in DSDP boreholes indicate a potentially prolific hydrocarbon yield from Type II kerogens. Modeling suggests that the source rocks are possibly mature for oil generation at about 3,000 metres below sea bed, and numerous play types can be predicted on the basis of the existing seismic data and by correlation with analogous basins.

The paper will highlight the entire basin potential of the offshore Falklands region (petroleum systems, sequence stratigraphy, tectonic evolution, etc), evaluate the pros and cons of the unique exploration sharing strategies adopted so far, and outline the E & P challenges posed by the particularly sensitive environmental concerns in the region.