The Falkland Islands lie at the western end of the Falkland Plateau, a relatively shallow water area of continental crust that extends out towards South Georgia.
The Islands comprise Pre-Cambrian to Permian rocks, with Jurassic dykes, and are surrounded by four major Mesozoic to Cenozoic sedimentary basins. These basins are set into the Falklands Plateau, which comprises probable Devonian and Permian age sedimentary rocks. The four basins are:
1. the North Falkland Basin to the north.
2. the Falkland Plateau Basin to the east;
3. the South Falkland Basin to the south;
4. the Malvinas Basin to the west;
In essence, all four offshore basins contain more or less thick Mesozoic and thinner Cenozoic sediments, and each has considerable but under-explored petroleum potential.
The North Falkland Basin
The North Falkland Basin comprises two main structural elements: a N-S trending graben, and a set of subsidiary basins to the west and south of the graben, also controlled by N-S trending extensional faults, but constrained by NW-SE oriented reactivated Palaeozoic thrust sheets.
The main North Falkland Graben is about 50 km wide at its northern end, and about 30 km wide near its southern margin, just 36 km or so north of the Islands; it is about 230 km long as presently mapped, but may extend further to the northeast.
The basin appears to be a structurally isolated feature set within a Devonian platform providing a potentially abundant provenance area for clean reservoir sandstones. Deposition appears to have been fluvio-lacustrine and lacustrine until late in the Cretaceous, when the southern Boreal Ocean appears to have inundated the area from the southeast.
The basin contains a late Jurassic to early Cretaceous lacustrine source rock of world-class quality. This source is mature in its lower parts, and has expelled over 1x1011 barrels of oil, all of which are thought to be still trapped beneath the regional seal formed by the non-mature, uppermost part of the lacustrine interval. Live oil has been recovered to surface from sandstones within the mature lacustrine source interval.
At least one other petroleum system has also been encountered in the basin; this late Jurassic/early Cretaceous fluvio-lacustrine interval beneath the pervasive lacustrine source rock produced significant levels of wet gas in one well.
Only six wells have been drilled in the entire basin, and all of these are concentrated in a very small geographical area.
Furthermore, because of back to back drilling, all six wells tested the same play concept, which proved to be a good clean sand, but located immediately above a regional seal. None of the target positions were at locations where the seal is breached significantly, and therefore all were under-charged. Significant numbers of play concepts and different targets remain to be tested in the basin, which is at the very earliest stages of exploration.
The Southern Basins - Introduction
Three connected basins surround the southern Falklands:
» the Falkland Plateau Basin lies to the east;
» the South Falkland Basin lies to the south;
» the Malvinas Basin lies to the west.
Although all connected, each of the three basins exhibits its own unique structural style.
These three basins are isolated from the North Falkland Basin, and have a completely different infill.
All three of the Southern Basins probably share a similar stratigraphic infill, which is more marine than the predominantly continental North Falkland Basin.
None of the three southern basins has been drilled in Falklands waters.
17 or so wells have been drilled in the Argentine part of the Malvinas Basin, with some limited success.
Boreholes drilled by the DSDP on the Maurice Ewing Bank at the easternmost extremity of the Falkland Plateau Basin tested rich marine source rocks that probably extend throughout much of the Southern Basin area, probably pinching out just into Argentine waters.
The Southern Basins are at the very earliest stage of exploration.
Only regional reconnaissance seismic data covers the area.
Twenty Production Licences cover a large swathe of the Southern Basins: 15 of these are licensed to FOGL, and 5 to Borders and Southern Petroleum.
A part of the Malvinas Basin is included within the so-called Special Co-operation Area (SCA), which has been set aside for eventual joint licensing between the Falklands/UK and Argentina.
Progress on licensing the SCA has been slow in recent years, but there is hope for improvement in the pace of activity, especially if there is compelling commercial interest in the area.
