The North Falkland Basin - Geology
Petroleum Geology of the North Falkland Basin (PDF, 2756k)
Ian Duncan 2006 Falkland Islands Newsletter
Journal of Petroleum Geology 2006 (PDF, 3259k)
vol 29 (3) –Richards et al “ Exploring for Fan and Delta Sandstones in the Offshore Falklands Basins”
(This article was originally published in the Journal of Petroleum Geology (www.jpg.co.uk) and is reproduced here with their kind permission)
The North Falkland Basin has predominately non-marine, Jurassic(?) to mid-Cretaceous infill above Devonian basement, overlain by a progressively more marine succession of late Cretaceous to Recent sedimentary rocks.
6 wells were drilled in the Northern part of this basin in 1998, 5 of which encountered good oil and oil and gas shows.
The wells drilled in 1998 established the presence of a very thick (1,000metres+) lacustrine source rock. Only the bottom part of this source rock is mature for oil generation, and it is believed that the overlying immature source rock has operated as an effective, basin-wide seal, which may have prevented the migration of large volumes of oil to the sandstone reservoirs encountered above it. These sandstones were the target of the initial drilling campaign and the presence of the seal could explain why commercial oil volumes were not discovered in 1998.
Only one well penetrated any depth below the source rock and, although it did encounter hydrocarbons, because the well was drilled in the centre of the North Falkland Basin, farthest from a potential sand source, only siltstone reservoirs, of poor quality, were encountered. However, this result does suggest that, if suitable reservoirs do exist in traps below and/or adjacent to the source rock, they are likely to be charged with oil.
It has been calculated that very large volumes of oil (up to 60 billion barrels) may have been generated and expelled from the source rock.
There is also a deeper gas source rock in the Basin which was penetrated by the 14/5-1 well.
In 2004 Desire acquired 800km2 of 3D seismic data to identify traps below and/or adjacent to the mature oil source rock. The survey particularly focussed on the margins of the basin where rivers may have flowed into the large lake which was present at the time, and deposited potential sandstone reservoirs.
In the Southern part of the Basin in Tranches I & L the rocks are undrilled and older in age. Re-mapping of this area in 2007 confirmed the presence of the Dawn, Ruth and Kate prospects and identifed three new prospects, Alpha, Barbara and Jacinta.
Recent studies have suggested that the potential in this area is more likely to be gas than oil and the volumetrics for the Alpha, Dawn, Ruth, Kate and Barbara prospects have now been calculated on this basis.
Further Information
