1、Oil, including oil exploration, is the next big subject for the Falkland Islands. We have pleasure in publishing this very full and detailed study of the oil prospects in the North Falkland Basin. Dr Ian Duncan is CEO of Desire Petroleum plc, which is a leading operator in this field, and his articl
2、e is an authoritative account of the current situation. Petroleum Geology of the North Falkland Basin by Dr Ian Duncan, CEO of Desire Petroleum plc Within the Falkland Islands designated area there are three major basins: North Falkland Basin, Falkland Plateau Basin and South Falkland Basin. The sub
3、ject of this article is the North Falkland Basin, where Desire Petroleum has been exploring for hydrocarbons since 1997. The North Falkland Basin is a failed rift, which formed during the break-up of the ancient landmass of Gondwana. Plate tectonic reconstruction suggests that the entire Falklands a
4、rea prior to the break-up was originally located to the South-east of South Africa and moved to its present position during the opening of the South Atlantic during the Jurassic to the Cretaceous. The North Falkland Basin can be further subdivided into a northern, or main, basin in which Tranches A
5、to Fare located and a southern basin in the area of Tranches I and L. The southern basin is undrilled and comprises an older suite of rocks than that found in the main basin to the north. This article concentrates on the main area in Tranches C and D where the next drilling campaign will take place.
6、 Exploration History The first phase of exploration was in the early 1990s when Spectrum acquired the first detailed 2D seismic across the area. These data defined the outlines of the N-S trending North Falkland Basin, approximately 180 kms long by 30 kms wide and formed the basis for the evaluation
7、 which led to the first round of licensing in 1996. Seven licences were awarded in 1997 to Shell, Amerada, Lasmo, International Petroleum Corporation (IPC) and Desire. These companies acquired more 2D seismic over their licences and in addition Shell acquired a small 3D survey. Shell, Amerada, Lasmo
8、 and IPC formed FOSA (Falklands Offshore Sharing Agreement) jointly to conduct a drilling campaign in 1998. The semi-submersible drilling rig the Borgny Dolphin was contracted and drilling began in April 1998. Amerada drilled two wells: 14/9-1 and 14/9-2； Shell drilled two wells: 14/5-1 and 14/10-1；
9、 Lasmo and IPC drilled one well each: 14/13-1 and 14/24-l.Drilling ended in November 1998. Of the six wells, five recorded good oil and or gas shows but the presence of hydrocarbons in commercial quantities was not established. Over the next few years Amerada, Shell and Lasmo withdrew from the Falkl
10、ands and as a result Desire Petroleum became the operator of Tranches C and D and Argos Evergreen became the operator of Tranche A. Following the acquisition of further seismic in 2000, IPC were acquired by Talisman who became the operator of Tranche F. Continuing low oil prices stifled all activity
11、 in the area until 2004 when Desire acquired 800km2 of 3D seismic over Tranches C and D. In the same year Rockhopper Exploration was awarded new licences in the area. At the beginning of 2005, Desire raised sufficient money to fund further drilling in the North Falkland Basin and Rockhopper farmed-i
12、n to Tranches C and D. At the time of writing (December 2005) Desire is seeking a rig to commence drilling as soon as one becomes available. During 2005 Desire assumed a 100% interest in Tranche F and Rockhopper acquired further licences in the area. The latest licence position is shown in fig.l. Ge
13、ology The North Falkland Basin has a predominantly nonmarine Jurassic to Lower Cretaceous fill overlying Devonian basement. These non-marine sediments are overlain by a marine sequence of Upper Cretaceous to Recent age. In the deepest part of the Basin in Tranche D the total section is over 5 kms in
14、 thickness. The non-marine rocks were deposited in a large lake, into which flowed several large rivers which formed sandstone deltas and fans as shown schematically in fig 2. This lake was of a size similar to the present day lakes of East Africa. The lake filled slowly with fine- grained claystone
15、s, which at times were deposited in oxygen-free conditions resulting in rocks with very high organic carbon content. These rocks are the source of the oil generated in the Basin. Eventually in the Upper Cretaceous as a result of a significant sea level rise marine conditions became established in th
16、e Basin. The North Falkland Basin contains all the ingredients necessary for the discovery of hydrocarbons, namely source rocks, reservoir rocks, seals and traps. Source Rocks The 1998 drilling campaign established the presence of a thick (over 1,000 metres) non-marine, oil source rock, believed to
17、be one of the richest in the world. These source rocks were immature in five of the six wells drilled but attained maturity in one of them； live oil of 27 degree API was recorded at the surface from well 14/ 10-1. The source rocks are mature in the deeper parts of the Basin where the temperatures an
18、d pressures are sufficiently high to generate and expel oil. The location of this area of mature source rocks the kitchen is shown in fig.3. Only the basal part of the source rock is mature with the majority of the source rock being immature. Richards (British Geological Survey) and Hillier (Shell)
19、in 2000 in which they estimated that up to 60 billion barrels of oil had been generated and expelled from this source rock. There is also a deeper separate source rock, mature for the generation of gas, as demonstrated by the good gas shows at this deeper level in well 14/5-1. Seals The abundant claystones throughout the section including the immature upper part of the source itself provide good sealing potential. Reservoirs Desire believes that finding effective reservoir rocks is the largest risk associated with the discovery of hydrocarbons in commercial quantities in this area； i.e.
