Abstract
Abstract The North Falkland Basin represents one of the frontier areas for hydrocarbon exploration in the South Atlantic. This study presents the results of new subsurface mapping using 2D seismic data in the north of the Falkland Islands offshore area, which has delineated a series of discrete grabens northwards of the main North Falkland Basin, referred collectively to as the Northern sector of the North Falkland Basin (NNFB). Six regionally significant seismic reflectors are interpreted within this data, dividing the sedimentary fill into six tectonostratigraphic packages, including: early syn-rift; late syn-rift; transitional unit; early post-rift; middle to late post-rift; and a sag unit. Structural interpretation of the 2D seismic data has led to the definition of four north-south orientated depocentres, namely: (1) the Eastern Graben, largest of the depocentres; 20 km wide by 45 km long, reaching depths of 3 km; (2) the Eastern Graben Splay, a smaller depocentre; 10 km wide by 20 km long, reaching depths of 2–2.5 km; (3) the Western Graben Splay, the smallest depocentre; 5 km in width and 20 km long, with a basin depth of 2 km and (4) the newly defined Phyllis Graben, which is 13 km wide and 30 km long, with a basin depth of 3 km. A network of NW-SE and NE-SW trending faults controls the development of these grabens, separated by a Western, Eastern and Intra-Basin high. These grabens represent a northern continuation of the Northern Falkland Basin to the south. Hydrocarbon discoveries to the south of this study area (e.g. Sea Lion, Casper, Beverley, Zebedee, Isobel Deep, and Liz) confirm a working petroleum system adjacent to the Northern sector. This study has identified a number of seismic anomalies, including amplitude brightening events, which potentially correspond to an extension of this petroleum system, indicating active migration pathways. The main targets, in terms of hydrocarbon interest in the northern sector, are likely to be stratigraphically trapped hydrocarbon accumulations, contained within vertically-amalgamated turbidite fan sandstone reservoirs, deposited within the early post-rift. A second, yet to be tested, syn-rift play, in which the trapping geometries are structural and the reservoirs are fluvial sandstones is also identified.
Highlights
The Falkland Islands offshore designated area for exploration covers approximately ∼460,000 km2 and has received relatively little attention in terms of hydrocarbon exploration
The NW-SE faults observed in the Northern sector of the North Falkland Basin (NNFB) may represent similar structures as those observed in the Southern North Falkland Basin, which were interpreted as reactivated thrust faults similar to those seen onshore (Richards et al, 1996b; Aldiss and Edwards, 1999; McCarthy et al, 2017)
This study has defined the structural configuration of the Northern sector of the North Falkland Basin
Summary
The Falkland Islands offshore designated area for exploration covers approximately ∼460,000 km and has received relatively little attention in terms of hydrocarbon exploration. The 2010–2011 exploration campaign, was successful in discovering commercial quantities of hydrocarbons in the NFB and proved the basin margin-derived reservoir concept (MacAulay, 2015; Richards et al, 2006). This campaign targeted easterly-derived turbidite fan deposits (Bunt, 2015; Williams, 2015; Dodd et al, 2019), which form a stacked, margin-fringing succession within the Lower Cretaceous packages of the early post-rift (Fig. 3), along the Eastern Flank of the North Falkland Basin's Eastern Graben (Fig. 2). What are the likely petroleum systems and plays in the NNFB?
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