The Fulmar Field, Blocks 30/16, 30/11b, UK North Sea

Abstract

The Fulmar Field is located on the southwestern margin of the Central Graben in Blocks 30/16 and 30/11 b of the UK sector of the North Sea. The Fulmar Field was discovered 1975 and began producing in 1982 . Currently (2000 the field produces at a rate of 8000 BOPD at a watercut above 90% mainly through the process of rinsing of residual oil. Total STOIIP is 822 MMBBL and ultimate recovery is 567 MMBBL ofoil and 342 BSCF of wet gas. As of the end of 1999, 547 MMSTB ofoil and 325 BSCF of wet gas had been produced. The high recovery factor (69%) of the field is thought to be linked to the combination of well density, large length of reservoir perforated, excellent reservoir quality, sweep by water injection, good pressure support and oil stripping from a secondary gas cap formed early in field life.The Fulmar Field is a small triangular, partly eroded domal anticline with steeply dipping flanks, located on a fault terrace within the western margin of the South West Central Graben at a depth between 9900 and 11 500 ft TVDss. The field has been shaped by three major tectonic processes: (1) halokinesis, (2) syndepositional reactivation of Caledonian basement faults; and (3) syndepositional through post-depositional displacements along the nearby Auk Horst Boundary Fault. The reservoir consists of thick Upper Jurassic, shallow marine, very bioturbated sandstones of the Fulmar Formation overlain by the deeper marine Ribble Sands interbedded within the Kimmeridge Clay Formation. Reservoir seal is provided by the Kimmeridge Clay in the west and Upper Cretaceous chalks which unconformably overlie the Fulmar Formation in the east. The reservoir section has been lithostratigraphically subdivided into six reservoir units and 24 sub-units. Integration of bio-and lithostratigraphic data has led to a sequence stratigraphic model of the Jurassic succession in the Fulmar Field. In total four depositional sequences are identified, which progressively onlap Triassic basement towards the southwest. The older Jurassic sequences are characterized by rapid progradation of shoreface sands, whereas aggradation of thick sediment packages is typical of the younger intervals. This change of depositional architecture is linked to syndepositional reactivation of basement faults. Major transgressive intervals form intra-reservoir barriers or baffles to flow. Facies changes (Mersey-Clyde Sands) from proximal to distal facies are abrupt and are also linked to basement faults.

Structural controls on the stratigraphic architecture of net‐transgressive shallow‐marine strata in a salt‐influenced rift basin: Middle‐to‐Upper Jurassic Egersund Basin, Norwegian North Sea

“…In some cases, syn-rift strata in the hangingwall display a strong tidal influence, implying that the depocentre-bounding structure was associated with a subaerial or shallow-marine scarp, which locally constrained and augmented tidal energy (Mellere & Steel, 1996;Maxwell et al, 1999;Jackson et al, 2005;Zecchin et al, 2006). The sediment provenance in most of the basins illustrated in Table 4 is extra-basinal, with the exception of the Upper Jurassic, shallow-marine sandstones of the Fulmar Formation in the UK Central Graben (Kuhn et al, 2003). The dip extent of the in the Fulmar Formation, which are genetically related to but slightly younger than the Sandnes Formation, is limited (up to 1.5 km) due to local sourcing from a relatively small, intra-basinal fault scarp (Table 4) (Kuhn et al, 2003).…”

“…Alves et al, 2003;Aschoff & Giles, 2005;Kieft et al, 2010) and in salt-free rift basins, synrift strata thicken from the footwall to hangingwall of active normal faults (Table 4) (e.g. Maxwell et al, 1999;Davies et al, 2000;Kuhn et al, 2003;Jackson et al, 2005;Zecchin et al, 2006). Such increase in thickness is typically accompanied by a decrease in sandstone content (i.e.…”

“…In contrast, where expansion index values are <2.0, sandstone content remains relatively unaffected by thickness variations across active structures, facies variations are absent, and aggradational successions are developed, implying that relatively low rates of subsidence did not result in across-fault changes in water depth and therefore depositional environment (Table 4) (e.g. Maxwell et al, 1999;Kuhn et al, 2003). In some cases, syn-rift strata in the hangingwall display a strong tidal influence, implying that the depocentre-bounding structure was associated with a subaerial or shallow-marine scarp, which locally constrained and augmented tidal energy (Mellere & Steel, 1996;Maxwell et al, 1999;Jackson et al, 2005;Zecchin et al, 2006).…”

“…The sediment provenance in most of the basins illustrated in Table 4 is extra-basinal, with the exception of the Upper Jurassic, shallow-marine sandstones of the Fulmar Formation in the UK Central Graben (Kuhn et al, 2003). The dip extent of the in the Fulmar Formation, which are genetically related to but slightly younger than the Sandnes Formation, is limited (up to 1.5 km) due to local sourcing from a relatively small, intra-basinal fault scarp (Table 4) (Kuhn et al, 2003). In salt-influenced basins, the depositional dip extent of the shallowmarine sandstones is <40 km (Alves et al, 2003;Aschoff & Giles, 2005;Kieft et al, 2010), whereas in active rifts, it is <10 km (Maxwell et al, 1999;Davies et al, 2000;Zecchin et al, 2006) and in passive foreland basins, it is <20 km (Olsen et al, 1999) (Table 4).…”

“…The sediment provenance in most of the basins illustrated in Table 4 is extra-basinal, with the exception of the Upper Jurassic, shallow-marine sandstones of the Fulmar Formation in the UK Central Graben (Kuhn et al, 2003). The dip extent of the in the Fulmar Formation, which are genetically related to but slightly younger than the Sandnes Formation, is limited (up to 1.5 km) due to local sourcing from a relatively small, intra-basinal fault scarp (Table 4) (Kuhn et al, 2003).…”