Fulmar: a mature field revisited

Abstract

The original STOIIP of the Fulmar Field is currently estimated as 853 x 10 6 STB and it is considered that approximately 540 x 10 6 STB of oil has so far been produced, representing 63.4% of the original reserves. This high recovery factor coupled with an increasingly high water-cut (currently averaging 90%) suggests that the end of field life is drawing close. Prior to making an abandonment decision however it was considered prudent to review and update both the geological and dynamic reservoir models in order to ensure that the full field potential has been realized before making provisions for abandonment. In this context, the depositional model and stratigraphic architecture of the Upper Jurassic Fulmar Sands have been reviewed. Two geological models have been considered: (1) the preexisting model; and (2) an alternative model, which reflects continuing uncertainties in the field's stratigraphic architecture.The main part of the Fulmar reservoir consists of a stacked sequence of shoreface sediments that were deposited within an extensional, back-stepping shallow marine setting. This sequence is punctuated by several minor flooding events, which are characterized by distal, poorer quality shoreface sediments. The latter deposits locally form small, but distinct, pressure and flow discontinuities in the reservoir. These heterogeneities were captured in detail, in a 3D geological model and input into the full field reservoir simulation using the Shell proprietary GEOCAP/MoReS software. The history match of the dynamic reservoir model predicted that by-passed oil could be locally trapped below these flooding events. This concept was confirmed in mid 1997 by two wells drilled on the crest of the field. The simulation model also indicates that a significant volume of potentially unswept oil may be present on the NE flank of Fulmar within the poorer reservoir quality, lower shoreface 'Clyde sands'. This concept will be tested by drilling a horizontal well into these sands in the mid part of 1998. As the architecture of the alternative geological model showed some differences to the pre-existing field geological model, particularly in the down flank areas, this model was also input into the GEOCAP simulation in order to compare and test the reliability of the simulation predictions. Only minimal differences were observed between the two simulation models, which reflects the dominantly high net: gross (N: G) in the main producing western part of the field and the similarity of the correlations in the crestal and eastern parts of the field.Both similation models show a significant improvement in the history match, which highlights the potential benefits to be gained by constructing detailed 3D reservoir models that better describe the architecture of the flow units and barriers in the reservoir than more 'traditional' layer-based (CPS-3) models. These studies are helping to maximize recovery from this highquality, strongly depleted reservoir.This paper primarily presents a review of the stratigraphic architecture model...

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

“…The non-reservoir units are found to be highly correlatable and are interpreted to be maximum flooding surfaces (Spaak et al 1999). The good quality reservoir sands intercalated between the maximum flooding surfaces are also found to be highly correlatable.…”

“…In a more recent study however, the Fulmar Main Sands were interpreted to locally comprise upper shoreface sediments; this points to deposition under intermediate wave energy conditions and is more likely to occur in an attached shoreface setting (Spaak et al 1999). The absence of associated coastal plain deposits is explained by the position of the Fulmar Field directly adjacent to a footwall high.…”

“…given by Johnson et al (1986), Mehenni & Roddenburg (1990), Van der Helm et al (1990), Stockbridge & Gray (1991) and Spaak et al (1999). Alongside up-to-date production figures, this paper presents a chrono-and sequence stratigraphic review of the Jurassic succession of the Fulmar Field, as well as new insights into the tectonic history of the field and the impact on sediment deposition.…”

The tectonic and stratigraphic framework of the United Kingdom's oil and gas fields

“…In the Central Graben, the main Fulmar Formation reservoir is either normally pressured as in the Clyde Field (Stevens & Wallis 1991;Turner 1993) and the Fulmar Field itself (Johnson et al 1986;Stockbridge & Gray 1991;Spaak et al 1999;Kuhn et al 2003;Fig. 35) or lie within the high temperature/high pressure (HP/HT) setting as with the Elgin, Franklin (Lasocki et al 1999), Erskine (Coward 2003) and Shearwater Fields (Erratt 1993;Penge et al 1993;Jeremiah & Nicholson 1999).…”

Facies Anatomy of a Sand‐Rich Channelized Turbiditic System: The Eocene Kusuri Formation in the Sinop Basin, North‐Central Turkey

“…Downie & Stedman, 1993;Jensen et al, 1993;Timbrell, 1993;Shanmugam et al, 1994Shanmugam et al, , 1995Anderton, 1995;Hiscott et al, 1997;Shanmugam, 1997Shanmugam, , 2000Spaak et al, 1999). A wide spectrum of natural hybrids, to be satisfactorily recognized and understood, obviously requires wide exploration, and hence the importance of all new case studies, including potential analogues for petroleum reservoirs.…”