Abstract Despite representing a widespread play in the Central North Sea, production from Lower Cretaceous chalks is currently confined to the Valdemar Field in the Danish Central Graben. The field comprises a heterogeneous reservoir succession, less than 100 m thick, consisting of hemipelagic chalks, marly chalks, and marlstones of Late Hauterivian-Early Aptian age. Although the field has in-place reserves in the order of 115 × 10 6 m 3 (725 × 10 6 BBL), the recovery from this complex reservoir was initially estimated to be only approximately 1%, primarily due to low permeability. The argillaceous chalks of the Lower Cretaceous reservoir are highly faulted and fractured, overpressured and undercompacted, giving rise to a complex distribution of hydrocarbons. Due to the lithological heterogeneity of the succession, internal stratigraphic barriers are common and result in stratigraphic compartmentalization. In addition, clay smearing in fault zones has created structural barriers and the development of structural compartments, as reflected by spatial differences in oil saturations, oil types and maturity, formation pressure and porosity distribution. Analysis of the reservoir properties and structural development of the Valdemar Field has provided data that can be extrapolated to the remainder of the Danish Central Graben, indicating that the Lower Cretaceous is most prospective in the central and southern Danish Central Graben.

Abstract Seismic data from the East Greenland shelf show that the northern part of the shelf, north of 75°N, can be subdivided into five, roughly northeast-trending, major tectonic elements. From west to east they are: the Koldewey Platform, the Danmarkshavn Basin, the Danmarkshavn Ridge, the Thetis Basin and the Marginal High. A sixth tectonic element, the Shannon High, has been defined in the southern part of this area. The offshore areas between 72°30′N and 75°N are dominated by Tertiary plateau basalts, which obscure the acoustic signals from the deeper sedimentary succession. Seismic data from the area north of 75°N indicate the presence of a fairly complete succession of ? Devonian to Neogene age, exceeding the recorded interval (8 sec TWT - 13 km) in thickness in the deeper parts of the Danmarkshavn Basin. The succession has been subdivided into 15 seismic mega-sequences. In absence of well control, they have been dated by comparison to the onshore successions of East Greenland and eastern North Greenland, and the offshore successions in the southern Barents Sea and on the mid-Norwegian shelf. The Upper Palaeozoic succession is broadly similar to that of the southern Barents Sea, i.e. marine-dominated, with thick Upper Carboniferous-Lower Permian halite deposits in the northern Danmarkshavn Basin. The Mesozoic succession seems to show greater similarities to the onshore basins of East Greenland: rifting started during the mid-Jurassic and peaked near the Jurassic-Cretaceous boundary. The post-volcanic succession reflects deposition on a passive margin subjected to temporary uplift during the early Miocene and the latest Miocene to earliest Pliocene.

Abstract Following the extensive flood basalt volcanism that accompanied the onset of seafloor spreading and arrival of the proto-Icelandic hotspot in the North Atlantic region, marine sedimentation resumed during the early Middle Eocene. In East Greenland, post-basaltic sediments exposed at Kap Dalton and Savoia Halv0 represent the scattered remains of a much more widespread, fluvial to shallow-marine succession. Deposition in the late Paleocene-Eocene was governed by a complex interplay between loading, thermal contraction of the oceanic crust, passage of the hotspot and eustatic sea-level changes. At Kap Dalton extrusion of Early Eocene, Chron C21r flood basalts was followed by subaerial erosion, creating an irregular relief dissected by fluvial channels. The area was transgressed during the early Middle Eocene and, during the Middle Eocene, a muddy, poorly oxygenated shelf was formed. The presence of clean quartz sandstones within the early post-basaltic succession indicates that areas with little or no basaltic cover became periodically exhumed. The depositional events documented in the Kap Dalton succession strengthen the possibility of Middle Eocene non-volcanic reservoir units being present in the offshore areas, lending support to the Eocene play in the northern North Atlantic region.

Abstract The Upper Permian of central East Greenland contains a relatively thick, widely distributed, oil-prone source rock. It occurs directly adjacent to large, carbonate buildups that constitute the main potential reservoirs. It is immediately overlain by thick, coarse-grained sandstones that are also a potential reservoir. The whole sequence is draped by Upper Permian and Lower Triassic shales that may act as a seal.