--> Abstract: The late Anisian to Ladinian Transgression on the Loppa High – A New Play in the Norwegian Barents Sea, by Terje Hellem; #90177 (2013)

Datapages, Inc.Print this page

The late Anisian to Ladinian Transgression on the Loppa High – A New Play in the Norwegian Barents Sea

Terje Hellem

A major transgression during the late Anisian into the early Ladinian flooded the Loppa High and left a drape of organic-rich mudstone forming the present regional seal at the base of the Snadd Formation encountered in several wells on the Loppa High and the Bjarmeland Platform. A questionable, and presumably erroneous, dating of the basal Triassic shale in the first exploration well on the Loppa High (7120/2-1) led to the misconception that this structural high was drowned already during the Early Triassic, leaving little chance for deposition of locally derived sands around the Loppa High at later stages of the Triassic period. Re-evaluation of the palynomorphs in well 7120/2-1 and the dating of the lowermost interval of well 7220/6-1 clearly show that the Loppa High must have been exposed through most of the Lower and Middle Triassic, and was not flooded completely until the early Ladinian stage. Seismic observations support the concept of an exposed structural high and a series of features that can be inferred as evidence of an active high-energy coastal environment on the eastern gently dipping limb of the Loppa High, coeval with the westward-prograding shelf across the Bjarmeland Platform during Anisian times. Stratigraphic pinch-out traps comprising Anisian transgressive sands within the upper part of the Kobbe Formation and sealed by organic reach shale at the base of the overlying Snadd Formation are identified along the eastern flank of the Loppa High. This is represents a new and untested play type in the Norwegian Barents Sea, equivalent to that of the Borg field and other Upper Jurassic discoveries on the Tampen Spur. Four-way dip closures on the northeastwards extension of the Loppa High may also comprise sands within the upper part of the Kobbe Formation derived from the Loppa High. It is inferred from both well data and seismic features that the present day Loppa High acted as a barrier island between a deeper and wider basin to the west and the epicontinental shallow basin to the east. The Anisian organic-rich shales proved in cores from the Svalis Dome north of the Loppa High and ascribed to the Steinkobbe Formation seem to extend southwards, and may have developed in a protected basin between the Loppa High and the clinoforms of the westward-prograding shelf on the Bjarmeland platform. These anoxig/dysoxic deposits form the local source rocks for the play model. The “dead oil” proved within Paleozoic carbonates in wells 7120/2-1 and 7220/6-1 on the Loppa High indicate charging from a Triassic source rock.

AAPG Search and Discovery Article #90177©3P Arctic, Polar Petroleum Potential Conference & Exhibition, Stavanger, Norway, October 15-18, 2013