Middle Triassic Kobbe Formation reservoir potential outside Hammerfest Basin (Barents Sea) in light of Aurelia (7222/1-1) well results: mud-prone prograding clinoforms that challenge similar sand-prone global analogues

Abstract

Following the successful Middle Triassic play at the Goliat discovery/field in Hammerfest Basin, intense exploration efforts have been made in recent years in the rest of the Barents Sea (Bjarmeland Platform, eastern Loppa High, Nordkapp Basin) in mapping and drilling several prospects with Kobbe Formation reservoir as, in most of the cases, the main target (secondary targets including Klappmyss and Snadd formations). At Goliat, the Kobbe play is composed of four-way down-faulted rollovers with fluvial to deltaic reservoir sandstones of the Middle Triassic Kobbe Formation sourced from Lower and Middle Triassic shales and sealed by Carnian shales. Triassic sediment provenance areas are well constrained by regional seismic and well correlations in the entire Barents Sea. Although locally northwards prograding wedges are observed offlapping the Finnmark Platform with provenance from uplifted Fennoscandia, the major provenance areas for the Triassic sediments outside the Hammerfest Basin were Novaya Zemlya and the Ural Mountains. During Induan-Ladinian times, marginal marine facies of the Havert, Klappmyss and Kobbe formations onlapped the eastern flank of the paleo-Loppa High and, in an elongated manner, were also deposited farther to the northeast along the Bjarmeland Platform at the Hoop Fault Complex. Farther west in the western Barents Sea, the Lower to Middle Triassic sequences, including the Kobbe Formation equivalents, comprise condensed sections, consisting of distal organic-rich deep marine mudstones and minor sandstones. The Aurelia well (7222/1-1; completed Aug. 2016; operated by Eni Norge) is located on the northeastern part of the Loppa High proper and is the latest well to target the Kobbe Formation reservoir as the main target along the SW-NE elongated, Anisian paleo-shoreline along the eastern Loppa High and Hoop Fault Complex area. The well results indicate a poor quality sandstone reservoir with traces of gas in the Kobbe Formation, as well as minor gas shows in two moderate reservoir quality water-bearing sandstone levels (Carnian and Ladinian) within the Snadd Formation. Characteristic clinoform surfaces were mapped in the available 3D seismic in Aurelia and several seismic amplitude anomalies are structurally comformable with the prospect. Despite the encouraging pre-drill accounts for presence of sandy deposits at the topset of these clinoform successions and their deltaic counterparts, the well encountered only heretolithic facies with poor reservoir quality at the Kobbe Formation main target. The Aurelia well results may, therefore, challenge global analogues of sand-prone topsets of prograding clinoforms. Furthermore, the well results may challenge the expectations for viable Kobbe Formation reservoir potential away from the Hammerfest Basin where the proximity to the Fennoscandia provenance and the interplay between fault-controlled changes in the delta system and facies appear to be the main reservoir controlling factors.

AAPG Datapages/Search and Discovery Article #90325 © 2018 AAPG Europe Regional Conference, Global Analogues of the Atlantic Margin, Lisbon, Portugal, May 2-3, 2018