--> Abstract: The Offshore-onshore Link of Lower Cretaceous Clastic Wedges in the Barents Sea and Svalbard: A Tool for Risk Mitigation of Plays, by Sten-Andreas Grundvag; #90177 (2013)

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The Offshore-onshore Link of Lower Cretaceous Clastic Wedges in the Barents Sea and Svalbard: A Tool for Risk Mitigation of Plays

Sten-Andreas Grundvåg

Lower Cretaceous clastic wedges occur along many basin margins in the Barents Sea, and several exploration wells have targeted these deposits. Although, none of the exploration campaigns proved successful in terms of commercial finds, there is a growing interest for the Lower Cretaceous as a potential play model in the Barents Sea. However, due to the general lack of well data and 3D seismic data coverage, detailed analyses of the depositional architecture of these wedges are problematic. In contrast to the northern Barents Sea and Svalbard, the successions in southwestern Barents Sea are linked to rift basins. However, seismic studies combined with outcrop analogue studies on Svalbard, may improve our understanding of the occurrence and facies architecture of prolific clastic wedges in the Barents Sea. In Svalbard, the Lower Cretaceous succession comprises the Rurikfjellet-, Helvetiafjellet- and Carolinefjellet formations, which together, form a >1000 m thick 1st-order R-T sequence. The Rurikfjellet Formation (Berriasian-Hauterivian) is up to 400 m thick, and consists of a lower mudstone-dominated, and an upper sandstone-rich part. The latter contain regressive shoreface and delta front deposits. Abundant hummocky cross-stratification (HCS) indicates deposition on a storm-influenced shelf. Recently, onshore wells have recorded mass transport deposits with rafted blocks of coastal plain facies, indicating a hitherto unknown Valanginian to early Hauterivian shoreline progradation. On the margins of the Hammerfest Basin, thick, well-sorted sandstones of turbiditic origin occur in the time-equivalent Knurr Formation, suggesting a regional-scale relative sea level change. Southeast-directed clinoforms in the northern Barents Sea, which downlap near the base Cretaceous reflector, were probably influenced by the same event. The Helvetiafjellet Formation (Barremian-early Aptian) is up to 155 m thick, and consists of a lower sandstone-dominated, and an upper heterolithic part. The lower part was deposited in a braid-plain setting, whereas the upper part was deposited in a paralic setting. Offshore, there are no equivalent formations to the Helvetiafjellet Formation, although, shallow marine and fan delta deposits occur along some basin margins. The Carolinefjellet Formation (Aptian-Albian) is up to 850 m thick, and consists of five units that are alternatingly sandstone and mudstone dominated. The sandstone-dominated units form southward-thinning wedges that are characterized by abundant HCS. The lowermost unit is suggested to represent the transgressive, storm-reworked shelf segment of the underlying Helvetiafjellet deltaics. Locally, the lowermost (early Aptian) part of the formation also includes organic-rich mudstones that may have source-rock potential. The Carolinefjellet Formation correlates with the Kolmule Formation offshore.

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