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GEOREF RECORD

Polygonal faults and their influence on deep-water sandstone reservoir geometries, Alba Field, United Kingdom central North Sea

Lidia Lonergan and Joe A. Cartwright
Polygonal faults and their influence on deep-water sandstone reservoir geometries, Alba Field, United Kingdom central North Sea
AAPG Bulletin (March 1999) 83 (3): 410-432

Abstract

Polygonal faults attributed to three-dimensional (3-D) volumetric contraction of muddy sediments during early burial are widespread within the Eocene-lower Miocene succession of the United Kingdom central North Sea. The analysis of a 3-D seismic survey encompassing the Eocene Alba field in the central North Sea has allowed us to investigate (1) the influence of polygonal faults in surrounding mudrocks on the geometry of the Alba deep-water sandstone reservoir and (2) how the presence of the reservoir sandstone influences the polygonal fault pattern above and below the reservoir. The main reservoir in the Alba field is an elongate (12 km long, 1-2 km wide, up to 90 m thick), fine-grained, massive sandstone body that may have been deposited in a deep-water channel or slope gully. Although depositional processes likely have been responsible for the dominantly linear sandstone distribution, the current reservoir geometry is largely controlled by the location of polygonal faults in the surrounding hemipelagic mudstones. Sandstones interpreted as injected along faulted margins of the Alba field indicate that faulting facilitated remobilization and sand injection during early burial, further modifying the reservoir shape. Unusual, isolated 1-km-wide subcircular mounds to the west of the main field also are attributed to sand withdrawal and remobilization during early burial. On a mapped marker horizon in the mudrocks 80-120 m above the reservoir there is a marked decrease in polygonal fault density compared to areas away from the reservoir. On a horizon in mudrocks within 5-50 m of the base of the reservoir there is an increase in horizon disruption due to small faults directly below the sand body. Changes in polygonal fault density and pattern thus may indicate the presence of sandstones and may be a useful exploration tool for explorationists searching for subtle Eocene deep-water sand bodies that typically are poorly imaged on seismic data in the North Sea.


ISSN: 0149-1423
EISSN: 1558-9153
Coden: AABUD2
Serial Title: AAPG Bulletin
Serial Volume: 83
Serial Issue: 3
Title: Polygonal faults and their influence on deep-water sandstone reservoir geometries, Alba Field, United Kingdom central North Sea
Affiliation: Imperial College of Science, Technology and Medicine, T. H. Huxley School of Environment, Earth Science and Engineering, London, United Kingdom
Pages: 410-432
Published: 199903
Text Language: English
Publisher: American Association of Petroleum Geologists, Tulsa, OK, United States
References: 37
Accession Number: 1999-034335
Categories: Economic geology, geology of energy sourcesStructural geology
Document Type: Serial
Bibliographic Level: Analytic
Illustration Description: illus. incl. block diags., sects., sketch maps
N58°00'00" - N58°04'60", E01°01'60" - E01°10'00"
Country of Publication: United States
Secondary Affiliation: GeoRef, Copyright 2017, American Geosciences Institute. Reference includes data supplied by American Association of Petroleum Geologists, Tulsa, OK, United States
Update Code: 199912
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