Episodic basin-wide hydrofracturing of overpressured Early Cenozoic mudrock sequences in the North Sea Basin

Cartwright, Joseph Albert 1994. Episodic basin-wide hydrofracturing of overpressured Early Cenozoic mudrock sequences in the North Sea Basin. Marine and Petroleum Geology 11 (5) , pp. 587-607. 10.1016/0264-8172(94)90070-1

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Abstract

A deformational fabric associated with the Early Cenozoic mudrock dominated sequences of the North Sea is described. Seismic data show that the mudrock sequences are pervasively faulted over a large area of the basin axis in the central and northern North Sea. Mapping the faults using regional two- and three-dimensional data shows that the faults are minor extensional structures, arranged in stratigraphically bound tiers in the deep water sequences and bounded by regional condensed sequences (seals). The geometry of the faulting is complex. Faults are organized into cellular networks comprising polygonal prismatic and pyramidal forms. A gravitational mechanism of downslope collapse faulting is rejected on the grounds that the distribution of the deformed sequences extends over large areas of formerly horizontal basin plain. A mechanism involving the repeated development of basin-wide overpressured compartments is proposed in which the cellular structure is related to deformation patterns associated with a density inversion between the overpressured units and the overlying seal. Hydrofracturing is invoked to account for the almost random strike distribution of the faulting. The region affected by the pervasive fluid expulsion faulting encompasses almost half of the North Sea Basin. Basin-wide collapse of the overpressured compartments could have resulted in a geologically rapid flux of enormous volumes of pore fluids. This mechanism has implications for concepts of steady-state compaction, heat flow in basins, hydrocarbon transport and the genesis of lead-zinc ore deposits.

Item Type:	Article
Date Type:	Publication
Status:	Published
Schools:	Earth and Environmental Sciences
Subjects:	G Geography. Anthropology. Recreation > GC Oceanography
Uncontrolled Keywords:	hydrofracturing; overpressures; mudrocks
Publisher:	Elsevier
ISSN:	0264-8172
Last Modified:	28 Jun 2019 02:15
URI:	https://orca.cardiff.ac.uk/id/eprint/46098

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