--> ABSTRACT: Structural Compartmentalisation of an Aeolian Reservoir Analogue, by John A. Howell, H. Ewart Edwards, Andrew D. Becker; #91020 (1995).

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Structural Compartmentalisation of an Aeolian Reservoir Analogue

John A. Howell, H. Ewart Edwards, Andrew D. Becker

Many aeolian sandstones suffer a decline in reservoir quality associated with structural compartmentalisation by tectonic features. The effects of these features are extremely difficult to quantify in the sub-surface and better understanding arises from studies of outcrop analogues. The Permo-Triassic of the Moray Firth in Scotland has been studied as such an analogue, being comparable to many similar aged plays in the Southern North Sea and Irish Sea areas of the United Kingdom Continental Shelf.

A hierarchy of structural flow barriers with impermeable fault rock vary from solitary deformation bands, via compound zones of bands to major fault slip surfaces. Episodic faulting resulted in growth from bands to larger fault zones. Increased cementation of the sandstones is seen adjacent to these tight fault zones and a zone of enhanced cementation, spatially governed by the main fault in the region has been mapped. Conjugate extensional systems of deformation bands decrease in density away from the major faults. Porosity reduction is related to proximity to faults, with porosity increasing abruptly away from the tectonic barrier; the deformation producing low-quality reservoirs and flow barriers. Tectonic features have intermittently acted as both fluid conduits and barriers, enha ced cementation of sedimentary features adjacent to 'tight' faults indicates migration of diagenetic brines along fractures.

Facies contrasts partially control resultant deformation fabrics, the well sorted aeolian Hopeman Sandstones display better developed flow barriers than the underlying, poorly sorted, hetrolithic, fluvial, Burghead Beds. Interaction of fluid flow, diagenetic cementation and structural deformation produce flow barriers that compartmentalize the sandstones on all scales.

AAPG Search and Discovery Article #91020©1995 AAPG Annual Convention, Houston, Texas, May 5-8, 1995