Reservoir damage around faults; outcrop examples from the Suez Rift

Abstract

Field observations in western Sinai show that damage zones around faults are characterized by (a) a decrease in the frequency of small-scale structures with increasing distance from the master fault, (b) clustering of these structures across damage zones, and (c) a positive relationship between damage zone width and master fault throw in logarithmic space, up to maximum width of about 80 m. This relationship allows damage zone width to be estimated from fault throw, a parameter obtainable from seismic data. Preliminary data on the interconnectivity of structures within damage zones indicate that granulation seams are more likely to intersect than tip out. The thicknesses of small-scale structures were measured, and the cumulative thicknesses of all small-scale structures within individual damage zones calculated. In the examples given, these cumulative thicknesses are up to 1 m within 10-30 m wide damage zones, implying that as much as 1 m of deformed rock, most likely with reduced porosity and permeability, occurs across damage zones. This, together with the interconnectivity data, suggests that the impact of faults on fluid flow may occur not only at fault planes, but throughout their damage zones.

Deformation bands in sandstone: a review

“…Passchier & Trouw 1996); however, it was first applied in the context of sandstone deformation by Aydin and co-workers (Aydin 1978;Aydin & Johnson 1978, 1983. Since then, the term has gradually been adopted to encompass terms such as microfaults (Jamison & Stearns 1982), cataclastic faults (Fisher & Knipe 2001), faults (Manzocchi et al 1998;Fisher et al 2003), (micro)fractures (Borg et al 1960;Dunn et al 1973;Gabrielsen & Koestler 1987), shear bands (Menéndez et al 1996), deformation-band shear zones (Davis 1999), Lüders' bands (Friedman & Logan 1973;Olsson 2000), cataclastic slip bands (Fowles & Burley 1994), and granulation seams (Pittman 1981;Beach et al 1999;Du Bernard et al 2002b). The most important characteristics of deformation bands (in the context of porous rock and sediment deformation) are summarized as follows.…”

“…Cataclastic bands are found in porous sandstones throughout the world; for example, in the Suez rift (Beach et al 1999;Du Bernard et al 2002b), France (Wibberley et al 2000), the UK (Underhill & Woodcock 1987;Beach et al 1997;Knott 1993), Ordovician sandstones of Oklahoma (Pittman 1981), Permian sandstones of the southern North Sea (Fisher & Knipe 2001) and southeastern Norway (Lothe et al 2002), and the Jurassic sandstones of southwestern USA (e.g. Aydin 1978;Jamison & Stearns 1982;Davis 1999).…”

“…), Navajo data from Shipton & Cowie (2001) and Fossen (unpubl. ), and Sinai data from Beach et al (1999) and Rotevatn & Fossen (unpubl. ) approximately one across nine orders of magnitude for faults as small as tens of centimetres long (Clark & Cox 1996;Schlische et al 1996) but was found to be c. 0.5 for a population of cataclastic deformation bands in Utah (Fig.…”

Structural heterogeneity and permeability in faulted eolian sandstone: Implications for subsurface modeling of faults

“…These may exhibit significant variability at the outcrop to oil field scale (Foxford et al, 1998;Walsh et al, 1998;Beach et al, 1999;Hesthammer and Fossen, 2000;Shipton and Cowie, 2001). The lowest permeability case, flow perpendicular to the fault zone (transverse flow), is considered for these analyses.…”

Deformation band populations in fault damage zone—impact on fluid flow

“…Fault frequency profiles across fault damage zones show an overall decrease in deformation band density away from the fault core [2,4,15,17,21,30]. Based on a comprehensive database consisting of damage zone data from Utah and Sinai (CIPR database), this decrease can be modeled as a logarithmic decline in more than 80% of the cases (Fig.…”