THE SCALING OF PULL-APARTS AND IMPLICATIONS FOR FLUID FLOW
IN AREAS WITH STRIKE-SLIP FAULTS
D.C.P. Peacock1* and M.W. Anderson2
1 Statoil, Sandsliveien 90, NO-5020, Bergen, Norway.
2 School of Geography,
Earth and Environmental Sciences, University
of Plymouth, Plymouth PL4 8AA.
* corresponding author, email: email@example.com
Widths of pull-aparts between strike-slip
fault segments appear to obey power-law scaling relationships, at least up to
the scale of hundreds of millimetres. Field data from the Liassic
limestones of Somerset, UK,
are presented and are discussed in relation to fluid flow through rock. The
established scaling relationships are used to predict the contributions of different-sized
pull-aparts to space created by strike-slip faults.
Fluid-filled pull-aparts are likely to be significant
in hydrocarbon reservoirs affected by strike-slip faulting because they are
sub-vertical tube-like structures that may extend through reservoirs and top
seals. There are, however, insufficient data to develop a model for permeability
along pull-aparts. Models of fluid flow in rock typically
assume a limited range of fracture apertures, so models can be improved by incorporating
information on the scaling relationships
of the fractures and the contributions of different-sized fractures to secondary
porosity. Also, geomechanical models that assume planar
strike-slip faults are likely to underestimate migration because they do not
consider the reduction of compressive stresses at pull-aparts.
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