A map of faults in a 60 km2
area of the southern North Sea has been produced from three-dimensional
seismic data. The faults shown on the map obey power-law cumulative-frequency
distributions for throw (power-law exponent, D,
~ 2.7) and length (D
~ 1.1). Simulations have been carried out to correct for sampling biases
in the data and to make predictions of the throw and length scaling characteristics
of the faults. The most important bias is caused by poor resolution of
the small displacement tip zones of faults. The raw data show considerable
scatter in their length:throw ratios, but they more closely fit a linear
relationship if a length of 500 m is added to each fault, thereby making
up for the zones near the fault tips with throws (~ 15 m) below seismic
resolution. Further variability in the data may be caused by such geological
factors as fault interaction.
Tip lengths have been extended to simulate
the actual fault pattern in the study area. Maps produced by this procedure
can be used to estimate the true connectivity of the fault network. Extending
the faults results in greater connectivity than shown by the raw data,
which may cause greater compartmentalization of the rock mass. This greater
compartmentalization has implications for hydrocarbon exploitation if the
faults
©Copyright
1996. The American Association of Petroleum Geologists. All rights reserved.
1Manuscript
received October 2, 1995; revised manuscript received February 15, 1996;
final acceptance July 15, 1996.
2Geomechanics
Research Group, Department of Geology, University of Southampton, Southampton
Oceanographic Centre, Empress Dock, European Way, Southampton, SO14 3ZH,
United Kingdom.
3Present
address: British Gas, Gas Research Centre, Ashby Road, Loughborough, Leicestershire,
LE11 3QU, United Kingdom.
4Department
of Geological Sciences, University of Plymouth, Drake Circus, Plymouth,
PL4 8AA, United Kingdom.
5Present
address: Rock Deformation Research Group, Department of Earth Sciences,
University of Leeds, Leeds, LS2 9JT, United Kingdom.
Mobil
North Sea Ltd. is thanked for funding G. Pickering and for providing seismic
data. Funding for field work in Somerset was given by the University of
Plymouth. Kevin Biddle, Nancye Dawers, James Handschy, and William Shea
are thanked for their careful reviews.
