AAPG Bulletin, V. 84,
No. 4 (April 2000), P. 472-488.
Information on Fault Orientation
from Unoriented Cores1
Jonny Hesthammer and
Jon Ottar Henden2
©Copyright, 1999. The American
Association of Petroleum Geologists. All rights reserved.
1Manuscript received October 26, 1998;
revised manuscript received July 26, 1999; final acceptance October 15,
1999.
2Statoil, GF/PETEK-GEO, N-5020 Bergen,
Norway; e-mail: [email protected]
We thank Norsk Hydro, Saga Petroleum,
and Statoil for permission to publish the results. The article has benefited
from comments by Haakon Fossen, Tore Odinsen, and Neil Hurley and from
reviews by Jeff Warner and Ronald Nelson.
ABSTRACT
Unoriented core data can be integrated
with other data types, such as seismic data, dipmeter data, and stratigraphic
isochore or isopach data, to provide a unique solution for bedding orientation.
In addition, such an integrated approach will help to identify erroneous
data and interpretations. Once a unique solution for bedding orientation
is obtained, this information can be used to find the orientation of faults
and deformation bands as observed in core data. Although larger scale faults
commonly are difficult to core due to brecciation and poor coherency of
the fault rock, structural studies demonstrate that faults (with discrete
slip surfaces) in sandstones are associated with numerous deformation bands
in damage zones that are typically several meters wide. Within the fault
zone itself, the deformation bands commonly are subparallel to the larger
scale fault. Analyses of the orientation of deformation bands within the
fault zone thus may yield information on the orientation of the larger
scale fault. Based on such an integrated approach, it is possible to find
information on faults on a subseismic scale that would otherwise be difficult
or impossible to obtain. Quality control against seismically resolvable
faults from the Gullfaks field, northern North Sea, demonstrates that this
simple approach is valid and can provide important additional information
for the structural interpreter. The results can be used to optimize well
planning and enhance the understanding of fluid flow patterns in the reservoir.
