AAPG Methods in Exploration No. 13, Chapter 19:
Characterization of Fracture Networks Using Data from Boreholes: An Example from the
Concealed Borrowdale Volcanic Group in West Cumbria, U.K. , by Robert P. Barnes, Stephen
J. Dee, and David J. Sanderson, Pages 269 - 283
from:
AAPG Methods in Exploration No. 13: Geological Applications of Well Logs, Edited
by M. Lovell and N. Parkinson
Copyright © 2002 by The American Association of Petroleum Geologists. All rights
reserved.
Chapter 19
Characterization of Fracture Networks Using Data from Boreholes: An Example from the
Concealed Borrowdale Volcanic Group in West Cumbria, U.K.
Robert P. Barnes
British Geological Survey
Edinburgh, U.K.
Stephen J. Dee
Badley Technology Ltd.
Hundleby, U.K.
David J. Sanderson
T. H. Huxley School of Environment
Earth Sciences and Engineering
Imperial College, London, U.K.
ABSTRACT
The Borrowdale Volcanic Group (BVG) in west Cumbria, northwestern England, comprises a
thick sequence of pyroclastic rocks dominated by relatively homogeneous, welded ignimbrite
units. Between 1989 and 1997, the group was investigated intensively by UK Nirex Ltd. as
the potential host rock for an underground repository for radioactive waste. At the
proposed repository location, near Sellafield, the volcanic rocks are concealed beneath
about 450 m of Permo-Triassic cover. Site-specific fracture data were acquired from
logging of cores and from processed electrical and acoustic wall images of 28 vertical or
steeply inclined boreholes. Cores and imagery produced large fracture datasets, but the
datasets could not easily be combined for purposes of interpretation. A simple graphic
method allowed rapid appraisal of a range of fracture attributes in relation to depth and
geological context. However, full characterization of the fracture network relied on
orientation data derived from borehole imagery.
