Journal of Petroleum Geology, Vol.2,
No.2, pp. 145-158, 1979
©Copyright 2000 Scientific Press,
Ltd.
RELATIONSHIP OF FACIES AND
RESERVOIR QUALITY IN ROTLIEGENDES DESERT SANDSTONES, SOUTHERN
NORTH SEA REGION
P. J. C. Nagtegaal*
*Koninklijke/Shell Exploratie en
Produktie Laboratorium, Rijswijk, Netherlands.
Abstract
Permian Rotliegendes desert sandstones
cored in two wells in the southern North Sea were grouped as
wadi, adhesion-ripple, dune-base and dune-top sandstones on the
basis of sedimentary structure and grain-size characteristics.
The porosities of these sandstones differ significantly. Those of
wadi origin have the lowest values ( av. = 5.5%) and the dune-top
sandstones have the highest ( av. = 14.6%). The present study is
aimed at explaining these differences. The sandstones, which have
been buried to a depth of approx. 4,000 m. have a complex
diagenetic history marked by environment and depth-related
changes. Apart from authigenic ferric oxide, dolomite, anhydrite,
K-feldspar and quartz, they are characterised by well-developed
pressure solution and well-crystallised authigenic illite and
chlorite. The chlorite has a pore-bridging growth habit which
disturbs the porosity-permeability relationship.
