Print this pageAbstract: Influence of Diagenetic Illite on the Permeability of a North Sea Sandstone Reservoir: An Image Analysis-Based Approach
BELIN, S., Centre de Geochimie de la Surface; Y. ANGUY, Laboratoire Energetique et Phenomenes de Transfer, J.B. FERM, Perception and Decision Systems, Inc., and B. FRITZ, Centre de Geochimie de la Surface
Abstract
The objective of this work is to quantify the relationship
between
the permeability and the micro-geometry of a set of samples
from a North Sea sandstones reservoir showing different degrees of
illite diagenesis. The approach is based on image analysis.
Back-scattered electrons images are digitized in gray level images.
Images consist of 5x5 elementary overlapping views (512x512 pixels
; pixel edge: 5.208 m) binarized and merged into mosaics. The
approach consists in characterizing a set of binary images of the
micro-geometry by a few 3-D objects, or Pore-Types (P.T.)
interpreted as the consequence of the initial depositional fabric
and/or post depositional diagenetic events. Using pattern
recognition algorithms, P.T.s are derived from the distributions of
sizes and shapes of closed patches of porosity (PORe Elements;
porels) exposed in the set of binary images. Each P.T. is expressed
by the distribution of sizes and shapes of the collection of porels
it yields in two-dimensions.
Multiple regression analysis procedures applied to P.T.s data
combined with capillary pressure (Pc) curves allows for a series of
discrete Pc intervals to quantify the relative amount of pores of
the kth type connected by a throat size representative a ith Pc
interval. Numerous case studies have revealed that the
pore-type/throat sizes relationship is not random. The structured
nature of the pore-type/throat sizes relation is a strong argument
to interpret P.T.s as the fundamental elements of a hierarchy of
structures and is interpreted; for sandstones, as the consequence
of a general structural model e.g. as the consequence of ‘...
the ongoing influence of a well-sorted depositional fabric coupled
with the presence of clasts resistant to dissolution or
recrystallization'. Such observed relation
is used to express
much of the flow variability as an indirect function of the
variations in the relative abundance of the P.T.s associated to the
largest throat sizes.
The target of this contribution is an illustration of this approach in the case of a North Sea Sandstones Reservoir (deltaic-, channel infilling- and deposit-facies) for a set of samples representative of the different stages of illite diagenesis.
AAPG Search and Discovery Article #90937©1998 AAPG Annual Convention and Exhibition, Salt Lake City, Utah