Estimating the permeability of reservoir sandstones using image analysis of pore structure
File(s)
Author(s)
Lock, Peter
Type
Thesis or dissertation
Abstract
In this thesis, a method is developed for predicting the permeabilities of a core using
only a small number of SEM images, without resorting to computationally intensive
procedures. The pore structure is idealised as consisting of a cubic network of pore
tubes having an arbitrary distribution of cross-sectional areas and shapes. The areas and
perimeters of the individual pores are estimated from image analysis of scanning
electron micrographs of thin sections, with appropriate stereological corrections
introduced to infer the true cross sections of the pores.
Effective medium theory is used to find the effective single-tube conductance, based
on the measured distribution of individual conductances, thereby allowing a prediction
of the permeability. The methodology has been applied to several reservoir sandstones
from the North Sea, and also an outcrop sample from Cumbria, UK, yielding predictions
that fall within a factor of two of the laboratory measurements in most cases.
The procedure, although based on Kirkpatrick's intrinsically isotropic effectivemedium
approximation, is not only capable of yielding reasonably accurate estimates of
the permeabilities, but also gives a qualitatively correct indication of the anisotropy
ratio. It also found that the use of an Bernasconi's anisotropic effective-medium
approximation does not lead to a systematic improvement in the results, perhaps because
the samples used in this study were insufficiently anisotropic for the approaches to yield
different results.
The validity of the effective medium approximation was also tested against exact
pore network calculations. For the rocks examined in this study, with pore conductance
distributions having log-variances less than 3, the effective medium approximation was
found to be accurate to within a few percent.
only a small number of SEM images, without resorting to computationally intensive
procedures. The pore structure is idealised as consisting of a cubic network of pore
tubes having an arbitrary distribution of cross-sectional areas and shapes. The areas and
perimeters of the individual pores are estimated from image analysis of scanning
electron micrographs of thin sections, with appropriate stereological corrections
introduced to infer the true cross sections of the pores.
Effective medium theory is used to find the effective single-tube conductance, based
on the measured distribution of individual conductances, thereby allowing a prediction
of the permeability. The methodology has been applied to several reservoir sandstones
from the North Sea, and also an outcrop sample from Cumbria, UK, yielding predictions
that fall within a factor of two of the laboratory measurements in most cases.
The procedure, although based on Kirkpatrick's intrinsically isotropic effectivemedium
approximation, is not only capable of yielding reasonably accurate estimates of
the permeabilities, but also gives a qualitatively correct indication of the anisotropy
ratio. It also found that the use of an Bernasconi's anisotropic effective-medium
approximation does not lead to a systematic improvement in the results, perhaps because
the samples used in this study were insufficiently anisotropic for the approaches to yield
different results.
The validity of the effective medium approximation was also tested against exact
pore network calculations. For the rocks examined in this study, with pore conductance
distributions having log-variances less than 3, the effective medium approximation was
found to be accurate to within a few percent.
Version
Open Access
Date Issued
2001-03
Date Awarded
2001
Advisor
Zimmerman, Robert
Jing, Xudong
Sponsor
Enterprise Oil (Great Britain)
Publisher Department
Earth Science and Engineering
Publisher Institution
Imperial College London
Qualification Level
Doctoral
Qualification Name
Doctor of Philosophy (PhD)
Author Permission
Permission granted