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@PHDTHESIS{Zhazha:824770,
author = {Zhazha, Hu},
othercontributors = {Littke, Ralf and Swennen, Rudy},
title = {{M}ulti-scale characterization of the petrophysical
properties of tight sedimentary rocks : examples from an
{O}rdovician {L}imestone, {C}anada and {S}ilurian and
{E}diacaran {S}hales, {C}hina},
school = {Rheinisch-Westfälische Technische Hochschule Aachen},
type = {Dissertation},
address = {Aachen},
publisher = {RWTH Aachen University},
reportid = {RWTH-2021-07808},
pages = {1 Online-Ressource : Illustrationen, Karten},
year = {2020},
note = {Veröffentlicht auf dem Publikationsserver der RWTH Aachen
University 2021; Dissertation, Rheinisch-Westfälische
Technische Hochschule Aachen, 2020},
abstract = {Understanding fluid transport processes in low-permeable
sedimentary rocks is required for a wide range of
geotechnical applications, especially for assessing their
sealing behavior during nuclear waste storage and their
transport properties as an unconventional reservoir. Fluid
transport is largely controlled by the pore structure. Apart
from pore structure characterization, sorption measurements
are of equal importance in assessment of shale gas
reservoirs. The first part of this study (chapter 2 and 3)
employed a series of petrophysical and imaging techniques to
characterize the fluid transport properties and pore
structure of Middle Ordovician Cobourg limestone, a
potential host rock for nuclear waste repositories in
Canada. For this purpose, porosity and permeability were
measured with helium on four dry cylindrical plugs in
pseudo-triaxial cells under defined isostatic stress
conditions (5-20 MPa). The experimental results indicate
that stress sensitivity coefficients of permeability are
about one order of magnitude higher than those of porosity,
which is the result of preferential closure or volume
reduction of interconnecting restrictions (pore throats) of
the pore network with increasing stress. The major
discontinuities observed in the most permeable sample are
identified by scanning electron microscope (SEM) as open
stylolites enhancing the permeability between two to three
orders of magnitude as compared to samples where stylolites
were absent. Pore morphologies and pore structures of the
intact Cobourg limestone were analyzed by focused ion beam -
and broad ion beam - scanning electron microscope (FIB- and
BIB - SEM). Mineralogy analysis indicates that it is
characterized as a tight rock dominated by calcite grains of
variable sizes (µm - cm) surrounded by idiomorphic or
subhedral minerals (quartz, dolomite and pyrite) and meshy
clay minerals. The clay mineral and calcite phases
contribute over $90\%$ of the total pore area. The clay
pores are relatively small and occur close to each other,
elongated in shape and are interpreted as interparticle
pores. On the contrary, the pores associated with calcite
have a large pore size range and are distant from each
other, equidimensional or elongated in shape and can mostly
be considered as intraparticle pores. Different pore size
distributions were identified for the two phases in BIB-SEM
maps, which can be characterized by power law relationships
between pore area and normalized pore frequency with
different exponents (1.93-2.18 for calcite and 2.50-2.59 for
clay). Based on the relationship, extrapolated porosities
are compared to porosities obtained by helium pycnometry
(HP). In Chapter 4 the pore structure and sorption capacity
of Ediacaran Doushantuo and Liuchapo shales were
characterized and compared with those of commercially
producing Silurian Longmaxi shales in Upper Yangtze
platform. The results show that computed maximum gas storage
capacities at present day reservoir conditions are lower for
the Ediacaran shales (0.054 - 0.251 mmol/g) when compared to
the Silurian shales (0.237 - 0.330 mmol/g), while the
maximum amounts of sorbed methane of Ediacaran and Silurian
shales were in the same range, between 0.02 - 0.19 mmol/g
and 0.08 - 0.21 mmol/g, respectively. Porosities were
smaller for Ediacaran shales (1.4 - $4.6\%)$ than for
Silurian shales (6.2 - $7.4\%).$ Low-pressure N2- and CO2
adsorption measurements also indicated larger micropore
volume fractions and smaller mesopore volumes for the
Ediacaran shales. This is likely related to burial and to a
silica-associated preservation of pores. TOC content
exhibits significant control on sorption capacity and CO2
micropore volume for both shales. The difference in sorption
contribution of clay minerals can be attributed to different
clay types and evolutionary differences of illite. The
findings presented in the thesis have important implications
for pore structure characterization, Gas-In-Place
estimations, fluid flow modelling and sealing efficiency
assessments.},
cin = {532410 / 530000},
ddc = {550},
cid = {$I:(DE-82)532410_20140620$ / $I:(DE-82)530000_20140620$},
typ = {PUB:(DE-HGF)11},
doi = {10.18154/RWTH-2021-07808},
url = {https://publications.rwth-aachen.de/record/824770},
}
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