| dc.description.abstract | To study the generation of basin structure, oil mine, oil extraction, and the
developing technology of sealing for safekeeping of CO2, etc., understanding
the spread of permeability of sedimentary basin is a fundamental job.
Additionally, the porosity of rocks is important as well, take the sealing and
safekeeping of CO2 for instance, it is necessary to know the porosity of rock
before we can get to know how much amount of CO2 can be stored in the layer.
Relative to the measurement of permeability, the measure porosity of rocks is
easier, therefore, many studies try to develop the relationship between
permeability and porosity of rocks, and estimate the permeability indirectly from
porosity of the rocks.
This study uses YOKO2 to measure the porosity and the permeability of
rocks under by stress. The sample is obtained from the deep well of CPC
(around 1~2km of depth), and from the ground surface of Kwetsuken of Beto.
According to this study, we find the permeability and the porosity of rocks
among sandstone, siltstone(or shale) are quite different, the porosity of
sandstone (12%~20%) and its permeability (10-13m2~10-16m2) are larger,
whereas the ones (7%~11%) & (10-15m2~10-19m2) of siltstone(or shale) are
smaller. Basically, the porosity of sandstone decrease as the buried depth
increase. From the elder to the younger, Cholan formation have the largest
porosity, Kueichoulin formation the next, then Nanchung formation,
Wuchishan formation have the smallest porosity.
The measuring permeability by gas flow should take the Klinkenberg
effect into account. After the modification of Klinkenberg effect on
permeability, we find the tiny difference between permeability by gas flow and
liquid flow, however, permeability of siltstone( or shale) using liquid flow are
1~2 orders samller than permeability using gas flow. It may overestimate the
permeability of siltstone(or shale) using gas flow to measure permeability.
The relation between stress and the porosity/permeability model of rocks
should take the maximum pre-consolidation stress into account, so as to model
the experiment data reasonably. This study determines the maximum preconsolidation
stress from the permeability-stress curve and porosity-stress
curve, respectively; as a result, we find the corresponding effective stresses to
the turning points of the normal consolidation and over-consolidation levels of
porosity-stress curve are very close to the one estimated from the buried depth
of sample, i.e. the maximum pre-consolidation pressure can be estimated
reasonably through the porosity-stress curves.
According to the stress-history-dependent models of between porosity
and permeability, this study proposed a stress-history dependent relation
between porosity and permeability. A stress-history dependent relation is
fuction of the maximum pre-consolidation stress find the relative between
porosity and permeability instead of the single curve as the equation of
Kozeny-Carman exhibits. That is, the stress history will influence the relation
between the porosity and the permeability.
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