Fluid Transport In Rocks Research Articles

ChemInform Abstract: Magnetic Resonance of Porous Media (MRPM). A Perspective

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Magnetic Resonance of Porous Media (MRPM): A perspective

Porous media are ubiquitous in our environment and their application is extremely broad. The common connection between these diverse materials is the importance of the microstructure (μm to mm scale) in determining the physical, chemical and biological functions and properties. Magnetic resonance and its imaging modality have been essential for noninvasive characterization of these materials, in the development of catalysts, understanding cement hydration, fluid transport in rocks and soil, geological prospecting, and characterization of tissue properties for medical diagnosis. The past two decades have witnessed significant development of MRPM that couples advances in physics, chemistry and engineering with a broad range of applications. This article will summarize key advances in basic physics and methodology, examine their limitations and envision future R&D directions.

Focus on the physics of magnetic resonance on porous media

Porous media are ubiquitous in our environment and their application is extremely broad. The common connection between these diverse materials is the importance of the microstructure in determining the physical, chemical and biological functions and properties. Magnetic resonance and its imaging modality have been essential for noninvasive characterization of these materials in the development of catalysts, understanding cement hydration, fluid transport in rocks and soil, geological prospecting and characterization of tissue properties for medical diagnosis. This focus issue highlights recent NMR/MRI technical development, the underlying physics associated with the new technology, as well as novel applications of the technologies.

Interaction between pressure solution and clays in stylolite development: Insights from modeling

Stylolites are localized dissolution surfaces commonly found in sedimen- tary rocks. Stylolites have been extensively studied due to their important role in controlling dissolution, precipitation, deformation, and fluid transport in rocks. Field observations indicate that stylolite formation and morphology are strongly correlated both with the surrounding stress and with the distribution of clays within the host rock, yet the mechanism by which they form remains enigmatic. We present results from a newly developed two-dimensional Spring-Network Model that studies stylolite forma- tion by pressure-solution with and without the presence of clays, where clays play a role of enhancing pressure solution. We use our model to test the relative role of stress and clays in controlling the localization of dissolution into stylolites. In contrast to the common paradigm, our results suggest that pressure solution alone, in the absence of catalyzing clays, does not lead to spontaneous localization of dissolution into stylolites. Instead, we propose a new coupled clay-pressure-solution feedback to localize stylo- lites, a coupling that we observe in our model: a region with a slightly larger clay fraction will experience enhanced dissolution, and will thus accumulate more residual clays, which will act to further enhance pressure solution in that region, and accumu- late even more clays. Stress is a necessary component in this feedback as it controls the direction of stylolite propagation, and facilitates lateral propagation.

Geometry of flow paths for fluid transport in rocks : David, C J Geophys ResV98, NB7, July 1993, P12267–12278

Geometry of flow paths for fluid transport in rocks : David, C J Geophys ResV98, NB7, July 1993, P12267–12278

Geometry of flow paths for fluid transport in rocks

Results from numerical simulations on two‐dimensional networks used as an analog to pore space in porous rocks are presented to emphasize the existence of preferential paths for transport processes in heterogeneous media. The simulations show that hydraulic flow and electrical current are mostly driven in the so‐called “critical paths” when the pore size distribution has a decreasing exponential‐like shape in opposition to nearly homogeneous or uniform like distributions. The geometry of these flow paths is controlled by spatially correlated large conductances and can be described by a tortuosity factor, τ2. The amount of flow carried by the critical paths is higher than that predicted by statistical or effective medium models which do not take into account the role of spatial correlation. Another interesting result is that the geometry of the critical paths may change in response to alterations in the properties of the pore space, like, for example, the reduction in connectivity due to pressure‐induced pore closure. The simulations also show that the critical paths for hydraulic flow are different from those for electrical current. A statistical analysis shows that the hydraulic tortuosity is higher than the electrical tortuosity by a factor of 1.5 on the average which implies that one must be cautious in using the electrical tortuosity in the equivalent channel model for determining the permeability of rocks. As the numerical simulations have been done on distributions of pore or crack geometries typically encountered in rocks, the existence of critical paths highlighted in this paper is likely to play an important role in the phenomenology of transport processes in the Earth's crust.