Permeability (earth sciences)

About: Permeability (earth sciences) is a research topic. Over the lifetime, 15424 publications have been published within this topic receiving 288535 citations.

Insights into pore-scale controls on mudstone permeability through resedimentation experiments

Abstract: At a given porosity, mudstone permeability increases by an order of magnitude for clay contents ranging from 57% to 36% (<2 μm). This increase in vertical permeability results from a dual-porosity system that develops through three mechanisms: (1) silt bridging preserves large pore throats, (2) stress bridges inhibit clay particle alignment, and (3) local clay particle compression within stress bridges alters pore throat size distribution. Uniaxial consolidation experiments on resedimented clay-silt mixtures illuminate how permeability varies as a function of clay fraction during burial. Backscattered electron microscope images show that silty mixtures have larger pore throats and fewer aligned clay particles than do more clay-rich mixtures. We describe the permeability of clay-silt mixtures with a geometric mean model. Our method provides a promising framework for modeling of mudstone permeability as a function of clay fraction and porosity. How permeability and consolidation evolve during burial affects the ability of mudstones to seal CO2 and hydrocarbons in the subsurface, how mudstones behave as gas reservoirs, and under what conditions mudstones will be overpressured. Dual-porosity systems have fundamentally different transient flow and solute transport behaviors.

The water retention curve and relative permeability for gas production from hydrate‐bearing sediments: pore‐network model simulation

Abstract: The water retention curve and relative permeability are critical to predict gas and water production from hydrate-bearing sediments. However, values for key parameters that characterize gas and water flows during hydrate dissociation have not been identified due to experimental challenges. This study utilizes the combined techniques of micro-focus X-ray computed tomography (CT) and pore-network model simulation to identify proper values for those key parameters, such as gas entry pressure, residual water saturation, and curve fitting values. Hydrates with various saturation and morphology are realized in the pore-network that was extracted from micron-resolution CT images of sediments recovered from the hydrate deposit at the Mallik site, and then the processes of gas invasion, hydrate dissociation, gas expansion, and gas and water permeability are simulated. Results show that greater hydrate saturation in sediments lead to higher gas entry pressure, higher residual water saturation, and steeper water retention curve. An increase in hydrate saturation decreases gas permeability but has marginal effects on water permeability in sediments with uniformly distributed hydrate. Hydrate morphology has more significant impacts than hydrate saturation on relative permeability. Sediments with heterogeneously distributed hydrate tend to result in lower residual water saturation and higher gas and water permeability. In this sense, the Brooks-Corey model that uses two fitting parameters individually for gas and water permeability properly capture the effect of hydrate saturation and morphology on gas and water flows in hydrate-bearing sediments.

Three-dimensional flow and reaction in porous media: Implications for the Earth's mantle and sedimentary basins

Abstract: We present a theoretical and numerical study of the reorganization of a porous matrix due to fluid flow coupled with dissolution or precipitation processes. We find that under certain conditions, flow of corrosive fluids results in unstable growth of the permeability and increasing disequilibrium in fluid chemistry with time. High-permeability channels may form parallel to the direction of flow. In time, these channels cause the distribution of porosity to become increasingly correlated and anisotropic and cause flow rates to be increasingly variable. Flow coupled with crystallization has the opposite effect: With time, permeability reduction occurs at a decreasing rate. Mineral composition in the fluid approaches chemical equilibrium. Precipitation destroys existing preferred paths for flow and acts to homogenize and disperse the flow. Connectivity of the porous media is reduced. Implications of these results for two geological systems are discussed: (1) Modes of melt extraction from the Earth's mantle, where the expected different modes of flow and reaction may help explain different geochemical and geological observations at hot spots and mid-ocean ridges, and (2) Precipitation and formation of abnormal pressure zones in sedimentary basins.