Fluid flow stress-permeability

Given the availability of hollow fiber membranes adequately permeable to substrates and products, and the control of fluid flow all around the fibers in the bundle in order to assure uniform flow distribution and to avoid stagnation (in order to reduce mass transfer diffusional resistances), the technique offers several advantages. Enzyme proteins can be easily retained within the core of the fibers with no deactivation due to coupling agents or to shear stresses, and the enzyme solution can be easily recovered and/or recycled. 

Early modeling of wellbore stresses assumed that the rock behaved elastically (52). Bratli and Risnes (27) and Risnes et al. (53) included a plastic zone around the wellbore with variable permeability (Figure 11). In unconsolidated sands, the plastic zone is of the order of about 1 m radius consolidated formations have a smaller plastic zone. For stress solutions with fluid flowing into an uncased wellbore (cylindrical geometry around the wellbore), a stability criterion that equates fluid flow parameters to rock strength parameters is found ... 

Figured. Outline of stochastic stress and fluid flow analysis for upscaling the srrmll-scale (e.g.. 1.56 m x 1.56 m) stress-permeability relation to a gridblock scale for a large-scale model.

Stress induced permeability change is of crucial importance in various kinds of applications such as nuclear waste disposal in deep geological formations, geothermal energy utilization and underground excavations. In particular, coupling between the stress and permeability is a key element in understanding the nature of flow in the fractured rock (Rutqvist and Stephansson, 2003). This is because fractures, which are the main pathways of fluid flow in fractured hard rocks, are heavily dependent on the stress conditions for their deformations. 

After the application of the various stress boundary conditions, differential hydraulic heads are applied to opposite model boundaries to introduce fluid flow through the models, and the equivalent permeability of the model is calculated as the function of the applied stress boundary conditions. 

As the k ratio is close to 1, no failure of fracture occurs and fracture normal closure is the dominating mechanism for fluid flow. Non-linear behaviour of fracture normal stress-deformation makes the permeability change at the lower stress levels more dramatic than that at the higher stress levels. The reduction of permeability is about two orders of magnitude and anisotropy in... 

The main emphases in oil and gas production are how to explore sites and how to operate resources for optimal flow, and long term resource management. The rock structure, rock stress field, primary and secondary rock permeabilities, wellbore locations and orientations, and fluid flow are all coupled and hence there are many interactions that require modelling. 

Han, G. Dusseault, M.B. May 2003. Description of fluid flow around a wellbore with stress-dependent porosity and permeability. J. Petro. Sci. Eng. In press. 

Abstract We analyse the effect of thermal contraction of rock on fracture permeability. The analysis is carried out by using a 2D FEM code which can treat the coupled problem of fluid flow in fractures, elastic and thermal deformation of rock and heat transfer. In the analysis, we assume high-temperature rock with a uniformly-distributed fracture network. The rock is subjected to in-situ confining stresses. Under the conditions, low-temperature fluid is injected into the fracture network. Our results show that even under confining environment, the considerable increase in fracture permeability appears due to thermal deformation of rock, which is caused by the difference in temperature of rock and injected fluid. However, for the increase of fracture permeability, the temperature difference is necessary to be larger than a critical value, STc, which is given as a function of in-situ stresses, pore pressure and elastic properties of rock. 

We considered here a jointed rock, i.e. a formation of rock blocks separated by thin joints / fractures. Fluid flows through the fractures, while fluid permeation into the rock blocks is neglected. The rock formation is at high temperature initially, and is subjected to in-situ confining stresses. Under the conditions, low-temperature fluid is injected from a point into the fracture network. For such a case, we examined how the fluid injection changes the fracture network permeability assuming 2-dimensional cases for simplicity. 

To investigate the stress on the fluid flow effect through the gap width variation, and this effect is responded by the permeability change. Numerous study has on the influence of normal stress to the fluid field, and has obtained many experienced formulas, such as. 

Bell, F.G. and Jermy, C.A. 2002. Permeability and fluid flow in stressed strata and mine stability. Eastern Transvaal Coalfield, South Africa. Quarterly Journai Engineering Geology and Hydrogeology, 35, 391-402. 

The outer walls of bifurcations and the inner walls of curved vessels are characterized by low mean wall shear stress, and significant temporal oscillations in wall shear stress direction (oscillatory shear stress) [2]. Endothelial cells in this low, oscillatory shear environment tend to assume a polyhedral, cobblestone enface morphology whereas endothelial cells in high shear regions tend to be elongated in the direction of flow. It has been suggested that these altered morphologies, which represent chronic adaptive responses to altered fluid mechanical environments, are characterized by distinct macro-molecular permeability characteristics [2,10] as direct responses of the endothelial layer to altered mechanical environments. In addition, a number of studies have shown that fluid shear stress on the endothelial surface can have an acute influence on endothelial transport properties both in vitro [34-37] and in vivo [38,39]. 

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