Fluid flow fracture permeability

A foam, aqueous or non-aqueous, that is injected into a petroleum reservoir to improve the productivity of oil- or gas-producing wells. Some mechanisms of action for foam stimulation fluids include fracturing, acidizing to increase permeability, and diversion of flow. 

The present hydrogeological framework of the sedimentary basin, which is characterized by the distribution, thickness and dip of porous and permeable hydrogeological units (aquifers/potential carrier-reservoir rocks, e.g. sands, sandstones, carbonates, fractured rocks) and poorly permeable hydrogeological units (aquitards/potential barrier rocks, e.g. shales, evaporites), and the location of geological structures and tectonic elements of importance for subsurface fluid flow, e.g. permeable or impermeable faults, unconformities... 

The high permeability of fractures causes them to preferentially focus fluid flow. The effectiveness of fractures as mass transport systems for fluids is evident from a casual examination of mineralisation in fractured rocks and leakage of groundwater at fracture outcrops. Similarly, these fractures act as preferential hydrocarbon pathways, focusing their flow from source beds to surface. 

In Mesozoic sandstones on Tampen Spur and Haltenbanken, normal faults are usually characterized by grain reorientation and enrichment of clay minerals which suggest that ductile deformation dominates. Abundant quartz cement is only observed along these faults associated with stylolites. Open fractures were not present in the sandstones from Tampen Spur and Haltenbanken. Fractures in these sediments therefore normally represent permeability barriers for fluid flow. 

Fracturing and fault compartmentalization of sandstones fundamentally affects reservoir properties and may significantly influence the fluid migration pathways in a basin (Knipe, 1993). Open fractures may form high-permeability conduits, whereas cement-sealed fractures form barriers to fluid flow. Seismic, petrophysical and reservoir performance data allow regional (field-scale) effects of faulting on fluid flow to be constrained. However, much fracturing and associated cementation may occur at sub-... 

Transport of stable isotopes in a moving fluid phase is called advection. Here infiltrating fluids move the isotopic species of interest. Fluid flow is restricted to connected pore spaces. The amount of connected pore space and the manner of connection determines the permeability of a rock. Mixing of stable isotope ratios by a flowing fluid on grain boundary intersections, micro crack intersections, and fracture intersections results in dispersion. Dispersion is similar to diffusion (at least mathematically), since this is a mixing process. 

It is also important to note that these factors influence permeability on different scales as described by Brace (1984), permeabilities measured on the scale of a drill hole (30-300 m) can be much higher, due to widely spaced fractures, than those measured on a laboratory sample (5-15 cm). Thus drill hole permeabilities may be appropriate for estimating the flux of channeled fluids through the crust, but laboratory scale permeability, if properly measured, affords a better estimate of truly pervasive fluid flow. 

Fan X, Li X, Zhang S and Xu X. 2000. Mathematical simulation of coupled fluid flow and geomechanical behaviour for full low permeability gas reservoir fracturing. Petroleum Exploration and Development, 27(1), pp.76-83. 

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. 

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... 

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. 

Let us consider fluid flow through fracture network in rock formations. When the fluid temperature is lower than that of rock, the fluid flow removes heat of rock and the rock cools down. The cooling will cause thermal contraction of rock, and as a result fractures are likely to open and to be more permeable. In reality, the test results of fluid injection into rock formations at depths of about 1000 m, show that cold-fluid injection is effective to increase permeability of the rock formations (e.g.. Home et al., 1988, Ariki and Hatakeyama, 1997, Clotworthy, 2000). 

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