Fracture porosity dependence

N2 injection rapidly increases the methane production rate. The timing and magnitude depends on the distance between injection and production wells, on the natural fracture porosity and permeability, and on the sorption properties. N2 breakthrough at the production well occurs at about half the time required to reach the maximum methane production rate in this ideal case. The N2 content of the produced gas continues to increase until it becomes excessive, i.e., 50% or greater. 

Five-millimeter wide strips of foil, 100 microns in thickness, were inserted between the inner walls of the tube and the glass strips. In this manner, the model formed a system of parallel strips, SO cm in length. The width of the fractures varied depending on their position along the cross section of the tube. The openings within these cracks were 100 microns wide, corresponding to the presumed size of fracture opening in the real reservoir of the fracture type. Fracture porosity of such models calculated by the method of material balance equation was 13.5%. 

Figure 8.22 Porosity dependence of fracture strength and fracture energy of porous silicon nitride with large fibrous grain alignment. Stress is applied parallel to the alignment direction. The vertical bars indicate standard deviations. Reprinted with permission from Ref [51] ...

Rasmus (1983) states that the ratio of fracture porosity to total porosity is critical for the amount of resistivity decrease in low porosity carlxMiates. For fracture porosity, m values are less than the common matrix value of 2.0 in a low porosity limestone and can approach values as low as 1.0. If a secondary vuggy porosity is present without any fractures, a resultant m value of at least 2.0 is recommended. Depending on the amount of non-connected vug porosity, Rasmus (1983) recommends values exceeding 2.0. 

Hydraulic conductivity is one of the characteristic properties of a soil relating to water flow. The movement of water in soil depends on the soil structure, in particular its porosity and pore size distribution. A soil containing more void space usually has a higher permeability. Most consolidated bedrocks are low in permeability. However, rock fractures could create a path for water movement. 

Materials science associated with fracture mechanics has mainly been confined to composite materials such as concrete, ceramics and metals. Much of the emphasis of the research has been on preventing fatigue and failure rather than designing for it to occur. The way a structure deforms and breaks under stress is crucial for properties such as flow and fracture behaviour, sensory perception of structure, water release and the mobility and release of active compounds. In the case of foods, the ability to break down and interact with the mouth surfaces provides texture and taste attributes. The crack propagation in a complex supramolecular structure is highly dependent on the continuous matrix, interfacial properties and defects and the heterogeneity of the structure. Previous structure-fracture work has dealt with cellular plant foods, and it has been demonstrated that the fracture path differs between fresh and boiled carrots due to cellular adhesion and cell wall strength as well as cell wall porosity and fluid transport (Thiel and Donald 1998 Stoke and Donald 2000 Lillford 2000). 

In spite of the above issues, consistent trends of increasing surface area with increasing intensity of natural weathering are observed (Brantley et al., 1999). An example of this increase is shown in Figure 12(a) in which BET surfaces of primary minerals increase with increasing age of soils in the Merced chronosequence (White et al., 1996). The extent of this increase depends on the specific mineral phase. The more readily weathered aluminosilicates exhibit greater surface area increases than quartz. Application of BET measurements to characterize fractures and porosity in consolidated rocks has remained generally untested these surface area estimates have been... 

The porosity and fracture content of rocks determine the maximum possible volume of gases in rocks and the gas permeability of rocks determines the speed of migration of these gases. On the basis of these parameters, typical geological structures may be divided into closed and open structures. Igneous and metamorphic rocks tend to have closed structures, whereas sediments have open structures. The porosity of igneous rocks is typically 0.5-2% and changes little with depth. Their gas permeability is typically less than 10 pm and mainly depends on fracture content. The porosity of sediments decreases from 30-35% at surface to 10-20% at a depth of 2 km. Their gas permeability varies from 10 pm to 3 pm (Fridman, 1970 Dortman, 1992). 

The chemical reaction between a solid and a reactive fluid is of interest in many areas of chemical engineering. The kinetics of the phenomenon is dependent on two factors, namely, the diffusion rate of the reactants toward the solid/fluid interface and the heterogenous reaction rate at the interface. Reactions can also take place within particles, which have accessible porosity. The behavior will depend on the relative importance of the reaction outside and inside the particle. Fractal analysis has been applied to several cases of dissolution and etching in such natural occurring caves, petroleum reservoirs, corrosion, and fractures. In these cases fractal theory has found usefulness for quantifying the shape (line or surface) with only a few parameters the fractal dimension and the cutoffs. There have been some attempts to use a fractal dimension for reactivity as a global parameter. Finally, fractal concepts have been used to aid in the interpretation of experimental results, if patterns quantitatively similar to DLA are obtained. 

Thus, the average catalyst particle fractures into from 1 billion to 1 trillion fragments. The fragment size probably depends on porosity, which explains why some low-pore-volume silicas are less active than the more porous ones. 

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