Complex pore, analysis

A microscopic description characterizes the structure of the pores. The objective of a pore-structure analysis is to provide a description that relates to the macroscopic or bulk flow properties. The major bulk properties that need to be correlated with pore description or characterization are the four basic parameters porosity, permeability, tortuosity and connectivity. In studying different samples of the same medium, it becomes apparent that the number of pore sizes, shapes, orientations and interconnections are enormous. Due to this complexity, pore-structure description is most often a statistical distribution of apparent pore sizes. This distribution is apparent because to convert measurements to pore sizes one must resort to models that provide average or model pore sizes. A common approach to defining a characteristic pore size distribution is to model the porous medium as a bundle of straight cylindrical or rectangular capillaries (refer to Figure 2). The diameters of the model capillaries are defined on the basis of a convenient distribution function. 

The technique of DDIF provides a quantitative characterization of the complex pore space of the rocks to supplement conventional mineralogy, chemistry and petrology analyses. A combination of DDIF, Hg intrusion, NMR T2 and image analysis has become the new paradigm to characterize porous rocks for petroleum applications [62, 61]. 

Although many adsorbents possess exceedingly complex pore structures, the mesopore size analysis carried out by several groups (Dollimore and Heal, 1973 Havard and Wilson, 1976) appears to indicate that the calculated pore size distribution is rather insensitive to the model. However, as was pointed out by Haynes (1975) such results may be due in part to the over-simplification of the computations. 

Analysis of vadose zone transport is more complex than analysis of saturated zone transport, in part because changes in soil water content have a strong inbuence on both hydraulic conductivity and pore pressure. How does a decrease in soil water content affect ... 

The human sense of taste occurs as a result of complex chemical analysis starting at a series of chemical active sites called taste buds located within a depression in the tongue. A taste bud is composed of several taste cells (gustatory cells), as shown in Figure 9.1. Each taste bud has a pore that opens out to the surface of the tongue enabling molecules and ions taken into the mouth to reach the taste cells inside. 

The simple carrier of Fig. 6 is the simplest model which can account for the range of experimental data commonly found for transport systems. Yet surprisingly, it is not the model that is conventionally used in transport studies. The most commonly used model is some or other form of Fig. 7. In contrast to the simple carrier, the model of Fig. 7, the conventional carrier, assumes that there exist two forms of the carrier-substrate complex, ES, and ES2, and that these can interconvert by the transitions with rate constants g, and g2- Now, our experience with the simple- and complex-pore models should lead to an awareness of the problems in making such an assumption. The transition between ES, and ES2 is precisely such a transition as cannot be identified by steady-state experiments, if the carrier can complex with only one species of transportable substrate. Lieb and Stein [2] have worked out the full kinetic analysis of the conventional carrier model. The derived unidirectional flux equation is exactly equivalent to that derived for the simple carrier Eqn. 30, although the experimentally determinable parameters involving K and R terms have different meanings in terms of the rate constants (the b, /, g and k terms). The appropriate values for the K and R terms in terms of the rate constants are listed in column 3 of Table 3. Thus the simple carrier and the conventional carrier behave identically in... 

We have seen in Section 8.6 that the analysis using the Stefan-Maxwell approach is readily carried out for the case of a simple capillary, namely a uniformly sized capillary. In this section we will extend the analysis to more complex pore networks and will consider the three cases ... 

Different types of porosity and complex pore size distributions also result in wide permeability variations for the same total porosity, making it difficult to predict their producibility. Therefore, the analysis of carbonate pore... 

The inherent sensitivity of NMR signals to the fluid-substrate interactions via a large number of mechanisms provides a direct connection between the NMR measurables, the pore structure and the motional characteristics of the imbibed fluid. While the large number of potential NMR variables makes the experimental design and analysis complex, it also provides the potential for a measurement method capable of measuring and spatially resolving the parameters of interest to functionalized ceramics. 

If the dominant mode of transport within the catalyst pores is ordinary molecular diffusion, the analysis becomes somewhat more complex. The ordinary molecular diffusivity is inversely proportional to the pressure so that in this case... 

Thermal analysis techniques reveal that water is bound in opal in more than one manner. Most of the water is physically held in inclusions or microscopic pores within the opal, that is, in spaces between the microspheres. Water held in this manner can escape through complex systems of microscopic fissures or cracks, induced by temperatures even below 100°C. Some water is held within the opal via chemical bonding ( adsorption ) to the surfaces of the silica microspheres and is retained to temperatures approaching 1000°CJ7J Furthermore, since the microspheres themselves are composed of much smaller silica particles, water is additionally coated on the surfaces of these minute particles. The porous nature of opal and its thermal sensitivity require special care, for dehydration may result in cracking that greatly diminishes the value of this gemstone. 

Of special interest in recent years has been the analysis of natural gas hydrates that form in marine sediments and polar rocks when saline pore waters are saturated with gas at high pressure and low temperature. Large and 5D-variations of hydrate bound methane, summarized by Kvenvolden (1995) and Milkov (2005), suggest that gas hydrates represent complex mixtures of gases of both microbial and thermogenic origin. The proportions of both gas types can vary significantly even between proximal sites. 

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