Porosity, secondary

Total porosity % Primary porosity% Secondary porosity... 

Fraction of secondary porosity (% secondary porosity / total porosity)... 

Fig. 5. The relationship between the fraction of secondary porosity (secondary porosity/ total porosity) as a function of depth shown by samples of the Etive Formation which forms part of the Brent Group of the North Sea. The secondary porosity in these samples is dominantly from the dissolution of feldspars. (After Giles et al. 1992)...

Oil Repellent. Fluorochemicals are the only class of material that can provide oil repeUency without altering the porosity of the paper or paperboard. Physical barriers to oil penetration are used primarily for their moisture- or gas-barrier properties, with retarded oil penetration as a secondary benefit. The most common od-repeUent additives are long-chain perfluoroalkyl phosphate salts of ammonia or diethanol amine. Commercial sources include Scotchban (3M), Zonyl (DuPont), and Lodyne (Ciba Specialties). There are also a fluorochemical carboxylate salt, Lodyne (Ciba Specialties), and fluorochemical copolymers, eg, Scotchban (3M). The widest range of oily fluid holdout is provided by the fluorochemical copolymers. 

Variables It is possible to identify a large number of variables that influence the design and performance of a chemical reactor with heat transfer, from the vessel size and type catalyst distribution among the beds catalyst type, size, and porosity to the geometry of the heat-transfer surface, such as tube diameter, length, pitch, and so on. Experience has shown, however, that the reactor temperature, and often also the pressure, are the primary variables feed compositions and velocities are of secondary importance and the geometric characteristics of the catalyst and heat-exchange provisions are tertiary factors. Tertiary factors are usually set by standard plant practice. Many of the major optimization studies cited by Westerterp et al. (1984), for instance, are devoted to reactor temperature as a means of optimization. 

Secondary porosity— o ds formed after the sediment was deposited. The magnitude, shape, size, and interconnection of the voids bears little or no relation to the form of the original sedimentary particles. Secondary porosity is subdivided into three classes. 

Therefore, it has been chosen here to study very particular and rare treatments performed in undamaged reservoirs. Equation 13 is then applicable, and a direct access to the values of both parameters df and A becomes possible. Two cases have been considered. First, a clean reservoir of secondary porosity only, where Equation 13 should not fit with actual data. Second, an undamaged, primary porosity formation, where it should. 

The actual response of Well A to the injection of acid cannot fit with any kind of theoretical equation for undamaged primary porosity or damaged double porosity reservoir. Therefore, the acid attack in secondary porosity formations proceeds very differently, as expected. 

Figure 1 Permeability profile in a damaged double porosity reservoir during acidizing. rw wellbore radius, re wormholes penetration, damage radius, kptp undamaged reservoir permeability (total contribution of both primary and secondary porosities), kPP damaged permeability (primary porosity contribution only).

Other wells in the same field had shown a limestone reservoir of fair permeability, with major tectonic faults and some associated fissures. Well data were provided by the operator. The low value of the wellbore storage demonstrates no coupling of the well with secondary porosity. However, the operator suspected the presence of some kind of fault not far from Well B, whose production test was unusual. He decided to acidize in an attempt to establish communication. 

Acidic micro- and mesoporous materials, and in particular USY type zeolites, are widely used in petroleum refinery and petrochemical industry. Dealumination treatment of Y type zeolites referred to as ultrastabilisation is carried out to tune acidity, porosity and stability of these materials [1]. Dealumination by high temperature treatment in presence of steam creates a secondary mesoporous network inside individual zeolite crystals. In view of catalytic applications, it is essential to characterize those mesopores and to distinguish mesopores connected to the external surface of the zeolite crystal from mesopores present as cavities accessible via micropores only [2]. Externally accessible mesopores increase catalytic effectiveness by lifting diffusion limitation and facilitating desorption of reaction products [3], The aim of this paper is to characterize those mesopores by means of catalytic test reaction and liquid phase breakthrough experiments. 

The N2 adsorption isotherms of the two Beta samples are depicted in Figure 1(b). The material prepared from silanized seeds exhibits a significant higher N2 adsorption compared to the Beta (0) sample, suggesting the presence of a secondary porosity. This is confirmed by the pore-size distributions derived from the Ar isotherms applying the... 

The catalytic activity of hierarchical and conventional Beta zeolites for acylation of 2-MN is displayed in Figure 2(a) The Beta (PHAPTMS) sample shows a superior catalytic activity than the conventional one, due to its enhanced textural properties. In this case, the bulky nature of both substrate and products may cause the existence of diffusional problems inside the zeolitic channels, which are attenuated in the modified Beta sample due to the presence of the hierarchical porosity. Regarding the product distribution (Figure 2(b)), two main products are observed and a third isomer, 8-A,2-MN isomer is produced just in minor amounts. Interestingly, the selectivity towards the desired isomer increases in the material obtained from silanized seeds, reaching values around 75%. Probably, the active sites located on the surface of the secondary porosity are able to catalyze also the formation of 6-A,2-MN by transacylation. However, this reaction is expected to be strongly hindered in the conventional Beta zeolite since it requires the participation of two bulky molecules as reactants. 

Mavor, M.J. Gunter, W.D. 2006. Secondary porosity and permeability of coal vs gas composition and pressure. SPE Reservoir Evaluation and Engineering Journal, April, 114-125. 

FIGURE 3.2 Petrographic criteria for secondary porosity. (After Schmidt et al., 1977.)... 

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