Gas-blockage performance

Figure 9. Gas-blockage performance of foams in 200-cm long 8-darcy bead packs at 0.50% foaming agent solution in distilled water except as indicated Conditions no oil 21 °Cf and initial outlet pressure VQut 6 bar.

Figure 13. Foam gas-blockage performance at indicated temperatures in the presence of a North Sea crude at S. using 200-cm packs of 8-darcy beads at 6 bar. (Reproduced with permission from reference 13. Copyright 1993.)...

Figure 15. Gas-blockage performance of 2-methyl-1-propanol foams in 8-darcy bead packs of indicated length at 21 °C with Poul 6 bar. Foam generated at a constant overall pressure gradient AP/L 2 bar/m. (Redrawn from data in reference 25.)...

Figure 16. Gas-blockage performance of 1.0% Fluowet OTN foams in bead packs of indicated length at screening conditions, and in Bentheimer sandstone at reservoir conditions. Permeability is 1.4—1.8 darcy, temperature is 70 °C, and residual crude oil is present (except, 24-cm pack 8 darcy and 21 °C).

The theory predicts that, in related data sets, the gas-blockage performance of different foams (expressed as kg should fall on a common straight line when plotted as a function of (AP — APT) /AP. 

Temperature gradients exist in a reservoir that has been subjected to steam-flooding, and therefore, a knowledge of the dependence of surfactant adsorption on temperature is important in the evaluation of steam-foam processes. Low adsorption levels in high-temperature or swept zones are beneficial to process performance because gas mobility reduction or gas blockage in the swept zones is desired. 

In [260], preparation conditions of gas-blocking foams were studied. Experiments were performed on cores filled with 100-pm glass beads with a permeability of 8.5 D. In absence of surfactants, the gas passed easily as a jet through the core filled with water. With the surfactant sodium alkyl ethoxysulphate increased from 0.1 to 0,5 wt.%, a foam piston was formed which pushed the surfactant solution. To achieve a gas blockage, the porous medium must exceed a certain minimum length greater than the length of travel for the displacement front to... 

The intracrystalline pore volume of the catalysts was evaluated by n-hexane sorption as shown in Fig. 6. Sorption capacities for samples SI to S3 are comparable to that of the zeolite before Ga impregnation and correspond to the value expected for an unaltered ZSM-5 type material (S10). Sorption capacity decreases for samples S3, S4, S5, and S6, because of intracrystalline volume blockage by coke deposits and possibly also (silica)-alumina debris [6] in the aged catalyt S6. In addition, the sorption rate for S6 is about twice the rate observed for the other samples, suggesting that adsorption occurs mostly at the external surface of the S6 catalyst crystallites. Thus, it appears that coke deposited on S6, probably as polyaromatic species, has almost blocked the channel pore mouths and/or practically occupied the whole intracrystalline pore volume. It explains the poor catalytic performance of S6. 

During induction, catalyst activity and selectivities to aromatics and propene increase steadily. Improvement of catalyst performance is due to increase in Ga dispersion and formation of dispersed Ga species (Gao) which are efficient for the heterolytic recombinative release of hydrogen [18,191. The Ga/H-MFI catalyst then reaches its optimal aromatisation performance (stabilisation). Ci to C3 hydrocarbons productions are at their lowest. The gallium dispersion and the chemical distribution of Ga are optimum and balance the acid function of the zeolite. Reversible deactivation during induction and stabilisation of the catalyst is due to site coverage and limited pore blockage by coke deposition. 

The coke can affect the performance of active sites of SR catalysts [11, 12], determining their partial deactivation, with progressive loss of selectivity towards synthesis gas production, blockage of reformer tubes and increasing pressure drop. 

When on-column injection is used the end of the transfer capillary is inserted into the column inlet or retention gap where decompression of the supercritical fluid occurs. Carbon dioxide gas exits through the column and the seal made between the restrictor and septum (unless a closed injector is used). The analytes are focused by cold trapping in the stationary phase. The transfer line must be physically removed from the injector at the completion of the extraction to establish the normal carrier gas flow for the separation. Analyte transfer to the column is virtually quantitative but blockage of the restrictor is more conunon and involatile material accumulates in the injection zone eventually degrading chromatographic performance. The on-column interface is probably a better choice for trace analysis of relatively clean extracts with modest fluid flow rates than the split interface. When optimized both the on-column and split interfaces provide essentially identical peak shapes to those obtained using conventional solution injection. 

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