Displacement efficiency

After completion of the drilling operation, steel casing is lowered down the well bore and into the drilling fluid. A spacer fluid is then pumped down the well bore to remove the drilling fluid and prevent contact of the drilling mud with the cement slurry. Efficient displacement of the drilling mud also promotes bonding of the cement slurry to rock surfaces. 

The reactions of the p-D-glucopyranosides 5, and with TASF yielded results which were very different in each case, but which were fully consistent with the current understanding of nucleophilic displacements in carbohydrates (, —- ). The less rapid and efficient displacement of trlflate anion from as compared with that from may be attributable to the increased steric hlnderance occasioned by the Introduction of benzyl and 2,2,2-trichloroethyl groups in place of methyl groups. 

Monoiminophosphines. As illustrated in Scheme II, PCHO condenses with a wide variety of simple and functionalized monoamines. Studies of the Mo(O) derivatives of several of these ligands demonstrate that they efficiently displace CO from Mo(CO)e affording (chel)Mo(CO)4 or fac-(chel)Mo(CO)3 derivatives (4). Similar, but bimetallic, complexes can be obtained from the ligands prepared by condensations with nonchelating diamines such as m- or p-diaminobenzene. 

To facilitate the nitro group displacement reaction, the thioethers 7, obtained by treatment of difluoride 6 with thiols, were oxidized with 3-chloroperbenzoic acid to afford the corresponding sulfones 8 (Fig. 4). The resulting sulfones 8 showed the expected high reactivity toward nucleophiles, as demonstrated by the efficient displacement of both the second fluoride and the nitro group with two different aliphatic amines to yield the highly substituted benzamides 10. 

Coal beds typically contain large amounts of methane-rich gas that is adsorbed onto the surface of the coal. The current practice for recovering coal bed methane is to depressurize the bed, usually by pumping water out of the reservoir. An alternative approach is to inject C02 gas into the bed. Tests have shown that the adsorption rate for COz to be approximately twice that of methane, giving it the potential to efficiently displace methane and remain sequestered in the bed. C02 recovery of coal bed methane has been demonstrated in limited field tests, but much more work is necessary to understand and optimize the process, particularly the capacity of coal beds with respect to COz and methane. 

The back pressure at which a gas-drive is operated will affect the efficiency of the displacement, as the data in Table IV indicates. As the back pressure is increased, the ultimate pressure drop also increases and the number of injected pore volumes before the final state (the point where essentially only gas is produced) decreases. A piston-like displacement would require one pore volume of injected gas before all the liquid was produced, while increasingly less efficiency displacements would require more volumes. 

Preconcentration of pervaporated analytes is the most effective way of favouring mass transfer. The equilibrium between phases can be efficiently displaced by continuous removal of the transferred species from the upper chamber, followed by concentration (either in a minicolumn placed before the deteetor or in the flow-cell itself)-... 

An anomeric acetate is efficiently displaced by a thiol under the influence of an acidic catalyst, and this is probably presently the most used and efficient way to produce thioglycosides of simple mercaptans, especially on a large scale. The standard procedure is to react a peracetylated aldose dissolved in dichloromethane with a slight excess of thiol using a hard Lewis acid as promoter, which generally gives a high yield of mainly the 1,2-trans product ( Scheme i) [11]. 

Following elution of the isotachic train and the displacer solution from the column, the column must be regenerated and reequilibrated with the carrier before any subsequent displacement separation. This reequilibration step can be lengthy and is frequently considered a major Umitation to efficient displacement operation. Displacement chromatography requires the competitive isotherms of the solutes and the displacer to be convex upward and to not intersect each other. (See the entry Distribution Coefficient for related information.)... 

Arylamines can be particnlarly nmeactive as nncleophiles and for these, the nse of fluorine or a snlfone as a leaving gronp, or paUadinm-assisted displacement (4.2.10) of bromine may be necessary. A 2-chlorine, deactivated by the presence of a 6-amino substituent, can be efficiently displaced by arylamines with trimethylsilyl chloride in bntanol. The displacements of fluorine, chlorine and butyl sulfone by anilines are greatly accelerated by carrying ont the reactions in 2,2,2-trifluoroethanol, with the addition of excess triflnoroacetic acid. ... 

Waterflood recoveries were similar in the clean cores with any of the oils, and recoveries were higher in the asphaltene-treated cores (Figure 19). This kind of behavior has been associated with mixed-wettability systems (124—126), defined by Salathiel (125) as systems in which the small pores are water-wet, and the larger pores form continuous oil-wet channels that allow efficient displacement of oil by water. All three criteria used for wettability assessment (contact angle, end-point relative permeabilities, and waterflood recoveries) indicate more oil-wet conditions after asphaltene treatment. 

Pulsing should also lead to better grouting practices and other benefits such as accelerated clean-up of potable water aquifers that are contaminated by NAPLs and other materials. In these cases, the suppression of advective instabilities and the aid to overcoming capillary blockages will lead to more efficient displacement, less fingering of flushing agents, and so on. 

In related work the same group achieved efficient displacement of the substituent at C-2 from polymer-bound 2,6-dihalopurines [51]. Whereas substitution of Cl at C-6 was readily achieved with primary and secondary amines, displacement of the C-2 substituent proved difficult. Under the action of microwave irradiation at 150 °C for 30 min, however, a variety of amines could be used for further decora-... 

The extremely high sensitivity of critical conditions to the eluent composition and possibly also to the continuous variations in the column interactivity, for example due to the irreversible retention of some sample components. The sensitivity of critical conditions rapidly increases with the molar mass of macromolecules concerned. It may be very difficult to repeatably prepare mixed eluents with exactly the same composition, as well as to prevent preferential evaporation from-, and absorption of humidity into- the eluent container. The colurtms should be frequently cleaned by flushing with an efficient displacer and then (laboriously) reequilibrated with the original eluent. Often, the log M versus dependence is not perfectly vertical and the exact critical conditions cannot be reached at all. Therefore, many measurements are done near the LC CC conditions, not at the proper critical point but in the critical range. This brings about additional imcertainty on accuracy of results. 

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