Reduced injectivity

Surfactants evaluated in surfactant-enhanced alkaline flooding include internal olefin sulfonates (259,261), linear alkyl xylene sulfonates (262), petroleum sulfonates (262), alcohol ethoxysulfates (258,261,263), and alcohol ethoxylates/anionic surfactants (257). Water-thickening polymers, either xanthan or polyacrylamide, can reduce injected fluid mobiHty in alkaline flooding (264) and surfactant-enhanced alkaline flooding (259,263). The combined use of alkah, surfactant, and water-thickening polymer has been termed the alkaH—surfactant—polymer (ASP) process. Cross-linked polymers have been used to increase volumetric sweep efficiency of surfactant—polymer—alkaline agent formulations (265). 

The term well plugging refers to any of a variety of processes that reduce the permeability of the injection formation or the screens that are placed in the well s injection interval. When permeability is reduced, injection rates must be reduced or injection pressures increased. Table 20.15 lists a number of ways in which plugging may occur. One or more of these situations will probably take place in most injection wells the number and severity of reactions will determine whether serious operational problems arise. If plugging is confined to the immediate vicinity of the injection well,... 

Reduced injectivity due to formation damage can be a significant problem in injection wells. Precipitate formation due to ions present in the injection water contacting counterions in formation fluids, solids initially present in the injection fluid (scaling), bacterial corrosion products, and corrosion products from metal surfaces in the injection system can all reduce permeability near the wellbore (153). The consequent reduced injection rate can result in a lower rate of oil production at offset wells. Dealing with corrosion and bacterial problems, compatibility of ions in the injection water and formation fluids, and filtration can all alleviate formation damage. 

Both nonionic and anionic surfactants have been evaluated in this application (488,489) including internal olefin sulfonates (487, 490), linear alkylxylene sulfonates (490), petroleum sulfonates (491), alcohol ethoxysulfates (487,489,492). Ethoxylated alcohols have been added to some anionic surfactant formulations to improve interfacial properties (486). The use of water thickening polymers, either xanthan or polyacrylamide to reduce injected fluid mobility mobility has been proposed for both alkaline flooding (493) and surfactant enhanced alkaline flooding (492). Crosslinked polymers have been used to increase volumetric sweep efficiency of surfactant - polymer - alkaline agent formulations (493). 

Electrophoretic injection can be used as a means for zone sharpening or sample concentration if the amount of ions, particularly salt or buffer ions, is lower in the sample than the running buffer. Because sample ions enter the capillary based on mobility, low-mobility ions will be loaded to a lesser extent than high-mobility ions. For this reason, the presence of nonsample ions will reduce injection efficiency, so electrophoretic injection is very sensitive to the presence of salts or buffers in the sample matrix. The disadvantages of electrophoretic injection argue against its use in routine analysis except in cases where displacement injection is not possible, e.g., in capillary gel electrophoresis (CGE) or when sample concentration by stacking is necessary. 

Column size is another important consideration. For equipment designed for most routine laboratory HPLC situations the relative sensitivity of APTelectrospray instruments is better at low flow rates (0.2-0.8 mL/min) whereas the relative sensitivity of APCI instruments is enhanced at high flow rates (0.5-2 mL/min). As a result, small columns are appropriate for API-electrospray/MS and, if only one or two compounds of interest are found in a particular sample, high-resolution separations are not necessary. For APTelectrospray analysis of complex samples, 150 mm x 4.1 mml.D., 3 pm columns (flow 0.5-1.0 mL/min) are usually sufficient. For drug quantification involving analysis of single or low numbers of compounds, small columns such as 30 mm x 2.1 mm I.D., 3.5 pm columns (flow rate 0.2-0.4 mL/min) provide sufficient separation and a saving in both column cost and solvent utilization. The reduced injection volume required for the small columns often results in better resolution and increased sensitivity. 

Reduce injection volume Clean column (see Support Protocol 1)... 

Replace fouled line or filter with clean part Prepare new solvents Reequilibrate system and reduce injection volume or dilute sample... 

Bloch Y, Levkovitz Y, Atshuler A, et al. Use of topical application of lidocaine-prilocaine cream to reduce injection-site pain of depot antipsychotics. Psychiatr Serv. 2004 55 940-941. 

Racemic methadone (13) continues to be used as a maintenance drug in the treatment of addiction to heroin (14).13 Methadone has also been used in treating severe pain.14 The value in using oral racemic methadone is that it also helps to combat the spread of human immunodeficiency virus by reducing injection of heroin.13 Under medical supervision, the addict can lead a more stable life, but there is a temptation to remain on racemic methadone to avoid the withdrawal symptoms known as cold turkey.13 The illegal use of methadone taken together with other drugs such as benzodiazepines... 

Tests will be conducted to ensure the acid gas is compatible with the reservoir rock and reservoir fluids. Adverse reactions could reduce injectivity with time, as the acid gas reacts with the formation rocks or the original fluid in the reservoir. 

At the surfactant concentrations employed in the core floodiil, there was no evidence of severe permeability reduction that would cause substantially reduced injectivity. 

In Spain, France and to some extent Germany (although a recent increase was reported), Italy and Austria, acute drug-related deaths have stabilised or decreased. This may reflect levels of problem drug use, reduced injecting and/or increases in access to treatment, including substitution treatment. 

Advantages Vapocoolant is sprayed directly onto the skin or applied to a cotton ball that is held on the area to be anesthetized provides local anesthesia within 15 seconds effective in reducing injection pain in children 4-6 years of age. 

Disadvantages Brief duration of action so that procedure should be completed in 1 or 2 min may not be effective in reducing injection pain in infants aged 2-6 months. 

Fignc 155 Plot of the logarithm of the plate count versus the logarithm of the reduced injection volume for columns of different plate counts. 

Brittle parts Wet resin or overdried resin Molded-in stresses Poor part design Check drying instructions and conditions Increase melt temperature/reduce injection pressure Review part design Review design for notches and other stress concentrators... 

To evaluate the effectiveness of FO to reduced injection water volumes several process parameters has been study. Results show that the draw solution concentration plays an important role in water production. Higher draw solution concentration yields higher flux due to higher osmotic pressure difference between the feed and draw solution. 

Training People who work around compressed air lines, hydraulic systems, and other pressurized fluid and gas equipment should leam about the hazards. They should learn not to place fingers or hands against a fluid stream and they should learn not to place the stream near anyone else. Protective gloves and clothing may help reduce injection injuries. 

The results from a typical injectivity test are given in Figure 12 where resistance factor (RF) and residual resistance factor (RRF) are plotted versus the number of pore volumes of polymer and brine injected. Resistance factor is the mobility of brine (k/p) divided by the mobility of polymer and is a measure of the reduced Injection rate the polymer produces in a given reservoir rock. Residual resistance factor is the mobility of brine before polymer injection divided by the mobility of brine after polymer injection. Thus, a permeability reduction of 99 percent corresponds to an RRF of 100. 

In addition to the above, the potential of a bacterial problem in the reservoir appears acute because of the species which were isolated in API shaker tubes and which were microphotographed in the SEM work on random samples of reservoir rock. This SEM microphotograph is illustrated in Figure 27. The rods shown in the microphotograph are very similar to the photomicrographs of bacteria [0.3 to 0.5 micron diameter by 0.7 to 2.0 micron length (10)] associated with Kelzan M.F. biopolymer. Such bacteria can cause wellbore impairment and reduced injectivity (10). 

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