Treatment injection rates

Equation (6.1) is a simplified radial-flow equation, accounting for an incompressible injected fluid in a homogenous formation only. It does not take multiphase-flow effects into account. This representation of Darcy s equation should be used only as a guideline for setting the initial treatment injection rate. It is good practice to limit acid treatments in sandstones to several hours at the most. Long HE residence time may be expected to increase precipitation of acid reaction products. Whenever possible, LIF contact time should be limited to 2-4 hours per stage. 

Pump-rate limitations must be considered. Smaller diameters cause higher friction pressures, which may limit treatment injection rates to lower-than-desirable levels. Acidizing through production tubing or drill pipe, for example, will allow higher injection rates. 

Both in the laboratory and theoretically, the optimum combination of treatment injection rate and stimulation fluid reactivity (fluid type) can be determined for a given set of conditions. These conditions include formation type and characteristics. In the field, though, it is very difficult (if not impossible) to make this determination. This is because leak-off of reactive fluid from the dissolution path, or wormhole, to the surrounding formation cannot be accurately determined. The difficulty in achieving accurate leak-off measurement persists despite the use of models and laboratory leak-off data. 

In summary, higher, rather than lower, treatment injection rates are preferable. Some degree of retardation is desired, rather than none or too much. Acid can be retarded with viscosity (e.g., gelling or emulsification). In addition, slower-reacting acids, such as acetic acid, and weaker stimulation fluids, such as chelating agents (EDTA, etc.), have applications. Cost can be a hmitation. 

Initial treatment should range from about 300 mg/L of scavenger, and injection rates should be as high as the pump will allow. Treatment has to be adjusted to achieve from 100 to 300 mg/L sulfite residual at the flowline. 

Liquid flowing into the chromium treatment module [T-21] is monitored by a pH instrument that controls a feed pump to add the required amount of sulfuric acid from a storage tank. The sulfuric acid is needed to lower the pH to 2.0 to 2.5 for the desired reduction reaction to occur. An ORP instrument controls the injection rate of sodium metabisulfite solution from a metering pump to reduce hexavalent chromium (Cr6+) to the trivalent state (Cr3+). 

So-called "wormholes" can be formed when the injected acid primarily enters the largest diameter flow channels in carbonate rock further widening them (107). Acid only invades the small flow channels a short distance greatly reducing treatment effectiveness. High fluid loss rates, low injection rates, and reduced rates of acid-rock reactions decrease the wormhole length. 

Injection rate can have a major effect on the economics of secondary oil recovery. Acidizing or carefully designed hydraulic fracturing treatments can be used in increase injection rates. 

More recently well treatments that do not interrupt normal water injection operations have increased in frequency. Addition of surfactant to the injection water (144,146) can displace the oil remaining near the production well. The lower oil saturation results in an increase in the water relative permeability (145). Consequently a greater water injection rate may be maintained at a given injection pressure or a lower injection pressure. Thus smaller and cheaper injection pumps may be used to maintain a given injection rate. While the concentration of surfactant in the injection water is relatively high, the total amount of surfactant used is not great since it is necessary only to displace the oil from a 6-10 foot radius around the injection well. 

Careful sizing of the treatment and choice of injection rates is required to prevent inadvertent overtreatment i.e., excessive treatment of oil-containing rock. The post-treatment fluid injection rate is usually significantly less than that prior to treatment. While successful applications of this technology in waterfloods and in surfactant polymer floods have been reported, temperature and pH stability limitations of the polymer and the crosslinking chemistry result in few if any applications in steam and CO2 injection wells. 

For this purpose, in addition to the continuous evolution of CR and exhaust gas recirculation (EGR), novel primary measures are under study, including the long route EGR to cool the recirculated exhaust gas, the use of premixed combustion [which implies, however, higher GO and unburned hydrocarbon (U HG) emissions], the reduction of the compression ratio, the shaping of the injection rate and so on. Still, the after-treatment catalytic technologies for O, removal and for CO/hydro-carbon (HG) and particulate matter (PM) reduction in passenger cars must be improved significantly. 

A multicenter, double-blind, randomized, placebo-controlled study in 320 patients with untreated hyperhidrosis showed a more than 50% reduction in sweat production at 4 and 16 weeks after treatment respectively in 94 and 82% of patients treated with botulinum toxin (50 MU per axilla) and in 36 and 21% of placebo-treated patients (7). The major treatment-related adverse effect was an increase in sweating in non-axillary sites after treatment. Open treatment with botulinum toxin A was offered to patients in whom sweat production was at least 50% of baseline values (8). Of 207 study subjects, 39% had one treatment, 45% had two treatments and 15% had three treatments. Response rates 4 weeks after treatment were 96, 91, and 83% after the first, second, and third treatments respectively. In one of 207 patients there was possible transient seroconversion from negative to positive for neutralizing antibodies to botulinum toxin, and subsequent treatment with botulinum toxin resulted in complete disappearance of axillary sweating 7 days after injection. 

The emergency room treatment for methanol poisoning is to inject ethanol intravenously to tie up the alcohol dehydrogenase enzyme so that methanol will not be converted to formic acid and formate, which causes blindness. The goal of this open-ended problem is to build on the physiological-based model for ethanol metabolism to predict the ethanol injection rate for methanol poisoning. One can find a start on this problem by reading problem P7-25c. 

Because volumetric rather than mass metering instruments are typically employed on actual treatments, conversion from standard condition gas injection rates to pumping condition liquid rates must be performed. Figures 8 and 9 can be used to estimate the pumping requirements at liquid conditions. 

Continuous injection of corrosion inhibitors is practiced in once-through systems where slugs or batch treatment cannot be distributed evenly through the fluid. This method is used for water supplies, oil field injection water, once-through cooling water, open annulus oil or gas weUs, and gas lift wells. Liquid inhibitors are injected with a chanical injection pump. These pumps are extremely reliable and require little maintenance. Most chemical injection pumps can be adjusted to deliver at the desire injection rate (Chen et al. 2010). 

Figure 8. Fraction of chlorinated contaminant remaining in groundwater for various batch treatment times via sonication alone (20 kHz, 12.3 W/cm ) and via sonication + vapor stripping (air injection rate 500 mUmin).

Four SGA long-acting injections are currently available risperidone microspheres, olanzapine pamoate, paliperidone palmitate and aripiprazole extended-release injection. The extended-release characteristics are achieved differently with each drug. A case analysis of clinical frials with olanzapine pamoate (2000-2008) reported an occurrence of postinjection delirium/sedation syndrome in approximately 0.07% of injections or 1.4% of patients [78 ]. A review of the published literature and clinical trial databases for olanzapine pamoate, risperidone microspheres and paliperidone palmitate found only one other case of postinjection delirium/sedation syndrome occurring in a patienf on placebo in a paliperidone palmitate trial. In four randomised, double-blind, placebo-controlled trials of paliperidone palmitate, the most common treatment-emergent adverse event was somnolence/sedation overall treatment discontinuation rates due to adverse events were similar to placebo. 

Compare the water-injection rates before and after treatment and determine the percentage of the injected fluid that enters each layer. 

The goal in acid placement is to equalize the acid injection rate per unit area Q/A) across the entire treatment interval, divided into n sections ... 

A. Control the injection rate. Maintain surface annulus pressure at or below 500 psi during treatment. 

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