Viscous acid stage

Viscous acid stage. The purpose of the acid stage is to simultaneously propagate the fracture and differentially etch its walls. The acid stage is typically gelled, emulsified, or foamed add. Combinations of the three are possible. 

This technique has also given rise to the pumping of viscous diverter stages down the annulus, while acid is pumped through coiled tubing, in both sandstones and carbonates. Dtiring treatment in this manner, coiled tubing can be... 

The basic method of viscous acid fracturing is sufficient for most applications. However, alternating-stage and alternating-acid techniques have been used very successfully. For the stimulation of a new well or a well in a field with no previous acidizing history, though, it is best to keep the treatment design as simple as possible. 

For polymer concentrations < 3 % the mixtures remain isotropic during polymerisation and become a rubbery mass that is too viscous to stir in the later stages of heating. In contrast polymer concentrations of 5-10% form yellow green stir-opalescent solutions within 30 minutes of the dissolution of the terephthalic acid. Such solutions remain stirrable throughout the polymerisation despite the higher concentrations — an indication of the liquid-crystalline nature of the medium. 

Chlorobenzilate [510-15-6], ethyl -dichlorobenzilate (140), is a yellowish viscous oil (bp 141—142°C at 8 Pa). The technical material id 1.281) contains ca 90% of the active compound, is insoluble in water, and is soluble to more than 40% in deodorized kerosene, benzene, and methyl alcohol. Chlorobenzilate is hydrolyzed in alkali and in strong acids to the inactive />>/>,-dichlorobenzihc acid and ethanol. The compound is active against all stages of mites and has an oral LD50 to the rat of 700 mg/kg. 

As the process takes place between a liquid and a solid substance the rate of the reaction depends, apart from the temperature, on the size of the contact surface of the reacting substances. For this reason, it is necessary to make sure that a thorough mixing takes place which should not be particularly difficult in the first stage as the reacting mixture is sufficiently thin. In the second stage, the fused acid sulphate reacts with the solid sodium chloride to solid sodium sulphate which makes the reaction mixture very viscous. 

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