1.Surfactants for stable clay
Stabilizing clay involves two aspects: preventing the swelling of clay minerals and preventing the migration of clay mineral particles. For preventing clay swelling, cationic surfactants such as amine salt type, quaternary ammonium salt type, pyridinium salt type, and imidazoline salt type can be used. For preventing the migration of clay mineral particles, fluorine-containing nonionic-cationic surfactants can be used.
2.Surfactants for acidizing measures
To enhance the acidizing effect, it is generally necessary to add various additives to the acid solution. Any surfactant that is compatible with the acid solution and easily adsorbed by the formation can be used as an acidizing retarder. Examples include fatty amine hydrochlorides, quaternary ammonium salts, and pyridinium salts among cationic surfactants, as well as sulfonated, carboxymethylated, phosphate-esterified, or sulfate-esterified polyoxyethylene alkyl phenol ethers among amphoteric surfactants. Some surfactants, such as dodecyl sulfonic acid and its alkylamine salts, can emulsify the acid solution in oil to form an acid-in-oil emulsion, which, when used as an acidizing working fluid, also plays a retarding role.
Some surfactants can act as demulsifiers for acidizing fluids. Surfactants with a branched structure, such as polyoxyethylene-polyoxypropylene propylene glycol ether and polyoxyethylene-polyoxypropylene pentaethylenehexamine, can all serve as acidizing demulsifiers.
Some surfactants can function as spent acid cleanup additives. Surfactants that can be used as cleanup additives include amine salt types, quaternary ammonium salt types, pyridinium salt types, non-ionic types, amphoteric types, and fluorinated surfactants.
Some surfactants can act as acidizing sludge inhibitors, such as oil-soluble surfactants like alkyl phenols, fatty acids, alkyl benzene sulfonic acids, and quaternary ammonium salts. Since their acid solubility is poor, non-ionic surfactants can be used to disperse them in the acid solution.
To improve the acidizing effect, it is necessary to add a wettability reversal agent to the acid solution to reverse the wettability of the near-wellbore area from oil-wet to water-wet. Mixtures such as polyoxyethylene-polyoxypropylene alkyl alcohol ether and phosphate-esterified polyoxyethylene-polyoxypropylene alkyl alcohol ether are adsorbed by the formation as the first adsorption layer, thereby achieving the wettability reversal effect.
In addition, there are some surfactants, such as fatty amine hydrochlorides, quaternary ammonium salts, or non-ionic-anionic surfactants, which are used as foaming agents to prepare foam acid working fluids, achieving the purposes of retarding, corrosion inhibition, and deep acidizing. Alternatively, such foams can be prepared as pre-pads for acidizing, which are injected into the formation before the acid solution. The Jamin effect generated by the bubbles in the foam can divert the acid solution, forcing the acid to mainly dissolve the low-permeability layers and improving the acidizing effect.
Post time: Jan-06-2026