Study On Preparation And Properties Of Temperature-controlled Variable Viscosity Acid

Acidification is one of the most important measure in gas and oil well in-jection stimulation, and viscosifier is a more important additive, which is used to inhibit acidification rate. A kind of more effective viscosifier can improve the viscosity of acid solution, reducing the mass transfer velocity of hydronium H+towards the rocks surface, thereby decrease the filtrate loss of acid solution and the reaction rate between acid and salt, and lengthen the distance of acid penetration.In this paper, through a large number of laboratory experiments, a new type of temperature-controlled variable viscosity acid viscosifier were synthesized via free radical solution copolymerization of vinyl monomers. Acrylamide(AM),2-acrylamide-2-methyl propane sulfonic acid(AMPS) and methacryloyloxyethyl trimethyl ammonium chloride (DMC) as the main monomers used in copolymerization. The performance of the polymer was studied. This paper was divided into three parts.Firstly, the temperature-controlled variable viscosity acid viscosifier was synthesized via aqueous solution polymerization, using ammonium persulfate/sodium formaldehyde sulfoxylate/azo-bis-isobutyrate hydrochloride ternary complex initiation system. We investigated the effect of the amount of monomers, monomer ratio, initiator concentration, polymerization processes on the polymers with orthogonal and single factor test analysis. The best synthetic formulation has been selected, and the structure of the product was characterized by Fourier Transform Infrared Spectroscopy (FTIR).Secondly, studied on the solution properties of viscosifier, including the solubility of viscosifier in water and hydrochloric acid, the thickening ability, thermal dilution. The thermal stability, shear stability, salt resistance, slow release, and the compatibility with other acids of thickening acid et al were also discussed. The results show that this thickening acid had good solubility, thermal stability, shear stability, temperature and salt resistance, and slow release, the viscosifier can be used as acid thickener.Thirdly, studied the performance of cross-linking agents for temperature-controlled variable viscosity acid, the effect of including the composition and concentration of viscosifier, crosslinker amount, hydrochloric acid content, crosslinking temperature et al on the temperature-controlled viscosity change process for variable viscosity acid were investigated which, based on on the formaldehyde/zirconium acetylacetonate cross-linking agents of equal weight index. Charateristic evaluation of variable viscosity acid indicate that, the crosslinked acid had high viscosity under high temperature, and the best retardance performance than hydrochloric acid and viscous acid. After gel-breaking, the crosslinked acid had low viscosity and less residue content, so it was a new type of variable viscosity acid with excellent overall performance.