Abstract:

Scale control through water mixing is an economically applicable, simple, highly effective and pollution free technology. Injection water is mixed with formation water or produced water in optimum proportion at surface. Ca(OH) 2solution is used to control pH value. All the cations, such as Ba²⁺, Ca²⁺, Fe³⁺, Fe²⁺ and Sr²⁺ and anions,such as OH^-, CO₃^2-, HCO₃^-, SO₄^2- and S^2- will be precipitated from the solution through reaction when the pH value in the mixed water is above 8.35. On the one hand,the scale-forming ions are removed and scaling is prevented when formation water mix with injection water in oil reservoir, so as to protect the oil reservoir. On the other hand,iron would be in a passivation state of corrosion,and water pipeline would be prevented from scaling and rusting.Experimental studies show that this technology can not only control scaling and damaging of oil reservoir and scaling and rusting of water pipeline, so as to realize reutilization of produced water and to reduce production cost, but is also applicable for waterflooding in various oilfields.

Key words: scaling mechanism, injection water, produced water, scale prevention, water mixing