Completion fluid pH value buffer agent and preparation method thereof

The invention discloses a completion fluid pH value buffer agent which is a mixed liquid of a first buffer liquid system and a second buffer liquid system, wherein the pH value of the mixed liquid is9.85-10.45; the first buffer liquid system is a mixed solution of an ammonium chloride solution and ammonia water; the pH value of the first buffer liquid system is 9.15-10.35; the second buffer liquid system is a mixed solution of sodium carbonate and sodium bicarbonate; the pH value of the second buffer liquid system is 9.0-10.5. The completion fluid pH value buffer agent is high in efficiency in removing hydrogen sulfide and the like and inhibiting iron scale and is capable of effectively preventing sleeve damage and cracks caused by hydrogen brittleness and hydrogen induced brittleness; inaddition, due to addition of the completion fluid pH value buffer agent, a completion fluid is constantly maintained under an alkali condition, corrosion products, namely ferric hydroxide and iron carbonate, have very low sol