Optimization Of Crosslinked Acid System In Acid Fracturing Of Tahe High Temperature Carbonate Reservoir

Acid fracturing is the main production stimulation measure for carbonate reservoirs,and the performance of acid fluid directly affects the effect of acid fracturing.Crosslinked acid have strong temperature resistance in acid solutions for acid fracturing.At present,most crosslinked acid have a temperature resistance not exceeding 150℃.In the acid fracturing of high-temperature formations,in order to solve the problems of high filtration,short effective distance,and excessive consumption of conventional acid solutions,this paper has carried out research on high temperature resistant crosslinked acid system.In this paper,CQ is selected as the thickener for acid through evaluation experiments.Using zirconyl oxychloride,glycerol and acetic acid as the main ingredients,the molar ratio of the three is 1:2:4,the reaction temperature is controlled at 70℃,and the reaction is performed for 3 hours to obtain the cross-linker CL-B.Through evaluation experiments,the additives and their concentrations were optimized to form a high temperature resistant acid solution system:20%hydrochloric acid+1.0%thickener CQ+1.2%cross-linking agent CL-B+2.4%conditioner+2.0%iron ion stabilizer CIS-15+2.0%corrosion inhibitor CCI-10+1.0%cleanup additive HBC+breaker（0.3%ammonium persulfate+0.2%EDTA）.Crosslinked acid base solution has good stability at room temperature,and various additives have good compatibility.The comprehensive performance of the acid solution has been evaluated.The results showed that the crosslinking time of the crosslinked acid is about 2.25minutes.After shearing at 160℃and 170s^-1for 90 minutes,the viscosity is stable at100 m Pa·s.The system has good gel breaking performance and the viscosity can be reduced to 3.75 m Pa·s.The system has obvious corrosion inhibition effect and has good retarding performance.The crosslinked acid can meet the acid fracturing requirements of high temperature reservoirs.