Synthesis Of Acid Retarder GL-1 And Its Application In Low Viscosity And Low Resistance Retarded Acid

Acidizing is one of the important measures to increase production and injection in oil and gas reservoirs.With the continuous development of acidizing technology in oil and gas fields,the length of effective action distance of acid solution in the formation is the core problem of reservoir acidizing transformation.At present,the thickened acid system is commonly used in the field.Which mainly depends on the viscosity of the system to reduce the acid rock reaction rate.The disadvantages of this acid system are high viscosity and high friction.Which makes it difficult to pump in the reservoir.Therefore,it is necessary to develop an acid retarder with high efficiency and no significant increase in the viscosity of the acid system.Through the evaluation and test of acid additives,a set of low viscosity and low resistance retarded acid system is formed to increase the effective action distance of the acid in the reservoir and improve the oil and gas production.(1)The optimal synthesis conditions of GL-1 were determined by single factor control variable method.With average acid rock reaction rate and intrinsic viscosity as evaluation indexes:the monomer ratio is n(AM):n(AMPS):n(SSS)=6.12:2.04:0.05,the initiator dosage was 0.35%(accounting for the total amount of monomers),the reaction temperature was 45℃,the pH value was 6.0,the monomer concentration is 20%,the reaction time was 5h,and the stirring time was 5 h,mixing speed is 600r/min.The molecular structure of the retarder was characterized by IR and NMR,which was in accordance with the initial design.The XRD results showed that the polymer was amorphous structure,which made it have good solubility in acid solution.The thermogravimetric analysis showed that the retarder had strong thermal stability.The onepoint method showed that the viscosity average molecular weight distribution of the copolymer was 392628.43-548714.91 to ensure that the retarder can disperse rapidly in acid solution.(2)NSJ-1 drag reducer,HJF-95 corrosion inhibitor,CF-5A drainage aid and TWJ-10 iron ion stabilizer were selected through laboratory evaluation and test.And their adding amounts were determined respectively.Compatibility test showed that the compatibility of speed reducer and acidizing additives in acid solution was good,no precipitation and stratification.(3)The influence of retarder dosage on acid rock reaction rate was studied by weight loss method.And the optimal dosage of retarder was determined by acid rock reaction test under different conditions.The static acid rock reaction test at 90℃ and dynamic acid rock reaction test at 140℃ was carried out.The results show that the average acid rock reaction rate of 3%GL-1+0.1%NSJ-1 added to 15%acid solution is 2.97×10-4 g/(cm2·s).The average acid rock reaction rate of thickened acid system is 3.20×10-4 g/(cm2·s).And the average acid rock reaction rates of the two acid solutions are basically the same.Therefore,the formula of retarded acid system is 15%/20%/28%hydrochloric acid+3%GL-1+0.1%NSJ-1+1%/2%HJF-95+0.3%CF-5A+1%TWJ-10.(4)The comprehensive performance evaluation of retarded acid system was carried out.The results show that the average acid rock reaction rate of low viscosity and low resistance retarded acid system is lower than that of thickened acid system under 90℃ static condition and 140℃ dynamic acid rock reaction test.And the viscosity of acid system is less than 5 mm2/s.The results show that the acid rock reaction rate increases with the increase of reaction temperature;the change of acid rock reaction rate is not affected by reaction pressure;the acid rock reaction rate decreases with the increase of rotation speed of rock plate.Through the core displacement test,it is proved that the retarded acid can form wormhole corrosion in carbonate rock,and has good retarded effect.(5)Through the pilot scale-up of the retarder in the factory,the pilot production process is determined.And the performance of the pilot product is evaluated.The results demonstrate that the average acid rock reaction rate of the pilot product is basically the same as that of the small sample synthesized in the laboratory.Therefore,the pilot scale-up of the retarder GL-1 is successful.(6)The acid fracturing test of gas wells in Changqing Oilfield Block shows that the system has the advantages of simple fluid distribution on site,stable pressure in acidizing operation,20-30%lower friction than conventional acid fluid.And the maximum open flow rate of test wells is 103×104m3/d.The preliminary effect of the transformation is achieved.