高温灰岩储层新型微乳盐酸体系的构筑及性能评价

Preparation and Comprehensive Evaluation of Acid Microemulsion for High Temperature Limestone Reservoir

为了提高微乳酸在高温储层中的稳定性,以0#柴油为油相、20%盐酸为水相,固定水油比为7∶3、微乳化剂SMT-3及助乳化剂SRA-5总加量为15.5%,通过考察微乳化剂与助乳化剂质量比对所形成微乳酸耐温耐盐性能的影响,优化构筑了可在100℃稳定10 h的耐高温微乳酸体系,研究了该体系的静态特性及在储层中的流动特性。研究表明,该微乳酸体系(SMT-3、SRA-5质量比为0.5∶1)分散相液滴平均粒径为30 nm,在100℃下保持10h澄清透明,抗Ca^(2+)能力达到20%;在170 s^(-1)下剪切2 h依然稳定,具备较高的抗剪切性。由于该微乳酸的酸液被油相紧密包裹,故对N80钢片的腐蚀性和对石灰岩的溶蚀性都显著低于同浓度盐酸与稠化酸;该微乳酸体系在100℃下酸岩反应速率仅为盐酸的1/30,具备优良的深部穿透性。岩心流动实验表明该微乳酸体系可使岩心渗透率提升至酸化前的500%,且对储层伤害性低,是一种较理想的高温石灰岩储层深部酸化工作液。

In order to improve the stability of the acid microemulsion under high formation temperature,a micro-emulsified acid microemulsion was developed with 0#diesel as the oil phase,20%hydrochloric acid as the water phase,the fixed water-oil ratio was 7∶3,and the total addition of microemulsifier SMT-3 and co-emulsifier SRA-5 was 15.5%,through investigating the effect of the mass ratio of SMT-3 to SRA-5 on the temperature and salt resistance of the acid microemulsion and its static and dynamic properties of the acid microemulsion with mass ratio of SMT-3 to SRA-5 was 0.5∶1 were thoroughly investigated.It was found that the developed acid microemulsion,which showed an average particle size of 30 nm,could remain stable at the temperature of 100℃for at least 10 hours.It was also able to withstand the Ca^(2+)as high as 20%.It remained clear and transparent after sheared for 2 hours under the shearing rate of 170 s^(-1),demonstrating its outstanding shear resistance.As the acid droplets were well separated by the oil,the acid microemulsion presented much lower corrosion rate on N80 steel slide and much slower dissolution rate on limestone,compared to those of hydrochloric acid and thickening acid with identical concentrations.The rotating disk experiments indicated that the reaction rate of the acid microemulsion was only 1/30 of that of hydrochloric acid,which enabled it to penetrate into the deep formation.The core flooding experiments showed that the core permeability had been increased by 500%after acidification and the formation damage was negligible.Overall,the proposed acid microemulsion may be applied as an ideal acidifying fluid for high temperature limestone reservoirs.