中低温清洁压裂液BVES-80的性能评价

Performance Evaluation of BVES-80 Clean Fracturing Fluid with Medium and Low Temperature Resistance

开发了一种新型甜菜碱表面活性剂压裂液BVES-80。该压裂液优化配方为2.5%甜菜碱表面活性剂DBA2-12+4.0%KCl+0.5%水杨酸钠+1.0%异丙醇+自来水。对BVES-80压裂液性能的评价结果表明,NaCl、CaCl2、MgCl2加量为3%时,压裂液的黏度分别为337、370、394 mPa·s,耐盐性较好。压裂液静置7 d后的黏度为321mPa·s,变化较小,稳定性较好。在170 s-1下连续剪切1 h后的黏度分别大于50(60℃)和30(80℃)mPa·s,在中低温下的耐温抗剪切能力良好。在30℃、0.01率10 Hz条件下,压裂液储能模量G'始终大于耗能模量G'',且G'大于10 Pa,G''大于0.3 Pa,黏弹性较好。60℃下,陶粒在BVES-80清洁压裂液中的沉降速度为0.14 mm/s,远小于0.5%胍胶压裂液的值(1.50 mm/s),携砂性能较好。在30℃下与煤油混合可在12 h内彻底破胶,破胶液黏度小于5mPa·s,残渣含量23.46率54.37 mg/L,破胶液表面张力26.3率27.5 mN/m,破胶液与煤油的界面张力0.55率0.62mN/m。该体系在80℃下的滤失系数为4.75×10-4m/min1/2,对岩心的渗透率伤害率仅为7.4%,适合不超过80℃的中低温低渗地层的储层改造。

A novel betaine surfactant fracturing fluid(BVES-80) was developed. The optimum formula of BVES-80 clean fracturing fluid was obtained as follows: 2.5% betaine surfactant DBA2-12,4.0% KCl,0.5% sodium salicylate,1.0% isopropanol and water. The results of performance evaluation showed that when the dosage of NaCl,CaCl2 and MgCl2was 3%,the viscosity of fracturing fluid was 337,370 and 394 mPa·s,respectively,indicating good resistance to salt. The viscosity of fracturing fluid(321mPa·s)did not change significantly after standing for 7 d,indicating good stability. Under the condition of 170 s-1shear rate and60℃ or 80℃ temperature,the viscosity of fracturing fluid was 50 mPa·s or 30 mPa·s respectively after continuous shearing for 1h,showing good temperature and shearing resistance at medium and low temperature. Under the condition of 30℃ and 0.01—10Hz oscillator frequence,the storage modulus G' of fracturing fluid was always larger than the loss modulus G'' with G' more than10 Pa and G'' more than 0.3 Pa,suggesting good viscoelasticity. The falling rate of ceramsite in BVES-80 clear fracturing fluid at60℃ was 0.14 mm/s,which was much less than that of 0.5% guanidine gum fracturing fluid with 1.50 mm/s,showing good sand-carrying capacity. Within 12 hrs and at 30℃,the clear fracturing fluid could completely break when mixed with paraffin. The viscosity of gel breaking fluid was less than 5 mPa·s,the residue was 23.46—54.37 mg/L,the surface tension of gel breaking fluid was 26.3—27.5 mN/m and the interfacial tension between gel breaking fluid and paraffin was 0.55—0.62 mN/m. The filtration coefficient was 4.75×10-4m/min1/2at 80℃ and the damage rate was only 7.4% for core permeability. BVES-80 clear fracturing fluid was suitable for the reservoir reform of medium and low temperature and low permeability formation below 80℃.