低浓度胍胶压裂液体系的研究与应用

Development and Application of Guar Gum Fracturing Fluid with Low Concentration

针对常规胍胶压裂液体系增稠剂浓度偏高,造成压裂成本较高、压裂液残渣含量高和对储层伤害较大的问题,用硼砂、多元醇和醚类助溶剂等合成了较高分子量的多核硼交联剂DY-1,研究了胍胶加量对压裂液黏度的影响,考察了压裂液的各项性能,并在新疆油田进行了现场应用。结果表明,胍胶加量在低于0.165%、高于0.135%时能与DY-1形成聚合物交联体。低浓度胍胶压裂液耐温耐剪切性较好,胍胶加量为0.18%~0.4%时,压裂液在30~140℃、170 s^(-1)下剪切60 min的黏度均大于100 mPa·s;30~100℃下压裂液的流动行为指数n(0.3~0.7)和稠度系数k(1.3~1.8)总体变化较为平缓,压裂液性能稳定;压裂液静态悬砂性能较好,在30~80℃下通过增加压裂液pH值可使陶粒的沉降速率降至0.05 cm/min;压裂液能有效控制滤失,造缝性能良好;在30~100℃下胍胶压裂液在3~4 h均能彻底破胶,破胶液黏度小于5 mPa·s,破胶液残渣含量低至76 mg/L。现场施工成功率100%,压裂液成本降低15.2%,增油效果明显,满足新疆油田储层改造的要求。

Higher thickener concentration of the conventional guar gum fracturing fluid system had led to higher fracturing cost, high residue content and serious formation damage. Aiming at these problems, multi-core boron crosslinking agent with higher molecular weight was synthesized by borax, polyhydric alcohol and auxiliary solvent. The effect of the addition of guar gum on the viscosity of fracturing fluid was studied, the performance of fracturing fluid was investigated and field application was carried out in Xinjiang oilfield. The results showed that when the mass fraction of guar gum was lower than 0.165% and higher than 0.135%, it could crosslink with DY-1 to form a copolymer. Guar gum fracturing fluid with low concentration had good rheological properties. When the dosage of guar gum was 0.18%-0.4%, the viscosity of fracturing fluid was greater than 100 mPa. s after shearing at 170 s^-1 and 30---140℃ for 1 h. Liquidity index n （0.3-0.7） and consistency coefficient k （1.3-1.8） changed relatively flat at 30-100℃ , indicating stable performance of fracturing fluid. Fracturing fluid had good static suspended sand property, the sedimentation rate of ceramsite could be reduced to 0.05 cm/min by increasing the pH value of fracturing fluid at 30-80℃. Fracturing fluid could effectively control fluid loss, and had strong fracture making ability. The gel breaking time of fracturing fluid was 3-4 h at 30-100℃, the viscosity of gel breaking liquid was less than 5 mPa, s and the residue content reduced to 76 mg/L. The cost of fracturing fluid was reduced by 15.2% in field application and the success rate was 100%. The system had obvious effect on increasing oil output, which met the requirement of reservoir stimulation in Xinjiang oilfield.