可降解纤维压裂液的破胶性能实验研究

Effects of Degradable Fiber on BXHPG Fracturing Fluid

所报道的可降解纤维为一种有机酸酯聚合物,可在高温下水解降解而释出酸,在压裂液中既具有降阻、防止支撑剂回流、降滤等纤维功能,又能促进破胶。加入该种纤维的模拟压裂液(不含增稠剂和破胶剂),在80℃和120℃下的pH值随时间延长而降低,降低幅度随温度升高和纤维加量增大(0～2.7g/L)而增大,纤维加量1.8g/L时,在80℃经过100h或在120℃经过30h,pH可降至5.5。有机硼交联0.45%HPG压裂液,加入过硫酸铵100或300mg/L并在100℃放置24h后,破胶残渣量为428或315mg/L,破胶液pH值为9.2或8.5,而加入可降解纤维1.8g/L的压裂液,破胶残渣量减至203或112mg/L,破胶液pH值降至4.5或3.7。以抗氧化剂稳定的有机硼交联0.45%HPG压裂液,120℃、1701/s黏度随剪切时间延长而下降,但剪切70min的黏度高于200mPa.s,可满足中等规模的加砂压裂,剪切105min后降低温度,则黏度迅速回升,出现返胶现象。只加入该种纤维而未加破胶剂的压裂液,破胶返排后可再利用。

The degradable fibrious material（DFM） presented was an organic acid ester polymer,which could undergo hydrolytic degradation at higher temperatures to release organic acid,and suggested to be used in fracturing fluids（FFs） for reducing friction and filtrate loss,controlling proppant backflow and promoting gel breakdown. For an experimental simulation FF without thickener and gel breaker added,introducing DFM led to decrease in its pH value at 80℃ and 120℃ with time and the pH decrement increased with increasing temperature and DFM dosage（0—2.7 g/L）：the pH value lowered to 5.5 at 80℃ in 100 hrs or at 120℃ in 30 hrs at DFM dosage 1.8 g/L. An experimental bor crosslinked 0.45% HPG FF with APS added at dosage 100 or 300 mg/L was let to break down at 100℃ over 24 hrs and the residue determined was of 428 or 315 mg/L and the pH value of broken FF was of 9.2 or 8.5;when DFM was introduced additionally at dosage 1.0 g/L the residue was reduced to 203 or 112 mg/L and the pH value of broken FF ——to 4.5 or 3.7. For the experimenta FF stabilized by an antioxigant,the viscosity at 120℃ and 170 1/s decreased with shearing time and kept at higher than 200 mPa·s in 70 min of shearing,which indicated that this FF with DFM added could be used in sand fracturing jobs of medium scale,and when the experimental temperature lowered after 105 min of shearing the viscosity fast rose,which demonstrated regelation of the FF.