致密砂岩气藏混醇酸液体系研究

Research on mixed alcohol acidizing fluid system for tight sandstone gas reservoirs

为解决巴喀油田致密砂岩气藏酸化时的水锁等地层伤害问题,研制出一种混醇酸液体系,用于改善地层气相渗透率和酸化效果。通过室内实验筛选了醇、酸的类型和浓度,评价了混醇酸液体系的表面张力特性及与添加剂配伍性,并通过岩心流动实验对混醇酸液体系的酸化效果进行了综合评价。实验结果表明,醇具有良好的降低表面张力作用,甲醇与6%多氢酸混合形成多氢酸+醇酸液体系后对致密砂岩气藏岩心溶蚀率达到了14.08%～15.45%;6%多氢酸+甲醇/乙醇酸液体系和黏土稳定剂、缓蚀剂、助排剂等添加剂具有良好的配伍性,并且其表面张力和残酸表面张力均低于25.8 mN/m;经多氢酸+醇体系酸化后岩心最终渗透率为基准渗透率的14.28～21.00倍,解堵效果明显,完全满足巴喀致密砂岩气藏酸化工艺要求。

The tight sandstone gas reservoirs in Baka oilfield has experienced formation damage problems such as water locking in acidizing treatment,therefore a mixed alcohol acidizing fluid system has been developed to improve gas permeability and acidizing result.Laboratory experiments have been conducted to screen the type and concentration of alcohol and acid,to evaluate the surface tension of the mixed alcohol acidizing fluid system and its compatibility with additives.The effect of the mixed alcohol acidizing fluid system has been evaluated through core flow experiments.The results show that alcohol is good at reducing surface tension;and the corrosion rate of tight sandstone reservoir cores by the acidizing fluid system of methanol mixed with 6% multi-hydracid can reach up to 14.08%～15.45%;the acidizing fluid system of 6% multi-hydracid + methanol/ethanol is well compatible with additives such as clay stabilizer,corrosion inhibitor and cleanup additive,with both surface tension and reacted acid surface tension less than 25.8 mN/m;after treated by the acidizing fluid system of multi-hydracid + alcohol,the ultimate core permeability is 14.28～21 times of the base permeability,showing obvious effect of plug removal and fully satisfied the technical requirements of acidizing the tight sandstone gas reservoirs in Baka oilfield.