新型表活剂压裂液的实验特性及其在水锁气层中的应用

An experimental study on the behaviors of new surfactant fracture fluid and its application in water lock gas reservoirs

水锁伤害是低渗透气层压裂面临的一个重要问题。首先从两个方面对新型表活剂压裂液展开了实验研究:①进行了岩心伤害实验,采用多次驱替方式发现,新型表活剂压裂液在岩心孔隙中72h还呈现自由状态,能够被驱动,随着驱替次数增多,岩心渗透率伤害程度减少,而其他液体没有这种现象;②进行了支撑裂缝导流伤害实验,通过不同驱替方式发现,采用不同液体驱替的支撑裂缝导流能力相差不大,通过氮气驱动后,新型表活剂压裂液支撑裂缝导流能力有所增加,继续通过CO2气体驱动后,该组裂缝导流能力继续增加,而胍胶类压裂液导流能力基本没有变化。通过实验认为:新型表活剂压裂液对岩石及裂缝的伤害可以改变,降低了对储层的水锁伤害,适合应用于易水锁气层压裂施工。现场试验证明,该类压裂液对低渗易水锁气层具有较好的压裂增产改造效果。

In view of water lock damage which occurs in the fracturing of low permeability gas reservoirs,experimental studies were carried out on the new surfactant fracture fluid in two aspects,one of which is the core damage experiment and the other is the fracture capacity damage experiment.In the former experiment,the multiple displacements were carried out at intervals,after 72 hours,this new surfactant fracture fluid existed in the core pore was still in the form of a free state.Water lock damage never occurred and as a result,the fracture fluid could be displaced freely.The more times the displacements,the lower damage for the formation permeability.However,this phenomenon never occurred when other fluids were used.In the latter experiment,after deploying various displacement patterns,there is little difference in fracture capacity when different fluids were used for displacement.However,the fracture capacity of this new fluid containing anion surfactant increased after the nitrogen displacement,and then after the displacement with CO2,the fracture capacity increases accordingly but little change was found in the guar gum-based frac fluid.According to analysis of results from the above-mentioned experiments,it is concluded that the damage of this anion surfactant frac fluid on the formation and fractures can be changed,and the damage on the formation can be lowered,therefore it is suitable for the fracturing in water lock gas reservoirs.Field experiments demonstrate that good performance of this frac fluid has been achieved in the fracturing especially for low permeability and water lock gas reservoirs.