粘弹性表面活性剂压裂液的破胶作用

压裂液在压裂过程中起传递压力和携带支撑剂的作用,但聚合物压裂液中聚合物因降解不完全会给储集层带来损害,严重时甚至造成油气井减产。表面活性剂分子是由亲水头基和亲油尾基构成的,溶于水时可聚集为胶束。粘弹性表面活性剂在某些盐存在时,可在低含量时形成类似于聚合物分子那样的棒状胶束,并相互缠绕,而产生粘弹性。粘弹性表面活性剂压裂液因不存在聚合物残渣,对裂缝损害小,而视为清洁压裂液。一般认为,这种压裂液遇到地层中原油或天然气时可破胶,无须外加破胶剂。然而研究表明,天然气并不能使该压裂液破胶,压裂气井时必须外加破胶剂,并为此研究出了一种适合的高分子破胶剂。

Break Mechanism of Viscoelastic Surfactant Fracturing Fluids

Fracturing fluid acts as pressure transfer and proppant carrier during the process of fracturing. However, polymer-based fracturing fluid will damage the payzones or even cause production decline of wells due to incomplete degradation of polymer in it. Surfactant molecules are made up of hydrophilic head group and lipophilic tail group, which become micelle by coalescence when dissolved in water. The viscoelastic surfactant fracturing fluid with some salinity is known as clean fracturing fluid for its little damage to fractures and absence of polymer residue. In general, such a fluid doesn't break till mixing with crude oil and gas in reservoirs without adding gel breaker. But this study shows that the viscoelastic fracturing fluid can not break when mixing with natural gas, so gel breaker has to be added for gas well fracturing. A suitable macromolecular gel breaker is presented in this paper.