致密气藏防水锁易返排滑溜水研究与应用

Study and Application of an Easy-to-flowback and Water Block Preventive Slick Water Fracturing Fluid for Tight Gas Reservoirs

吉林油田致密气储层微纳米级孔隙发育,喉道窄小且连通性差,属低孔低渗储层。随着气藏的长期开发,地层压力、产能的逐渐降低,水锁伤害的影响逐渐显现,导致压后返排难度大,加之黏土的膨胀运移与堵塞,进一步降低了储层有效渗透率,严重制约了气藏采收率的提高。针对此问题,研发了防水锁易返排滑溜水压裂液体系,该体系主要由减阻剂XY-205、纳米微乳助排剂与黏土稳定剂XY-63组成。实验证明该体系具有速溶与低黏特性,能够满足快速连续混配要求,减阻率能够能达到70%以上,表面张力比常规气井滑溜水降低40%以上,利于致密气井压后助排,且能够较好地抑制黏土膨胀,对地层伤害小。该滑溜水对岩心的伤害率为9.45%,24 h岩心渗透恢复率接近90%,解除水锁伤害程度较高。该滑溜水体系在致密气区块现场应用4口井,压裂成功率100%,压后返排率提高2倍以上,试气效果显著,具有较好的大规模推广应用前景。

The tight gas reservoir in Jilin Oilfield,a low porosity and low permeability gas reservoir,is full of micrometer-and nanometer-sized pores with narrow pore throats and poor connectivity.Long period of development of this gas reservoir has resulted in reduction of formation pressures and productivity.Water block of the reservoir formations is aggravating and making flow back after fracturing more and more difficult.Swelling and migration of clay particles inside the formation caused blocking of the flow channels,further reducing the effective permeability of the reservoir and restricting the increase of oil recovery.A slick water fracturing fluid has been developed to address these problems.This slick water fracturing fluid is able to prevent water block and is easy to be flowed back after fracturing job.It is mainly composed of the drag reducer XY-205,a nanometer micro emulsion cleanup additive and the clay stabilizer XY-63.Laboratory experiments showed that this fracturing fluid has the properties of instant dissolving and low viscosity,which are beneficial to fast and continuous mixing.Friction reduced using this fracturing fluid was at least 70%.This slick water fluid has surface tension that is 40%lower than the surface tension of the slick water fracturing fluids used in other gas wells,indicating that the slick water is beneficial to the clean-up of the well after fracturing job.The slick water fracturing fluid is also useful in inhibiting clay swelling,the permeability of cores tested with this slick water fracturing fluid was only reduced by 9.45%,and the recovery of the permeability of the cores 24 hours after test was nearly 90%.Application of this slick water fracturing fluid on 4 wells gave 100%rate of success.Fracturing fluid flowed back was increased by a factor of 2.In well test,gas production rate was increased remarkably.This slick water fracturing fluid has good prospects of large-scale promotion and application.