压裂液返排模型的建立及应用

Establishment and application of flowback model of hydraulic fracturing

压裂液返排过程中通过合理控制返排时间和流量,可使支撑剂在产层区获得较好的铺置,从而使裂缝具有较高的导流能力。目前压裂液返排工作制度的确定一般依靠现场工程师的经验,缺少可靠的理论依据。为此建立了包含考虑二维滤失的裂缝扩展模型,停泵后即刻返排、停泵后关井闭合返排的数学模型,模拟了返排期间压力、排量随时间的变化规律,建立了压裂液返排模型,得到压裂液返排控制的优化设计方法,并编制了计算程序,指导现场选择合适的返排时间和返排流量。现场实例表明,应用编制的压裂液返排计算软件得到的结果,可为压裂液返排时间和流量的确定提供依据,有助于现场返排的科学化和定量化。

The flowback of the fracturing fluid after treatment is significant parts of hydraulic fracturing.The appropriate flowback step may make great contribution to the fracture flow conductivity.This paper focused on the researches of the fracture propagation,fracturing fliud transportation,fracturing fluid loss property,fracture closure and mathematical model of the flowback procedure.According to the theory of petrology and fluid flow in porous media,mechanism of leakoff of fracturing fluid,fracture propagation and 2D dynamic leakoff fracturing fluid of non-Newtonian fluid were established.On the basis of fluid mechanics,lithomechanics and the rule of material balance,mathematical model of fracture closure was established.The mathematical model of proppant settling in power law fluid was set up after analyzing the influential factors on proppant settling.Moreover,the flowback optimization software was compiled.On the basis of predecessors＇ and field successful practice＇ experiences,these are good for scientific and quantitative design of flowback in fields.