【作者】 张永晖；

【导师】 艾池；

【作者基本信息】 东北石油大学 ， 油气井工程， 2011， 硕士

【摘要】 水力压裂的目的是为了获得高导流能力的裂缝,工程技术人员希望通过对返排流速的控制使支撑剂在裂缝内获得较好的铺置,进而使裂缝具有较高的导流能力。但在现场施工时由于没有选择合理的时机对支撑剂的回流进行控制,导致大量的支撑剂回流到井筒。存在这些问题的一个很重要的原因就是压裂液返排流速控制中经验成分过多,缺少可靠的理论依据。对于支撑剂的回流,前人的研究是集中在对缝口的支撑剂回流进行分析,认为只要缝口的支撑剂不发生回流,就判定支撑剂在裂缝内具有很好的分布。但大量的现场实验表明,支撑剂发生回流是压裂返排施工的普遍现象,要分析裂缝内的支撑剂分布,必须对裂缝内支撑剂回流规律进行研究。本文考虑压裂液返排过程中缝宽的动态变化,根据质量守恒定律和伯努利方程,建立压裂液返排任意时刻裂缝内任意位置缝宽数学计算模型;考虑返排过程压裂液的滤失,建立裂缝内任意垂直截面的压裂液返排流速计算模型;结合椭圆管流中流体流动压降规律,建立了返排过程裂缝内压力分布模型,得出裂缝内压力分布规律;对压裂返排过程中裂缝内的支撑剂进行力学分析,根据力矩平衡原理,建立了返排不同时期支撑剂发生回流的压裂液返排临界流速计算模型,进而提出控制支撑剂回流的合理返排方案。本文研究的意义在于通过分析压裂液返排速度对裂缝内支撑剂回流的影响,进而优选出控制支撑剂回流的合理返排制度,指导压裂返排作业。更多还原

【Abstract】 The purpose of hydraulic fracturing is to gain flow conductivity of fractures. Engineer wish to obtain better proppant distribution by controlling speed of flowback, so that flow conductivity of fractures will be better. In site, a large number of proppants back to the wellbore because of engineer fail to choose reasonable opportunity to control backflow of proppant the important reason of arising these problems is too much experience component used in controlling current speed of flowback and leaks of dependable theory.Previous researches of proppant backflow focus on proppant in seam, those theories said that the proppant in the fractures should have a uniform distribution as long as the seam of the proppant does not back flow. But experimental results demonstrate that the backflow of proppant is common phenomenon in the process of fracturing flowback work. In order to analyzing the distribution of proppant in the fracture, the regular pattern of backflow of proppant must be researched.In this paper ,taking the dynamic variation of slot width in the process of flowback of fracturing fluid into account, according to mass conservation law and Bernoulli′s equation, the model for calculating the slot width in the fractures of fracturing fluid backflow anywhere at any time is established. Considering filtration of fracturing fluid in the process of flowback, a model for calculating speed of flowback in the fractures in any vertical section is established. Combining the fluid flow differential pressure regular pattern in ellipse tube,the pressure distributive model is established in the process of flowback,the pressure regularities of distribution in the fractures is obtained . the proppant in the fractures is been studied in the process of flowback, according to moment balance principle, the model for calculating flowback critical flow velocity of fracturing fluid in different flowback times when proppant flow back, and then appropriate scheme of flowback for controlling backflow of proppant is proposed. The research significance of this thesis lies in that, according to analysis the influence of the speed of flowback for backflow of proppant in the fractures, and optimizing the appropriate regime for controlling backflow of proppant, guiding the work of fracturing flowback.更多还原