The Research On Law Of Proppant Backflow In Process Of Fracturing Fluids Flowback

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.