Fracturing Fluid Flowback Model And Its Application

As an important technology in low permeable reservoir reconstruction, hydraulic fracturing has become more and more popular. The flowback after fracturing is one of the most important parts after fracturing management, fracturing effects is directly affected by flow back technology. However, the flow back theory is not mature at present because of the complication of flowback problem. The flowback technology is always depended on experiences in fields and has many ambiguities and randomness. On the basis of the demand of fracturing fluid flowback technology, comprehensive consideration of some questions after fracturing, such as fracture closing, fluid loss, proppant migration, formation fluid flows and well bore flow. The paper does a systemic and deep research on the model of fracturing fluid flowback, pay more attention to the proppant motion model, start model and calculation model of fracturing flowback rate and firstly analog gas well productivity of flowback. The achievement of research has theoretical meaning to fulfill fracturing design model and has practical significance to guide fracturing fluid flowback. The main content that has obtained are as follows:Firstly, on the basis of comprehensive consideration of two dimensional fracturing fluid leak off and well bore flow of fracturing fluid, a forced fracture closure mathematical model is established and a solving method is given. Because of the comprehensive consideration on more factors, a more accurate fracture close time and the relation between wellhead pressure and time are obtained and provide the time to shift choke.Secondly, the moving and stress status of proppant from and out of the fracture are analyzed at the first time. And the proppant motive model and start model after and before fracture close are established. A critical velocity of the proppant flowback is obtained, a critical choke diameter is determined by comparing with the velocity of fracturing fluid flowing in well bore during flowback.Thirdly, considered the change of viscosity with time and formation porous media deformation, the numerical calculation model of fracturing fluid flowback is established and analyzes the effect of fracture parameters and formation parameter to fracturing fluid flowback rate. The effect of flowback rate to postfrac productivity is calculated and analyzed at the first time.Finally, the fracturing fluid calculation software is programmed at the first time. By using the software, the time of fracture forced close and the choice of blowout choke diameter and the rate of flowback are all obtained. These are good for scientific and quantitative design of flowback in fields.