Research On Solid-Liquid Flow Character And Erosion In Hydraulic Fracturing Tubing

In the fracturing process of deep gas wells and large-scale multi-stage horizontal well in Daqing oil field, fracturing tubings were produced a serious erosion at some locals, due to the higher flow rate of fracturing fluid, and a high concentration of solid particles in the fracturing fluid contains. Which lead to the fracturing can not been constructed, and has seriously constrained the development of hydraulic fracturing technology. Based on the erosion and wear of deep oil and gas well fracturing tubing in Daqing oil field, the establishment of the mathematic model of the solid-liquid two-phase flow and erosion wear not only have important theoretical significance but also have important applications value. After reviewing the progress of the two-phase turbulent mathematical model, practical problems is combined in this paper. In the condition of continuum theory,based on the Euler-Euler two-fluid basic equations and two-phase turbulence theory, the solid-liquid two-phase flow in the fracturing tubing were studied by the numerical simulation method, and the theory of erosion wear was applied to predict the erosion rate of fracturing tubing.The two-dimension axial symmetry solid-liquid two-phase two-fluid turbulence model in the rectangular coordinate system was constructed, the boundary condition is determined, and the equation is closed to make up the completed definite condition. The finite volume method is adopted to solve the control equations. The characteristics of time-averaged, the sand concentration field, fluid pathline, and so on, in the sudden expansion and constrictied tubing were computed. The flow distribution and the impacting angles were analyzed in the condition of variational inlet flow rates and the sand volum fraction. With the view of reducing the erosion caused by the fluid, the shapes of inernal flow channels were optimized.A three-dimensional solid-liquid two-phase two-fluid turbulence model in the fracturing tubing in rectangular coordinate system was proposed to study the fluid flow in the the horizontal well frac-sandjet by the numerical simulation method, which was solved by finite-volume method. The fuild pathline, the time-averged velocity, sand concentration distribution and pressure distribution in the frac-sandjet were achieved. In order to verify the correctness of complicated fluid field in the frac-sandjet, the experiment model of the frac-sandjet is designed by the similarity principle. The LDA measuring system was established to measure the internal flow field distribution in the frac-sandjet. Comparisons between numerical results and experimental results show that the flow field distribution described the two-fluid turbulence model is agree with the results of experiment, which verifies the reliability of the turbulence model and computation method.The failure analysis of fracturing tubing was carried out to determine the main pattern caused erosion, the erosion suitable theory model was established, based on classical erosion theory combined with the results of erosion experiment studies. The erosion rate of sandjet holes in the frac-sandjet where the erosion is more serious is studied. The established erosion model was applied in the numerical simulation results, in order to predict the erosion rate of inner bushing. Applied to the inter flow field simulation and erosion simulation method, the structure of frac-sandjet was optimized, and new multhole non-isometric frac-sandjet was designed, which effectively improves the fuild flow state, reduces the damage to fracturing tubing , and puts forward new ideas for the design of frac-sandjet.This study not only provide an effective theoretical basis for the optimization design of fracturing tubing, but also can be predict the erosion rate of fracturing tools in fracturing production of oil field, and provide important guiding significance for the design of fracturing tools. Moreover it can promote the further development of fracturing tubing, extend its service life, improve the success rate of fracturing, and reduce the cost of construction operations, so it has good economic and application prospects.