A coupling algorithm for simulating multiple hydraulic fracture propagation based on extended finite element method

Combining fluid mechanics, fracture mechanics, and extended finite element method, a coupling algorithm for simulating multiple hydraulic fracture propagation is established in this research. In comparison with the current existing XFEM models for hydraulic fracturing, this approach neither needs to introduce leak-off coefficient to describe the fluid leak-off phenomenon, nor requires to predetermine fracture propagation orientation. The single-fracture propagation results obtained from our numerical model and semi-analytical (KGD) solution show similar trends. Based on our numerical model, the effect of cluster space on multiple hydraulic fractures propagate in the horizontal well is discussed. Simulation shows that the stress interference among the fractures decreases with the increase in cluster space, and the average width of fractures increases with an increase in cluster space, the fracture width at the fracture inflection point may have a local minima value, which can lead to proppant screen out; therefore, in fracturing design, designer should use the quartz sand with smaller particle size as the slug to grind fracture. Since bottom and top fracture are interfered by the middle fracture, they are both away from the middle fracture, while middle fracture extends in straight line due to the symmetry of stress interference. At the beginning, the pressure at the fracture entrance increases with increase in injection time, and then the pressure decreases rapidly as the injection time increases.