Three-dimensional model for space reorientation of hydraulic fractures near deflecting well bore

The complicated stress distribution around deflecting well bore always results in the reorientation of hydraulic fractures. A three-dimensional model for reorientation of hydraulic fracture near well bore was presented using the maximum tensile stress criterion and the Lagrange multiplier method. The model can be used to analyze the initiation position and propagation shape of hydraulic fractures under the action of the three-dimensional underground stresses and well-bore pressure. Some numerical calculation procedures were made for simulation. According to the model, laboratory experiments on rock samples with three-dimensional size of 300 mm were performed on the true tri-axis simulation equipment of hydraulic fracturing. The calculated results are basically in agreement with the experimental results. The fundamental patterns of the three-dimensional reorientation of hydraulic fractures near well bore were drawn. The results show that the three-dimensional reorientation of hydraulic fractures near deflecting well bore exists indeed and occurs generally within the range of three times of the well bore diameter.EI0451-552