Study On The Fracture Initiation And Propagation Model For Horizontal Well Fracturing

The producticity of single well sometimes is very low in the low and ultra-low permeability oil fields, can not meet the requirements of economic development, so, the horizontal well usually required for the implementation of hydraulic fracturing. Because of the lacking in understanding the initiation mechanism of the formation in fractures, there is no good theoretical basis for designing the fracturing.A large number of micro-cracks was considered in the rock in the low-permeability reservoir in this paper, simplifying and assuming the conditions, sum up the initiation mathematical model adjusted to the formation. After calculation, discuss the effects of the horizontal wellbore azimuth, vertical stress, maximum horizontal principal stress, minimum horizontal principal stress, perforation, orientation angle of the horizontal well to fractures initiating pressure, which provides a theoretical foundation for the calculation of fracture initiating pressure, angle and perforation optimization.An improved P3D (pseudo three-dimension) hydraulic fractures propagation model that vertical flowing of the fluids is constructed. Calculated the effective elastic modulus of the rock that considered the character of the liquid in the micro-cracks. Because of the changes of Young's modulus and Poisson's ratio in the reservoir rock, it caused an increase the width of hydraulic fracture in the crack width equation. The height of the cracks reduced after iterative calculation. Field application shows that the results of the improved model appear to have a good consistency with that of the Fracpro-PT fractures design software.Calculated the height of cracks under reservoir stress difference, rock fracture toughness, modulus difference etc., which will have a certain significance on improving the success rate of fracturing.In addition, analyze the crack geometry and the stress intensity factor.