Three dimensional multi fracture induced stress model for highly deviated wells

Abstract

ABSTRACT At present, the development of some oil and gas fields has gradually shifted from vertical to highly deviated wells. To improve the intensity of reservoir reconstruction, highly deviated wells mostly adopt staged fracturing for reservoir reconstruction. The fracture interference law of multiple fractures in highly deviated wells is not clear, and the fracture steering and stress interference problems in the fracturing process are obviously different from those in horizontal wells, resulting in a lack of a theoretical basis for fracture spacing design. Therefore, it is necessary to study the stresses induced by multiple fractures in highly deviated wells. To reproduce the spatial distribution of multiple fractures in highly deviated wells and analyze the changes in induced stress more accurately, a three-dimensional numerical model of the fracture-induced stress field in highly deviated wells was established based on the finite element method and elasticity theory, which can simulate a fracture-induced stress field under different angles of inclination. The results indicate that the key to mutual exclusion or proximity of the two fractures is whether the fractures overlap in the plane parallel to the fracture height direction. Based on the analysis of the control variables, the first fracturing fracture height is the key factor affecting the induced stress, and the fracturing fracture height has slight effect on the induced stress. As the angle of inclination increases, the probability of the two fractures overlapping in space increases and the critical distance from the induced tensile stress to the induced tensile stress decreases. The influence of the fracture half-length, net pressure, and stress difference on the induced stress is related to whether the spatial projection of the two fractures overlaps. The research results provide a theoretical basis for the optimal design of staged fracturing in highly deviated wells.