Numerical simulation of stress field distribution before re-fracturing treatment

Abstract

Due to the first fracturing failure at the middle and final stages of oil and gas field development, re-fracturing technology has become a key method to increase production in oilfield. So, stress field distribution should be the key successful factor to impact re-fracturing technology after the initial fracturing in reservoir. In order to accurately describe the initial stress field distribution of reservoir after fracturing and provide theoretical basis for subsequent re-fracturing, this paper with theory of rock fracture mechanics and fluid-solid coupling equation had built several ABAQUS numerical model of hydraulic fracturing according to the basic theory of XFEM, to analyses the stress influence by horizontal stress difference, rock elastic modulus, Poisson’s ratio and production time before re-fracturing. Numerical simulation results show that due to the initial crack and the change of pore pressure in the process of production, the direction and size of the original stress field change a lot, which lead a stress field redirection; Reservoir and rock physical mechanical parameters bring a significantly change of reservoir stress field distribution; with the difference of horizontal stress, rock elastic modulus and oil field production time increasing, induced stress effect and stress redirection area decrease; the greater of Poisson’s ratio, the induced stress effect and redirection area is smaller.