Fracture Optimization for Multi-stage Fractured Horizontal Well with Time & stress-sensitive Parameters

Abstract It is widely acknowledged that the conductivity of fracture is influenced by both effective stress and producing time. As a result of dynamic conductivity, the permeability-dependent non-Darcy flow in fracture is also time&stress-sensitive. In this paper, the variations of conductivity and non-Darcy flow velocity coefficient on both time and stress are taken into account to contribute to hydraulic fracture optimization. The relationship between core permeability and effective stress is first investigated with laboratory experiment, which is modified by taking overburden stress into consideration and conducting core aging treatment to eliminate interspaces. Then, both stress-sensitive and time-sensitive of fracture conductivity is discussed with relative experiments. A new production data analysis method is also proposed to assist in time&stress-sensitivity determination. Afterwards, numerical simulation method together with a simplified economic evaluation procedure is presented to evaluate the impact of unfixed fracture conductivity and non-Darcy flow on fracture optimization. With laboratory experiment, we find that after taking overburden stress into consideration and conducting core aging treatment, the stress-sensitive of core permeability is weaker than traditional expected result. Besides, the fracture conductivity change exponentially with stress while logarithmically with producing time. However, the combine effect of stress and time should be determined with the modified production data analysis method. Based on numerical simulation and economic evaluation, we come to the conclusion that due to the unfixed fracture conductivity and non-Darcy flow, the fracture conductivity designed should be higher than the value obtained with conventional methods. Technical contributions in this paper including (a) investigating relationships between stress and reservoir/fracture permeability with modified experiment procedures; (b) discussing the combine effect of stress and time on fracture conductivity; (c) unfolding the impact of time&stress-sensitive conductivity and non-Darcy flow on well performance and fracture parameters optimization.