Choke Management Strategies for Hydraulically Fractured Wells and Frac–Pack Completions in Vertical Wells

Abstract

AbstractWhen a well is brought on production, the selection of an optimum choke management strategy is aimed towards maximizing well productivity and minimizing the risk of typical wellbore failures during the early life of a well. In this study, a quantitative method is presented for the selection of a choke management strategy that minimizes the risk of the predominant failure mechanisms in hydraulically fractured wells and frac-pack completions. For example, in unconventional resources, an improper choke management strategy may trigger the back flow of excessive amounts of proppant, resulting in fracture closure and possible wellbore damage and loss of production. In frac-packs and high-rate water packs, an abrupt increase in the rate (or drawdown) may induce completion damage resulting in impaired production and possibly sand production, requiring excessive and costly workovers.It is shown that in hydraulically fractured wells, choke management strategies should aim towards minimizing pressure gradients along the fracture, thus making proppant flowback and potential reduction/loss of fracture conductivity or its connectivity to the wellbore less likely to occur, for a given set of formation properties and closure stress. Choke management strategies are compared for a wide range of formation and fracture properties including fluid properties, matrix permeability, fracture conductivity and fracture length. Results indicate that in unconventional formations (k<0.01md) there is a unique choke management strategy, which consistently appears to be the best. The methodology is coupled with previous studies that have focused on determining the critical pressure gradient for which proppant flowback is observed.In frac-packs and high-rate water packs, completion failure may occur due to excessive fluid velocities along the frac-pack or exaggerated pore pressure gradients at the completion sandface. Choke management strategies are compared for a wide range of formation and completion properties. Results indicate that in frac-packs and high-rate water packs, the selection of the optimum choke management strategy is similar to that of open-hole completions, with bean-up operations achieving a relatively higher reduction in pressure gradients for the case of low values of dimensionless fracture conductivity. The greatest reduction in pressure gradients can be achieved by considering bean-up operations during completion design.The results of this study provide, for the first time, a clear methodology for selecting choke management strategies in hydraulically fractured wells and frac-pack completions for a wide range of reservoir and fluid properties.