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

Abstract

Summary 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. In unconventional resources, an improper choke-management strategy may trigger proppant crushing or the flowback of proppant, resulting in fracture closure 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 sand production and requiring excessive and costly workovers. Choke-management strategies should aim to minimize near-wellbore pressure gradients along the fracture, thus making proppant flowback and loss of fracture conductivity or connectivity with the wellbore less likely to occur. 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 < 0.01 md) there is a unique choke-management strategy that 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 because of excessive fluid velocities along the frac pack or exaggerated pore-pressure gradients at the completion sandface. Results indicate that the selection of the optimal choke-management strategy is similar to that of openhole completions, with beanup 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 beanup 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. A general framework for beanup operations is defined and then used to compare beanup strategies for hydraulically fractured and frac-pack completions. It is hoped that this paper will contribute a theoretical foundation to the current diverse operator practices.