An evaluation of fiber-based lost circulation material for fracture plugging using simulations

Lost circulation during drilling operations is a major problem owing to the prolonged non-productive time, especially in naturally fractured reservoirs. Incorporating granular lost circulation materials (LCM) in the drilling mud has been the traditional first-approach method with the industry moving towards incorporating fibers and flaky LCMs with the goal of improving the fracture sealing effectiveness of the LCM blends. Although the fracture sealing mechanism and the particle transport for granular LCMs are well understood, there is limited knowledge on the behavior of fibers as LCMs in flows governed by high differential pressures at the bottomhole. Further, considering limited lab studies to understand the effectiveness of fiber LCMs, we tried to fill this gap by developing and using coupled numerical models that are now able to incorporate the axial and bending deformations of fibers to assess the impact of different design parameters. We evaluate the effects of fluid rheology, the LCM concentration, fiber stiffness, interparticle friction, and fracture roughness on fracture sealing. The mechanism driving fracture sealing in fiber-based LCM is vastly different from the proposed mechanisms for granular LCM. Bridge initiation in fiber-LCM originates with 'initial fiber jamming' leading to consecutive fibers further being trapped forming a net-like entrapment that further impedes and retains incoming particles. The ability of this initial bridge initiation to develop into a complete seal is dependent on several factors. The presented model provides an initial assessment tool for evaluating the significance of different LCM parameters for effective fracture sealing. We attempt to showcase the importance and reliability of bringing coupled simulation techniques into the domain for effective fiber LCM evaluation with the results of our work.