CFD investigations on Multiphase Flow in Well-Control Operations

Multiphase flow problem encountered during well control involves managing the circulating drilling fluid within the wells and avoiding kicks and blowouts as these can lead to loss of life and damage to the large-scale facilities. BP Deepwater Horizon disaster on April 20, 2010, is an iconic example of how destructive, costly, and deadly blowouts can be with eleven died workers in the explosion. Ninety-four crew members were rescued by lifeboat or helicopter, 17 of whom were treated for injuries. Since the Macondo explosion, kick detection has emerged as a primary concern. Around 172 million gallons of gas-saturated oil leaked during the 87-day rupture, which occurred at a depth of 1522 meters into the Gulf of Mexico. Modern days computational tools and simulation offer great opportunities to perform predictive simulations to improve the extant understanding of the intricacies associated with these problems. As such the current methodologies to model “kick” phenomena are limited by the assumption that only one gas bubble exists in the annulus that gradually rises after shut-in. This assumption over-simplifies the fluid flow models to satisfy the volumetric well control leading to erroneous pressure loss calculations. This thesis provides a comprehensive review of the work carried out in this important direction of research over the past 30 years outlining the progress on simulating multiphase fluid flow for well control operations. It then addresses the issue of multiphase fluid flow by proposing novel way to model this problem using computational fluid dynamics with assist of high-performance computing (HPC) system. Gas kick solubility in drilling fluid was considered in conjunction with the k-ε realizable turbulence model. Two-dimensional and three-dimensional flow simulations, integrated with a volume of fraction multiphase model, were conducted. These simulations aimed to predict and model both bottomhole pressure and gas kick magnitude. This comprehensive approach reflects a thorough consideration of fluid dynamics and multiphase interactions, providing a more accurate representation of the drilling process.
Flow simulations, incorporating two and three-dimensional models, were conducted to predict bottomhole pressure and gas kick magnitude. New fluid flow models, accounting for fluid miscibility and non-Newtonian properties, aimed at realistic kick treatment. This improved early kick identification, crucial for preventing gas blowouts. Gas ingress scenarios were analysed, focusing on phase interface precision between drilling fluid and gas. Temporal and spatial changes in wellbore flow patterns during gas inrush were discussed, considering rising gas density and solubility effects on flow appearance. The models closely matched experimental results, leading to enhanced understanding of gas kick formation and growth during drilling. The study also highlighted a shift in wellbore composition, with liquid fraction decreasing from 25% to under 9%, and gas void fraction increasing from 75% to over 91%, indicating a transition from liquid to gas dominance.