Mitigation of Multiple Fractures from Deviated Wellbores

Abstract

Abstract While over six hundred Kuparuk A Sand wells have been hy-draulically fractured or re-fractured successfully from deviated wellbores, a number of wells in the field have not responded to the conventional fracture treatments. In these wells, the conventional design resulted in premature, near-wellbore screenouts, with low proppant placement, and consequently, poor productivity. A symptom common to each of the failed treatments was a near-wellbore friction pressure loss too high to be explained by perforation restriction or simple fracture twisting and turning. An extensive analytical study of hydraulic fracture initiation and propagation from deviated wellbores suggested multiple fractures as a mechanism to account for the abnormally high near-wellbore friction pressure loss and the reduction in fracture width, A model was developed (XFRAC) which correlates these responses to formation stress, wellbore parameters and treatment conditions. A counter-intuitive fracture treatment which employed lower pumping rates combined with higher viscosity fracturing fluids was designed to minimize the formation of multiple fractures and increase fracture width. This unconventional design has been successfully pumped in eleven wells which exhibited the premature screenout problem. Proppant placement was increased over ten fold with a tripling of post-frac production rates and a 35 percent increase in estimated recovery.