Key Considerations in the Design and Execution of Extension Packs or Frac Packs When in the Proximity to a Main Thrust Fault

Abstract

Devotion of quality time, effort, and dedicated resources during the planning phase of frac or extension packed wells and establishing a clear communication path to a collaborative execution, will ensure the achievement of a successful stimulation with a reliable sand control. These diligent planning efforts become more crucial when faced with challenging thrust fault environments which can adversely affect the outcome of a frac or extension packs. Thrust faults traversing a target reservoir needs to be carefully evaluated for activation or uncontrollable fluid loss during the frac pack process to ensure adequate mitigation can be implemented for a successful job. This paper illustrates the systematic approach used to optimize sand control and productivity for a deepwater well including the following challenges that were encountered: TCP overbalance concerns, brine density, and the need to manage potential high fluid losses in a depleted zone (hydrostatic pressure less than 80 psi below estimated fracture pressure). Fracpack was designed without any frac length constraint. Gel concentration, pad volume and pump rate were maximized to manage low fluid efficiency. The job was pumped as per design with hard screenout at nominal rate, 70% of proppant placed behind casing and good annular pack. The well in question was an oil producer which was drilled with the wellbore crossing the main thrust fault at the reservoir level. It was drilled with no wellbore stability issues reported. The sand-face completion presented major challenges as summarized below. Lower Zone: short perforation interval that was 25 ft above the OWC and less than 80 ft away from the main thrust fault. Middle Zone: depleted sands with the main thrust fault crossing the wellbore few feet above the top perforation (top of the reservoir sand). Upper Zone: thrust fault was less than 90 ft away from the wellbore.