A New Treatment Increases the Fracture Gradient to Cure Lost Circulation and Control a Flowing HPHT Well in the East Mediterranean Sea

摘要

This paper addresses a well-control issue in a challenging highpressure/high temperature (HPHT) exploration well where apossible underground crossflow was in progress and the wellwas losing oil-based mud before reaching the final targetdepth below 15,000 ft (4572 m). Several days were spenttrying to control the well using various formation-sealingtreatment systems (some conventional and others new), butwith no success. Eventually a new wellbore pressurecontainment improvement system (WPCIS) was implemented,and it controlled the losses effectively. Full circulation wasthen re-established to overbalance the HP zone and kill thewell. The well had been losing at an equivalent circulatingdensity (ECD) of 16.4 lb/gal. Application of the WPCISprocess improved the wellbore pressure containment (WPC)side of the mud weight window, also called the fracturegradient (FG), to sustain an equivalent of 17.0 lb/gal mud asmeasured by a formation integrity test (FIT). This remarkableWPC and apparent FG improvement was achieved along withseveral other cost-saving factors.Upon re-entry of the well seven months after thesuccessful WPCIS treatment, the seal in the exit zone(s) wasstill holding against pressure of more than 12,000 psi andtemperatures of 300°F. This sustained WPC seal by theWPCIS saved even more cost and enabled a liner to be setwithout losses for a successful completion of the well.As a followup to previous discussions,1 this paper furtherdescribes the WPCIS process and its applicability and thendemonstrates how the system can help optimize well plans,leading to lower costs for drilling fluids, casing design,cementing, and completion equipment. A post-treatment studyis also included to help explain how the WPCIS sealingmechanism shut off the HPHT flow into the exit zone andincreased the near-wellbore FG.