Deepwater HPHT Drilling through Ultra Narrow PPFG Window: A Case Study by ENI Where the Combination of Continuous Circulation Technology Together with MPD Drilling has been Successfully Applied to Extreme Drilling Environment Condition in HPHT Ultra Deepwater Well

Abstract

Ultra Deepwater wells are commonly characterized by a narrow margin between pore and fracture gradients. Eni pioneer of the Continuous circulation technique has pushed the control of annulus dynamic pressure to the limit. The experience presented in this paper cover the drilling of an HPHT Deepwater well, through an ultra narrow PPFG window by means of technology application and strict procedural control. In the case study presented the reservoir section of an HPHT well was planned to be reached with an adequate kick tolerance and choke margin by applying the ENI near balance drilling technique (e-nbd™) in order to ensure strict control on the primary barrier and achieving the aimed operational and safety performance. The plan required the use of e-cd™ (eni circulating devices) system installed for the first time on a drilling ship with the 6 5/8″ DPs.