Perforating Using MPD Techniques: Design and Execution

Abstract

An appraisal well was drilled in Brazilian pre-salt area using overbalance drilling fluid, with conventional techniques. While drilling reservoir (in a 12 1/4" phase), total losses were found. Unsuccessful attempts with LCM and cement pills revealed that only MPD/PMCD techniques could deliver the well to TD. It was decided to anticipate the installation of the 9 5/8" casing, covering only the upper portion of the reservoir, and well was suspended. The remaining reservoir could be drilled later with a rig equipped with MPD system. This well was designed as a 2-zones intelligent completion in cased hole configuration. Due to the fluid losses a new design had to be considered. Due to reservoir uncertainties, definition on the separation between zones would only be taken after drilling the remaining reservoir section. To overcome this challenge without adding time and complexity to the overall design, the best solution was to perforate the cased hole section after drilling the remaining section, meaning doing it with reservoir communicated to the wellbore and in PMCD mode. Several options were evaluated to design the TCP operation in PMCD. Well control strategies, contingencies, thermal effects, and dynamic shocks were considered. The solution consisted in running the TCP with a closed string, without NRVs and having robust contingencies in case of washout or drillpipe failure after perforating. The well was drilled, and total fluid losses occurred again. It was then successfully perforated still in PMCD, then lower and upper completion were installed. Despite these challenges, this was the fastest intelligent completion in all Petrobras pre-salt fields so far.