Pressurized Mud Cap Drilling Used to Drill and Complete Carbonate Gas Reservoir with Poor Injectivity and Severe Dynamic Losses Offshore Malaysia

Abstract

This paper describes how PMCD with an overbalanced drilling mud, instead of Light Annular Mud, was used to successfully drill and complete a well in gas bearing carbonates offshore Malaysia. This unconventional approach was adopted after encountering poor formation injectivity and severe dynamic losses in the 8-1/2″ reservoir section.

Dynamic losses of 700 bbl/hr were encountered after drilling into the carbonate formation, but the subsequent injectivity test surface pressure prevented the well being converted to PMCD with LAM. LCM pills were spotted and the mud weight was cut by 0.2 ppg but severe dynamic losses continued. An injectivity test was performed with seawater and the surface pressure stabilized around 500 psi. Drilling resumed with overbalanced drilling mud in the annulus, which was top filled during connections to keep the hole full and to monitor the annulus with a nominal surface pressure, while seawater was pumped down the string.

After reaching TD, the drilling BHA was retrieved to surface and the 7″ lower completion was run in hole while the well continued to take around 50 bbl/hr static losses. When the lower completion entered the open hole, PMCD was activated to run in and set the liner hanger.

This method of unconventional PMCD may be implemented to successfully drill through carbonates with poor injectivity and severe dynamic losses, thereby improving the safety and efficiency of the drilling operations compared to conventional or floating mud cap drilling.