Angsi field in Malaysia consists of 5 (five) production platforms and has long provided the backbone of domestic oil and gas production for PETRONAS in Malaysia. Located in the Malay Basin, about 167 kilometers off the East Coast of Peninsular Malaysia in a water depth of 70 m, Angsi is a joint venture development field between PETRONAS and ExxonMobil Exploration & Production Malaysia (EMPMI), with PETRONAS as the operator.
Angsi ERD AST-2 (not actual well name) is an Extended Reach Drilling (ERD) well of 2.7 ERD ratio, one of the three (3) successful wells drilled in the un-drained area of Angsi E under the Angsi Early Monetization Project Phase 1.0. Previously, the well experienced two (2) stuck pipe incidents which resulted in lost in hole (LIH) in both the original 8-1/2" hole (ERD A) and the sidetrack hole (ERD AST-1) at the similar true vertical depth (TVD) which was due to wellbore instability issues. Deviation from the original plan by utilizing the Managed Pressure Drilling (MPD) application and adopting best bottome hole assembly (BHA) selection strategy in the final hole (ERD AST-2) has turned these failures into success. Target well total depth (TD) was achieved and the liner was cemented in MPD mode with minimal issues.
In the process of drilling this ERD well, the extended reach and highly deviated production hole section carry drilling risks, complexities, and operational challenges which relate to wellbore instability, high torque and drag, poor hole cleaning, cutting bed formation, differential sticking, and also excessive equivalent circulation density (ECD). Reservoir depletion had led to changes in rock stress and a reduction in pore pressure, creating more complications such as wellbore stability and ECD management. The consequences of not utilizing MPD will create a huge potential risk associated with stuck pipe, lost hole sections and failure to complete the well.
Managed Pressure Drilling was introduced to control cyclical fatigue forces by maintaining the bottom hole pressure (BHP) constant across the weak formations and use the ability to drill with low mud weight in order to reach higher flow rates and as a consequence, improve hole cleaning. The drilling mud weight (MW) was designed to be 2 ppg below the mechanical stability point and the ECD was maintained within a window of 0.3 ppg during the entire drilling and tripping operations. Scheduled MPD rollovers from light to a heavy and heavy to a light MW at the shoe were carefully followed in order to maintain ECD within the pre-established window prior to pulling the BHA out the hole or changing rotating control device (RCD) sealing element.
This paper aims to describe the application of Automated MPD for this specific ERD case from conceptual, planning to execution. Moreover, it is intended to share the challenges observed during the execution phase as well as the decisions taken to overcome these challenges and share the strategy of ensuring the wellbore being stable prior to POOH and proceed with MPD liner running and cementing.