Malaysia's First Use of Subsea Release Plug System for Dual Barrier Offline Cementing (DBOC) Across Hydrocarbon Section Helps Streamline Activities
Authors: Kamaludin Ashikin , M Ariffin M Syafiq , Chee Hen Lau , Kishore Kumar Avinash , Noh Aizat 
Published: February 2023

Completing primary cementing operations under the rig floor (also known as offline cementing) instead of conventional cementing is an emerging approach that continues to gain industry interest. This is because of the opportunity this method presents for reducing operational flat time and optimizing rig use, resulting in significant cost savings.

It is essential to relate the concept of offline cementing with regards to hydrocarbons (HCs) presence in the formation. Offline cementing is a straightforward method when there are no HCs present in the wellbore and when the pore pressure is at hydrostatic. A single barrier in the form of overbalance mud weight is acceptable for this condition. However, when HCs are present and/or over-pressured formation, a dual barrier (mechanical and Kill Weight Mud, KWM) is necessary to help prevent uncontrolled influx from the borehole to the external environment. During the Malaysian operation discussed here, this barrier requirement was also essential to local regulatory procedures and guidelines for upstream activities as well as the operating company's technical standard for well barriers and integrity. Thus, two well barriers were required during all well activities and operations.

A dual barrier offline cementing (DBOC) system with special application of Treating Iron Works Valves (TIW Valves) and a Subsea Release (SSR) plug set was constructed to enable offline cementing within the HC section. This concept not only allowed cementing job to be executed, but at the same time allows other offline drilling activities, such as surface equipment rig-up, pressure testing lines, pre-job circulation, and cementing operations to be done while at the same time maintaining the two-barrier requirement while the blowout preventer (BOP) is removed.

A new set of challenges were encountered while completing offline cementing across a HC section. Because the environment for placing a competent cement slurry was not optimal, the quality of the wellbore seal could have potentially been affected. Thus, a tailored job procedure coupled with continuous engagement between the operating company, service partners and rig owner (through joint risk-assessment sessions) established alignment and suitability of individual operations. The cement slurry design was carefully tailored, and a detailed computer aided simulation was performed to help ensure cementing operations could be accomplished without compromising operational objectives. As a result, the DBOC concept was successfully implemented for the first time in Malaysia across three highly deviated development wells, thus streamlining cementing activities.

A recent collaboration in a major Malaysian National Oil Company (NOC) is highlighted, discussing the materialization of unconventional offline cementing objectives across a HC section in a challenging wellbore environment while minimizing rig time and maintaining safety standards. Various challenges encountered are discussed with the intention of sharing information and industry lessons learned. The application of the DBOC system could be a game-changer, offering significant variation from the conventional rig floor cementing currently being practiced.