Case Study: Utilization of a Hydraulic Workover Unit to Recover Highly Corroded 35 Years Old Dual String Tubing Completion with Dual Tubing and Dual Annulus Valve in Mahakam Offshore

Abstract

An operator has been significantly performing re-entry well drilling to increase operational efficiency. Therefore, a temporary abandonment campaign is critical to successfully achieving the objective of providing a well slot for the upcoming drilling program. Abandonment work has high uncertainties that require more time to prepare and to solve the possible situation in the work progress itself. Particularly in the old wells where the tubing completion has been installed for 35 years with limited sources of preliminary information or reference. Hence the operator has been utilizing a hydraulic workover unit (HWU) to perform an abandonment campaign in the offshore field. This paper presented a case study of multiple wells abandonment of which an HWU is operated. The well was completed with dual string production tubing with dual tubing and dual annulus valves in 1987. Highly corroded tubing and difficulties to recover the existing tubing and annulus valves have been the challenges identified before the campaign began. Moreover, the history record of each well was limited has become additional challenge to start the project. Evaluating the tubing conditions, and preparing HWU with Blow Out Preventer (BOP) and related equipment such as tubing cutters and fishing tools are essential parts of this campaign. Besides, collaboration work with the drilling team for designing the most accurate cutting depth and developing the abandonment program is crucial to abandon the well safely and efficiently. Finally, the abandonment campaign was successful with zero incidents allowing the drilling team to conduct the operation in the drilling re-entry wells campaign.