Drill Out Long Interval Hard Cement and Metal Plug Using Coiled Tubing at Sidetracked Well: Lesson Learned from Mahakam Offshore Campaign, Indonesia

Objectives/Scope With the current mature production environment, massive drilling campaign is subject for cost efficiency to unlock marginal reserve in Mahakam Offshore Field which also lead to unexpected problem and restrict the production of the well, such as under displace problem during cementing job which result cement presence inside production tubing. A rigless intervention job such as drill out cement operation is required to regain access from restriction and unlock well potential. Method, Procedures, Process The decision to utilize coiled tubing for cement removal was driven by its ability to offer small equipment footprint & cheaper drill out cement cost from snubbing or electricline. Maximum coiled tubing yield strength (up to 53,000 lbs) and circulating pressure (up to 4,500 psi) will limit the pumping rate that can be applied, thus it will be the challenge to reach critical annular velocity for lifting cuttings so periodical long sweep need to be done. The simulation shows maximum net of WOB that can be applied to bit around 3881 lb, to compensate low WOB it is proposed to gradually increase the flow rate until got optimum ROP. Results, Observations, Conclusions The operation used cement mills, such as turbo scale mills and junk metal muncher mills, to clear wellbore access until float collar depth. Mill bit several times got stopped at downhole safety valve depth and needed to be pumped to be able to pass through without damaging the downhole valve. Mill bit inspection result after the operation shows the rubber of the stator got damaged and plugged the bit nozzle, thus, decreasing the rate of penetration. High pulling weight occurred frequently due to annular velocity not being achieved and cuttings locked up at the tangential section, thus, many long sweep is needed and prolong the operation. The drill-out operation of approximately 2,200 ft of hard cement and metal plug using coiled tubing was successfully done with a cost of about 500,000 USD and a duration of 24 days, with a production gain of 11 million cubic feet gas per day and 800 barrels of condensate per day. The successful of pilot well, the engineering review and the implementation of specific mitigation strategies set a strong foundation for considering the very shallow reservoir as a development target and industrialized. This determination can be solidified by evaluating the results from multiple trial campaigns to give solid safe conclusion in producing very shallow reservoir with robust and comprehensive data.