Industry First Subsea Reentry Multilateral Wells: Case Study

To rapidly increase production from the Goliat Field without adding costly subsea equipment and infrastructure or mobilizing a high-end subsea construction vessel, an operator transformed two single-bore subsea wells into multilateral producers with independently controlled branches. A multidisciplinary team was assigned to perform a feasibility study for the introduction of multilateral wells. Work started with a reservoir geomechanics/wellbore stability review, based on which well construction/completion basis of design was made. The design and operations sequence were analyzed by a well engineering team. As a result, the main risks, uncertainties, and assumptions were clarified. Two candidate wells were identified, and then a multidisciplinary team was assigned to manage the project, finalize design, initiate procurement, and write procedures. Workshop preparation was closely monitored and reported on a weekly basis. The onshore team closely followed up and supported operational execution. The new laterals were added to the existing wells, and multilateral junctions were installed and tested. An intelligent completion was installed, and independent branch production started. In addition, the estimated reduction in generation of CO2 is estimated to be between 10 to 20 thousand metric tons per well as compared with drilling two new subsea wells and installing the associated infrastructure. The technology enables an exploration and production (E&P) company to introduce subsea reentry multilateral technology to increase production while minimizing costs. The process includes well candidate identification, planning, and execution. This practical example can be used for future reference by drilling and production-focused petroleum industry professionals to better understand the benefits and limitations of existing technologies.