Implementation of Top-Hole Collision Risk Management for Drilling a Well with a Separation Factor Below 1.0 in a Dense Fixed Platform: A Success Story from Offshore North West Java, Indonesia

Abstract This paper introduces a risk management strategy for a drilling campaign with a high collision risk. ELG-X was drilled from an existing platform, necessitating the wellpath to pass within close proximity of an adjacent well with an SF of 0.79. An SF below 1 poses a risk of collision due to overlapping Ellipsoid of Uncertainty (EoU), jeopardizing drilling and company's business plan. Hence, effective mitigation and directional planning were crucial for safe well execution. A comprehensive risk mitigation strategy was developed to manage adverse consequences to an acceptable risk level, encompassing two primary activities during the drilling process. Firstly, the 12-1/4" pilot hole, typically employed for shallow gas risk mitigation, was endorsed in this case to reduce the likelihood of hole contact in the top-hole interval, with engineering mitigations including GWD utilization, high bend-degree mud motor application, passive rock bit employment, subject & adjacent well monitoring, and well integrity placement. Secondly, the 17-1/2" hole enlargement process involved maintaining drilling parameters and employing a less aggressive hole opener to prevent damage to the adjacent well. The developed strategy was implemented during drilling in the top-hole section. The 12-1/4" rock bit, paired with a 1.83-degree bend mud motor, was utilized for controlled drilling in the collision risk interval, allowing for precision and effective maneuvering. By applying control parameters and tight survey monitoring per joint drilled, the result shows that no major indications of well collision were observed. ELG-X trajectory convincingly separated away from the adjacent well and got SF above 1. The mud motor's bend degree was subsequently adjusted to 1.5-degree, facilitating the continuation of drilling toward the casing point in alignment with the planned trajectory. Positive signs were also noted during the 17-1/2" hole enlargement, with no significant evidence of well collision or damage to the adjacent wellbore. The upcoming operations, such as running 13-3/8" casing and cementing, can be managed properly without encountering any issue or findings. In summary, the top-hole section can be secured without any safety incidents and related NPT. This paper details the implementation of a collision mitigation strategy in the ELG-X well, Offshore North West Java Operation, serving as a valuable reference for future drilling. It showcases a successful case of top-hole drilling in a dense fixed platform with a minimum SF. The strategy is anticipated to provide insights for unlocking idle wells facing similar challenges as ELG-X.