Managing Well Collision Risk by Disruptive Ranging Technology Without Impacting Rig Time
Authors: ElGizawy M. , Rakhmangulov R. , Allen W. , Sanders J. E. , Arroyo A. C. , Nunes T. Q. , Prats F. C. , Lowdon R. 
Published: September 2024

Drilling a surface section from an offshore platform or a multi-well pad has an increased risk of well collision due to the close proximity of the nearby offset wells. Managing well collision risk is a high priority during well construction. It is currently performed by taking stationary surveys and projecting ahead of the bit to calculate the minimum allowable separation distance MASD from the offset well to allow the well to be drilled ahead safely. It does not, however, have any means to confirm the distance and direction of the offset well. This paper presents a continuous passive magnetic ranging technique that can provide a real-time distance and direction to the offset well while drilling without interrupting the drilling operation.

The new ranging technique uses the definitive dynamic surveys (DDS) from a rotating measurement-while-drilling MWD tool which operates without need to stop for a stationary survey for ranging. These DDS surveys are sent to surface every few minutes providing a high-density survey log. It utilizes measurements from magnetometers and accelerometers to detect external magnetic interference from the offset well casing. The data is then analyzed while drilling to determine the distance and direction between the drilling well and the offset well. Passive magnetic ranging has been around for years however it has not been fully utilized by the industry due to the need to stop frequently and take a ranging shot that consists of 15 of more stationary surveys. This had a considerable impact on the rig time, often with an increased risk of washout and stuck pipe. The novel definitive dynamic surveys used with passive magnetic ranging techniques can monitor the offset well distance and direction while drilling without the requirement for stationary ranging shots.

The presented case study is from a well drilled offshore in deep water. The collision risk was managed by anti-collision rules, and the definitive dynamic surveys passive magnetic ranging was utilized as an additional layer of protection to monitor for the offset well while drilling. The closet anticipated distance as per the plan was 41ft and had a maximum allowable deviation from the plan of 10 ft. Results show a successful detection and determination of the offset well distance and direction while drilling and without impacting rig time. A total of 16 ranging shots were confirmed with the largest detected distance of 72 ft and closest distance of 41 ft from the offset well. The results closely matched the planned anti-collision scan based on both wells surveys and surface coordinates.

The innovative ranging technique presented has been proven as a practical well collision avoidance tool while drilling. This technique has applications in other drilling activities, such as well interception, and well twinning. This case study highlights a novel new collision avoidance technique which allows an offset well to be ranged to continuously while drilling. This enables the approach and deviation from an offset well to be continuously monitored to ensure a safe and efficient well delivery.