Well Interception to Plug and Abandonment of Inaccessible Wellbore

Abstract An operator in the State of Western Australia (WA) needed to decommission a legacy production well to comply with State regulations and allow for future repurposing of the field for produced water disposal. For one specific well where direct access to the wellbore was unavailable, an intercept well was drilled to carry out the Plug & Abandonment (P&A) operation. Since a precise interception was needed to install well barriers above reservoir depth, a fit-for-purpose survey and ranging program was developed to achieve the interception well objectives. The survey and ranging program were a combination of advanced wellbore survey processing, continuous Passive Magnetic Ranging (PMR) and Active Magnetic Ranging (AMR). PMR operates by estimating the magnetic field naturally generated by the steel casing within the original wellbore. Unlike AMR, which requires the active generation of a magnetic field, PMR leverages the intrinsic magnetic properties of the well's steel casing. The strength of the magnetic field detected by the magnetometers decreases with distance from the source. By measuring the three-axis magnitudes of the magnetic field at different points as the drill string moves, the system can estimate the distance to the nearby well. The direction to the nearby casing or fish is calculated based on the orientation of the magnetic interference field lines detected by the magnetometers. Multiple measurements are taken from different positions as the tool moves. By combining these measurements, the system can estimate the direction and orientation of the nearby casing or fish relative to the drilling tool. The combination of PMR and AMR techniques resulted in successful interception on the first attempt and ensured that the original well was securely plugged and abandoned in compliance with the State's regulations. Both PMR and AMR techniques played crucial roles in achieving a precise interception of the original wellbore. The successful application of PMR allowed for the elimination of multiple AMR runs, resulting in significant rig time savings. Traditional AMR available at the time of the project required the Bottom Hole Assembly (BHA) to be pulled out of the hole to be able to run the wireline AMR tool. While the PMR tool is part of the BHA and ranging is done continuously while drilling and rotating the drill-string. The successful correlation of continuous PMR with AMR data reinforced the reliability of PMR, which can be confidently used in other applications such as anti-collision applications, where PMR alone is typically sufficient, or as an auxiliary method for drilling relief wells, where combination of active and passive ranging techniques is typically advised. This is the first deployment of next generation measurement-while-drilling technology to perform continuous PMR while drilling and rotating to successfully intercept the target well and complete the P&A operation. The successful correlation of PMR with AMR data reinforced the importance of continuous PMR, which can be applied in other applications such as well collision avoidance applications or relief wells.