Improved Magnetic Ranging Tool–Assisted Milling for Wells with Casing Deformation and Misalignment: A Case Study in Mature Oil Fields

Summary In this paper, we introduce an integrated system that combines magnetic ranging and milling technology for wells with casing deformation and misalignment. Many mature oil fields, such as Saudi Arabia’s Ghawar Field and the North Sea Field, have entered a decline stage. Extended exposure to perforations, fluid corrosion, and formation movement has led to various forms of casing deformation and misalignment. These issues disrupt the original well networks and allow oil and water to migrate through the broken casings into upper formations or even to the surface, significantly impacting water injection development. Conventional methods for sustaining stable production in mature oil fields, such as direct cement squeezing at the casing breakpoint, often fail to achieve satisfactory sealing results. Additionally, techniques like casing pulling or well repair operations are costly and can lead to more complex downhole accidents. Therefore, there is an urgent need for more efficient disposal methods to address the challenges of abandoning and disposing of old wells with deformed casings and reconstructing well networks in mature oil fields. The system uses improved magnetic ranging tools (IMRTs), specifically the IMRT combined with measurement while drilling (MWD), to determine the direction and distance of the misaligned casing firstly. The directional drilling (DD) assembly then adjusts the trajectory in real time, guided by MWD data, to avoid misalignment points and casing joints. The drill bits connect to the lower intact casing at a minimal entry angle. After successful connection, tools such as reamers or milling cones are used to grind and create a window in the casing. Smaller drill pipes or coiled tubing are subsequently deployed to re-enter the lower casing, with continuous MWD monitoring to ensure precise alignment during re-entry. Once extended into the caprock, cement is injected under pressure, and the well is shut in for sealing. The application of this system demonstrates its effectiveness, achieving long-distance accompaniment and multiple connections, with the results verified using downhole monitoring. Cement squeezing was performed according to the established procedure, and the entire block saw a production recovery of 4 tons/d. The IMRT-assisted milling system offers a novel solution to enhance well network reconstruction and ensure sustainable production in mature oil fields.