Open-Hole Well Interception and Re-Entry Application of Inaccessible Wellbore Utilizing Active Acoustic Ranging

Abstract An operator needed to gain access to the plugged old vertical well for re-plugging at a deeper interval to avoid aquifer sand exposure to the formation that is to be completed in the upcoming lateral wells. This paper presents a case study of the first deployment of active acoustic ranging (AAR) as a sole ranging technology to perform interception and re-entry of the target well to complete the plug and abandon (P&A) operation. The focus is on the application and limitations of the AAR method, with a discussion of the planning and execution of the jobs. After unsuccessful attempts to drill out the original plug and blindly intersect the well below the plug by sidetracking from above it, the operator decided to proceed with AAR—one of the few methods available that doesn't require access to the original well. For example, other magnetic ranging methods require either access to the original well for source installation (e.g., solenoid) or need the well to be cased to serve as a reflector for electromagnetic waves. AAR was used in two separate intercept jobs with similar complexity. In one case, the intercept was successful, while in the other, the well was not intercepted. In the thefirst job, AAR detected the target open wellbore at a bearing of northeast 30–40° and a distance of 7–11 ft. Drilling targets were established, accounting for the uncertainty of the AAR results and the wellbore positioning uncertainty. A cement plug was set at a shallow depth in the mapping wellbore. Then, the intercept side-track wellbore was initiated from the cement plug, and the target well was successfully intercepted. The second job, where the exact workflow established previously was strictly followed, was unsuccessful despite two attempts, the second from an additional mapping hole to verify the target’s position. The challenges included the method's limitation to range only very short distances and the difficulty of targeting very narrow objects. For the future project, it was recommended to use rotary steerable systems with at-bit sensors instead of a motor for better trajectory control. At the time of writing this article, another successful job had been completed, further increasing the demonstrated success rate of such operations. However, this paper will not discuss the third job. The method enables access-independent open-hole intercepts, including applications in relief well drilling. The findings provide insights into the operational constraints of AAR and offer recommendations for optimizing future intercept operations.