Increasing Reliability of Cutting/Pulling Casing in a Single Trip

Abstract This paper discusses the tools, technology and methods developed to significantly reduce pipe cutting and recovery time in subsea plug and abandonment operations and in the slot recovery program for existing platforms. Conventional apparatuses and techniques for cutting and extracting well casing involve multiple trips downhole to run and retrieve the cutting and spearing equipment, because the required tools do not function cooperatively. In certain slot recovery operations, cutting and pulling the casing may be difficult due to firm cement bond, barite settling from drilling fluid in the annulus, or both. Accordingly, such slot recovery operations require cutting the casing several times to locate a friction free point for safe extraction of the severed casing resulting in multiple trips. The authors describe a recently developed pipe cutting system with multiple sets of cutters which can be selectively activated while the tool is downhole. When one set of cutters wears down, a replacement set can be selectively activated to resume cutting actions. The tool currently has three sets of cutters; however more sets can be added. Also, each set of cutters feature knives dressed with novel inserts made from a specially formulated compound which extends cutter life. Each set has a positive knife return mechanism to ensure full collapse. The tool also enables pressure to be monitored from the surface by means of an indicator device, which registers a pressure drop at the rig floor to indicate a cut has been completed. Additionally, the spearing device can be run in the same drill string and selectively activated to retrieve casing after it is severed. North Sea field runs involving slot recovery programs in which operators faced stuck casing that required several cuts to locate a free point will be outlined to document tool success. The pipe cutting system performed successfully in all cases thus validating the objective of allowing multiple cuts in the casing and minimizing the number of trips required for casing cutting and recovery operation.