When performing a slot recovery or a well abandonment, the casing can frequently be difficult to pull. This could be due to scale, barite buildup, or cement stringers. Other considerations are the limitations of the rig and its ability to apply the force needed to pull a long string of casing. Removing stuck or lengthy sections of casing typically requires multiple cut-and-pull attempts as well as high-capacity rigs capable of pulling high loads, resulting in increased costs and potentially nonproductive time (NPT) and associated HSE risks.
An alternate method that uses a downhole hydraulic pulling assembly enables operations to overcome these limitations and increase efficiencies. The hydraulic-activated assembly uses a pressure differential to anchor into the casing above the section to be removed while pulling as much as 1.8 million pounds through a casing spear that is engaged in the cut section. The pulling force is focused between two downhole anchor points, isolating the high loads from the derrick. This isolation protects the derrick and drillstring from upward drill pipe movement if the casing releases abruptly.
Recent operations have proven the successful retrieval of casing in multiple offshore applications. When attempting to pull 9⅝-in. casing, the rig was limited to 570,000 pounds over-pull, which was insufficient to retrieve the stuck casing string. The hydraulic pulling assembly was set in the 13⅜-in. parent casing and pulled the casing free with 1.2 million pounds of over-pull. The operation was completed in one run, eliminating multiple cut-and-pull attempts. The time saved reduced operational expenses by USD 450,000. The system has also been used to pull 13⅜-in. casing from inside 18⅝-in. casing, and has been used on fixed and floating platforms.
Deploying the hydraulic pulling assembly in cut-and-pull operations provides customers the ability to use lower-capacity rigs in plug-and-abandonment (P&A) operations and to safely pull loads up to 1.8 million pounds because the forces are confined downhole. Using specialized equipment to ensure successful cut-and-pull attempts enables safer jobs and provides a more cost-effective abandonment operation.