Single Trip, Vessel Deployed Cut and Retrieval of Wellheads

‍ ‍By Grant Pierce, Intervention Performance Ltd.‍‍ ‍ ‍

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Upon permanent isolation of the reservoir through certified cement plug placement, the final phase of a subsea plug and abandonment (P&A) campaign requires the complete removal of all seabed infrastructure. This includes the subsea wellhead assembly and its associated casing strings, such as 30" conductor, 20" surface casing, 13-3/8" intermediate casing. These must be severed and retrieved to restore the seabed to an unobstructed state. Regulatory bodies across major offshore jurisdictions mandate that all subsea structures be removed to a minimum depth of 10 to 15 feet below the mudline, eliminating hazards to commercial fishing operations and future subsea construction activities.  

Historically, this scope of work required two discrete trips: the first for casing severance and the second for mechanical wellhead retrieval, resulting in high operational costs. These limitations have driven the development of integrated Single-Trip P&A systems, which consolidate both functions into a single tool assembly capable of latching onto the wellhead, severing all internal casing strings, and recovering the entire infrastructure in a single lift. 

Several systems are currently available in the industry to achieve these objectives, each designed as a single-trip cut-and-retrieve solution operable from a vessel, thereby eliminating the need for a drilling rig on location. The primary distinction between these systems lies in their cutting method: either abrasive water jet cutting or hydraulic-powered mechanical cutting. 

Here are the systems listed below: 

  1. Acteon (Claxton) Multi-String Cutting Tool & Multi-Wellhead Retrieval Tool. The MSC is a proven and reliable cutting method that can sever all strings in a single deployment, ranging from 7-inch inner casing to 30-inch. Combined with the multi-wellhead retrieval tool, the ability to perform recovery directly after cutting is possible. 

  2. Baker Hughes Terminator - Mechanical Hercules™ cutter with hydraulic motor, including wellhead connector. Terminator has no depth limitations, a small system footprint, and can be mobilized quickly, and it only requires two personnel to operate. Once the Terminator is deployed subsea, no equipment remains on deck. The cutting time is less than an hour for single cuts and within a few hours for multi-casing cuts. 

  3. James Fisher Decommissioning ICLT - Collaboration with First Subsea has led to the development of a one-component system, Internal Cut and Lift Technology (ICLT), which merges market-leading cutting and lifting tooling, optimized with Ballgrab gripping technology, to provide a simple, flexible, and quick mechanism to remove retired subsea assets and tubulars. ICLT offers a simple solution that streamlines the number of contractors, operations, and personnel required on offshore platform operations. 

  4. Oceaneering Subsea Wellhead Picker - Abrasive Waterjet cutter, Internal Multistring Cutting Tools (IMCT), including wellhead connector. The Subsea Wellhead Picker is a combination of a connector that latches onto the wellhead and the Internal Multistring Cutting Tool (IMCT). The IMCT uses the highly effective Abrasive Waterjet Cutting method to sever all layers of casing in a single pass. It can cut from 7 to 36 inches. 

  5. Sapura Energy Well Services AXE Cutting System - Abrasive Waterjet cutter, Multistring Cutter, including wellhead connector. The AXE uses entrained grit water at 10,000-14,000 psi system pressure as a cutting medium. The standard cutting tool is capable of entering and cutting wellheads with 7-inch or larger casing and severing through multiple casings of 7, 9⅝, 13⅜, 20, and 36 inches in a single pass cut. An optional four-inch cutting tool can provide a solution for smaller-bore applications.