in P&A of
subsea wells
ell abandonment is a crucial and inevitable stage in the life cycle of all wells. While many in the industry have historically viewed decommissioning as an expenditure without financial return, this view is rapidly changing due to progressively stringent regulatory requirements and heightened ESG awareness. The higher operational costs and risk associated with offshore operations makes the permanent abandonment of subsea wells a worthy challenge, especially when the full scope of project logistics, vessel day rates, costs associated with the number of personnel on board and full suite of services is factored in.
As an increasing number of fields reach the end of their productive lives, and countries impose stringent regulations aimed at restoring the seabed to an undisturbed condition, subsea plug and abandonment (P&A) technologies are gaining traction. Time spent on subsea wellhead recovery is often the biggest determinant of the cost of an abandonment campaign, and hence the rightful area of focus for a value hungry industry.
There are two different approaches to well abandonment and wellhead recovery in the subsea environment, and both involve internal cutting of the surface and conductor casings, followed by recovery of the wellhead by internal or external latching.
The newly released second-generation MOST Plus system includes several technologies that improve tool capabilities and performance. This latest release packages a newly designed tension-cut mandrel, nonrotating flexible stabilizer (NRFS), large-diameter cutter and high-angle knives to provide pulling capabilities up to 1 MMlb, and record-breaking rotary cutting depths of 600 m. Deeper cutting depths are achievable by adding a precision mud motor.
The system latches and releases to inspect the cutting knives and confirm the cut without the need for tripping. The external latch protects the internal wellhead sealing profiles from damage, while also providing superior lateral support for the wellhead assembly to eliminate any lateral whipping that might impede cutting. An additional fail-safe feature enables releasing the outside latch by ROV, if required. Swarf buildup is prevented through a design that allows for a much larger flow area within the wellhead (Figures 1 and 2).
in P&A of
subsea wells
ell abandonment is a crucial and inevitable stage in the life cycle of all wells. While many in the industry have historically viewed decommissioning as an expenditure without financial return, this view is rapidly changing due to progressively stringent regulatory requirements and heightened ESG awareness. The higher operational costs and risk associated with offshore operations makes the permanent abandonment of subsea wells a worthy challenge, especially when the full scope of project logistics, vessel day rates, costs associated with the number of personnel on board and full suite of services is factored in.
As an increasing number of fields reach the end of their productive lives, and countries impose stringent regulations aimed at restoring the seabed to an undisturbed condition, subsea plug and abandonment (P&A) technologies are gaining traction. Time spent on subsea wellhead recovery is often the biggest determinant of the cost of an abandonment campaign, and hence the rightful area of focus for a value hungry industry.
There are two different approaches to well abandonment and wellhead recovery in the subsea environment, and both involve internal cutting of the surface and conductor casings, followed by recovery of the wellhead by internal or external latching.
The newly released second-generation MOST Plus system includes several technologies that improve tool capabilities and performance. This latest release packages a newly designed tension-cut mandrel, nonrotating flexible stabilizer (NRFS), large-diameter cutter and high-angle knives to provide pulling capabilities up to 1 MMlb, and record-breaking rotary cutting depths of 600 m. Deeper cutting depths are achievable by adding a precision mud motor.
The system latches and releases to inspect the cutting knives and confirm the cut without the need for tripping. The external latch protects the internal wellhead sealing profiles from damage, while also providing superior lateral support for the wellhead assembly to eliminate any lateral whipping that might impede cutting. An additional fail-safe feature enables releasing the outside latch by ROV, if required. Swarf buildup is prevented through a design that allows for a much larger flow area within the wellhead (Figures 1 and 2).
The MOST Plus system also features a newly developed and propriety NRFS. The flexible stabilizer blades can pass through the wellhead inner diameter (ID) restriction and then expand against the larger ID of the casing to be cut, giving an effective casing range of 18⅝ inches to 22 inches. Once through the wellhead, the NRFS positively engages the ID of the casing, centralizing the cutter assembly and improving performance during casing-cutting operations while the stabilizer blades naturally dampen lateral vibration. The combination of the stabilizer blades with the unique marine bearing eliminates metal-to-metal contact, and lateral vibration significantly reduces damage to the cutter knives, improving cutting performance and saving valuable rig time.
A newly developed large diameter M-24 cutter further reduces the possibility of an eccentric cut. The geometry of this cutter provides additional stabilization, which equates to more efficient cuts and reduced operating times. In addition to the new cutter, new knives have an aggressive high-angle profile that reduces contact area with the conductor casing by more than 25% of standard straight knives and reduces the total amount of material removed from the casing to complete the cut. The knives also include an aggressive two-blade contact cutting geometry and special tungsten carbide inserts to further increase cutting efficiency (Figure 4).
The average cutting time observed with the MOST Plus represents more than a 50% reduction in cutting time compared to traditional techniques used for cutting 18⅝-inch to 36-inch conductors.
Executing abandonment campaigns successfully in a safe, efficient and environmentally prudent manner is critical to the reputation of the service provider and operator alike.
The MOST system provides a resource for subsea well abandonment that saves a significant amount of rig time. It cuts and recovers the wellhead and multiple casing strings quickly and reliably in a single trip, minimizing operational risk, reducing rig time and overall operating costs.
The MOST Plus system demonstrated its operational effectiveness with reduced cutting times compared to traditional cut-and-pull operations, even in large heavy-wall conductors. The breakthrough design of the NRFS and large-diameter cutter increases stabilization and minimizes vibration during cutting. The reduced surface vibration eliminates the need for derrick inspections after the cutting operation, saving several hours of valuable rig time compared to traditional cut-and-pull operations.
The average cutting time observed with the MOST Plus represents more than a 50% reduction in cutting time compared to traditional techniques used for cutting 18⅝-inch to 36-inch conductors.
Executing abandonment campaigns successfully in a safe, efficient and environmentally prudent manner is critical to the reputation of the service provider and operator alike.
The MOST system provides a resource for subsea well abandonment that saves a significant amount of rig time. It cuts and recovers the wellhead and multiple casing strings quickly and reliably in a single trip, minimizing operational risk, reducing rig time and overall operating costs.