Riserless Cementing System for Subsea Well Abandonment
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Solution Overview
Problem
Conventional riserless subsea well abandonment operations are costly and time-consuming, requiring semi-submersible drilling vessels and extensive equipment, typically taking seven to ten days per well.
Innovation Solution
A cementing system involving a packer and pressure control assembly is used to set a lower cementing tool against the subsea wellhead, with an upper cementing tool perforating the casing and pumping cement slurry through perforations to seal the annulus between casings, allowing for efficient cementing without a riser.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional riserless subsea well abandonment operations are performed using semi-submersible drilling vessels and extensive equipment, then the well can be abandoned and sealed, but the operation becomes costly and time-consuming, typically taking seven to ten days per well
Solution Approach 1:
The abandonment operation is divided into distinct functional modules: a lower cementing tool with packer for sealing, an upper cementing tool for cement placement, and a perforating gun for creating access holes. These segmented components can be deployed and operated independently, reducing overall operation time while maintaining sealing reliability
Solution Approach 2:
The wellhead is pre-equipped with a polished bore receptacle and pressure control assembly before the abandonment operation begins. This preliminary preparation eliminates the need to install complex equipment during the abandonment process, significantly reducing operation duration from 7-10 days to a much shorter timeframe
2Reliability
If conventional riserless subsea well abandonment operations are performed using semi-submersible drilling vessels and extensive equipment, then the well can be abandoned and sealed, but the operation becomes costly
Solution Approach 1:
The invention extracts and eliminates the need for expensive semi-submersible drilling vessels and extensive support equipment by using a simplified subsea wellhead system with integrated cementing and perforating tools that can be deployed from smaller, more economical vessels
Solution Approach 2:
The subsea wellhead system is designed with multi-functional components: the pressure control assembly can accommodate both cementing tools and perforating guns, and the polished bore receptacle serves multiple purposes in the abandonment process. This universality reduces the need for specialized expensive equipment
3Reliability
If a packer is set against the subsea wellhead with cementing tools to seal the annulus, then the sealing effectiveness is improved, but the device complexity increases
Solution Approach 1:
The cementing tools are designed to nest within the subsea wellhead structure. The lower cementing tool with packer nests in the lower portion, while the upper cementing tool nests in the upper portion. This nested arrangement achieves effective annulus sealing without requiring complex external support structures
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This method reduces the time and cost of well abandonment by enabling riserless operations, facilitating faster and more economical sealing of the well annuli using a subsea wellhead system.
Implementation Method 1
a packer (37) connected to the PBR (36) and operable to seal against a bore (6c) of the inner casing (6)
Implementation Method 2
a perforating gun (93, 94) connected to the hanger (91) and having an igniter (100) and a shaped charge (103)
Implementation Method 3
The cementing plug drives the cement slurry through the perforations below the packer and into an inner annulus formed between the inner casing and the outer casing
Data Source
AI summary
A method for abandonment of a subsea well includes: setting a packer of a lower cementing tool against a bore of an inner casing at a location adjacent to an outer casing; fastening a pressure control assembly (PCA) to the subsea wellhead; hanging an upper cementing tool from the PCA and stabbing the upper cementing tool into a polished bore receptacle of the lower cementing tool; perforating a wall of the inner casing below the packer; perforating the inner casing wall above the packer by operating a perforator of the upper cementing tool; and pumping cement slurry followed by a release plug through bores of the cementing tools. The release plug engages and launches a cementing plug from the lower cementing tool. The cementing plug drives the cement slurry through the perforations below the packer and into an inner annulus formed between the inner casing and the outer casing.