Subsea Well Capping System Using Precharged Hydraulic Accumulators
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Solution Overview
Problem
Existing methods for capping a subsea wellbore with a failed blowout preventer (BOP) are slow and risky, often requiring another mobile offshore drilling unit (MODU) and relying on remotely operated vehicles (ROVs) with limited flow capacity, leading to potential environmental damage and safety hazards due to uncontrolled fluid discharge.
Innovation Solution
A replacement blowout preventer system is lowered into the water from a vessel, equipped with a hydraulic pressure source to actuate well closure elements, allowing for rapid operation and deployment without the need for another MODU, using precharged pressure accumulators to reduce reliance on surface control signals and fluid pumps.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If another MODU is deployed to cap the failed wellbore, then the wellbore can be capped, but the time required and risk of uncontrolled fluid discharge increase
Solution Approach 1:
The patent introduces a remotely operated vehicle (ROV) as an intermediary device to deploy and operate the capping device on the failed wellbore. This intermediary approach eliminates the need to deploy another MODU while maintaining reliable well capping capability. The ROV can position and operate the capping device remotely, significantly reducing deployment time and associated risks.
2Reliability
If fluid pumps on ROV are used to operate hydraulic actuators, then the wellbore can be closed, but the limited flow capacity causes extended closure time
Solution Approach 1:
The patent pre-charges hydraulic accumulators with hydraulic fluid before the ROV arrives at the wellbore. This preliminary action stores sufficient hydraulic energy to operate the actuators and close the wellbore rapidly without requiring continuous pumping during the critical closure operation. The pre-stored hydraulic energy enables fast actuation of closure elements, eliminating the time constraint imposed by ROV pump flow capacity.
3Ease of operation
If extended time is taken to close the wellbore, then hydraulic actuators can be operated, but seal element erosion risk increases
Solution Approach 1:
The patent pre-charges hydraulic accumulators with sufficient hydraulic energy before the ROV arrives. This preliminary preparation ensures that all necessary hydraulic actuators can be operated rapidly and simultaneously when the capping device is deployed, minimizing the time seal elements are exposed to erosive fluid flow. The pre-stored energy enables immediate actuation without prolonged exposure to harmful conditions.
4Productivity
If precharged pressure accumulators are used, then rapid hydraulic closure is achieved, but the system complexity increases
Solution Approach 1:
The patent uses pre-charged pressure accumulators that are integrated into the capping device's hydraulic system. These accumulators are charged during the deployment process itself, utilizing the motion of the capping device through the water column to compress the accumulators. This approach incorporates the charging function into the deployment sequence, avoiding the need for separate complex charging infrastructure while enabling rapid closure operation.
Data Source
AI summary
A method for capping a subsea wellbore having a failed blowout preventer proximate the bottom of a body of water includes lowering a replacement blowout preventer system into the water from a vessel on the water surface. The replacement blowout preventer system includes an hydraulic pressure source disposed proximate well closure elements on the replacement blowout preventer system. The replacement blowout preventer system is coupled to the failed blowout preventer. The well closure elements on the replacement blowout preventer system are actuated using the hydraulic pressure source.