Subsea Pressure Control Assembly Without a Riser
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Solution Overview
Problem
Conventional managed pressure operations in subsea environments require the use of a riser to control wellbore pressure, which increases installation costs and time, and existing pressure control devices do not effectively accommodate rotating tubular strings.
Innovation Solution
A subsea assembly that conducts managed pressure operations without a riser, utilizing a pressure control device with a rotatable annular seal and annular seal barriers to isolate the wellbore, along with a system that includes a pump and cleaning assembly to manage fluid pressure and cleanliness of the tubular string, all connected via an umbilical to a rig.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a riser is used to conduct fluids between the wellbore and rig in subsea managed pressure operations, then fluid control and pressure management are enabled, but installation costs and installation time increase
Solution Approach 1:
The patent extracts and eliminates the riser component from the subsea managed pressure system, replacing it with a direct connection between the subsea assembly and wellhead. This removal of the intermediate riser component reduces installation complexity and time while maintaining the essential fluid control function through alternative means (flexible conduit and direct subsea assembly connection).
Solution Approach 2:
The subsea assembly is designed to perform multiple functions: it provides pressure control, fluid management, and wellbore isolation capabilities directly at the wellhead connection point. This multi-functional integration eliminates the need for separate riser infrastructure, achieving both cost reduction and maintained operational reliability.
2Adaptability or versatility
If a conventional pressure control device with a rotatable seal is used to accommodate rotating tubular strings, then rotational movement is permitted, but the seal complexity and potential for leakage increase
Solution Approach 1:
Instead of making the seal rotatable to accommodate the rotating tubular string, the patent inverts the approach by making the tubular string rotation occur outside the pressure control device. The BOP stack remains stationary with a non-rotatable seal, while the tubular string rotates in the open water column above, eliminating the need for a complex rotatable seal mechanism entirely.
Solution Approach 2:
The system separates the rotation function from the pressure control function. The tubular string rotation is decoupled from the BOP stack, allowing each component to perform its primary function independently - the BOP stack provides pressure control with a simple stationary seal, while the tubular string rotates freely above it without interfering with the sealing mechanism.
Data Source
AI summary
A subsea assembly can include a pressure control device having an annular seal configured to seal off an annulus formed between an outer housing and a tubular string, a connector, and a guide configured to guide the tubular string into an internal flow passage extending through the subsea assembly, the pressure control device being connected between the connector and the guide. A method can include assembling a subsea assembly with a pressure control device and a connector, the pressure control device including an outer housing and an annular seal, lowering the subsea assembly through water from a rig to a subsea wellhead installation, connecting the subsea assembly to the subsea wellhead installation, and positioning a tubular string in the subsea assembly, so that the annular seal seals against an external surface of the tubular string, the tubular string being exposed to the water between the rig and the subsea assembly.