Subsea Pressure Control via Alternating Valve Sequencing
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Solution Overview
Problem
High pressure differences in subsea oil and gas pumping systems make it difficult to accurately and reliably regulate fluid pressure, leading to potential valve failures and time delays in pressure control, especially in deep water hydrocarbon field developments.
Innovation Solution
A method and apparatus using a pressure regulating unit with two valves connected by a conduit, where the valves are alternately opened and closed to achieve the desired pressure in a closed system, potentially aided by an electronic control unit and quick-connect connectors for remote operation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If pressure regulating is performed from the surface through an umbilical in deep water systems, then pressure control is achieved, but time delays occur making effective control difficult
Solution Approach 1:
The pressure control system is segmented into two independent parts: a surface-based pressure regulator and a subsea pressure control unit. The subsea unit includes local sensors and actuators that can autonomously adjust pressure without waiting for surface commands, eliminating time delays while the surface unit provides overall system management.
Solution Approach 2:
A subsea pressure control unit acts as an intermediary between the surface umbilical system and the subsea pipeline. This intermediate device receives pressure setpoints from the surface but performs actual pressure regulation locally using piezoelectric actuators and sensors, decoupling the control response time from the communication delay.
2Stress or pressure
If valves are opened across high pressure differential in high pressure fluid systems, then pressure equalization is achieved, but valve failures and seal failures can occur
Solution Approach 1:
Instead of opening valves fully across high pressure differentials, the system uses piezoelectric actuators to make small, incremental pressure adjustments. The partial action approach gradually equalizes pressure while keeping the pressure differential across any valve opening within safe limits, preventing seal and valve failures.
Solution Approach 2:
The system changes the operating parameters of pressure regulation by using piezoelectric materials that can make precise, small-displacement adjustments. This allows pressure control through incremental parameter changes rather than large-step valve openings, maintaining reliability while achieving pressure equalization.
3Reliability
If barrier fluid pressure is increased to prevent process fluid leaking, then sealing effectiveness is improved, but barrier fluid bleeds through seals into process fluid
Solution Approach 1:
The system employs feedback control with pressure sensors monitoring both the barrier fluid side and process fluid side of seals. By continuously measuring the pressure differential across seals and adjusting barrier fluid pressure in real-time, the system maintains minimum sealing pressure while preventing excessive pressure that would cause barrier fluid to bleed through seals.
Data Source
AI summary
A method of controlling fluid pressure in a closed system including using a pressure regulating unit connected to the system, the unit including a first conduit fluidly connecting the closed system to an external system. A first regulating valve is interposed between the external system and one end of the conduit and a second regulating valve interposed between the closed system and the other end of the conduit. The method further includes: a) opening one of the first or second regulating valves; b) closing said one regulating valve; c) opening the other regulating valve; d) closing the other regulating valve; and e) repeating steps a) to d) in turn until the desired fluid pressure is achieved in the system.