Overview
The dual-wall dual-passage single-seal plug valve is a manually operated plug valve designed for reverse circulation drilling operations and connected to dual-wall drill pipes. Its structure features two isolated flow paths:
- The annulus between the valve body and the inner central tube serves as the gas or liquid passage.
- The inner central tube provides a separate liquid or gas passage, with the two channels being hermetically sealed and isolated from each other.
Working Principle
1. Normal State (Open Position)
- The valve is normally open during standard drilling operations, allowing simultaneous flow through both channels (annulus and inner tube).
2. Emergency Closure (During Overflow or Kick)
- When an overflow or kick occurs (uncontrolled influx of formation fluids), the valve can be quickly closed by rotating the ball 90° using a specialized wrench. This action:
- Blocks upward flow of formation fluids through the drill string’s inner bore.
- Maintains isolation between the dual channels to prevent cross-contamination.
3. Key Functions
- Dual-Passage Flow Control: Enables independent or combined use of the annulus and inner tube for fluid/gas circulation.
- Single-Seal Inner Bore Shutoff: Seals the inner tube while maintaining annulus integrity, critical for emergency well control.
- Synchronized Operation: When paired with a downhole dual-wall annular check valve, it ensures simultaneous opening or closing of both channels, enhancing operational flexibility and safety during complex drilling scenarios.
Applications in Drilling Operations
- Reverse Circulation Drilling: Efficiently transports cuttings to the surface via the annulus while injecting clean fluid through the inner tube.
- Well Control: Rapid response to kicks or blowouts by isolating the inner bore, buying time to activate primary barriers (e.g., BOPs).
- Multi-Fluid Management: Supports simultaneous injection of different fluids (e.g., drilling mud, gas, or foam) through separate channels.
Advantages
- Emergency Response: Manual override enables immediate action during power or system failures.
- Dual-Channel Flexibility: Optimizes fluid management for complex drilling conditions.
- Robust Isolation: Prevents intermixing of fluids/gases, critical for wellbore stability.
- Compatibility: Integrates seamlessly with dual-wall drill pipes and downhole check valves.
Summary
The dual-wall dual-passage single-seal plug valve is a critical component in advanced drilling systems, enabling precise control over dual fluid/gas channels while providing rapid emergency shutoff. Its design ensures safe and efficient reverse circulation operations, making it indispensable for managing high-risk scenarios like kicks or blowouts in petroleum drilling.
