Managed Pressure Drilling (MPD): Equipment, Components, and Functions 

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Managed Pressure Drilling systems can range from a simple Rotating Control Device (RCD) with a choke manifold to fully automated MPD packages with integrated control software. The key components and their functions are described below. 

1. Rotating Control Device (RCD) 

Function 

The RCD provides the primary annular seal at the rig floor, allowing the drillstring to rotate and reciprocate, while diverting all returns into a closed-loop system for MPD operations. 

Key Notes 

  • The RCD is available in top-drive, rotary-table, or BOP/spool-mounted configurations. 

  • It is typically rated between 2.5 kpsi and 5 kpsi, although certain specialized models are designed to handle pressures up to 10 kpsi. 

  • The selected RCD should be matched to the expected surface pressure and should provide full-bore access or a removable seal cartridge for maintenance or emergency milling. 

2. Choke Manifold (Manual or Automated) 

Function 

The choke controls annular outflow to apply the required Surface Backpressure (SBP). In MPD operations, the pressure is continually adjusted to maintain the desired circulating bottom-hole pressure, rather than being opened or closed. 

Key Notes 

  • Automated chokes use pneumatic, hydraulic, or electric actuators with position feedback to provide fast, accurate, and repeatable control. 

  • Manual chokes and pressure relief valves (PRVs) are installed to provide redundancy and support emergency operations. 

  • The manifold specifications vary based on the pressure rating and whether the piping configuration is designed as a single-line or dual-line system. 

3. Metering Manifold and Flow Measurement 

Function 

Accurate measurement of inflow and outflow is essential for early detection of kicks or losses. These measurements must always be evaluated in conjunction with pressure trends, pit or riser level changes, and variations in cuttings load. 

Meter Types 

  • Coriolis meters provide direct measurements of mass flow and density, making them most effective for liquid or low-gas flows. However, their accuracy decreases at high gas fractions unless specifically engineered for multiphase use. 

  • Ultrasonic or turbine meters: These meters can be effective in certain applications but are sensitive to the presence of entrained gas, solids, and changes in flow regime. 

  • Multiphase flow meters (MPFMs): These meters may be required when returns involve highly variable multiphase flow conditions. 

  • Calibration requirements, installation constraints, and acceptable uncertainty limits should always be clearly defined during equipment selection. 

4. Closed-Loop Returns Handling and Gas Management 

Components 

Gas busters, separators, degassers, knock-out drums, flare stacks, compressors, and associated tanks are used to manage returns and handle gas safely. 

Function 

These systems process and dispose of produced gas or formation influxes safely during MPD or underbalanced operations. 

Design Considerations 

  • All gas-handling equipment must be sized to safely accommodate the maximum credible gas influx while remaining compliant with environmental and regulatory requirements. 

  • All piping, manifolds, PRVs, and flare systems must be properly pressure-rated and adequately protected. 

  • The equipment layout must support safe venting, flaring, or gas recovery as required by the operation. 

5. Pressure Sensors and Transducers 

Function 

Redundant, high-accuracy pressure sensors installed at critical locations, including the choke manifold, annulus, and standpipe, enable precise control of Constant Bottom-Hole Pressure (CBHP). 

Guidance 

  • All sensors should be installed and verified in accordance with API/IADC recommendations for redundancy, calibration traceability, and periodic performance checks. 

  • Sensor performance criteria and verification intervals should be captured within the MPD integrity management program. 

6. Automated MPD Control System (Software + PLC) 

Functions 

  • The system captures real-time data on flow, pressure, pump, and torque to support MPD operations. 

  • It provides automated choke control to maintain consistent CBHP setpoints. 

  • It includes alarm logic to identify kicks, losses, or abnormal pressure or flow behavior. 

  • It offers data logging, trending, and user-friendly Human-Machine Interface (HMI) displays. 

Safety Requirements 

  • All MPD controllers and PLCs must undergo HAZOP reviews and Failure Mode and Effects Analysis (FMEA). 

  • Safety-critical interlocks must be kept independent from normal operational control logic. 

  • The system must include documented testing procedures, calibration requirements, and cybersecurity safeguards. 

7. Auxiliary Components 

Common Supporting Components 

  • Check valves, PRVs, and pressure relief devices are installed to safeguard the system from overpressure. 

  • U-tube or riser level sensors are used to monitor fluid levels and annular stability. 

  • Pressure-rated manifold piping and quick-connect fittings are used to ensure safe and secure system connections. 

  • Gas detectors, emergency stop systems, and HSE interlocks are integrated to support operational safety. 

Guidance 

API RP 92M/S requires clear documentation of safety functions, redundancy planning, and validation testing for all safety-critical components. A site-specific HAZOP should define the necessary backups and appropriate testing intervals. 

8. Expanded Component Details 

8.1 Rotating Control Device (RCD) — Additional Detail 

  • RCDs are commonly classified into two types: bearing-type and slip-type units. 

  • All cartridges and seals must be selected based on expected torque, RPM, temperature, and chemical compatibility. 

  • Spare cartridges should always be available, and procedures must allow quick seal replacement or emergency milling when required. 

8.2 Choke Manifold — Additional Detail 

Manual Chokes 

  • Manual chokes are primarily used for redundancy and to manage emergency conditions when automated systems are unavailable. 

Automated Chokes 

  • Automated chokes are actuated pneumatically, hydraulically, or electrically and operate using position feedback loops. 

  • These chokes are integrated with PLCs and MPD control software for continuous automated operation. 

  • They must have clearly defined fail-safe modes established through HAZOP evaluations, such as holding the last position, moving to a safe preset, or using a spring-return mechanism. 

  • All automated chokes must undergo acceptance testing to confirm correct operation under all expected conditions. 

  • Choke manifolds must include PRVs and overpressure protection devices for vessels, separators, and flare lines. 

  • The manifold design must allow for a manual bypass or provide the ability to swap chokes in the event of an actuator failure. 

8.3 Flow Meters — Additional Detail 

  • Coriolis meters provide excellent mass and density measurement, but must always be evaluated for performance sensitivity to gas content. 

  • Multiphase flow meters or blended metering systems may be required for high-gas or unstable multiphase return flows. 

  • Turbine and ultrasonic meters can perform well in specific flow conditions but require clearly defined calibration, installation, and operating limits. 

8.4 Pressure Sensors — Additional Detail 

  • Sensors should be installed at the annulus, standpipe, choke inlet, choke outlet, and other strategic locations. 

  • The installation should account for dynamic pressure fluctuations and system response times. 

  • Each sensor must have a traceable calibration certificate and must be verified at regular intervals according to the maintenance program. 

8.5 Control Software — Additional Detail  

  • The control software must integrate seamlessly with rig systems and HMI displays to support efficient operation.  

  • The system should include a reliable manual override, strong alarm prioritization, and robust cybersecurity protections.  

  • All control logic must be fully assessed during the HAZOP and functional safety reviews. 

 8.6 Gas Handling & Separation — Additional Detail 

  • All gas-handling equipment—including gas busters, KO drums, separators, flare systems, tanks, and compressors—must be sized for the maximum credible influx. 

  • The system must comply with the operator’s safety case and with all applicable regulations. 

  • Gas detection, automatic shutdowns, and isolation systems must be incorporated. 

  • Gas recovery solutions, such as compression or diversion to gathering systems, should be used where flaring is restricted.