HomeEngineeringMechanicalPetroleum EngineeringDrilling EngineeringAccumulator
Print

Accumulator

on . Posted in Drilling Engineering

Accumulator is a critical component in oil and gas drilling operations, particularly in blowout preventer (BOP) systems.  It is a pressurized device used to store hydraulic energy and deliver it quickly when needed to operate the BOP and other associated equipment.  It uses compressed gas (typically nitrogen) to apply pressure to the hydraulic fluid, which can then be quickly released when needed.  The accumulator ensures the system can function effectively, even during emergencies or power failures, to prevent blowouts and maintain well control.

Accumulator Types

Bladder Accumulator  -  It contains a flexible rubber bladder inside a metal casing.  The bladder separates the gas from the hydraulic fluid.  When fluid enters, the bladder compresses the gas.
Piston Accumulator  -  It uses a piston to separate the gas and fluid chambers.  The piston moves as fluid enters or exits the chamber, compressing or decompressing the gas.
Diaphragm Accumulator  -  Similar to a bladder type but uses a diaphragm to separate gas and fluid.  The diaphragm flexes as the fluid enters and compresses the gas.

Key Features and Components

Pressure Storage  -  It uses a combination of hydraulic fluid and compressed gas (usually nitrogen) to maintain energy.  The gas provides the force to pressurize the fluid.
Hydraulic Fluid Reservoir  -  Stores and supplies hydraulic fluid under pressure to activate the BOP.
Nitrogen Chamber  -  Provides the compressive force needed to maintain the hydraulic fluid under high pressure.
Accumulator Bottles  -  Cylindrical containers where the hydraulic fluid and nitrogen are stored.  Multiple bottles are typically used to ensure adequate energy storage.
Control System  -  Regulates the release of hydraulic fluid to operate the BOP valves and rams.

Functions in Drilling

Actuate BOP Equipment  -  Provides the hydraulic force necessary to close the BOP, seal the well, and cut through the drill pipe if required.
Emergency Backup  -  Ensures the system remains operational during power outages or pump failures.
Quick Response  -  Delivers stored hydraulic energy rapidly to control wellbore pressure and prevent blowouts.

 

Step-by-step Explanation of How it Functions

Charging the Accumulator

Compressed Gas Storage  -  The accumulator is pre-charged with a specific volume of gas (usually nitrogen) in one chamber.
Filling with Hydraulic Fluid  -  Hydraulic fluid is pumped into the accumulator's fluid chamber.  As the fluid enters, it compresses the gas.
Pressure Balance  -  The gas pressure increases as it is compressed, balancing against the pressure of the hydraulic fluid.

Energy Storage

The compressed gas acts as a spring, storing potential energy by applying force on the hydraulic fluid.  The pressure inside the accumulator is maintained as long as the hydraulic system remains charged.

Energy Release

Activation  -  When the system requires hydraulic power (to close a valve or activate a Blowout Preventer), a valve in the accumulator opens.
Fluid Flow  -  The compressed gas forces the stored hydraulic fluid out of the accumulator and into the hydraulic system.
Rapid Delivery  -  This provides a quick and powerful burst of hydraulic energy to the system, even in emergencies.

Recovery and Recharge

Once the demand for hydraulic power is met, the system's hydraulic pump refills the accumulator.  The gas re-expands slightly as hydraulic fluid re-enters, resetting the system for future use.

 

Accumulator Advantages and Disadvantages

AdvantagesDisadvantages
  • Accumulators store hydraulic energy efficiently, providing a reserve for high-demand periods.
  • They can release stored energy almost instantaneously, ensuring rapid response in critical situations.
  • In case of power failure or pump malfunction, accumulators ensure continued operation of hydraulic systems.
  • They help maintain consistent pressure in hydraulic systems, reducing fluctuations that could damage components.
  • Reduces the need for continuous operation of hydraulic pumps, lowering energy consumption and operational costs.
  • Absorbs shocks and vibrations in hydraulic circuits, protecting components from damage caused by pressure spikes.
  • Provides a powerful energy source in a relatively small and lightweight form factor compared to other energy storage options.
  • Can be used in a wide range of applications, including drilling, industrial machinery, and braking systems.
  • The energy stored is finite and depends on the size of the accumulator and the pre-charge pressure.
  •  Regular inspection and maintenance are necessary to ensure the gas pre-charge and seals remain intact.
  • Over time, nitrogen or other compressed gases may leak, reducing the efficiency of the accumulator.
  • Overcharging or undercharging the accumulator can lead to reduced performance or even system failure.
  • High-quality accumulators and associated components can be expensive to purchase and install.
  • Performance can be affected by temperature changes, as the gas pressure varies with temperature.
  • A damaged or poorly maintained accumulator can lead to sudden hydraulic failure, which can be dangerous in critical applications.
  • While compact, they still require sufficient space for installation, especially when multiple units are needed for higher energy requirements.

 

Piping Designer Logo 1

 

 

Tags: Advantages and Disadvantages Drilling

Latest Articles