separators

Separators Overview

  • Definition: A separator is a pressure vessel used for separating a well stream into gaseous and liquid components.

  • Installation Locations: Can be found in onshore processing stations or offshore platforms.

  • Types of Separators:

    • Based on Vessel Configuration:

      1. Horizontal Separators

      2. Vertical Separators

      3. Spherical Separators

    • Based on Fluid Separation:

      • Gas/Liquid Two-Phase Separator

      • Oil/Gas/Water Three-Phase Separator

Horizontal Separators

  • Operation: Gas flows horizontally while liquid droplets fall toward the surface.

  • Components: Moisture gas forms a liquid film that is drained to the liquid section.

  • Advantages:

    • Lower costs and widely used for high gas-oil ratio well streams.

    • Facilitates easy skid-mounting and servicing.

    • Requires less piping for connections.

  • Ideal For: High gas-oil ratio well streams, foaming well streams, and liquid-from-liquid separation.

Vertical Separators

  • Operation: Uses a centrifugal inlet device that forces liquid droplets to fall to the bottom due to gravity.

  • Key Features:

    • Sufficient surge room to manage liquid slugs without carryover.

    • Mist eliminator reduces liquid in the gas outlet.

  • Advantages:

    • Suitable for low to intermediate gas-oil ratio streams.

    • Requires less floor space.

    • Reduces risks of liquid vaporization into gas phase.

  • Disadvantage: More expensive to fabricate and transport.

Spherical Separators

  • Configuration: Compact design with limited surge space and settling section.

  • Critical Component Location: Liquid level control is critical.

Conventional Separator Names

  • Oil/Gas Separator

  • Gas/Liquid Separator

  • Degasser

  • Deliqulizer

  • Scrubber Trap

Components of Oil/Gas Separators

  • Key Components:

    • Inlet device for improved flow distribution.

    • Mist extraction device to reduce liquid in gas stream.

    • Weirs for controlling liquid levels.

    • Liquid level and interface detection systems.

    • Outlets for gas, oil, water, and pressure relief devices.

Oil & Water Quality Standards

  • Oil Requirements:

    • Less than 1% water by volume

    • Less than 5 lbm water/MMscf gas

  • Water Stream Requirements:

    • Less than 20 ppm oil for overboard discharge (Gulf of Mexico).

Factors Affecting Separation

  • Key Factors:

    • Operating pressure

    • Operating temperature

    • Fluid stream composition

  • Effects:

    • Increased pressure or decreased temperature leads to higher liquid coverage.

    • Operators optimize conditions for maximum revenue recovery, focusing more on liquid hydrocarbons.

Controllers and Internal Components of Gas–Oil Separators

  • Liquid Level Controller (LLC): Maintains liquid level, uses a float to signal diaphragm motor valve for liquid outlet control.

  • Pressure Control Valve (PCV): Automatically maintains constant pressure by adjusting gas flow.

  • Pressure Relief Valve (PRV): Safety device that vents pressure above design limits.

  • Mist Extractors: Remove fine liquid droplets from gas before exit.

    • Types of Mist Extractors:

      1. Wire-Mesh Mist Extractor: High efficiency but prone to plugging.

      2. Vane Mist Extractor: Coalesces droplets using flow direction change.

      3. Centrifugal Mist Extractor: Uses centrifugal force but sensitive to flow rate.

Additional Components

Wave Breakers

  • Used to reduce wave fluctuations at gas-liquid interface, supporting stable liquid level control.

Defoaming Plates

  • Address foaming at gas-liquid interface using inclined plates to break up foam.

Vortex Breakers

  • Prevent vortex formation at liquid outlet to avoid gas blowby during liquid withdrawal.

Sand Jets and Drains

  • Manage sand accumulation at the bottom of separators, especially in horizontal designs, by fluidizing sand with produced water.