Oil-Gas Separator

Overview

An oil-gas separator is the first vessel a wellstream meets at a production facility. The raw flow from a well is a turbulent mix of gas, crude oil and produced water, and the separator splits it into those phases so each can be metered, treated and sent on. A horizontal three-phase separator does the job by giving the fluid time and space: gas rises and exits the top while oil and water stratify by density in the liquid pool below. The vessel is an ASME-coded pressure shell, because it holds the well's flowing pressure while doing this.

Separation is driven by gravity and momentum, with no moving rotor, so the vessel internals are arranged to slow the flow and let the phases find their own levels.

How it works

The wellstream enters through the Inlet Section, where a diverter breaks the jet's momentum and drops out the bulk liquid. Gas and fine droplets carry forward into the Pressure Shell, the cylindrical body that contains process pressure across its rolled course and elliptical heads.

In the Liquid Section, the oil and water slow down and stratify; water settles to the bottom while oil overflows a weir into a separate compartment, each phase drawn off through a vortex breaker. Gas travels the length of the vessel to the Gas Section, where a wire-mesh mist extractor coalesces remaining droplets so only dry gas leaves the top nozzle.

Steady operation depends on control. The Level Control System system senses the oil and water levels and modulates actuated dump valves to hold them; the Pressure Control Valve throttles the gas outlet to keep vessel pressure on setpoint. The Relief Valve is the last-line safety device, lifting if pressure runs away, and the Gauge Set gives operators local pressure and level readings. The whole vessel rests on two Saddle Support cradles.