The closed-loop separation system is based on water-injection methods to separate gas, liquids and solids in a closed tank. The separated return streams are individually handled so they can be disposed of in the most appropriate manner.

The compact system is made up of two skid-mounted units. One unit is the deluge pump, which provides water for the process. The pump recirculates water within the system to improve dust suppression by pre-wetting cuttings and solids surfaces in the flow line. The deluge pump is also used in conjunction with automated level gauges to maintain constant liquid levels automatically.

The second unit contains a large tank and the remaining separation system components. Cuttings, gas and liquids from the rig enter the tank through a blooie line. Water is injected into the primary flow line, and an expandable inlet reduces the flow velocity rate of the incoming well returns.
 

A chain curtain in the tank knocks most of the solid particles to the bottom of the tank as they pass through the expandable inlet. Water droplet spray nozzles wets fine solids and allows gas to break away from the larger solids remaining in the mixture after it passes through the chain curtain.

The tank is built to contain a deflagration caused by a back flash flare when flaring gas. In addition to the chain curtain, the tanks have several other components: a plate-back separator splits oil and fine solids from water, which cleanses the water so that it can be recycling through the system; a mist pack prevents water from entering the flare line; and sensors in the tank monitor system fluid levels. A programmable logic controller monitoring the sensors automates the system’s fluid level management.

The flare line routes separated gas components to the company’s flaring equipment, which operates more effectively because solids content has been minimized. Separated liquids and solids pass through a slurry pump for transport to the rig’s solids control system, and an oil pump sends skimmed oil to a separate container.

Solids control is a technique used in drilling rig to separate the solids in the drilling fluids that are crushed by the drill bits and carried out of the well surface. Normally solids control system is consisted of five stages, including shale shaker, vacuum degasser, desander, desilter, decanter centrifuge. Shale shaker is used to separate the big solids with diameter above 75μm, and 45~74μm for desander, and 15~44μm for desilter. Sometimes desander & desilter are combined as high efficient mud cleaner. When air entrains the drilling fluids, vacuum degasser is used to separate the air. If no air is in the mud, the degasser will work as a big agitator. All these equipment are mounted on the top of the mud tank. After separating the solids, the clean mud will be pumped into the borehole again.