Sanjack special pumps used in high gas cut well:

Anti-gas locking pump, Long plunger anti-gas locking and anti-sand pump, Mechanical forcing valve type pump and Double-plunger valve type pump

Gaseous-fluid pumps are designed to increase the efficiency of pumps in high gasto-liquid ratio (GLR) wells.

The stationary portion of a gaseous-fluid pump consists of short barrels coupled with extensions to form a chamber between them.

The plunger is long enough to bridge the chamber and produce a seal during the pumping cycle.

All through the cycle, the plunger strokes completely in and out of each barrel.

During the upstroke, turbulence and low-pressure cause gas in the fluid to expand, separate and rise toward the top of the suction chamber.

The fluid in the middle chamber is pressurized after exposure to the total column of fluid in the previous pump cycle.

Gas remaining in this fluid is under pressure, and the gas-fluid ratio, by volume, is lower than that of the fluid entering the pump.

Free gas rises toward the top of the chamber as the plunger makes the downstroke.

Gas and fluid are trapped in the middle chamber as the plunger continues downward.

When fluid below the traveling valve is displaced, the valve opens, allowing gas and fluid to flow upward through the plunger.

As the plunger nears the bottom of the stroke and the chamber is opened at the top, the collected gas escapes and rises through the fluid.

When the chamber again closes on the upstroke, the chamber contains fluid that is as free of gas as possible.

Proper valve spacing during operation to allow minimum clearance between the travel and standing valves maximizes the compression ratio and increases the total volume of fluid transferred on each stroke.

Gaseous-fluid pumps are primarily assembled from components and are offered in  mechanical hold down.

Because of their oversized chambers, gaseous-fluid pumps are not recommended for wells containing large volumes of sand or solids.