Modern developments in raising oil during the past two or three years have been in the direction of handling small production to best advantage, owing to the severe curtailment programmes in nearly all of the world's producing oilfields.
In pumping operations, the centrifugal pump has been employed to advantage at moderate depths in raising oil mixed with a large volume of water.
The hydraulic pump has provided some interesting data, but its use has not become sufficiently widespread as yet to permit definite conclusions to be drawn as to application and economy.
The duplex compressed-gas cylinder and the single compressed-air cylinder have given promise of adapting themselves to pumping in an efficient and economical manner. Power plants that have been employed in direct gas-lift operations can be converted directly into service for handling these compressed-gas pumping units at only a nominal expenditure for regulators.