Problem:?Humbly Grove onshore oilfield in Hampshire produces between 200 and 400 barrels of oil a day. The oilfield, owned by Star Energy, contains a number of wells, which feed into the recovery plant at Lasham. Here, extracted oil and water are separated, with the oil being transferred for processing at Fawley. The Produced Water resulting from the separation process has to be treated and returned to the natural aquifer, so an effective pumping system was required.

Solution: There were two main factors that needed to be considered when specifying the pump – the produced water is held at the highest point on the Lasham site, while the Cat pump that injects it back into the depleted reservoirs is at the lowest point. This meant there was a complex transition from high to low pressure at the inlet to the pump and there was also the risk of transients at start-up and shutdown which had to be considered at the design stage.

Secondly, in order to ensure a controlled flow of produced water into the underground reservoir, a pumping system that could provide steady flow and sufficient pressure was required. Star Energy consulted with Cat Pumps, resulting in the installation of a high pressure triplex plunger pump.

In order to meet Star Energy’s requirements, a Model 6761 was converted to a model 6741 which has smaller diameter plungers. This means for a given pump operating speed there is less flow, but the pump will withstand higher pressures because there is less projected surface area on the plungers on the forward pumping stroke. The pump is constructed from 316 stainless steel, has solid ceramic plungers and has the appropriate ATEX approval to meet site requirements.