In the art and science of recovering hydrocarbons from reservoirs beneath water, such as through off shore drilling platforms and other subsea operations, it is necessary to inject treatment chemicals into the well or wellbore, the drilling fluid therein, or in hydrocarbon transmission pipelines, etc. Such treatment chemicals may include, but are not necessarily limited to, corrosion inhibitors, scale inhibitors, paraffin inhibitors, hydrate inhibitors, demulsifiers, and the like, and mixtures thereof.

The injection of treatment chemicals into these systems requires generally only low flow rates. When delivering low flow rates using positive displacement-type pumps in an atmospheric system, net positive suction head (NPSH) is often a problem. Bellows Seal ValvesA good design for a subsea pump should try to inherently eliminate NPSH problems. Further, a major problem with positive displacement pumps, especially at high pressure, is that the check valve seats and piston/plunger packing can be inherently leaky, and cause fluid to leak through the pump, back to the suction side or back into the suction piping. Reducing ValvesAnother problem with small volume, positive displacement diaphragm or plunger pumps is that they can vapor or air lock very easily. Small bubbles in the pump chamber can expand and contract with plunger movement and cavitate and stall the pump.

Further, because the location of such chemical injection pumps is by definition at the bottom of the ocean or sea, they are subjected to severe conditions and are difficult to service due to their remote location.REDUCING VALVES Thus, subsea chemical injection pumps should be strong, durable, and if possible, reparable at a distance.

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2011-12-01

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