Page 272 - Hydrocarbon Exploration and Production Second Edition

Well Dynamic Behaviour 259

diffuser

throat

power
fluid
reservoir
fluids

nozzle
power fluid pressure
Figure 10.30 Jet pump.

10.8.5. Jet pump
Like the HSP, the jet pump relies on the hydraulic power being delivered
subsurface. There the similarity ends. The high-pressure power fluid is accelerated
through a nozzle. The high velocity creates a low pressure through the Bernoulli or
venturi principle. This low pressure sucks up reservoir fluids (Figure 10.30).
The low-pressure mix of power fluid and reservoir fluid then enters the diffuser
where the velocity is converted to pressure. The pressure is then sufficient to deliver
the fluids to surface. The jet pump has no moving parts and can be made very
compact and is typically installed on wireline. It is applicable to low-to-moderate
rate wells, but the efficiency is poor. The power fluid is either water injection
quality water or high-pressure crude oil. Unlike an HSP, the power fluid always
mixes with the reservoir fluid and must be separated at surface and either reused or
disposed of and a fresh supply found.

10.8.6. Gas lift

Gas lift systems aim at lightening the liquid column by injecting gas into it,
essentially stimulating natural flow. In its simplest form, hydrocarbon gas is dried
and compressed at surface and enters the well via the wellhead. It travels down
inside the production casing and, as deep as possible, it enters the completion via
a gas lift valve (GLV, comprising a check valve and restriction or orifice). The GLV is
replaceable by wireline as it sits inside a side pocket mandrel (SPM). The reservoir