One if of the two two major Well Controls with Lift Mechanism trying to maintain the the actual flowrate manually specified value of the flowrate.the flowrate :
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q_L(t) = q_{LL} = \rm const |
Liquid control is most common for producing wells, except the case when bottomhole pressure is being reduced by the downhole pump to its minimal value, specified by the pump location inside the wellbore.
In case this happens the well is switching to pressure control until the formation pressure and allow pump produce efficiently above minimal bottomhole pressure value.
with SRP and ESP.
The mechanical pump is trying to maintain the target flowrate
but it only succeeds when the wellbore fluid level is above pump location.If dynamic fluid level lowers all the way down to the pumping chamber, then the pump efficiency deteriorates and the flowware reduces:
while the fluid level and corresponding BHP are getting stabilized:
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p_{wf}(t) = p_c = \rm const |
This value of BHP is called critical BHP
and the fluid can not be lifted at the wellbore pressures below critical BHP.This does not actually qualifies the well operation as Pressure Control and the well is still under Liquid Control conditions and once bottomhole pressure raises above critical value the pump returns to producing the target liquid rate
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body | q^{\uparrow}_L(t) = q^{\uparrow}_{LL} = \rm const |
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. Despite that many wells are operating under pressure control de facto they can be still simulated as under Liquid control assuming that their liquid rates have been manually pre-set adequately by Production technologist.
See also
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Petroleum Industry / Upstream / Production / Subsurface Production Operations / Well Control
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