Page History

One of the two major Well Controls with Lift Mechanism trying to maintain the  actual flowrate 

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.

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.

...

Dynamic Flow Model (DFM) / Well control

 with SRP and ESP.

The mechanical pump is trying to maintain the target flowrate 

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:

p_{wf}(t) = p_c = \rm const

This value of BHP is called 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 

See also

...

Petroleum Industry / Upstream /  Production / Subsurface Production Operations / Well Control

[ Pressure Control ]

[ Liquid Control (Reservoir Flow Modelling)[ Pressure Control ]