Definition - What does Gas Lock mean?
Gas Lock is a condition caused due to free gas induction in processing and pumping equipment. This condition is sometimes confronted in pumping wells when the dissolved gas that is released from the solution during the upstroke of plunger crops up as free gas between the valves. On downstroke, the pressure present inside a barrel, which is completely filled with gas, might not reach the desired pressure required for opening and allowing liquid to enter the pump. Hence, fluids do not leave or enter the pump and it is locked.
Petropedia explains Gas Lock
Gas Lock can be caused by the failure of a pump to open on downstroke in gassy wells. It does not cause a failure of the equipment, but with a non-functioning pump the pumping system is useless. The decrease in the rate of pumping is accompanied by the increase in bottomhole pressure. This increase in the bottomhole pressure in many cases of Gas Locks can exceed the pressure in the barrel and allow liquid to enter through the standing valve. Adequate liquid enters into the pump after a few strokes and the pump starts functioning normally.