Patent ID: 6945762

Claim:
A downhole pump, comprising: a barrel and a plunger located inside of the barrel, with one of the plunger and the barrel reciprocating with respect to the other, the barrel having a lower end; b) a first one-way valve located in the plunger; c) a second one-way valve located in one of the plunger or the barrel; d) a first chamber being a compression chamber formed by the plunger and the barrel and communicating with the first and second one-way valves; e) a second chamber formed by the plunger and the barrel, the second chamber being located closer to the lower end of the barrel than is the first chamber, the second chamber being subjected to expansion and contraction due to the reciprocation between the plunger and the barrel, the barrel having an orifice to the second chamber, the orifice creating a pressure drop for fluid passing through the orifice, the orifice structured and arranged to draw formation fluid in and out of the second chamber; f) the plunger having an intake, which intake draws in fluid from a location other than second chamber.