Multi-chamber gas anchor

Claim 1

A gas anchor for use with a reciprocating well pump for producing fluid from a subterranean reservoir, comprising; an internal liquid discharge tube in fluid communication with the suction chamber of the pump; a substantially concentric sleeve surrounding the discharge tube; a plurality of vertically elongated chambers formed between the discharge tube and the sleeve by means of substantially flat, radially-extensive baffles that extend from the discharge tube to close enough to the sleeve to impede the flow of fluids between the baffles and the sleeve, with each elongated chamber having a volume at least equalling that the suction chamber of the pump; and, in each elongated chamber, an outlet opening for liquid through the discharge tube wall near the bottom of the chamber and at least one combination fluid inlet and gas outlet opening through the sleeve wall at a location near the top of the chamber, each outlet opening for liquid being relatively small but large enough to resist plugging by solids entrained in the fluid produced from the reservoir, and the combination fluid inlet and gas outlet openings being large enough so that within each elongated chamber the fluid inflow resistance is significantly less than the outflow resistance.