Patent ID: 8672026

Claim:
A method of controlling fluid phase in a pumping system, said method comprising: operating a pumping system to pump fluid from a formation in a reservoir at a pumping rate, wherein the pumping system comprises a probe to suction a fluid from a fluid reservoir; a pump in fluid communication with said probe; and a fluid exit from said pumping system, said fluid exit being in fluid communication with said pump; sensing a phase change in said pumping system, wherein said sensing comprises sensing with a first sensor between said probe and said pump and sensing with a second sensor between said pump and said fluid exit, and detecting a fluid phase change using a time correlation method by comparing temporal traces of fluid properties sensed by said first sensor and said second sensor, said traces time-shifted to accommodate the holdup volumes in said pumping system; and adjusting said pumping rate of said pump in response to said sensed phase change; wherein said controlling comprises configuring the force of a variable force check valve, said configuring comprising varying the force of said check valve utilizing a force variance mechanism other than force variability due to the Hooke's law force variation in a spring as the spring is compressed and extended during operation of said check valve and other than by mere assembly of said check valve.