Patent ID: 7565835

Claim:
A method of sampling reservoir fluid from a rock formation penetrated by a borehole, comprising: positioning a downhole tool having a flow line in the borehole; establishing an inlet port through which fluid passes from a first point in the formation into the flow line; establishing an outlet port through which fluid passes from the flow line into a second point in the formation; passing fluid between the formation and the flow line through the inlet and outlet ports until the fluid in the flow line is of sufficient quality to be sampled; and after the fluid in the flow line is of sufficient quality to be sampled, pumping the fluid in the flow line into a fluid chamber in the downhole tool; wherein pumping the fluid comprises exposing a first side of a movable barrier disposed in the fluid chamber to fluid pressure at the inlet port and exposing a second side of the movable barrier to fluid pressure at the outlet port.