Patent ID: 7779684

Claim:
A system for testing a subterranean formation penetrated by a well, the system comprising: a downhole tool configured to be coupled to a work string, the downhole tool comprising a tool body having a longitudinal bore for circulating a fluid and at least one probe cavity configured to receive a probe; a probe comprising a piston slidably engaged with the probe cavity, wherein the probe piston and the probe cavity at least partially form a retracting chamber and an extending chamber; an actuator fluidly coupled to the probe extending chamber via a fluid passage, the actuator being configured to vary pressure in the extending chamber; a resilient member operatively coupled to the probe and configured to store energy when the probe is projected from the downhole tool; a first valve fluidly coupled to the probe retracting chamber, wherein the first valve is configured to open when power is removed from the first valve; and a second valve fluidly coupled to the extending chamber, wherein the second valve is configured to vent pressure in the extending chamber when power is removed from the second valve.