APPARATUS AND METHOD FOR MEASURING FORMATION PRESSURE USING A NOZZLE

摘要

A method for measuring a downhole formation pressure is disclosed which includes lowering a formation testing tool to a desired measuring position i n a well borehole. Then a nozzle in the tool is extended so that the nozzle extends through the mud cake layer on a surface of a formation, forming a seal between the mud cake layer and a sealing surface of the nozzle. In an embodiment of the invention, the nozzle has a porous tip that extends into the invaded zone beyond the mudcake layer and i s exposed to the formation pressure. In an alternate embodiment, the nozzle has a retractable tip that retracts into the nozzle. The nozzle and retractable tip are positioned in t he mudcake and the retractable tip is retracted into the nozzle. The formation pressure is then communicated through the nozzle to a pressure sensor operatively connected t o the nozzle.