A METHOD FOR MEASURING A FORMATION PRESSURE AND A FORMATION TESTING TOOL

摘要

ABSTRACT A METHOD FOR MEASURING A FORMATION PRESSURE AND A FORMATION TESTING TOOL A method for measuring a downhole formation pressure is disclosed which includes lowering a formation testing tool to a desired measuring position in 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 mud cake layer and is 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 the mud cake and the retractable tip is retracted into the nozzle. The formation pressure is then communicated through the nozzle to a pressure sensor operatively cormected to the nozzle. Figure 7.