Wireline formation testers are increasingly being used to obtain formation pressure and permeability measurements which in turn are used in geological evaluations and in designing well completions. It is generally assumed that the pressure measured by the tester probe is near formation pressure. Unfortunately, in many instances such as in low permeability formations, the mudcake is not adequate to isolate the hydrostatic pressure from the formation near the wellbore. As a result, the sandface pressure measured with the formation tester is "supercharged" and not the formation pressure after all. This sandface pressure may be as much as l.000 psi over the actual formation pressure of interest. This paper demonstrates that a new analytical model can be used along with a new testing technique to correct the measured pressure to actual formation pressure.

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