Apparatus and method for accurately measuring formation pressure

Details Apparatus and method for accurately measuring formation pressure Apparatus and method for accurately measuring formation pressure

1991-04-22

1993-08-10

Williams, Hezron E.

Measuring and testing

Borehole or drilling

Downhole test

E21B 4900

Patent

active

052338665

ABSTRACT:
Test apparatus, and method for accurately and quickly measuring formation pressure, and permeability in oil and gas producing formations; especially low or high permeability formations. The test apparatus can be transported on a drill string, or cable. Preferably, it is employed as a component of a wireline test apparatus. The test apparatus includes, as part and parcel of the combination, an extended drawdown subassembly, or formation pressure test unit, directly associated with the tool flowline. By applying a very slow rate of pressure decrease in the tool flowline, the formation pressure and permeability can be quickly determined, generally during the first minute of testing. In high permeability and soft formations, the formation pressure is determined even if the seal is lost during the flowing period. In low permeability formations, corrections can be made for the supercharging effect using the data collected. A simple mathematical model can be used for determining formation pressure, formation permeability, supercharging, and mudcake characteristics from the data obtained.

REFERENCES:
patent: 3011554 (1961-12-01), Desbrandes et al.
patent: 3858445 (1975-01-01), Urbanosky
patent: 3859850 (1975-01-01), Whitten et al.
patent: 3859851 (1975-01-01), Urbanosky
patent: 4434653 (1984-03-01), Montgomery
patent: 4513612 (1985-04-01), Shalek
patent: 4742459 (1988-05-01), Lasseter

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