Method for measuring formation properties with a time-limited formation test
AssigneeSchlumberger Technology Corporation
InventorsJean-Marc Follini, Julian Pop
Life of this patent
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Abstract
An apparatus and method for determining at least one downhole formation property is disclosed. The apparatus includes a probe and a pretest piston positionable in fluid communication with the formation, and a series of flowlines pressure gauges, and valves configured to selectively draw into the apparatus for measurement of one of formation fluid and mud. The method includes performing a first pretest to determine an estimated formation parameter; using the first pretest to design a second pretest and generate refined formation parameters whereby formation properties may be estimated.
Claims7
A method for determining a termination condition for a drawdown operation using a formation tester in a formation penetrated by a borehole, comprising:
- setting a probe of the formation tester against a wall of the borehole so that a pretest chamber is in fluid communication with the formation, a drilling fluid in the pretest chamber having a higher pressure than the formation pressure;
- decompressing the drilling fluid in the pretest chamber by withdrawing a pretest piston at a constant drawdown rate;
- collecting data points representing fluid pressures in the pretest chamber as a function of time;
- identifying a range of consecutive data points that fit a line of pressure versus time with a fixed slope, the fixed slope being based on a compressibility of the drilling fluid, the constant drawdown rate, and a volume of the pretest chamber;
- and
- terminating the drawdown operation based on a termination criterion after the range of the consecutive data points is identified.
Dependencies are inferred from the claim text.