The Formation Tester, a wireline tool for safely and rapidly testing formations in the open hole, was introduced to the oil industry in 1955. Since its inception, it has proved to be a valuable evaluation tool. It provides a wireline method for obtaining an actual sample of formation fluids substantiated with formation pressure recordings.

Application of wireline testing has been extended to cased-hole testing, and improved in the open-hole testing of hard formations by the addition of the Formation Interval Tester. Thus, testers are currently available for use in almost any possibly productive zone — whether that zone be in open hole or behind casing/hard formation or soft.

Open-hole tests can be run in hole sizes of 6 to 12–1/4" in diameter under a hydrostatic pressure range of 500 to 20,000 psi. Cased-hole testing is available for casing sizes of 5–1/2 to 13–3/8" O.D. Fluid samples of 1, 2– 3/4 or 5–1/2 gallons may be recovered.

The purpose of this paper is to discuss the applications of these testers and the inter-pretation of their recoveries.

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