Abstract: The most important factor for evaluating the capability of foam drilling mud is the foam stability, that is the foam half-life. Currently the most common method used to determine the foam half-life is the conventional measuring cylinder method which is simple and convenient. However, the disadvantages are artificial errors and it can not be recorded the foam decay process. To overcome such a limitation, a newmethod has been used to evaluate the foam stability. An apparatuswhich is calledMA-2000 Turbi Scan has been used
to analyze the foam stability. The measurement is more advanced and accurate and is controlled by a computer operating automatically. The analyzing results are two curves exported by computer. From the curves we can observe clearly the foam decay process and numerate the foam half-life.

Key words: foam drilling fluid, stability, half-life