The alteration of shales, caused by adsorption of water while drilling, is one of many contributors to the wellbore stability problem that costs the industry in the order of $ 400-500 million annually (Bol, 1992). This alteration of shale problem has acquired a logging perspective due to the increasing use of measurements while drilling. The capability of taking real time and time-lapse measurements while still drilling introduces the possibility of detecting a swelling problem while something can still be done about it.

The objective of this study (Adisoemarta, 1999) is to observe the changes of complex electrical characteristic of shale as a function of water content. The word "complex" in the electrical characteristic term means this study will not only observe the "in-phase" electrical response but also the "out-ofphase" response.

By taking the ratio of the in-phase to the out-of-phase electrical response, this study found that this ratio, the dissipation factor, changes linearly as a function of shale water content. This method can be easily applied to both the drilling / wellbore stability or formation evaluation areas.

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