**1. n. [Formation Evaluation]**

The proportion of a wet clay that is clay-bound water. A formation that has 100% clay would have a porosity equal to the wet-clay porosity (WCLP), all of it being clay-bound water, and a volume of dry clay equal to (1 - WCLP). The concept is used to relate the volume of clay-bound water, CBW, to the volume of dry clay, V_{dcl}, in an actual rock, since the ratio of the two is the same and equal to: