Apparatus and method for determining characteristics of subsurface formations

A method of determining a free water parameter of formations surrounding a borehole comprises determining a parameter, e.g. attenuation, of the water in a region of the formations where substantially all of the water present is free water, e.g. a clean sand region. The water content of the formations at a particular depth level of interest is also determined. First and second signals representative of the parameter and the water content thus determined are then combined to determine the free water parameter at the particular depth level of interest. (author)