Patent ID: 7168310

Claim:
A method of obtaining a measure of subsurface formation water saturation characteristics adjacent a well borehole in a formation characterized as containing a shaly sand, clay, and fluid as formation constituents, comprising the steps of: obtaining a measure of the total porosity of the formation based on measurements obtained from a porosity log; obtaining a measure of the dry clay volume of the formation based on measurements obtained from the group consisting of an X-ray, gamma ray log, or elemental capture spectroscopy log; obtaining a measure of the clay-bound water volume of the formation based on the obtained measure of the total porosity and a measure of a clay cation-exchange-capacity; determining the effective porosity of the formation based on the obtained measure of the clay-bound-water volume and the obtained measure of the total porosity; obtaining a measure of the total water saturation of the formation based on the obtained measure of the total porosity and on an obtained model of formation conductivity; obtaining a measure of the clay-bound water saturation of the formation based on the obtained measure of the total porosity and the obtained measure of the clay-bound-water volume; determining the free water saturation of the formation based on the obtained measure of the clay-bound-water saturation and the obtained total water saturation; and determining the effective water saturation of the formation based on the obtained measure of the free water saturation and the obtained measure of the total porosity.