Patent ID: 7576543

Claim:
A method of determining a resistivity parameter of an earth formation during drilling of a borehole in said earth formation by a device on a bottom hole assembly (BHA), the method comprising: (a) maintaining a resistivity sensor on said BHA substantially at a specified offset from a wall of the borehole; (b) using said resistivity sensor for making measurements indicative of said parameter during continue rotation of said BHA by (i) using a current electrode of said resistivity sensor for conveying a measure current into the formation through a fluid, (ii) using at least one guard electrode proximate to the current electrode for maintaining focusing of the measure current, and (iii) using monitor electrodes to support the focusing in the presence of non negligible contact impedances; (c) using an orientation sensor on said BHA for making a measurement of a toolface angle of said BHA during said continued rotation; and (d) using a processor for estimating from said measurements made by the resistivity sensor and the orientation sensor a value of said parameter.