Tool for imaging by focused at depths for recordings during drilling applications

摘要

A resistivity tool for use in an LWD system includes a transmitter array with multiple transmitters (T1, T2, T3) positioned above a pair of receivers (R1, R2). The transmitters (T1, T2, T3) are selectively energized, causing current to be induced in the collar of the tool. The axial current in the tool collar is measured by the pair of receivers (R1, R2) to determine the amount of current that flows into the formation between the receivers (R1, R2). From this, the formation resistivity can be measured for each transmitter to provide multiple depths of investigation. A plurality of discrete electrodes (500) are positioned between the two receivers (R1, R2) to permit imaging of the borehole by obtaining azimuthally sensitive resistivity readings based upon the voltage level at each discrete electrode and the amount of current flowing into the formation.