APPARATUS AND METHOD FOR DOWNHOLE ELECTROMAGNETIC MEASUREMENT WHILE DRILLING.

摘要

A directional resistivity tool (100) includes a pair of transmitters (T1,T2) deployed between at least one pair of receivers (R1,R2). Each of the transmitters and receivers (T1,T2; R1,R2) preferably includes collocated z-mode and x-mode antennae (122,124; 132,134; 142,144). Exemplary embodiments may further include additional receivers (R3,R4,R5,R6), for example, additional pairs of receivers deployed axially about the transmitters or one or more deep reading receivers (R3,R4,R5) deployed on one axial end of the transmitters (T1,T2). Tools (100) in accordance with the invention enable directional resistivity measurements to be acquired at multiple depths of investigation using fewer transmitter firings than conventional tools (50).