Resistance test set for a borehole surrounding geological formations

摘要

Apparatus for sensing the resistivity of geological formations surrounding a borehole includes a tubular body member (1) which is adapted to form a portion of a length of drill string. An antenna (10) is mounted within the body member (1) and the body member (1) has apertures (2) adjacent to the antenna (10) to permit an electro-magnetic signal to pass through the body member (1) after transmission from, or for reception by, the antenna (10).