Geological formations porosity and permeability determn. method

摘要

The NMR probe (12) is lowered down a drilling in association with an electronic emitting and receiving unit (14). Signals detected from the surrounding medium are transmitted to a unit measuring amplitude (16) and then to a unit (18) which adds successive amplitudes. The signals detected are a train of echoes which decrease exponentially with time. A memory (20) and comparator (22) enable successive amplitude totals to be compared. If the difference between successive totals is small compared to a threshold a new sequence of signals is commenced by a sequence (24).