Philip Cheung

Method of acoustically detecting fractures in a borehole

According to the method an acoustic transmitter/receiver tool is lowered in measured manner down a borehole. The tool possesses separate transducers for transmitting and receiving sound waves and includes at least one pair of spaced apart transmitter and receiver spacing. As it is lowered, the tool is caused to repetitively transmit sound waves and on each occasion the waveforms of the echoes received by the tool are recorded in relation to the spacing. Fractures are detected by processing portions of the waveforms which are representative of at least one of two different local effects corresponding to fractures, which effects are amplitude peaks due to a local increase in acoustic coupling, and criss-cross patterns due to mode conversion.