Method and Apparatus for Spectral Noise Logging

• Main Authors: ARTHUR M ASLANYAN, DMITRY A DAVYDOV
• Format: Patent
• Language: English
• Published: 19.02.2014
• Subjects: EARTH DRILLING; EARTH DRILLING, e.g. DEEP DRILLING; FIXED CONSTRUCTIONS; MINING; OBTAINING OIL, GAS, WATER, SOLUBLE OR MELTABLE MATERIALS OR ASLURRY OF MINERALS FROM WELLS

Methods and apparatus for performing spectral noise logging (SNL) within a borehole are described. In particular an SNL tool is described that comprises an acoustic detector 2, a first channel comprising a gain stage 3a, 3b an analogue to digital convertor 19, a CPU 5 and an internal memory 7. The tool operates over a frequency range of 117 Hz to 60 kHz. A second low frequency channel 21 may be incorporated within the tool so as to further extend the operating frequency range down to 8 Hz. The SNL tool is used to detect and characterise leaks through a casing and detect and characterise fluid flow from behind the casing of channelling or acoustic noise associated with surrounding fractures or matrix formations. In use the device is used to record two or more power-frequency spectrum data sets at two or more positions within the borehole, the data sets are processed to give a single power frequency spectrum at each position. The data sets are calculated for multiple equally spaced points in the borehole to determine the power frequency spectrum variation with depth.