Interpretation And Application Of Borehole Televiewer Surveys

A borehole televiewer log is comparable to a picture of a continuous core and may yield even more information since it is a picture of the cores host environment; i.e., the inside of the borehole as it exists in the subsurface. Important relationships are preserved which can be lost when cores are brought to the surface. Fractures, bedding planes, vugs and lithology changes are identifiable on borehole televiewer logs. The televiewer has had limited usage since being introduced by Mobil in 1969. However, technical improvements in equipment and improved logging techniques now make it possible to run borehole televiewer logs routinely in many of the major fractured reservoirs in the U. S. and Canada. A normal televiewer log is formed from the amplitude of the reflected televiewer signal. The travel time of the signal from the sonde to the borehole wall and back to the sonde has recently been used to form a second log: the Transit Time Log. Both logs used together provide much more useful information about the surface of the borehole than is obtainable from a conventional televiewer log alone. Interpretation problems due to noncircular boreholes and eccentered logging sondes are easily overcome using the combination of amplitude and transit time logs. Examples are given to demonstrate the potential use of both logs.