Datensatz

Zusammenfassung

Borehole geophysics is one aspect of borehole measurements, partially overlapping with other aspects such as borehole sampling, borehole testing, and borehole monitoring. Borehole geophysical investigations apply special downhole instruments, so-called logging sondes, to measure, record and analyze continuously or at discrete depths physical properties of the geological formations around a borehole, which is termed borehole or downhole logging. The logging sondes perform their measurements most commonly while being moved down or up inside a borehole, delivering the typical downhole log recorded as a function of depth. The sondes can be deployed in the hole by a special logging cable or by a drill string. Several different logging sondes are usually applied to collect all parameters necessary for the desired geological and structural interpretation of the subsurface. Borehole logging is the most important measuring method in deep drilling and has in some areas largely replaced the time- and cost-consuming coring. Borehole logging is complementary to measurements on cores and cuttings and most helpful in zones with core loss. Logging yields information on well stability, lithology, fractures, porosity, permeability, stress state, and fluid content and many other properties. Here, we summarize the most common borehole geophysical methods of wireline logging but most methods also work with other deployment techniques.