Caliper Logs

Caliper logs provide a continuous record of borehole diameter and are used widely for logging at environmental sites. Changes in borehole diameter may be related to both drilling technique and lithology. Caliper logs are essential to guide the interpretation of other logs, because most types of logs are affected by changes in well diameter. They also are useful in providing information on well construction, lithology, and secondary porosity, such as fractures and solution openings. Vesicular and scoriaceous tops of basalt flows, cinder beds, and caving sediments were identified with three-arm caliper logs. Caliper logs are useful for determining what other logs can be run and what range of diameters will be accepted by centralizers or decentralizers. Hole-diameter information also is essential for the calculation of volumetric flow rate from many types of flowmeter logs. Caliper logs can provide information on lithology and secondary porosity.