Caliper Logging

Caliper logging is a practice of measuring the variations in the diameter ofthe open hole in a well. This information is useful for many purposes, amongwhich are: Determining the volumetric capacity of the portion of open hole tobe cemented; the amount of gravel to be used for gravel-packing a well; thesize and location of seat for a packer to be placed in a well; studying theeffects of nitroglycerin shots; studying the effects of acidizing; studying thecause of drill-pipe failures; studying drilling technique; geologicalcorrelations. This is a new practice in oil fields and is eliminatingconsiderable guesswork. Introduction Caliper logging of the open hole in oil wells, recently introduced and nowshowing initial results in many sections of the country, is providinginformation that is filling a long-felt need in oil-well cementing and innumerous other oil-field practices. Briefly, it measures the variations indiameter of the open hole in a well. This direct physical measurement of thestratigraphic profile has considerable value for subsurface interpretations bythe geologist, engineer, driller and others charged with the responsibility ofproperly completing and repairing oil and gas wells. The caliper shown in Fig. I is run into a well in closed position. The fourarms are released when logging is to start. These arms are independent of eachother. As the calipers are pulled upward through the open hole, the arms arelike nimble fingers feeling the changing profile of the hole. This mechanicalaction is in turn converted into an electrical circuit, which is connected to arecording mechanism at the surface. The recording of the diameter of the holeis directly in inches. T.P. 1474