Compensated density well logging tool

Claim 1

A compensated density well logging device for use with a lowering mechanism for measuring the density of subsurface formations through an open well bore coated with filter cake and containing drilling fluid and transmitting density signals to receiving devices on the surface, comprising: (a) a hollow first housing having an upper end connected to the lowering mechanism and a lower end adapted to guide the tool downward through the well bore; (b) a connection means mounted at the upper end of said first housing; (c) a pad mounted with said first housing by said connection means, said pad having a second housing and a pad interior member mounted therewith in said connection means enabling the pad to be shifted from a first position within the first housing and a second position extended through a first longitudinal slot; (d) radioactive source means mounted within the pad interior member, said pad interior member being opaque to radiation emitted thereby, said pad interior member defining directional window means for the controlled emission of radiation exteriorly of the device; (e) a plurality of radiation detection means for detection of backscatter radiation from irradiated subsurface formations, and coversion of the level of radiation into an electronic signal, mounted on collimating windows formed in the pad interior member is spaced relation to said radiation source means; (f) a caliper arm having a first end pivotally mounted on said first housing radially opposite said pad and a second end for extension through a second longitudinal slot so as to contact the well bore and position the device adjacent the opposite wall of the well bore during measurement operations; (g) extension means connected to said pad connection means for urging said pad into said second position and further connected to said caliper arm for radial extension thereof so as to thrust said pad into the filter cake, said extension means enabling the shifting of said pad into said second position independently of the extension of said caliper arm; (h) actuating means mounted on said first housing connected to said extension means for restraining the shifting of the extension of said caliper arm and pad until measurement of formation densities is desired; (i) measurement means mounted on said actuating means responsive to the position of the caliper arm with respect to the first housing for measurement of the well bore diameter; and (j) electronic means mounted within said first and second housings for receiving, processing, and transmitting signals from said detector means and measurement means exteriorly of the device and for transmitting electric power within the device.