NIOSHTIC-2 Publications Search
Caliper location of leached zones in Colorado shale.
Thomas HE; Smith JW
Log Analyst 1970 Jul-Aug; 11(4):12-16
Accurate estimation of oil yields in Green River Formation oil shale requires knowledge of the presence or absence of cavities (vugs) left after the natural removal of the mineral nahcolite (nahco3). Conventional well logs have not provided a means for detecting the vugular porous zone. This paper describes a 3-arm caliper logging system, logging technique, and mathematical correction method used by the Bureau of Mines to locate and compensate for the vugular porosity. The caliper defines the zone by sensing a high frequency of minor diameter variations as small as 1/10 inch. Estimations of oil yields and oil shale reserves from density logs can be significantly improved when the vugular zone's thickness is known. A porosity-density correction method is presented.
Issue of Publication
Page last reviewed: April 12, 2019
Content source: National Institute for Occupational Safety and Health Education and Information Division