Combination of epithermal and inelastic neutron scattering methods to locate coal and oil shale zones

摘要

A pulsed source of high energy neutrons is used to irradiate the earth formations in the vicinity of a well borehole. Gamma rays produced by the inelastic scattering of the fast neutrons are observed in four energy regions of the gamma ray energy spectrum corresponding to the inelastic scattering of neutrons by carbon, oxygen, silicon and calcium. Signals representative of the carbon/oxygen, calcium/silicon and carbon plus oxygen gamma rays observed are developed. By appropriately combining these signals with a separately derived hydrogen index log the quality of coal bearing formations or oil shale regions penetrated by the borehole may be determined.