Abstract: An apparatus, system and method are provided for measuring state properties without requiring an internal or proximate power supply. The apparatus provides a sensing device that is responsive to fluctuations in a state property that are encountered within the test zone. Due to the fluctuations experienced by the sensing device, a sensing signal is generated and transmitted to an optical device, such as an interferometer. The sensing signal's affect on the optical device produces an interference pattern that may be detected remotely and correlated to the fluctuation experienced by the sensing device.

Abstract: 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.

Abstract: Methods and apparatus are provided for making improved pulsed neutron derived measurements of the carbon: oxygen ratio in subsurface earth formations. Plural radiation measurements are made as a function of time from the initiation of the neutron pulse to distinguish inelastic and thermal neutron interactions. These measurements are also within their respective time functions, energy dependent. The time and energy dependent radiation measurements are then combined in several different manners to provide an improved carbon: oxygen ratio measurement and multiple porosity and formation lithology indication measurements.