Abstract: A method for detection and monitoring of hydrocarbon deposits by measuring infrasonic spectral characteristics of microseismic noise of the earth. The method is used onshore and offshore for detection of hydrocarbon deposits and for monitoring of producing oil and gas fields and subsurface storage of natural gas. In one method of the invention, at least one receiver of seismic vibrations capable of recording vibrations in the infrasonic range is placed over an area being surveyed. The spectral characteristics of the microseismic noise of the earth recorded within a 2 to 5 Hz frequency range are used as a “passive” information signal. A hydrocarbon deposit is determined by the presence of a spectral anomaly on a spectrum of the passive information signal relative to a spectrum of an information signal from the area known not to contain hydrocarbons.

Abstract: A downhole thermoacoustic device comprises a heater with a terminal chamber, connected to a source or radiator of acoustic oscillation, including a hollow housing having mounted therein a longitudinal shaft carrying coils with cores in the form of a plurality of flat rings of a magnetostrictive material, operable as the active elements adapted to generate acoustic oscillation. Accommodated intermediate the coils is a member for focusing the acoustic field, in the form of a sleeve, while the longitudinal shaft carries a tube-shaped reflector of acoustic oscillation internally of the core of each coil. The top and bottom portions of the hollow housing of the radiator of acoustic oscillation have mounted therein damping elements including sleeves of a resilient material, while a heat-insulating member including a sleeve with a fluted surface is provided intermediate the terminal chamber of the heater and the hollow housing of the radiator.