Thermal Groundwater in Deep Stratified Reservoirs in Oita Prefecture, Japan

Abstract

Most of hot springs are commonly seen at valleys of rocks exposed or on fan deposits in mountaineous regions in Japan. They have been flowing out naturally from ancient times. accompanying occasionally with surface geothermal activities behind them, though hot waters nowadays are usually extracted by drilling and pumping out directly from shallow aquifers or fractured formations in their environs. Such hot waters have been frequently considered as a result of ascending of geothermal fluid from deep zones through faults or fractured systems, and subsequently sometimes spreading laterally into aquifers in shallower zones as the fluid being diluted.

This paper concerns with the distribution of underground temperature from this point of view. that is. the effect of upward flow of deep thermal groundwater stored within stratified formations through a vertical fault. The difference and connection between the shallow hot waters in geothermal fields and the deep thermal waters in thickly stratified formations will be discussed.