The Zhacang thermal field, Qinghai Province, China: its geology, geophysics, chemistry, and conceptual model

Abstract

The Zhacang thermal field has the highest temperature and the most typical characteristics among the 84 geothermal anomalies discovered in Qinghai Province, China. It is located 15 km southwest of Guide County and has a total area of 8.4 km2, where two geothermal wells have been drilled since 2011. This paper summarises the geological conditions, drilling data, geophysical exploration data, and hydrochemical characteristics of the Guide–Zhacang geothermal field. The Zhacang geothermal field has a high geothermal flow value and is rich in geothermal resources with high thermal conductivity (2.910 W/(m•K)) and high geothermal flow value (87–117 mW/m2). The main strata are made up of Neogene mudstone, Triassic sand slate, and Indosinian granite and granodiorite, which provide a good thermally insulating cover layer and storage zone. The Zhacang and Reguang faults are deep, which helps the deep heat source and underground hot water move upward. The source of borehole hot water and hot spring water in the Zhacang geothermal field is atmospheric precipitation with a recharge elevation of 3320–3470 m, and the circulation depth is −2888.6 m. The results of explorations and surveys are integrated to propose a new conceptual model of the Zhacang geothermal reservoir.