A Preliminary Assessment of a Medium-Enthalpy Geothermal Resource in Nagqu (Tibet) People's Republic of China

Abstract

The Riagqu geothermal field is a single-phase. liquid-dominated svst-eiii at reservoir. condi-tions. having a high gas content. T l i is field is located at an elevation of about 4.500 iii (asl), in the vicinity of the City oÄ Nagqii I which is one of the most iniportant c i t i e s of Tibet. The resei:voir rock is made of a highl>- fractured. low-perineahili t y sedimentary sequence, During t.he iinpleinenratiriii of the study descrihed i i i this paper, fluid pi.oductivn w a s inainl?- otitained froiii two out of foul possible productive wel.15. Tlie i i i a i 11 fault sl~sterns are located i r i a NE-SG; and F.-K t l i - r e c t i o i is, which seem to cont.1 t i l fluid iiiuremeiit at depth. The geotlierinal field is ?.es t r i c ted to a siiiall area diere h>-drotliel-ni:il iiiaiiiEes tations are locat-erl I Reservoil triiiperattire is 114 OC. gas coiitent is i i i tlir range of 0. 5 to 0.6 percent h>- iiiass, being mainl>- CO Reservoir tiansmlssivit>- in the area oi ' L e wells is -er>- Iiigli. Reservoir iesponse to changes in floij rate in air? of the producing wells could be detected aliiiost iiliiiiediat el>- in the l.JtibCl v:itiuli wells I whii,li were di.stant between 300 to 900 m, ilepenc-liug on the production-obser ation well airange- Illen t.. Cal.ciuiri cartmiat e scaLittg was preseiit in a1 I producing wells. This deposit ioii was colit roll e d by the C02 partial pressure. Drscriptiori of well testing results is proicled. as well RS t.he tlieriiiod?n;iiiiics and geodieinistry of reser-vuir f l i i i d s .