Issues of Air-Lift Reverse Circulation Drilling Technologies for Geothermal Wells in China

Abstract

Geothermal energy is starting to boom in China. Hard formation and frequent drilling fluids loss are the most common challenges encountered in geothermal well drilling construction. While hard formation results in low rate of penetration, fluid loss increases consumption in loss control materials and drilling muds along with severe formation damage and subsequently diminished productivity. Low rate of penetration and poor productivity contribute to the rising drilling costs while depress public confidence to this new type of renewable energy. Air-lift reverse circulation drilling is recognized by geothermal industry and is expected to overcome the above-mentioned problems. There are many successes, still some problems remained, however. This article analyzed the pressures and established the demanding depth of dual-wall drill pipes for different well depth under various conditions; furthermore, borehole stabilization was discussed by analyzing the pressure profiles and other hydraulic parameters in the annulus of borehole and appropriate properties of drilling fluid for some not very consolidated formation to use air-lift reverse circulation was proposed.