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Abstract In the process of hot dry rock(HDR) geothermal energy development，the first issue to be resolved is deep drilling. According to the geological characteristics of HDR geothermal resources in China，the three key issues during HDR geothermal drilling construction are proposed based on the experimental research，theoretical analysis and numerical simulation. They are drilling surrounding rock stability control technology，rock breaking technology under high temperature and high pressure and drilling fluid technology under high temperature and high pressure. And then，from the main factors of surrounding rock instability in exploitation of HDR geothermal energy，rheological properties of drilling surrounding rock under thermo-mechanical coupling，drilling surrounding rock deformation failure law and the critical failure condition under high temperature and high pressure，the drilling surrounding rock stability control technology during the HDR geothermal deep drilling is proposed. Through the experimental research on rock breaking in granite with three methods which are impact grinding rock breaking，cutting rock breaking，impact-cutting compound breaking rock under high temperature and high pressure and the comparison of the three rock breaking methods under different temperatures，the rock breaking laws of the three methods are obtained under high temperature and high pressure. Finally，from the effect of high temperature on drilling fluid，the general requirement of high temperature treatment for geothermal drilling and the effect of the performance of drilling fluid on wall stability and its countermeasures，the drilling fluid technology requirements of HDR deep drilling are solved. The research on deep drilling technology under high pressure and temperature has important scientific and engineering significance to the human exploration of Earth and the development of deep earth energy and resources.
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Received: 21 April 2011
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2011, Vol. 30 
