The development of deep geothermal systems to boost global electricity production relies on finding cost-effective solutions to enhance the drilling performance in hard rock formations. In this work, we investigate a novel drilling method combining thermal spallation and conventional drilling. This method aims to reduce the rock removal efforts of conventional drilling by thermally assisting the drilling process by flame jets. Laboratory experiments are conducted on the combined drilling concept by studying the effects of flame treatments on the mechanical strength of hard and soft rocks. In addition, investigation on the interaction between the rock and a cutting tool, permits to show that the combined method can drastically improve the drilling performance in terms of rate of penetration, bit wearing and the required mechanical energy to remove the material. As a proof-of-concept of the method, a field demonstration is presented, where the technology is implemented in a conventional drill rig in order to show the process feasibility as well as to quantify its performance under realistic conditions.


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