Design and Experimental Study of Intensifier for Deep Geothermal Drilling

Abstract

The rock of deep geothermal reservoir has the characteristics of high in-situ stress, high strength and high abrasiveness, which leads to slow ROP and low drilling efficiency during the drilling process of geothermal resource development. Ultra-high pressure jet slotting can effectively release local stress at the bottom-hole area and improve the rock-breaking ability during drilling. Therefore, in order to increase the pressure of the jet as much as possible and form an effective slotting at the bottom of the well, this paper designs an efficiently downhole intensifier device directly driven by the energy of the drilling mud. The parameters affecting the supercharging performance and stagnation pressure of the intensifier are analyzed by means of CFD simulation, and the output characteristics of the intensifier are tested by means of laboratory experiments. The results show that the area ratio between the two ends of the piston in the boosting chamber is an important factor affecting the boosting performance. Increasing the stroke of the piston has no effect on the output pressure of the Intensifier, but it can prolong the holding time of the high-pressure water jet. The stagnation pressure decreases with the radial distance, the maximum of which is at the center of the jet. The length of the isokinetic core is about 6 times the nozzle diameter. Therefore, the jet distance of the ultra-high pressure drill should be controlled within the isokinetic kernel range. Compared with conventional geothermal drilling methods?the ultra-high pressure jet generated by the intensifier studied in this paper is coupled with the mechanical shock, which can provide a new deep geothermal drilling speed-up method and technology, So it can provide a theoretical and technical support for promoting the efficient and low-cost exploitation of geothermal resources.