Applications of Radial Jet Drilling Techniques in Geothermal Wells

Abstract

Developing geothermal reservoirs as enhanced geothermal systems (EGS) is becoming increasingly popular as a renewable energy resource. Hydraulic fracturing improves the permeability of these resources by stimulating their reservoirs. Nevertheless, creating controllable fractures in deep geothermal wells can be challenging because the rocks are strong and their crystal structure is intact. Radial Jet Drilling (RJD), which creates microholes through the rock, could effectively stimulate geothermal reservoirs. RJD is an emerging technology that utilizes high-pressure water to drill several radial holes from an existing vertical well. The technique has been developed for stimulating oil and gas wells. It provides unique features required for effective reservoir stimulation. There is evidence that RJD could increase oil and gas production by more than fivefold. However, in geothermal wells, its applications are limited due to the challenge of jetting hard magmatic formations. Even though successful jetting of hard rocks was performed under atmospheric conditions, field tests demonstrated the challenge of drilling laterals in geothermal wells. Thus, further research is needed to advance RJD for use in geothermal wells with hard rock formations. The purpose of this article is to review recent RJD studies conducted to stimulate geothermal wells. Globally, various efforts have been made to adapt RJD to exploit geothermal resources in recent years. Several factors affect RJD technology's effectiveness, including jetting bit design, fluid composition and properties, circulation rate, injection pressure, stress state in the formation, borehole pressure, and temperature. These factors determine performance parameters such as penetration rate and propulsion force. The RJD operation requires a high rate of penetration (ROP) to drill at an economical rate, while propulsion force is needed to propel the bit at the achieved ROP.