A case study of radial jetting technology for enhancing geothermal energy systems at Klaipeda geothermal demonstration plant

In 1996 a geothermal energy project was initiated at Klaipėda, Lithuania, to demonstrate the feasibility of using low enthalpy geothermal water as a renewable energy resource in district heating systems. The Klaipėda geothermal plant is situated within the West Lithuanian geothermal anomaly with a relatively high heat flow density of 70-90 mW/m2 and contains two geothermal injectors and producers. The injectivity of the wells has been deteriorating ever since plant start-up due to chemical precipitation, fines mobilization and scaling. In November 2014, radial jetting technology was identified as a possible solution for enhancing injectivity of the wells. With radial jet drilling, several open hole laterals of 100 m maximum length and with a diameter of 0.03 m to 0.05 m are jetted from the main well bore in order to enhance the connectivity of the well to the rock and thereby the well productivity or injectivity. In one of the injection wells at Klaipėda, 12 horizontal laterals of around 40 m in length were jetted in a number of highly permeable layers present in the aquifer. Production data post drilling of the laterals suggest an improvement in injectivity of approximately 14%. A base case scenario was constructed based on the specifications of the radial jetting job at Klaipėda. For the base case scenario, assuming the laterals were all jetted according to the specifications, the increase in injectivity was estimated at 56%. An uncertainty analysis was carried out to investigate the impact of uncertainties in the length, positioning, diameter, inclination, and pre-existing near wellbore damage of the laterals on the water injection rate. The sensitivity of the injection rate to uncertainties in the lateral design parameters varies between 2.2% and 13.4% for the parameters evaluated.