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Abstract The Geretsried project in southern Germany is a production sized closed loop advanced geothermal system at reservoir depth of 4500m TVD and 150 degrees C. A loop system consists of two motherbores, each having a series of 3000m lateral pairs departing the motherbores and intercepting at the toe. The system is fortified in open hole with a proprietary completions fluid. Collectively, the network of laterals creates an underground radiator, where water circulation through the loop brings heat to surface. Typical loops accommodate several lateral pairs, translating to thousands of meters of hard rock drilling per loop. Successful economics demand maximum drilling performance while overcoming complex well construction challenges. Each lateral departs the mother bore through a whipstock. Initiation of the lateral requires precise directional work on departure, followed by high dogleg turns toward the intended lateral orientation. The lateral pairs require controlled proximity at all times, ensuring effective heat transfer once producing. Intercepting the lateral pairs at the toe, greater than 8000m measured depth, is an industry first. The long laterals run east-west, and at such high latitude, the residual magnetic azimuth error is large. Combined, these factors compound the wellbore position accuracy and steering complexity. Optimizing the extensive drilling time and cost are the main ingredients to deliver project economics. Several laterals depart from each mother bore so excessive casing wear was a risk, meaning string RPM must be limited over the duration of the project. To preserve wellbore isolation, drilling fluid additives are limited, challenging hole cleaning. High wellbore friction in the reservoir resulted in excessive dynamics in the BHA, and in the string during drilling.