Enablement of High-Temperature Well Drilling for Multilateral Closed-Loop Geothermal Systems

Abstract

Constructing a multilateral closed-loop geothermal system (MCLGS) requires magnetic ranging tools in the bottomhole assembly (BHA) to intersect the wellbores and create the closed loop. The levelized cost of energy (LCOE) of such an MCLGS is largely driven by rock temperature – the hotter the rock, the more energy that is produced from a given well configuration, and the lower the levelized cost. However, the magnetic ranging tools have a maximum temperature limit above which they are not functional. To enable drilling of high-temperature rock formations and thereby decrease the LCOE, methods for estimating the temperature of the BHA critical components are required. To simulate this process, two models of increasing complexity were developed. The first model is a one-dimensional pseudo steady state wellbore + thermal resistance model capable of estimating the temperature and pressure profile of the drilling mud throughout the drill pipe and annulus. This model is used to understand key performance drivers and technology requirements to achieve high-temperature drilling. The second model is a fully coupled transient, two-dimensional heat conduction and wellbore model. This coupled model is capable of simulating dynamic drilling processes such as connections, running in hole, pulling out of hole, and circulating without drilling. This paper illustrates the capabilities of the two models and presents case studies and key learnings for high-temperature drilling, as well as field results from Eavor’s deep hot test well drilled Q4 2022 in the southwestern US.