Case Study of a Multilateral Closed-Loop Geothermal System

Abstract

A full-scale demonstration project of a multilateral closed-loop geothermal system is presented. The project consortium contains several major diversified energy companies and service providers, and participation from Canadian federal and provincial technology agencies. The project is located near Sylvan Lake, Alberta, Canada and consists of two 2.5 km long multilateral horizontal wellbores connecting two 2.4 km deep vertical wellbores to create a U-tube shaped closed-loop system. The horizontal wellbores are intersected using magnetic ranging technology, and sealed with a novel completion technique, resulting in a giant subsurface heat exchanger. It is an entirely closed system with no flow into or out of the formation. Water is then circulated through the system, entirely driven by the thermosiphon effect created by the density difference between the inlet and outlet wells. Design, planning, and execution of the project is described, along with key items learned. Key performance indicators are drilling efficiency, operational leak-off rate, solids production, and thermodynamic performance. Thermodynamic performance of the system is modeled and compared to simulation models developed prior to drilling. The pilot results are scaled-up to a realistic commercial project to demonstrate that a closed-loop multilateral system in sedimentary basins is technically and economically feasible. This technology is agnostic to formation permeability and enables projects in areas without high flow capacity.