The Most Productive Low-Temperature Geothermal Production Well in Iceland/the World?

Abstract

The low temperature geothermal field at Hjalteyri, Eyjafjordur, Iceland, has been utilized since 2003 when well HJ-19 was connected to Nordurorka’s district heating facilities for Akureyri. An initial 9-month production test along with the first years of utilization, indicated a highly permeable and productive reservoir. In 2005 another well, HJ-20, was drilled to increase production from the powerful geothermal system. The drawdown evolution so far, with up to 115-135 l/s average production of 87°C hot water, over the last fifteen years has validated a high-permeability model for the Hjalteyri geothermal system. Hence, a new well, HJ-21, was drilled in 2018. Permeability tests performed on HJ-21 indicate permeability properties beyond previously known capacities, both in terms of production index and estimated transmissivity. The simulation of the pressure response of the well during initial flow- and buildup-testing at the end of drilling on basis of a pressure diffusion equation solution for a lateral reservoir of constant thickness, uniform permeability and infinite extent, yielded a good fit to observed pressure changes. The simulation results indicated a permeability thickness of more than 1000 Darcy-m near well HJ-21.