Heat Transfer and Flow Paths in the Deep Part of the IDDP-2 Well in Reykjanes, SW Iceland
Saeunn HALLDORSDOTTIR, Egill Árni GUDNASON, Inga BERRE, Gudni AXELSSON, Eirik KEILEGAVLEN and Gunnar THORGILSSON
[University of Bergen, Iceland]
Generally, it is assumed that the main mechanism that transfers heat from heat sources of volcanic geothermal systems is driven by a Convective Downward Migration (CDM) process: a cooling front, driven by convecting water, migrates into hot rock through fractures that open up due to thermo-elastic contraction by cooling of the rock. Drilling into superheated formations in Iceland has revealed extensive fluid losses at depth for reasons that are not fully understood. A possible mechanism is that, as in the CDM process but on much shorter timescale, the introduction of cold drilling fluids leads to thermo-elastic contraction of the rock that opens fractures to significantly enhance the fluid injectivity. In the present study the focus is on the deep part of the Reykjanes geothermal system, on seismic events induced during drilling and stimulation of the IDDP-2 well and other data that can reveal the permeability structure and flow paths below the present production field. Double-difference earthquake relocations during drilling and stimulation of the well, i.e. from August 2016 to end of September 2017 map possible flow paths stimulated by injection of fluids. The mapped flow pathways can be used to restrain thermo-hydro-mechanical models of the proposed conditions that enhance permeability by opening of fractures. The results will be used in an ongoing study of the CDM process and possible effect on heat transfer close to the IDDP-2 well.
|        Topic: EGS - Enhanced Geothermal Systems||Paper Number: 31094|