The Iceland deep drilling project: Its global significance

Abstract

The Iceland Deep Drilling Project (IDDP) is a long-term program to improve the economics of geothermal energy by producing supercritical hydrous fluids from drillable depths. Supercritical fluids have higher enthalpy than steam produced from two-phase systems. Large changes in physical properties near the critical point can lead to extremely high flow rates. Studying supercritical fluids will require drilling wells and sampling fluids and rocks to depths of 3.5 to 5 km and at temperatures of 450-600?C.Although drilling such deep wells is expensive, the power outputs from supercritical wells should be considerably enhanced. Iceland is a very favorable environment for this study. It is the largest landmass straddling a mid-ocean ridge, where active rifting provides the permeability and volcanism provides the heat sources for a major geothermal industry. Very high heat flows within these rifts indicate that supercritical temperatures exist at drillable depths. Seismic activity continues to below 5 km in thesehigh temperature geothermal fields, indicating that even at supercritical temperatures, the rocks are brittle and therefore permeable. Similarly because of the high rain and snowfall, most of Iceland??s geothermal systems produce very dilute fluids. If the IDDP is an economic success this same approach could be applied in other high-temperature volcanic geothermal systems elsewhere, an important step in enhancing the geothermal industry worldwide. Given Iceland??s unique position as the largest landmass astride the Mid-Atlantic Ridge, the wide-ranging scientific and engineering program that is an integral part of the IDDP will be of global significance. As well investigating supercritical phenomena, drilling in this environment can address a wide range of world-class scientific questions, such as the formation of ophiolites, hydrothermal ores, andblack smokers on mid-ocean ridges..