Rejuvenizing aged conventional geothermal reservoirs with supercritical geothermal energy

Abstract

New Zealand has set an ambitious target to achieve 100 percent renewable electricity generation by 2030 and net-zero emissions by 2050. In addition to hydro, solar and wind energy, geothermal is also expected to play a more important role in achieving these goals. But the problem we are facing is that the conventional geothermal energy potential for further development is limited and unlikely to meet the demand. Most of New Zealand's conventional high temperature geothermal fields have already been developed for electricity generation and the remaining are restricted for commercial development due to environmental concerns. Some of the developed geothermal fields have been expanding their generation capacity or have plans to do so already. While concerning the limited resource potentials and some of them are approaching the late stage of life spans, significantly largescale increase in power generation seems to be impossible with current development patterns.
A prospective solution to this problem is to develop deeper supercritical geothermal energy for electricity generation to make up the extra energy demand. Even though geothermal communities throughout the world have been trying to extract superhot fluids from the deeper heat source in the past two decades, and have indeed made some achievements, building a power plant making use of supercritical fluids still has a long way to go. The main obstacle, among lots of others, is the temperature and pressure being too high for the well-casing and wellhead equipment to cope with, resulting in well casing collapse and wellhead equipment failure. The author in this paper has proposed some innovative ideas to develop supercritical geothermal energy by using the existing conventional geothermal power generation facilities without directly coping with the super high temperature and pressure fluid. This new development strategy will greatly benefit the existing power plants by expanding their life spans and production capacities. The technical challenges we are facing in coping with supercritical geothermal fluids can also be by-passed, though not be solved at the early stage of supercritical development.