| Title | Assessing the potential of low to intermediate temperature geothermal resources for direct use |
|---|---|
| Authors | M. Ambunya, C. Wambua, N. Mariita, J. Mariaria, E. Ako, W. Ambusso, I.O. Bekkevold |
| Year | 2023 |
| Conference | New Zealand Geothermal Workshop |
| Keywords | wellbore simulation, geothermal resources, low-to-medium enthalpy reservoirs |
| Abstract | Electricity generation by use of direct condensing conventional turbines or by organic Rankine binary systems remain the most viable options for exploiting geothermal resources. Wells used for the two power systems typically have adequate and consistent steam flow rates at relatively high pressure. However, with the development of geothermal fields, some of the many drilled wells may not meet the required steam and heat flow rates at the required well head pressures. Such marginal wells will probably have intercepted low-to-intermediate temperature formations or poor permeability zones. These wells are typically used for either re-injection of waste brine/blowdown or for monitoring temporal changes in reservoir conditions. With increased emphasis on green forms of energy, marginal wells have proved useful as source of heat, and their exploitation for direct use purposes. These uses are predominantly at local boiling conditions or below. However up-take of direct use at higher temperature above local boiling, and at large scale has been slow. Consequently, a need to design and develop direct use methodologies usable to applications that use intermediate temperature in the range, 1000C to 1400C. Temperatures in this range may be more usable for industrial applications leading to better utilization of geothermal resources. To justify the accompanying investment in the heat conveyance system from the source to the utilities, it is important to ensure a priori that the resources tapped by the wells can sustain production and usage of heat for long enough periods and at competitive costs compared to traditional sources of fuel. This paper looks at effect of the wellbore design on developing and exploitation of a geothermal resource at intermediate temperature for direct use. In addition, production sustenance through re-injection will need to be done differently from regular reservoirs. This paper addresses these aspects and proposes methods of assessing the energy potential of these reservoirs. |