Geothermal reservoirs are hot deep waterbearing systems (hydrothermal systems) or systems without or with limited amount of water (petrothermal systems). Hydrothermal systems include geologic formations with naturally sufficient hydraulic permeability, i.e. the capacity of the geological medium to transport fluids. Crucial for the economic operation of hydrothermal systems is a sufficient temperature of the aquifer, and a high hot water production rate.
EGS – Enhanced Geothermal Systems
Enhanced geothermal systems are geothermal reservoirs which have promising high temperatures but the rock permeability or the abundance of fluids in the rock is not high enough for the production of electricity. EGS are also referred to as Hot Dry Rocks.
In EGS, stimulation techniques are used to generate an artificially higher hydraulic permeability in initially low-permeability rocks. Such stimulation techniques are hydraulic, thermal, or chemical stimulation, advanced well configurations, or soft stimulation techniques such as cyclic/fatigue stimulation or multi-stage stimulation. EGS technologies represent the sum of the engineering measures that are required for the transfer of heat and to optimize the exploitation of the reservoir. Therefore, the concept of EGS is designed to make geothermal energy utilization feasible in most environments and thus offers an enormous untapped potential.
In GEMex we aim to explore the EGS in Acoculco. Two wells have shown high temperatures around 300 °C at 2km depth, but hardly any fluids were found. During the project we are going to use the full range of geological, geophysical and geochemical exploration methods to find out more about the geothermal system and to recommend EGS measures for the economic usage of the Acoculco reservoir.
SHGS – Super Hot Geothermal Systems
Super Hot geothermal systems are geothermal reservoirs with an exceptional high geothermal gradient. In SHGS temperatures of more than 380 °C can be reached. This makes them ideal candidates for the exploitation of geothermal energy and geothermal electricity production.
However, we often also find exceptional fluid chemistry in SHGS - the aggressive fluid and the high temperature pose a challenge to the methods and materials used for drilling and well completion. That is why SHGS are up to now rarely used for geothermal energy production.
In GEMex, we will investigate the SHGS in Los Humeros. The northern part of the geothermal field, which shows the super hot temperatures, will be characterized by geological, geochemical and geophysical methods and numerical models will permit the simulation of reservoir characteristics. At the end, GEMex will provide a list of suitable materials to be used in SHGS and recommend designs for drilling, well completion, and sustainable usage of the reservoir.