Doublet deployment strategies for geothermal Hot Sedimentary Aquifer exploitation

Abstract

Huge amounts of heat are stored in sedimentary aquifers in the Dutch subsurface. The amount of heat would be sufficient to provide our national heat demand for decades without any greenhouse gas emissions. Exploitation of this type of resource started some 10 years ago in the Netherlands. In 2016, 16 geothermal doublet systems had been installed that produce geothermal heat, and each year 2 to 3 new systems are realised. A doublet system consists of a production well that extracts hot formation water from kilometer deep aquifers. After the heat is extracted from the water in heat exchangers, the cooled water is reinjected into the same aquifer at approximately 1 to 1.5 km distance from the production well. Most of the current Dutch doublet systems provide heat for the horticulture sector. These systems have an average net energy production of approximately 10 MWth and therefore hundreds of additional systems are required to significant amounts of our heat consumption with geothermal energy. This PhD thesis investigated doublet system design and deployment strategies to optimise exploitation and increase the possible number of doublet systems exploiting the same aquifer. Based on detailed geological models, subsurface flow simulations are used to evaluate parameters such as required injector-producer distance, the preferred orientation of a well pair with respect to geological trends and required doublet distance to avoid negative interference. Based on the results, regional doublet deployment strategies can be developed to make optimal use of geothermal heat from sedimentary resources.