3D numerical modeling of hydrothermal processes during the lifetime of a deep geothermal reservoir

Abstract

Understanding hydrothermal processes during production is critical to optimal geothermal reservoir management and sustainable utilization. This study addresses the hydrothermal (HT) processes in a geothermal research doublet consisting of the injection well E GrSk3/90 and production well Gt GrSk4/05 at the deep geothermal reservoir of Groß Schö nebeck (north of Berlin, Germany) during geothermal power production. The reservoir is located between )4050 to )4250 m depth in the Lower Permian of the Northeast German Basin. Operational activities such as hydraulic stimulation, production () change the HT conditions of the geothermal reservoir. The most significant changes affect temperature, mass concentration and pore pressure. These changes influence fluid density and viscosity as well as rock properties such as porosity, permeability, thermal conductivity and heat capacity. In addition, the geometry and hydraulic properties of hydraulically induced fractures vary during the lifetime of the reservoir. A three-dimensional reservoir model was developed based on a structural geological model to simulate and understand the complex interaction of such processes. This model includes a full HT coupling of various petrophysical parameters. Specifically, temperature-dependent thermal conductivity and heat capacity as well as the pressure-, temperature-and mass concentration-dependent fluid density and viscosity are considered. These parameters were determined by laboratory and field experiments. The effective pressure dependence of matrix permeability is less than 2.3% at our reservoir conditions and therefore can be neglected. The results of a threedimensional thermohaline finite-element simulation of the life cycle performance of this geothermal well doublet indicate the beginning of thermal breakthrough after 3.6 years of utilization. This result is crucial for optimizing reservoir management.

Hydrochemical characterization of a mine water geothermal energy resource in NW Spain

“…available water resources) which are essential for optimal geothermal exploitation (Ordóñez et al, 2012;Jardón et al, 2013). The long-term temperature of the mine water reservoir, particularly under different scenarios of water extraction, use and injection is of key concern and several models have been implemented to predict it (Loredo et al, 2016;Andrés et al, 2015;Uhlík and Baier, 2012;Raymond et al, 2011;Blöcher et al, 2010;Renz et al, 2009). …”

Influence of major fault zones on 3-D coupled fluid and heat transport for the Brandenburg region (NE German Basin)

“…Local reservoir-scale models integrating more highly resolved structural data, information derived from boreholes, and in situ measurements may provide better constraints for the characterization of fault zones (e.g. Cacace et al, 2013;Blöcher et al, 2010). Better constraints on the hydraulic behaviour of fault zones may be provided by prospective integrated geophysical methods (e.g.…”

“…(2) and (3) are coupled by the fluid density according to an equation of state after Magri (2004) and Blöcher et al (2010).…”

Deep 3D thermal modelling for the city of Berlin (Germany)

“…Any identified warmer domains can at last be the focus of reservoir-scale modelling. This may include simulations of the dynamic behaviour of the hydraulically enhanced reservoir under specific in-situ working conditions, such as already have been performed for the deep geothermal reservoir of Groß Schönebeck (north of Berlin; Blöcher et al 2010;Wong et al 2013 -this issue), the city of Den Haag (Mottaghy et al 2011), and for a fractured carbonate reservoir in the Molasse Basin (Germany; Cacace et al 2013). …”