A New Hybrid Simulation Approach to Evaluate the Efficiency of Hydraulic Stimulation Treatments

Abstract

The development and operation of Enhanced Geothermal Systems (EGS) is governed by complex interactions of geological, hydraulic (H), mechanical (M), thermal (T) and chemical (C) processes occurring during a relatively short term stimulation phase and a long term production phase. An adequate representation of these highly non-linearly coupled and time-dependent processes is only possible by numerical modeling. To date, no single modeling approach is capable of sufficiently describing these coupled and time-dependent dynamic processes. This paper introduces coupling of two modeling methods: H-M coupled dynamic discrete element model by PFC2D (Particle Flow Code 2D) and T-H coupled finite element model by OpenGeoSys (OGS). The two simulators are combined by an interface module in which the results of hydraulic stimulation modeling by PFC2D are passed on to OGS for long term T-H coupled flow simulation in the stimulated reservoir. The combination of these two simulators, therefore, provides relatively short-term reservoir behavior by hydraulic stimulation (stimulation phase) and long-term behaviors in production/circulation phase. This paper describes the work flow of reservoir modeling using the hybrid simulator. A re-stimulation scenario of a volcanic rock layer in the in situ geothermal laboratory Groß Schönebeck (Northeast German Basin) is given as demonstration application.