WP4 Demonstration of combined hydraulic-thermal-chemical treatments in sandstones, carbonatic rocks and granites






D4.1 Detailed report on thermal, hydraulic, and chemical parameters before and after the stimulation treatment. Indication of significant changes.

D4.2 Detailed report on the performance of permeability enhancement, simplified skin effect, and the productivity and injectivity indices

D4.3 Detailed report on reservoir performance in terms of sustainability each 12 month

D4.4a Report on the laboratory experiments and subsequent simulator development and simulations of hydraulic, thermal, chemical stimulation. This will feed into the other deliverables in this task.

D4.4b Report of the detailed list of measured parameters, the predictive modelling, data acquisition and analysis, as well as monitoring needs, depending on the stimulation method.

D4.4c Input data for the business plan, including cost of treatment/stimulation, cash flow expected, magnitude of increase in productivity/injectivity, and business impact: Indepth report on baseline monitoring and mining authority regulations, Report on preparation of site and performing treatment, Report on FOI and long term hydraulic tests of sustainable performance, and publication of results.

In recent years, many sites have been investigated and developed to determine if they are suitable for economic geothermal energy development. One of the major limitations for geothermal energy development is the low natural fluid productivity, especially in low- and medium-enthalpy reservoirs. Stimulation treatments are widely used to increase the magnitude of productivity to levels that enable economic use of natural geothermal systems. Hydraulic, thermal and/or acidic stimulation techniques and new well designs adapted from the oil and gas industry have been developed to enhance the performance of such enhanced or engineered geothermal systems (EGSs). Although application of hydraulic, thermal or chemical stimulation in isolation can increase initial productivity, the use of a single stimulation technique cannot always achieve a sufficient and sustainable increase in productivity. Therefore, combining thermal-hydraulic-chemical (THC) stimulation techniques enables us to demonstrate the effectiveness of combined THC stimulation at particular sites.

The objective of this work package is therefore to identify the current baseline conditions at sites of interest, to perform combined and site-specific THC treatments, to demonstrate productivity sustainability by monitoring the long-term performance of the sites (Rittershoffen), and to develop and deploy intelligent tools to quantify and predict the transient productivity behaviour of the reservoirs. To achieve these tasks in a reasonable time frame, the stimulation and the use of intelligent tools (monitoring and simulation) will be performed simultaneously at different sites. Subsequently, a combination of thermal-hydraulic-chemical stimulation concepts will be applied at a minimum of two newly developed EGS sites (Tasks 4.1 to 4.2). Application and adaptation of the techniques to specific sites and individual scheduling of field stimulation treatments will be performed to demonstrate utilisation for different types of reservoir rocks (sandstone, carbonates and granites). This will be accompanied by numerical simulation of the coupled processes (Task 4.4). At the same time, the sustainability of a developed EGS (Task 4.3) will be demonstrated using long-term circulation tests that quantify the injectivity index and the permeability of the reservoir.