The objective of WP 2.02 was to improve the understanding of the behavior of geothermal reservoirs by integrating geo-mechanics modeling into reservoir modeling and best workflows for reservoir management. The developed methodologies will be tested and demonstrated in well known and developed geothermal reservoirs in order to optimize performance.
Important issues are (among others):
- improved volume assessment and productivity prediction
- advice on a monitoring plan and well planning procedures
For the reservoir management, coupled models and data assimilation technology were implemented in close cooperation with Indonesian partners. The data assimilation technology needed to be translated to guidelines on well planning, which was important for the optimization of the field production. Further, the data assimilation needs require extensive information from the reservoir. Therefore for each of the case studies a monitoring plan needs to be put into place which optimizes the value of information of the data collected. Without being complete, data to be incorporated will include dynamic reservoir data (pressures, temperatures, and flow rates) and geomechanical data (induced seismicity, gravity, subsidence).
To properly train personnel we will organize two (on-site) workshops.
Key to the quality of the results of these studies is intensive communication and cooperation. The workpackage is now supported by the PhD work of Famelie Nurlaela who has started her PhD research at ITB and TNO. The abstract below gives an insight of her topic, which covers part of the deliverables of the work package.
The research proposed here focuses on the effect of fluid flow, heat and geomechanics changes in geothermal reservoirs due to production. The production in such reservoirs can often be good at the beginning but decreasing after a while, not being optimal for the power plant. This is caused by the decline of pressure and/or temperature. The reduced fluid pressures within the reservoir due to production can cause fracture closure. A closing fracture may cause a permeability decline. Fluid flow, heat transfer, and rock mechanics properties are related to each other. Therefore, this study intends to develop a concept for geothermal reservoir simulation with thermo-hydro-mechanics coupling that represents the relationship between those properties in the reservoir. The study is divided into three parts; thermo-hydro-coupled model, data assimilation, and optimization. In the first part, the thermo-hydro-mechanics coupled model is created with a semi-analytical approach. This semi-analytical method will be used to create a robust model that is suitable for data assimilation. Dual porosity with single permeability will first be implemented. Sensitivity studies on various parameters will be conducted to see the changes in pressure, temperature, permeability, porosity, and permeability. In the second part, data assimilation will be used for conditioning the thermo-hydro-mechanics coupled model with field data by using a stochastic mathematical method. Data assimilation changes the geomechanics and heat-flow parameters used to predict the reservoir behavior. The Ensemble Kalman Filters method will be used. The results to be obtained will be an ensemble of many models employing ranges for each parameter that can also be used for forecasting purposes. In the third part, the production and injection scenarios will be evaluated to the thermo-hydro-mechanics coupled model. The assimilated properties in geomechanics and heat-flow will be used to predict the fracture conditions; open or remain closed, and the associated production. The best scenarios are the ones with maximum production improvement.
Two papers have been published within this workpackage:
Pizzocolo and Fokker (2018): Coupling Flow-Geomechanical model for stimulation of fractured geothermal fields
Candela and Fokker (2018): Thermo- poro- elastic stressing and time-dependent earthquakes nucleation: a semi-analytical injection model
Candela, Fokker en van der Veer (2018) On the importance of thermo-elastic stressing in injection-induced earthquakes