Scenario analysis on operational productivity for target EGS reservoir in I-lan area, Taiwan

A basic production scenario analysis (BPSA) using the TOUGH2 code (coupled with a fit-for-purpose modified EGS module) as a relevant simulator was conducted to study a potential geothermal site in I-lan Triangle, Taiwan. The outcome of numerical simulation shows that the capability of the code is compliant with heat production model analysis under a pair of recharging and production wells. In the BPSA application, the model was constituted with an assumed size of 2 km × 2 km × 2.5 km, taking into consideration a relevant boundary condition and using Case-A, B, and C to represent varied depths of recharging points. Heat production histories of target reservoirs containing a fault zone were simulated using a deterministic approach, and a collection of 30-year heat production P/T histories was obtained for all 3 cases. The effects of a fault zone near the production point are evaluated and found to be significant only when distance between the fault's boundary and production point is minimum. The study also shows that relative locations of the recharging point from production point are important to reach an adequate design of production well layout in a geothermal plant. Significant temperature decline can be observed in Case-C of BPSA, where the distance between R-1 and P-1 is the least among the 3 cases studied. Results of this study would provide a useful numerical tool for evaluating future EGS development projects in Taiwan. By adopting a suitable conceptual model and a group of carefully selected relevant parameters, site-specific reservoir engineering problems associated with the recharging and production operation in a representative EGS geothermal field can be foreseen and predicted in a quantitative way.