Stochastic inversion of tracer test data with seismicity constraint for permeability imaging in enhanced geothermal reservoirs

Abstract

Inference of permeability distribution in an enhanced geothermal reservoir is crucial for the sustainable management of geothermal energy. However, interpreting the uneven permeability distribution in deep geothermal reservoir remains a challenging task, because in practice there are often merely one to two wells available for hydro-geophysical tests. Considering that the induced seismicity data are widely captured during reservoir stimulation in enhanced geothermal systems, a framework of tracer test data inversion with the constraint of induced seismic data is proposed for permeability imaging. Hydraulic diffusivity, representing the prior estimation of permeability, is inferred from the occurrence time of seismic event. This is followed by the determination of petrophysical model, which relates hydraulic diffusivity to permeability, by tracer test data inversion based on the Monte Carlo Markov Chain algorithm. Implementation of seismicity-constraint tracer data inversion algorithm in the Habanero enhanced geothermal system, Australia, demonstrates that the proposed inversion model allows uneven permeability estimation at field scale in shorter burn-in period and lower uncertainty, than the traditional inversion model without seismicity constraint. Using the estimated permeability in the hydrothermal model enables accurate prediction of thermal performance in a 150-day trial-production test. Results indicates that the proposed algorithm can reliably characterize the spatial distribution of permeability in deep enhanced reservoirs, based on tracer test via doublet wells.

A Multi-stage inversion framework for dynamic fracture characterization and long-term thermal performance prediction in an Enhanced Geothermal System

“…Previous research indicates that microseismic data enables the identification of fracture networks in EGS reservoir (Tarrahi et al, 2015), while tracer data can effectively inform hydraulic characteristics of reservoirs and provides key information about fracture aperture and distribution (Egert et al, 2020;Elahi & Jafarpour, 2018;Liu et al, 2023;Ren et al, 2023;Wu et al, 2021a). Interwell tracer test have been applied in conventional/unconventional reservoirs for decades, demonstrating its effectiveness in reservoir characterization (Abbaszadeh-Dehghani & Brigham, 1984;Chen et al, 2022;Shook & Suzuki, 2017). Our previous work successfully developed a data assimilation framework to interpret tracer test data, facilitating the inversion of the fracture aperture distribution in an EGS (Wu et al, 2021a).…”