Impact of fractures with multi-scale aperture variability on production observations of geothermal reservoir units

Abstract

We incorporated aperture variability considering contact obstacles into an ensemble of fractured geothermal reservoir simulations to quantify how variations in this multi-scale aperture feature could impact flow field organization and heat transport behavior at the fracture scale. This work considered the variability of the correlation length and successfully developed two observational parameters for production prediction. Our calculations demonstrated that the degree of flow tortuosity was increased by the correlation length, which in turn affected heat transport. The results showed that using the traditional parallel plate model could overestimate the production temperature and could underestimate the cumulative heat production, and these two observation parameters exhibited scale dependence on the correlation length. However, the plate model with the effective hydraulic aperture inferred from flow could capture the production trend of fractured geothermal reservoirs, which indicates that considering a correction coefficient related to the correlation length could effectively improve the prediction accuracy. We also found that the cumulative heat production attained a positive logarithmic correlation with the channelized flow area and a linear negative correlation with the flow tortuosity. This study contributes to a greater understanding of the uncertainty in production observations of fractured geothermal fields with heterogeneous aperture characteristics.