Experimental investigation of seepage and heat transfer in rough fractures for enhanced geothermal systems

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Highlights

The repeatable rock samples with rough fracture are manufactured by 3D printing technology based on JRC profile.

The variations of rock external wall temperature with time under initial temperature and flow rate are obtained.

The effects of roughness on seepage and convective heat transfer are analyzed quantitatively.

Abstract

Enhancing the heat transfer efficiency between working fluids and hot dry rocks (HDRs) in fracture reservoirs is important. In this paper, we present the seepage and convective heat transfer experiment to investigate the behavior of distilled water in the artificial rock samples. The reproducibility of the experimental studies can be achieved based on Barton’s JRC profiles and advanced 3D printing technology. The roughness of two rock samples is 10–12 &18–20 and 18–20 &10–12 respectively. The effects of roughness and confining pressure on seepage characteristics were analyzed. The variation of rock temperature with time under initial temperature and flow rate was obtained. And the effects of roughness on heat transfer performance for two specimens were evaluated. The results indicated that large roughness in the direction perpendicular to flow would decrease seepage capacity and the confining pressure had great influence on seepage. And higher flow rate would extract more heat in fractured reservoir. Furthermore, the outlet temperature was almost linear with the original rock temperatures. Finally, the large roughness in the direction perpendicular to flow would strengthen heat transfer and large roughness in the direction parallel to flow would reduce effective heat transfer area.

Keywords

Joint roughness coefficient (JRC)

Enhanced geothermal system (EGS)

Seepage characteristics

Rough fracture

Convective heat transfer

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