Investigation of the aperture-dependent flow characteristics of a supercritical carbon dioxide-induced fracture under high-temperature and high-pressure conditions: A numerical study

• Published in: Engineering geology 2020-11, Vol.277, p.105789, Article 105789
• Main Authors: Isaka, B.L. Avanthi, Ranjith, P.G., Wanniarachchi, W.A.M., Rathnaweera, T.D.
• Format: Article
• Language: English
• Subjects: 3-D scanning; COMSOL model; Fracture permeability; Shear-induced permeability; Supercritical carbon dioxide fracturing
• ISSN: 0013-7952; 1872-6917
• DOI: 10.1016/j.enggeo.2020.105789

A numerical model was developed to simulate heat extraction and flow behaviour of fractures under deep geological conditions by incorporating a real fracture morphology induced by supercritical carbon dioxide (ScCO2) injection. 3-D scanning technology was used to generate the geometry of the fracture in the model in order to provide a realistic reflection of the tortuous and rough fractures induced by ScCO2 fracturing. The fracture exhibits a tortuosity of 1.44 and a JRC (Joint Roughness Coefficient) of 14.6. The flow characteristics along the ScCO2-induced fracture was evaluated under different in-situ stresses and at high-temperature of 100 °C, by integrating coupled thermal-hydraulic (TH) processes into the model. In addition, the influence of shearing on aperture alteration and flow enhancement was evaluated using the model. The model accurately simulates the permeability characteristics at 100 °C and under varying confining pressures (20–60 MPa) and injection pressures (1–8 MPa) with more than 87% accuracy compared with the corresponding experimental results. The results indicate a non-linear pressure gradient over the highly varying aperture profile along the fracture. Furthermore, the orientation of flow channels and the streamline network heavily depends upon the aperture profile. The fluid injected at 20 °C into a narrow, tortuous fracture is heated to 100 °C while flowing along a distance 63% of the fracture length towards the outlet, whereas the heat transfer efficiency is decreased by 26% with the increase of injection pressure from 1 MPa to 8 MPa. The increase in confining pressure up to 60 MPa results in reduction of fracture permeability by 90% due to stress-induced fracture closure. Shearing of the fracture surface by 5% results in increments in mean aperture, outlet flowrate and average fracture permeability by 44%, 45% and 113%, respectively. •Fluid transport properties of a supercritical carbon dioxide induced fracture were determined.•A numerical model was developed incorporating a real fracture profile generated using 3-D scanning technology.•The flow characteristics along a supercritical carbon dioxide induced fracture at high temperatures and high pressures was investigated.•Non-uniform aperture distribution influences the flow characteristics significantly by developing a non-linear pressure gradient and complicatedly oriented flow channels along the fracture.•Shearing of fracture surfaces by 5% leads to an increase in average apert