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Investigation of Pore-Scale THMC Acid Fracturing Process Considering Heat Conduction Anisotropy

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1 State Key Laboratory of Multiphase Flow in Power Engineering, Xi'an Jiaotong University, Xi'an, 710049, China
2 School of Mechanical Engineering, Beijing Key Laboratory of Pipeline Critical Technology and Equipment for Deepwater Oil & Gas Development, Beijing Institute of Petrochemical Technology, Beijing, 102617, China

* Corresponding Author: Dongxu Han. Email:

The International Conference on Computational & Experimental Engineering and Sciences 2023, 27(4), 1-5. https://doi.org/10.32604/icces.2023.09168

Abstract

Acid fracturing is critical to improving the connectivity inside underground reservoirs, which involves a complex thermal-hydro-mechanical-chemical (THMC) coupling process, especially deep underground. Heat conduction anisotropy is one of the intrinsic properties of rock. It determines the heat response distribution inside the rock and alters the temperature evolution on the reactive surface of fractures and pores. In another way, the rock dissolution rate is closely related to the reactive surface temperature. Predictably, heat conduction anisotropy leads to different rock dissolution morphologies from that of the heat conduction isotropy situation, then the cracks distribution and permeability of rock would also be significantly changed. This work uses a pore-scale THMC coupled model recently developed by us to investigate the effect of heat conduction anisotropy on the THMC coupled acid fracturing process. The model adopts the lattice Boltzmann and discrete element methods to calculate the particle mechanical behaviors and hydro-mechanical-chemical transport processes, respectively. Particularly, the coupling phenomena of chemical damage, rock dissolution, and solute transport are covered in the simulation. A chemical damage variable based on the cohesive bond is proposed to characterize the alteration of mechanical parameters caused by local rock dissolution. The influence of the anisotropy ratio of heat conduction and Damkohler number (Da) on the THMC coupled acid fracturing process is qualitatively analyzed. Results indicate that the dissolved solid is more sensitive to the heat conduction anisotropy in the middle level of Da, where a conical area tends to generate upstream of the main fracture. However, for the large Da, it is the diffusioncontrolled process, and it shows uniform dissolution around the injection hole even in large heat conduction anisotropy, and little acid reactant can flow into fractures.

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