Speaker
Description
With the exploitation of gas in the naturally fractured gas reservoir driven by aquifers, the natural gas stored within matrix pore generally tends to be trapped by invaded water in the neighboring fractures and relaxed by injected nitrogen gas. Understanding gas/water flow in multiscale porous media is challenging due to the presence of a wide range of pore sizes. In this paper, four rock samples drilled from a typical ultra-deep gas reservoir in the Tarim Basin are selected to conduct micro-focus CT scanning experiments. The 3D digital rock models are reconstructed to combine multiscale pore space and micro fractures, and pore structures of multi-scaled fractured porous media are quantified. The pore-scaled models are extracted and subsequently integrated with the direct simulation methods to explore the underlying mechanisms of gas-water two-phase flow at the pore-scale. Here, the phase-field method employed for tracking the phase interface is utilized to simulate the generation of residual gas during water displacing gas (i.e., imbibition), while the lattice Boltzmann method (LBM) is applied to simulate the reactivation process of the residual gas during gas displacing water (i.e., drainage). The existence of micro fractures improves the pore-throat topological properties and gas-water flow conductivity. The proposed methodology provides a framework for analyzing immiscible gas/water flow behavior both for drainage and imbibition cycles. Finally, the influence of rock wetting properties, fracture geometries and gas/water mobility ratio are carefully investigated. These results underscore the importance of incorporating multi-scale pore and micro fractures into flow models for improved characterization of fractured reservoirs.
| Country | China |
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