Pore Structure Reconstruction and Gas-Water Dual-Flow Simulations Combined with CT Scans and NMR Measurements on Coal...

Area of Science:

• Geosciences
• Petroleum Engineering
• Material Science

Background:

• Coalbed methane (CBM) drainage is crucial for energy production.
• Understanding coal pore structure is key to optimizing gas-water migration.
• Heterogeneity in coal samples significantly impacts fluid flow.

Purpose of the Study:

• To investigate the 3D coal pore structures and their relation to gas-water migration during CBM drainage.
• To compare the pore characteristics and fluid flow behavior of two distinct coal samples (CN01 and CN02).
• To assess the productivity potential of different coal samples based on pore structure and permeability.

Main Methods:

• Computed Tomography (CT) scans for 3D pore structure visualization.
• Nuclear Magnetic Resonance (NMR) measurements for porosity and fluid analysis.
• Single water and gas-water flow simulations to determine permeability.

Main Results:

• Coal samples exhibit significant heterogeneity; CN01 is diffusion-pore dominated, while CN02 includes fractures.
• CN01 has low effective porosity (1.64%) and poor fluid mobility, whereas CN02 has higher effective porosity (3.26%) and better mobility.
• CN02 demonstrates a more uniform pore-throat arrangement and better bedding development, leading to higher relative water permeability.

Conclusions:

• Coal pore structure complexity (shape factor) correlates with pore diameter.
• Relative water permeability is indicative of pore-throat arrangement and bedding development.
• Sample CN02 possesses greater CBM productivity potential due to superior pore connectivity and permeability.