Seepage and blockage characteristics of methane hydrate-bearing porous media under different hydrate distribution conditions

Blockage commonly occurs in and severally affects natural gas (mainly methane) reservoir exploitation, combustion ice (methane hydrate) exploitation and oil and gas pipeline transportation. The formation of methane hydrates is known as one important cause of blockage, but the effects of hydrate distribution on seepage and blockage are rarely studied in experiments. This study employed different proportions of dry and wet sands to simulate three thickness of hydrate-bearing porous media and obtained a uniform kinetic relationship of hydrate formation $(N=K\left(1-\frac{1}{{\mathrm{e}}^{rt}}\right))$. Quantitative results indicate that both water and methane seepage can induce hydrate saturation increase in both hydrate-bearing and hydrate-free zones, which gradually causes the blockage of up to 12.5 MPa (at 6.0 MPa backpressure). The hydrate-bearing porous media with a uniform saturation is not easy to cause blockage unless the hydrate saturation is high enough. In addition, based on the hydrate-bearing porous media with different thicknesses, this study successively measured the water phase permeability. In addition, the calculation method for blockage location based on pressure evolution was proposed with an error of less than 8%. These findings can help understand and mitigate issues related to flow blockages during oil and gas exploitation and transportation.