Study of the Physical Characteristics of a Pore-Filling Hydrate Reservoir: Particle Shape Effect

Abstract

Methane gas hydrate (MGH) is an important clean energy source. In submarine continental margins, the main hydrate occurrence in the sediment is the pore-filling type, and there is a huge difference in the sediment particle shape. Thus, in this study, with a new algorithm based on X-ray computed tomography (CT), 16 three-dimensional models were reconstructed with different hydrate saturations and particle shapes. Pore network modeling (PNM) was used to characterize the pore space evolution, and the impacts of various hydrate saturations and particle shapes on the other physical properties were studied using PNM and the finite volume method (FVM). It is found that (1) when both the sediment particle size and the hydrate saturation are certain, the hydrate-bearing sediment (HBS) with rounder particles presents a smaller average radius of the pore and throat, (2) when hydrate saturation increases, the tortuosity appears as an upward trend and the HBS with irregular particles presents a faster increased rate, (3) when hydrate saturation becomes higher and higher, the permeability of HBS emerges as a downward trend and the HBS with rounder particles presents a lower permeability, (4) under the same hydrate saturation, the HBS with rounder particles presents a higher apparent thermal conductivity, and (5) the electrical conductivity of HBS will gradually decrease as hydrate saturation increases, and the HBS with rounder particles presents a lower electrical conductivity and a higher resistivity.

Permeability Anisotropy of Hydrate-Bearing Sediment during Consolidation Process: Insights from CT Scanning and Pore Network Modeling

“…The projection data were obtained using InspeXio (Shimazu, Japan) CT scans and reconstructed as two-bit grayscale slices, followed by image noise reduction as well as grayscale correction using median The dimensions of the actual strata in this study were much larger than those of the specimens, so it made more sense to choose REV and observe changes over a region. This method of intercepting REVs was also used in Wu et al 54 and Li et al 55 Figure 1 shows the morphology of NGH under different effective stresses. It can be found that the pore space is gradually compressed with the increase of σ 31 ′.…”

“…The dimensions of the actual strata in this study were much larger than those of the specimens, so it made more sense to choose REV and observe changes over a region. This method of intercepting REVs was also used in Wu et al and Li et al Figure shows the morphology of NGH under different effective stresses. It can be found that the pore space is gradually compressed with the increase of σ 31 ′.…”