Gas permeability and shape factor of natural sediments in the South China Sea

The permeability measurement of marine natural sediments is helpful to evaluate the characteristics of seawater immersion in the sediment layer and the difficulty of upward escape of gas below the sediments. In this work, the stress on the natural sediments in the Shenhu Area of the South China Sea with different buried depths was simulated by confining pressure. The effective gas permeability of natural sediments with different initial porosities during confining pressure loading and unloading was investigated. Experimental results indicated that the gas permeability was very sensitive to particle size distribution, confining pressure and initial porosity of the sediments. The gas permeability of sediments decreased with the increase of confining pressure and the decrease of porosity. The isoline of porosity related to gas permeability was obtained, and this isoline could predict the gas permeability of natural sediments in the South China Sea under different porosities and buried depths. The particle size term in the Kozeny-Carman equation was modified by particle size correction factor N, and the uneven particle size distributions of four natural sediments could be eliminated when N was about 2.44. The specific surface areas of four natural sediments increased with the increase of buried depth. Finally, a new model for the calculation of shape factor was proposed, and this model showed practical performance in predicting the shape factors of natural sediments.