Gas phase diffusion coefficient in cemented porous media

Abstract

The effect of cementation on the diffusivity of gas was determined in column experiments using four sandy sediments. Cementation of the sediments simulated various natural types of cementation. Naturally cemented marine carbonate sediment was also studied and compared with the laboratory-produced materials. The size, shape, and arrangement of the cemented material was determined using a scanning electron microscope (SEM).Based on the results of diffusion coefficient measurements in the laboratory, it is evident that the overall rate of gas diffusion through cemented layers can be controlled by the mass and geometry of the cemented material. General equations describing the diffusion coefficient as a function of air-filled porosity for non-cemented porous media are not adequate for cemented materials because not all of the air-filled pore volume is available for gas diffusion. However, by evaluating the air space geometry and connectivity the general equations can be modified and shown to be appropriate for evaluating diffusion coefficients in cemented materials as well.