Flow through drying of porous media

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Mahadevan, Jagannathan

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The flow of a saturated gas through a porous medium, partially occupied by a liquid phase, causes evaporation due to gas expansion. This process, referred to as flow-through drying, is important in a wide variety of natural and industrial applications, such as, natural gas production, convective drying of paper, catalysts and membranes. X-Ray imaging experiments were performed to study the flow-through drying of water-saturated porous media during gas injection. Our results show that the liquid saturation profile and the rate of drying are dependent on the viscous pressure drop across the porous medium, the state of saturation of the gas and the capillary characteristics of the porous medium. During the injection of a completely saturated gas, drying occurs only due to gas expansion. Capillarydriven flow from regions of high saturation to regions of low saturation lead to more uniform saturation profiles. During the injection of a dry gas, a drying front develops at the inlet and propagates through the porous medium. The degree of spreading of the drying front is dependent on the permeability and capillary characteristics of the porous medium. A model is developed to explain the observed imaging results. The model includes compressibility effects and capillary pressure-driven film flows. It is solved numerically and compared with X-Ray imaging results for gas injection to obtain the relevant film flow parameters. The model results agree well with experimental observations. The above theory is applied to the problem of drying of water in natural gas formations. When water occupies the pore spaces in the near wellbore porous reservoirs and causes a “waterblock” to gas flow during production it can cause a significant loss in gas production. The model developed in this dissertation helps to identify the role of various parameters such as temperature, viscous forces, volatility and the capillarity of the formation on the rate of clean-up of the waterblock.




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