Abstract:

In the process of developing deformable-media gas fields, the pore pressure decreases when fluids flow out of the reservoir, and the difference of pressure inside and outside the reservoir increases. As a result, pore volume, porosity and permeability decrease. These changes significantly affect the recovery performance. The present work discusses the mode of deformation of porous media, analyzes the influence of microscopic physical properties (material constituents, unit type and their contacting, arrangement and cementation patterns) on deformation, and experimentally studies the regularity of changes of pore volume, porosity and permeability with the variation of pressure. The experimental results show that the pore volume, porosity and permeability decrease with the increase of net confining pressure, and that permeability is more sensitive to pressure changes than that of porosity. Therefore, in developing deformable-media gas fields, maintaining the original reservoir pressure is important to stabilize and improve production and to prolong production life.

Key words: deformable media, elastic deformation, plastic deformation, elastoplastic deformation, net confining pressure