Chapter 6 - Fluid-rock interactions in tight gas reservoirs: Wettability, pore structural alteration, and associated multiphysics transport

Abstract

Tight and unconventional reservoirs such as shales are rich in clay minerals that give rise to several fluid–rock interactions. The effect of such fluid–rock interactions is manifested at multiscales. The fluid–rock interactions induce changes in various physical responses of the rock, which is termed as multiphysics. An underlying property that influences the multiphysics process is wettability which has remained a conundrum for shale researchers. This chapter provides a detailed perspective on shale wettability in the context of fluid–rock interactions. Pore structural alteration induced by fluid–rock interactions is also discussed specifically from the standpoint of recent advances using digital techniques. The chapter also presents recent developments in explaining the role of pore sizes in causing configurational diffusion of water and oil in shales. Lastly, multiphysics constitutive modeling to predict shale rock responses is discussed. Specifically, new developments regarding the incorporation of sorptive fluid–rock interaction in constitutive models are presented.