Phase Behavior of Gas Condensates in Shales Due to Pore Proximity Effects: Implications for Transport, Reserves and Well Productivity

Abstract

Abstract The present study investigates the alteration of the properties, transport, and production of gas-condensates in shale gas reservoirs and develops and demonstrates an effective and practical methodology to apply these modifications in existing numerical simulation software. Simple models that investigate the phenomena can be investigated without the need for any modifications to an existing simulation code, but realistic models will require significant modifications. Our modeling results indicate that when pore sizes are in the sub-10 nm range, typical of many gas shales, the influence of pore walls on the phase behavior and viscosity of typical gas-condensate fluids is dramatic, in both organic and inorganic pores, and creates favorable fluid and transport conditions leading to enhanced production. This is because the fluid mixture in such porous formations tends to exhibit behavior similar to that of a dry gas or a leaner gas-condensate system, thereby reducing the condensate banking effect considerably in the near-wellbore region and consequently, not impairing the productivity of the producing well. The results also underscore possible reasons for the significant production of condensate liquid from these nanoporous media in contrast to what is expected based on the industry's collective experience with conventional reservoirs. Consequently, the analysis and exercises carried out in this article provide valuable insights into the nature of fluid behavior and advances our understanding of the mechanisms of gas-condensate transport in extremely low permeability nanoporous media.