Abstract
This paper investigates the influencing factors on the liquid recovery from the Duvernay Shale Condensate Reservoirs by using reservoir simulation methods with multi-fracked horizontal wells and gas recycling injection. In the simulation of case studies, three key factors (nano-confinement, adsorption, and diffusion effects) related to the gas condensate phase behavior and liquid recovery are simultaneously considered and quantified. The outcomes of this study create an efficient approach to identify sweet spots with high liquid recovery from the Duvernay shale condensate by evaluating these three factors. As widely known, liquid recovery from shale is very low, which is different from conventional reservoirs. It is believed that phase behaviors of gas condensate are changed significantly by a confinement effect, causing gas production performance in shale different from that in the conventional formations. Hence, multi-mechanistic flow regimes are employed in a dual porosity/dual permeability model, including matrix and fractures, to simulate the gas condensate flow mechanisms in the Duvernay shale. The nano-confinement, adsorption and diffusion effects on the gas condensate phase behavior are simultaneously considered in the simulations. Using the Duvernay shale condensate properties with an equation of state (EOS) model, the nano-confinement effect works better when a pore diameter is less than or equal to 4 nm. Simultaneously considering the nano-confinement, adsorption and diffusion effects, the total liquid recovery is increased by 49% in five years of production. The gas recycling injection operation permits to inject dry gas separated from the condensate fluids. The gas condensate phase behavior is significantly affected by both pressure and concentration gradients because the matrix permeability is extremely low in shale. Through adjusting field operations with favorable production-injection ratios, the optimization of improving liquid recovery is definitely achieved.
