The reservoir fluid properties exhibit significant deviation from their bulk properties under confinement in nanopores. As a result, storage capacity and recovery can be impacted in the shale reservoir due to nanoscale pore structure. It is therefore critical to investigate the impact of pore confinement to accurately estimate the gas resources and the phase behavior in the shale reservoirs. In this study, the shift in critical properties of the typical Marcellus Shale gas confined in different size nanopores were determined. The adjusted fluid properties was then used to estimate the gas deviation factor for dry gas and to predict the phase behavior of gas/condensate. The gas/condensate fluid model was then used in a compositional reservoir simulator in order to estimate the liquid recovery from a Marcellus Shale gas/condensate reservoir developed by hydraulically fractured horizontal well.
The results indicate that the gas storage capacity of the shale is altered by the pore confinement. The degree of the fluid properties alteration by pore proximity in the shale depends on the composition of the gas mixture and the size of the nanopores. Therefore to accurately estimate the gas resources in the shale reservoirs, it is necessary to incorporate the alteration of the gas deviation factor by pore proximity. In gas/condensate shale reservoirs the fluid confinement could have either positive or negative impact on the liquid recovery depending on the pore size. The results of the investigation can provide an insight relative to production optimization and economic recovery of gas/condensate reservoirs in the unconventional resources.