Numerical modeling of diffusion in fractured media for gas injection and recycling schemes

H. Hoteit*, A. Firoozabadi

*Corresponding author for this work

Research output: Chapter in Book/Report/Conference proceedingConference contributionpeer-review

42 Scopus citations

Abstract

Diffusion in fractured reservoirs, unlike in unfractured reservoirs, can affect significantly the efficiency of gas injection in oil reservoirs and recycling in gas condensate reservoirs. The physical diffusion, similar to gravity, results in the change of the path of the injected gas species from the fractures to the matrix, giving rise to late breakthrough. In this work, we present, for the first time, a consistent model to incorporate physical diffusion of multicomponent mixtures for gas injection schemes in fractured reservoirs. The multicomponent diffusion flux is related to multicomponent diffusion coefficients, which are temperature, pressure and composition dependent. These coefficients are calculated from a model based on irreversible thermodynamics. Current simulation models of fractured reservoirs that include diffusion are based on inconsistent models of gas to liquid diffusion at the fracture-matrix interface. We avoid this deficiency by assuming that the gas and liquid phases are in equilibrium at the interface. The concept of crossflow equilibrium (that is, vertical equilibrium) is invoked in our model to avoid the use of transfer functions. In this work, we use the combined discontinuous Galerkin and mixed methods to calculate fluxes accurately and to have low numerical dispersion to study physical diffusion. Four examples are presented. In one of the examples, a field scale study is performed to investigate gas injection in a fractured reservoir away from miscibility pressure and close to miscibility pressure. Results show a significant effect of diffusion on recovery performance away from miscibility pressure. In another example, recycling in a fractured gas condensate reservoir is presented to demonstrate that diffusion has a significant effect on condensate recovery.

Original languageEnglish (US)
Title of host publicationProceedings - SPE Annual Technical Conference and Exhibition, ATCE 2006
Subtitle of host publicationFocus on the Future
Pages4713-4727
Number of pages15
Volume7
StatePublished - 2006
Externally publishedYes
EventSPE Annual Technical Conference and Exhibition, ATCE 2006: Focus on the Future - San Antonio, TX, United States
Duration: Sep 24 2006Sep 27 2006

Other

OtherSPE Annual Technical Conference and Exhibition, ATCE 2006: Focus on the Future
CountryUnited States
CitySan Antonio, TX
Period09/24/0609/27/06

ASJC Scopus subject areas

  • Fuel Technology
  • Energy Engineering and Power Technology

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