Research institute of Petroleum Industry (RIPI) Journal of Petroleum Research 2345-2900 27 96-1 2017 05 22 Molecular Diffusion Investigation During CO2 and Hydrocarbon Gas Injection in a Single Matrix Block and a Fractured Reservoir Sector Model Molecular Diffusion Investigation During CO2 and Hydrocarbon Gas Injection in a Single Matrix Block and a Fractured Reservoir Sector Model 55 68 738 10.22078/pr.2017.738 FA Ahad Freydooni Thermodynamics Research Laboratory, School of Chemical Engineering, Iran University of Science and Technology Mehdi Assareh Thermodynamics Research Laboratory, School of Chemical Engineering, Iran University of Science and Technology Mehdi Assareh Thermodynamics Research Laboratory, School of Chemical Engineering, Iran University of Science and Technology Journal Article 2016 02 20 One of the common methods of enhanced oil recovery in naturally fractured reservoirs is gas injection. The majority of Iranian hydrocarbon reservoirs are fractured reservoirs. Producing mechanisms is different in fractured reservoirs in comparison with conventional reservoirs. Molecular diffusion is one of the mechanisms that along with gravity drainage can increase oil recovery in fractured reservoirs during gas injection. In this work, the effect of molecular diffusion in CO₂ and hydrocarbon gas injection as an EOR (enhanced oil recovery) process is investigated using compositional simulation in a single matrix block and a sector model of an Iranian natural fractured reservoir. The effect of the matrix permeability, matrix and fracture permeability difference, matrix porosity, matrix gas-oil capillary pressure and injection gas composition are checked in single matrix blocks, and then the influence of diffusion is investigated on the recovery of the sector model during the CO₂ and hydrocarbon gas injection. The results show that molecular diffusion raises oil recovery by increasing the mass transfer rate between the matrix and fracture during miscible gas injection (CO₂ and hydrocarbon gas). The low matrix permeability and high gas-oil capillary pressure within the matrix oil make smaller displacement efficiency during gravity drainage. In the sector model, the molecular diffusion increases the ultimate oil recovery by about %2 and %5 in CO₂ and hydrocarbon gas injection, respectively by delaying gas breakthrough in an production well and maintaining reservoir pressure. One of the common methods of enhanced oil recovery in naturally fractured reservoirs is gas injection. The majority of Iranian hydrocarbon reservoirs are fractured reservoirs. Producing mechanisms is different in fractured reservoirs in comparison with conventional reservoirs. Molecular diffusion is one of the mechanisms that along with gravity drainage can increase oil recovery in fractured reservoirs during gas injection. In this work, the effect of molecular diffusion in CO₂ and hydrocarbon gas injection as an EOR (enhanced oil recovery) process is investigated using compositional simulation in a single matrix block and a sector model of an Iranian natural fractured reservoir. The effect of the matrix permeability, matrix and fracture permeability difference, matrix porosity, matrix gas-oil capillary pressure and injection gas composition are checked in single matrix blocks, and then the influence of diffusion is investigated on the recovery of the sector model during the CO₂ and hydrocarbon gas injection. The results show that molecular diffusion raises oil recovery by increasing the mass transfer rate between the matrix and fracture during miscible gas injection (CO₂ and hydrocarbon gas). The low matrix permeability and high gas-oil capillary pressure within the matrix oil make smaller displacement efficiency during gravity drainage. In the sector model, the molecular diffusion increases the ultimate oil recovery by about %2 and %5 in CO₂ and hydrocarbon gas injection, respectively by delaying gas breakthrough in an production well and maintaining reservoir pressure. https://pr.ripi.ir/article_738_3ecc11f7e81df1065832251e845e64e2.pdf