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Investigating the Role of Molecular Diffusion on the Performance of Non-Equilibrium Gas Injection in One of the Fractured Reservoirs in Iran

Rigi, Ahmad | 2023

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  1. Type of Document: M.Sc. Thesis
  2. Language: Farsi
  3. Document No: 56631 (06)
  4. University: Sharif University of Technology
  5. Department: Chemical and Petroleum Engineering
  6. Advisor(s): Ghazanfari, Mohammad Hossein; Fatemi, Mobin
  7. Abstract:
  8. Major parts of Iran's oil reservoirs are fractured carbonates, which need time to produce oil due to their much lower permeability than sandstone reservoirs. Molecular diffusion mechanism is an efficient mechanism in oil recovery from fractured reservoirs under gas injection conditions. The main subject of this work is to investigate the role of molecular diffusion mechanism in the non-equilibrium gas injection project and its role in increasing the oil recovery rate in two southern fractured reservoirs located in the west of Iran, taking into account the capillary pressure, as well as the change of interfacial tension closely miscible conditions is also investigated through simulation. The different stages of oil production from these reservoirs and the mechanism according to each time frame will be investigated and identified. For this purpose, in order to simulate the combination of the gas injection process with the 2D Cartesian model in two Iranian oil reservoirs, it has been investigated using the unique pore model. Injection gases of methane, dry gas, carbon dioxide and dry gas enriched with carbon dioxide are used. The diffusion coefficients of injected gas and methane gas in reservoir 1 have been made from laboratory calculations. Flow functions for block and fracture have been simulated in the same way, and different effects of porosity, permeability and block height, fracture aperture, fracture capillary pressure and distance between vertical fracture pairs have also been investigated. A controlling system in the amount of oil recovery in the process of using non-equilibrium gas to the fracture oil reservoir 1 and 2, and this effect is more noticeable in the oil reservoir 2. In reservoir 2, as a result of carbon dioxide injection, each three mechanism (gravity drainage, molecular diffusion, capillary pressure) was observed in three different stages of production. But in reservoir 1 just Two stages were observed, but in case of dry gas injection, all three mechanisms are observed in three stages of production in both reservoirs. The wider and shorter the desired block and the lower its permeability is, the effect of the molecular mechanism is less in both reservoirs, and it Also, with the increase of porosity and enrichment of dry gas, oil recovery increases, which is more evident in reservoir number 2. In the absence of molecular diffusion, the final recovery is increased by increasing the fracture capillary pressure. This is if in the presence of molecular diffusion, this effect does only increase the production in the initial stages and does not the effect on the final recycling
  9. Keywords:
  10. Molecular Diffusion ; Capillary Pressure ; Non-Equilibrium Gas ; Production Mechanism ; Single Porosity ; Gap Capillary Pressure ; Fractured Carbonate Reservoir

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