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Experimental and computer based simulation study of WAG process

Taheri, S ; Sharif University of Technology | 2006

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  1. Type of Document: Article
  2. Publisher: 2006
  3. Abstract:
  4. In reservoirs that have been water flooded or gas injected, it is still a significant amount of the remaining oil. Water alternative gas injection is a tertiary oil recovery method which was used for the first time in Canada for recovering remained oil in place of reservoir. The pore-scale mechanisms of this process are not fully understood yet. Such knowledge is essential for accurate modelling of reservoir. In this study various experiments on the WAG process is carried out by means of high pressure glass type micromodel instrument. The micromodel apparatus in this experiment was capable to operate at pressures up to 3500 Psi and temperatures up to 85°C which is similar to conventional reservoir condition. Several glass type micromodels with different patterns were constructed for simulation of various reservoir geometries and parameters by chemical methods. A computerized model of glass type micromodel by using of CMG simulator was set up based on the estimated parameters. A good match observed between simulation and experimental results for breakthrough-time and residual oil saturation in gas and water flooding scenarios. This model was used for sensitivity analysis of different parameters such as heterogeneity, oil viscosity, wettability and initial reservoir pressure on the recovery of water injection, gas injection and water alternative gas (WAG) process. Also the effect of some other parameters like as water slug size, WAG ratio and sequence of water or gas injection in WAG were studied by this model. Experimental results show that displacement mechanism in water wet system during water flooding is water filament flow. Also gas avoids entering most of the water-filled pores and preferentially invades oil-filled pores. The better compressibility and expandability makes gas easily separated by throats and gas becomes a bubble to go into the next pore. The swept throat displaced efficiency is high, but the whole sweeping area is narrow. Simulation results demonstrated that due to presence of continues oil film on the poreswall, lower oil viscosity results higher oil recovery in the oil wet system rather than water-wet; however inverse behaviour was observed with increasing oil viscosity, this is attributed to less ability of water to sweep the more viscose oil film. Also it obtained that WAG compensates decreasing of recovery in heterogeneous reservoirs
  5. Keywords:
  6. Computer simulation ; High pressure effects ; Mathematical models ; Petroleum reservoirs ; Viscosity ; Water injection ; Wetting ; Gas injection ; Micromodels ; Reservoir pressure ; Water alternative gas injection ; Tertiary recovery
  7. Source: CHISA 2006 - 17th International Congress of Chemical and Process Engineering, Prague, 27 August 2006 through 31 August 2006 ; 2006 ; 8086059456 (ISBN); 9788086059457 (ISBN)