The present work addresses the contributions, in both individual and combined forms, of the driving mechanisms, namely, solution gas, CO2 generation, steam distillation, capillary imbibition and gravitational drainage, for the recovery of oil and gas during the continuous steamflooding of a naturally fractured reservoir containing heavy oil. The investigation is carried out via numerical simulation of the phenomena in representative pattern cells. Two numerical models were used to represent the matrix heating process. The first describes the heating of a horizontal cross-section of a matrix block surrounded by a fracture, in which the steam is steadily flooding. The second model is similar to the first, except for the position, which is changed to vertical to incorporate gravity effects. The studies were performed for a fractured rock saturated with live oil. The rock properties are representative of a real fractured carbonate reservoir, as well as the fluid properties referring to the same field case. Also, the operational conditions used for pressure and temperature were the ones observed in the field, conferring to the work and conclusions, the character of a case study. A strategy was adopted to isolate the effects of each recovery mechanism. The results show that the main mechanisms of oil recovery for the matrix block during steamflooding are the integrated action of steam distillation and solution gas. The first is the dominant mechanism and it is responsible for the quality improvement of the produced oil. The other mechanisms have a minor contribution to ultimate oil recovery. Such results are vital for the design of a steam injection project in similar oil fields.
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