Abstract

The Steam Assisted Gravity Drainage (SAGD) process has been studied theoretically and experimentally in conventional models and reservoirs and is found a promising EOR method for certain heavy oil reservoirs, but its applicability for fractured systems has not yet been investigated. In this work simulation studies of the SAGD process were made on different fractured models consisting of fractures in both Near Well Region (NWR) and Above Well Region (AWR) and also in the presence of networked fractures. Double porosity/double permeability fractured models were developed and results were compared with conventional non-fractured model. Various fracture geometries such as orientation, length, discontinuity, dispersion, location, and networking were studied. Results indicated a better performance in terms of oil recovery and sweep efficiency in the presence of vertical fractures. Longer vertical fractures seemed to have even more beneficial effects. Horizontal fractures revealed detrimental effect on oil recovery and the performance became worse for longer horizontal fractures. Discontinuous horizontal fractures produced a better performance especially when combined with continuous vertical fractures (networking). Vertical fractures helped growth of steam chamber in vertical direction which resulted in higher oil recovery. However, horizontal fractures seemed to inhibit growth of the steam chamber in vertical direction, hence retarding oil recovery. In addition to SAGD, ES-SAGD process has also been investigated for both conventional and fractured simulation models. Simulation analysis confirmed the synergetic effect of solvent injection along with steam since for both conventional and fractured models ES-SAGD had a higher rate of production and higher ultimate oil recovery.

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