Experimental and Numerical Modeling Study of Gravity Drainage Considering Asphaltene Deposition

This paper presents an experimental investigation of gas-assisted gravity drainage (GAGD) performance while taking into account the effects of asphaltene deposition. The experiments were conducted at high pressures and high temperature (15-37 MPa and 102 degrees C) using carbonate cores and real reservoir fluids in the absence of water saturation. An 85% methane-enriched hydrocarbon gas mixture was employed as an injection fluid in the laboratory runs. The final recovery factor for a fairly tall core was 52% of the original oil at immiscible conditions during hydrocarbon gas injection when the operating pressure and the amount of injected gas were 28.3 MPa and 1.2 pore volume, respectively. In all of the experiments, the total amount of asphaltene deposition was less than 2 wt % of the original oil and no considerable reduction in permeability was found. A numerical two-phase (gas-oil) simulator coupled with a deposition model was also developed to evaluate the importance of different parameters contributing to the final recovery. There was a good agreement between the modeling and experimental results, showing an average error percentage lower than 5%. This study can aid the prediction of the performance of gas injection processes experiencing asphaltene deposition and also aid in proper design of gravity drainage-assisted enhanced oil recovery methods.