Experimental and dimensional analysis of CO2-assisted gravity drainage in low permeability dip reservoirs of east China

In this paper, we attempted to analyze the experimental results about different CO(2)injection rates affect the oil recovery and pressure gradient in low permeability dip reservoirs. For these experiments, a special core holder was designed to load a core of 100 cm long and 2.5 cm in diameter; furthermore, it could have different dip angles to simulate gravity segregation condition. Different CO(2)injection rate was chosen to analyze how affect the frontal speed of CO(2)plume, oil recovery, and CO(2)sequestration. The results show CO(2)storage efficiency could be greatly enhanced about 20% by decreasing the injection rates from 0.4 to 0.05 mL/min in dip system. Nevertheless, the ultimate oil recovery will achieve to be 63% when CO(2)injection rate drop to 0.1 mL/min, further reduction of injection rate to 0.05 mL/min will lead to lower recovery 58.1% and higher CO(2)storage efficiency 64.7%. We found there was a huge pressure loss in the middle of core when injection rate is too slow, it is beneficial to CO(2)storage efficiency. The dimensionless numberN(vp)that we proposed take pressure changes and displacing front velocity into account, which has a better correlation with oil recovery compared to capillary and gravity dimensionless numbers. Analyzing the results suggest that conducting reasonable CO(2)injection rate, monitoring pressure changes along with flooding process may be dominated factors to CO2-assisted gravity drainage in low permeability dip reservoirs.