Abstract: Aiming at the poor oil displacement efficiency of steam flooding with a constant steam injection rate, oscillatory steam injection rate is put forward for the whole process of steam flooding.The oscillatory steam injection rate can be divided into two types.One is constant amplitude change type and the other is random amplitude change type.In order to determine the optimal steam injection rate for each cycle,a steam injection rate evaluation model with cumulative oil steam ratio as the target of appraisal is built based on the principles of mass conservation and energy conservation.Particle swarm optimization algorithm is used to optimize the optimal oscillatory steam injection rate for each cycle.Qi-40 Block in Liaohe oilfield was taken as case to evaluate the influences of oscillatory steam injection rate on the performance of steam flooding.Results show that the oil displacement efficiency of the oscillatory steam injection rate is better than that of the constant steam injection rate,and the cumulative oil steam ratio can be increased by 23.50%.In addition,the oscillatory steam injection rate with random amplitude change is better than that with constant amplitude change,and the cumulative oil steam ratio of the former is 8.98% higher than that of the latter.

Key words: oscillatory, steam injection rate, particle swarm optimization algorithm, steam flooding, enhancement of oil recovery