Reservoir Simulation Study Of Air Injection After Steam Stimulation For Heavy Oil Reservoir

Air injection is a novel creative thermal recovery method, which has a great development prospect. However, it is mainly used to recover the light oil reservoir with low permeability and seldom used for heavy oil reservoir at the present time.In this paper, according to the case that residual heat in the heavy oil reservoir after steam stimulation couldn't be made full use of, air injection into the reservoir was proposed as an interim method after steam stimulation technology. A three-phase six-component numerical model was built according to some references. And numerical simulation was done using commercial software. On the basis of the model, sensitive analysis was carried out about steam and air parameters.For one-round steam stimulation, in order to study air injection's influence on the recovery, some parameters were considered, such as steam temperature, steam injecting time, soaking time, steam quality, air temperature, air injecting time, gas production rate, and nitrogen-oxygen ratio of the gas which was injected into reservoir, etc. Then, the security of this technology was analyzed, in the light of the produced oxygen in gas phase. After that, some parameters were optimized to provide reference for next steps of the study.For multi-round steam stimulation, the air injection volume's impact on the recovery was studied. Under the condition of the amount of air injection in a single cycle and two cycles, the timing of gas injection rate's influence on oil rate, oil recovery, light oil recovery, medium oil recovery and heavy oil recovery were studied to help to determine the appropriate cycle. The analysis of the three components'quantity in crude oil provided data for the study of air injection in the process of this mechanism. Meanwhile, it offered guidance for practical application and post-operation in the later period.