超稠油注空气辅助地下原位裂解改质试验和数值模拟

Experiment and reservoir simulation on air injection assisted in situ upgrading for ultra heavy oil recovery

超稠油地下原位裂解改质工艺的原理是通过井筒电加热器加热地层,促使稠油组分发生热裂解反应生成轻质油和气体,实现超稠油在地下的原位裂解改质。但单一的原位裂解工艺主要通过热传导传递热量,地层加热速率缓慢。考虑到注空气强化采油工艺的原理和原油的氧化放热特性,提出超稠油注空气辅助原位裂解工艺方法,利用注入空气的对流效应和氧化反应的热效应提高地层传热速率,同时具有气驱助采的效果。针对此工艺过程,进行超稠油在高压空气条件下的热裂解试验,研究其热裂解反应机制和模型,并建立超稠油注空气辅助原油裂解改质工艺的油藏模拟模型,研究高温条件下注空气对原油原位裂解工艺的影响和开发效果。结果表明:超稠油在350℃的温度下即可发生裂解反应,生成气体、轻质油和焦炭类物质;相对于单一的原位裂解改质工艺,注空气可有效增加传热速率,提高地层温度,提高原油采收率及能量效率。

In situ upgrading(ISU)via underground heating and thermal cracking is regarded as an effective technique for exploiting ultra heavy oils,in which heavy oil components can be cracked into light oils and gases for production.This technique has some advantages over conventional thermal recovery technique,such as high oil recovery rate,high thermal efficiency and improved oil quality.However,slow heating rate via conduction from wellbore to oil formation is one of the main issues concerned in the conventional ISU process.Considering the exothermic characteristics of oxidation reaction of oil during the air injection process,an air injection assisted ISU technique(AAISU)was proposed,which can enhance the heat transfer through gas convection and utilize the thermal effect of low temperature oxidation(LTO)reaction.In this study,thermal cracking experiments of ultra-heavy oil in the presence of air were conducted at high pressure to study the thermal cracking reaction mechanism of heavy oil components,and reservoir simulation the AAISU process was carried out.The experimental and numerical simulation results show that ultra heavy oil can be effectively cracked into gases,light oils and coke-like substances in the presence of air at temperature over 350℃.The heat transfer rate can be effectively enhanced by air injection comparing with the conventional ISU without air,and the total oil recovery factor can be increased over 21%and the energy conversion efficiency can be improved by 53%via air injection.