463. 非等温条件下二氧化碳/溶剂注入提高采收率的混相效应模拟研究

Simulation Study on Miscibility Effect of CO₂/Solvent Injection for Enhanced Oil Recovery at Nonisothermal Conditions

最小混相压力（MMP）决定了二氧化碳驱油的主要机理，即非混相或混相过程。本文研究了二氧化碳驱油的采收率提高情况，重点分析了注入温度和溶剂组成两个方面。结果表明，较低温度的注入和液化石油气（LPG）混合物可以显著提高采收率，这是由于注入的溶剂降低了被波及区域的MMP。对于在储层温度下纯二氧化碳注入，经过1.0孔隙体积（PV）二氧化碳注入后采收率为59%。

通过二氧化碳-LPG混合物注入，采收率随着LPG摩尔分数的增加而提高，当LPG摩尔分数为0.1时采收率为73%，当LPG摩尔分数为0.2时采收率为81%。低温二氧化碳注入的采收率为78%，比恒温情况高32%。低温二氧化碳-LPG混合物注入的采收率可提高至初始石油的87%。为了更准确地描述该过程，应考虑储层与上下覆盖层之间的热传导。此外，与原始非恒温模型相比，热传导模型的采收率降低了4%-12%。

CMG软件应用情况

本文使用了CMG（Computer Modeling Group）公司的GEM模拟器进行二氧化碳驱油的模拟研究。GEM是一个三维、多组分、多相模拟器，考虑了混相气体注入过程的重要机理，如储层流体的组成变化、原油的膨胀、粘度降低以及通过多次接触形成混相溶剂带等。

CMG软件在模拟过程中能够精确地计算流体的相态行为和混相特性，帮助研究人员分析不同注入方案下的油藏响应和采收率变化。同时，CMG软件还具备热力学模块，可以模拟储层内的热量传导过程，这对于研究非恒温条件下的驱油效果具有重要意义。

Abstract

The minimum miscibility pressure (MMP) determines the main mechanism of CO₂ flooding, which is either an immiscible or miscible process. This paper examines the recovery improvements of CO₂ flooding in terms of both the injection temperature and solvent composition. The results show that a lower temperature injection and LPG (liquefied petroleum gas) mixture can considerably improve oil recovery due to the reduced MMP in the swept area caused by the injected solvent. For the pure CO₂ injection at the reservoir temperature, oil recovery is 59% after 1.0 PV CO₂ injection. The oil recoveries by CO₂-LPG mixtures are improved to 73% with 0.1 mole fractions of LPG and 81% with 0.2 mole fractions of LPG. The recovery factor from low-temperature CO₂ injection is 78%, which is 32% higher compared to the isothermal case. The recoveries obtained by low-temperature CO₂-LPG injection increase up to 87% of the initial oil. Heat transfer between the reservoir and the formation of over/underburden should be considered in order to describe the process more accurately. Additionally, the recovery factors from the heat transfer models are decreased by 4–12% in comparison with the original nonisothermal models.

作者单位

韩国首尔汉阳大学自然资源与环境工程系