超临界CO2/水交替微观驱油特征研究

针对水气交替驱过程中CO_2与水能否接触、对剩余油动用能力等热点问题,利用高温高压微观可视模型,研究了不同密度CO_2驱后剩余油分布类型及挖潜对策,描述了水气交替微观封堵特征及对剩余油动用能力。实验结果表明,超临界CO_2的高密度特性,可扩大CO_2向油藏中下部的扩散运移;CO_2驱后剩余油以油膜类、盲端类、等势点类、未波及区域为主,其中等势点及未波及区域是下步挖潜主要对象;水气交替的注水阶段与注气阶段呈现出不同的贾敏效应,其中注气阶段贾敏效应明显;水气交替可显著改善等势点类剩余油,但未波及区域动用程度不高。

Study on the microscopic flooding characteristic of water-alternating-gas

Aiming at problems of contact area of CO₂ and water, the displacement efficiency of remaining oil during the process of water-alternating-gas (WAG), a series experiments by microscopic visual device were proceed. Types of remaining oil distribution and potential tapping measures after CO₂ flooding in different density, the microscopic characteristics of formation plug and displacement efficiency of remaining oil in WAG injection were observed in this study. Study shows that supercritical CO₂ diffusion and migration could expand to the middle and bottom in reservoir when the density is high. Remaining oil distribution after CO₂ flooding could mainly divide into four types: oil slick, blind side area, equipotential point and un-swept areas. The equipotential point and un-swept areas were the key types to EOR. The Jamin effect in WAG injection was different at the stages of water flooding and gas flooding. The Jamin effect in gas flooding was stronger than in the water flooding. The equipotential point oil could be swept by WAG injection, but the un-swept areas were inefficiency.