二氧化碳驱储集层堵塞机理实验分析

Experimental analysis on reservoir blockage mechanism for CO_2 flooding

结合细管实验、组分分析实验、微观模拟实验3种实验方法,分析CO2驱油过程中储集层堵塞、原油开采速度降低的现象,研究储集层堵塞机理。细管实验表明,较低驱替压力条件下,CO2驱油效果较差,驱替压力越高,驱油效果越好,在驱替压力超过最小混相压力后,储集层会出现堵塞现象,对产能有较大影响。组分分析和微观模拟实验表明,CO2与原油接触后产生组分分异,在较低驱替压力下,组分分异不明显,不会产生堵塞,但驱替压力较高时,原油中芳烃被CO2快速萃取,造成非烃和沥青质快速沉积,从而堵塞喉道。因此,控制驱替压力是防止储集层堵塞的主要措施,CO2驱油最佳压力应在最小混相压力附近,过高或过低的压力都不利于CO2驱油。

The slim-tube experiment, component analysis experiment and microscopic simulation experiment are used to analyze the phenomena of reservoir blockage and drop of oil production rate, and to find out the reservoir blockage mechanisms in the process of carbon dioxide flooding. The slim-tube experiment shows that the effect of carbon dioxide flooding was poor under low displacement pressure, and the higher the displacement pressure, the better the effect of flooding. When the displacement pressure exceeded the minimum miscibility pressure, reservoir blockage could occur, affecting the reservoir productivity significantly. Component analysis and microscopic modeling experiments show that oil component differentiation could occur after oil contacted with carbon dioxide. Under low displacement pressure, component differentiation was not significant, so reservoir blockage did not occur; but when the displacement pressure was higher, aromatics in oil were extracted rapidly by carbon dioxide, resulting in quick deposition of non-hydrocarbons and asphalt and the blockage of pore-throats in reservoirs. Therefore, controlling the displacement pressure is the main measure to prevent reservoir blockage. The best pressure of carbon dioxide flooding should be near the minimum miscible pressure, pressure, too high or too low, is not good for carbon dioxide flooding.