幔源CO_2充注驱油机理——以松辽盆地南部长岭凹陷为例

分析天然气(CH4)驱油、原油驱水原理,建立了幔源CO2流体的充注驱油模型,在模型中CO2能否形成足够驱动力是驱油的关键。松辽盆地南部长岭凹陷泉四段储层与该模型相符合,在储层中发现幔源CO2与油气混层现象,并且CO2充注时间晚于油气注入时间。根据研究区地质条件,对幔源CO2驱油动力和阻力以及影响其大小的参数(CO2与原油的密度、界面张力、孔喉半径和CO2柱高度)进行分析,得出幔源CO2与原油所产生的浮力足可以突破油气运移阻力(毛细管阻力)。从物理和数学的角度证明幔源成因CO2能够对油气运移起到推动作用。

Mechanism of mantle- derived carbon dioxide infilling and oil displacement: a case studying in Changling sag of southern Songliao Basin

Through the analysis on the theory of natural gas (CH 4 ) displacement and oil driving water，we established the model of mantle- derived CO 2 - bearing fluid infilling and displacement． The key of the model is whether CO 2 could form sufficient driving force． The fourth- member of Quantou Formation reservoir in Changling sag of southern Songliao basin is matched with the model， and we found the mixed layers of mantle- derived CO 2 and oil-gas，moreover，the infilling of oil and gas was earlier than that of CO 2 ． According to the geological conditions of the studied area，we analyzed the driving and resistant force as well as the parameters which related to them，such as original CO 2 density，interfacial tension，pore throat radius and CO 2 column height． We concluded that the buoyancy created by mantle- derived CO 2 and crude oil is enough to break through the migration resistance (i. e． ， capillary resistance)． It can be proved that mantle- derived CO 2 plays a promoting role in the migration of oil and gas in perspectives of physics and mathematics．