火驱油藏岩矿与原油演化特征

Evolution of Rocks and Crude Oil in Resevoirs During Fire Flooding

温度是影响火驱储集层岩矿和流体性质变化的主要因素。为细分火驱各阶段变化特征,采用热重-差示扫描量热法,刻画了原油氧化过程,同时运用X射线衍射、背散射电子成像等技术,研究不同温度区间岩矿演化过程及其对储集层物性的影响。研究结果表明,火驱过程中存在原油氧化启动、高温燃烧门槛、岩矿热活化、岩矿深度变质等4个温度关键节点,将油岩演化过程分为地层预热、原油低温氧化、原油中温氧化和黏土分解、原油高温氧化和黏土烧结、非黏土矿物深度变质5个阶段。其中原油高温氧化和黏土烧结阶段为整个过程的激烈期,原油燃烧释放热量占总放热量的60%左右,黏土矿物发生烧结作用,使储集层孔隙结构和物性发生明显变化。

Temperature is the main factor influencing the changes of reservoir rocks and fluid properties during fire flooding. In order to subdivide the changes in each phase of fire flooding, the paper uses the thermogravimetric-differential scanning calorimetry method to characterize oxidation process of crude oil, and studies rock evolution and its influences on reservoir properties at different temperature intervals by using X-Ray diffraction and back scattered electron imaging technologies. The study results show that there are 4 critical temperatures during fire flooding, i.e., crude oil oxidation activation, high-temperature combustion threshold, thermal activation of rock, and deep rock metamorphism, and the rock evolution can be divided into 5 phases such as formation preheating, low-temperature oxidation of crude oil, medium-temperature crude oil oxidation and clay decomposition, high-temperature crude oil oxidation and clay sintering, and deep metamorphism of non-clay minerals, among which the phases of high-temperature crude oil oxidation and clay sintering are the maximum mobility period during the evolution with the released heat of crude oil combustion accounting for about 60% of the total released heat, and the clay minerals have sintering, resulting in the obvious changes of reservoir pore structures and properties.