石油沥青质的吸附、沉淀机理及其影响因素

对于原油中石油沥青质的存在状态尚无统一认识,存在多种石油胶体体系理论模型。沥青质有两种方式从石油中分离出来,即吸附和沉淀,它们具有完全不同的机理。吸附的沥青质不能被溶解,要通过解吸才能消除,且解吸过程相对溶解而言很慢。沉淀是由于石油胶体体系的变化引起的,而吸附则是由石油胶体体系以及体系外的水介质环境和周围岩石矿物特征等所控制的。影响吸附的主要因素有:矿物本身的化学性质和结构特征、矿物质表面水层的性质、原油组成。影响沉淀的因素主要有:原油的组成、温度和压力、石油所处的状态、孔隙特征。低渗储层比高渗储层更容易导致沥青质的沉淀。

Adsorption and Precipitation Mechanism of Petroleum Asphaltene and its Influence Factors

The petroleum asphaltene is a given ingredient in oil which can be dissolved by benzene or toluene, but can not bedissolved by pentane or heptane. Many models of petroleum colloid system have been built to analyze the states of petroleum as-phaltene in crude oil, however none of them is unanimous.The petroleum asphaltene can be separated out from oil by adsorptionand precipitation.There are differences in mechanism and effects between the two modes. The adsorbed asphaltene cannot bedissolved and removed by desorption and the process of desorption is slower than that of dissolution.The precipitation of asphal-tene results from the change of colloid system while besides the change,the adsorption is controlled by the environment of for-mation water and the characteristic of surrounding rock and minerals.The factors influencing adsorption include the compositionof crude oil,the chemistry and structure of minerals,and the characteristics of water film on minerals.The factors influencingprecipitation mainly are the composition of crude oil, the state of oil, the character of porosity, and the temperature and pressureof the environment that the system of crude oil is in. Low-permeable reservoir is more likely to cause precipitation of asphaltenethan high permeable reservoir.