三元复合驱过程中砂岩储层的溶蚀和沉淀机理研究

The oil fields are now in the late stage of development in eastern part of China. Scientists gave their effort designed an new technic, i.e. ASP which were combined .alkaline-surfactant-polymer in order to maintain the production and EOR. ASP can enhance the recovery as high as 20% verified by the pioneer experiments. There still .exists some weakness in practice in ASP flooding. Alkaline chemicals react with reservoir rock and fluids to produce precipitates as scale phenomena at production well. The scale, general speaking, is very complicate compounds. There is a large boody of literature on alkaline flooding and its variations. In laboratory tests evaluating alkaline flooding reported a white precipitate in the coreflood effluents that added to the alkaline consumption. They also noted that silicates are more effective at precipitating divalent metal ions. Highly hydrated alumino-silicate precipitates in alkaline core tests have also been observed. A number of other studies show that alkaline react strongly with the various reservoir-rock constituents. These reactions can produce very complex ionic effluent downstream in both laboratory core tests and field production wells.Injection of alkaline solution leads to mineral dissolution and precipitation with likely resulting changes in permeability and porosity of reservoir which is in turn alter solution pH. Upon injection of alkaline solution, 0.5 pH unit different between inlet and out let pH was observed. This is an indication of weak pH buffering capacity of this rock during alkaline flooding. However, few authors noticed the scale formation or not in the reservoir during alkaline flooding which is very important for using widely in fields. This research directly focus on the alkaline-rock interaction, especially on scale formation in reservoir or only at production wells. The position of scale formation is also important for ASP flooding. The new methods should be used in this study so as to determine the condition of alkaline-rock interaction and the proceeding during ASP flooding. The order and location of scale formation should be carefully studied in this program. The results of this program hopefully are to establish the mechanism of dissolution and precipitation in sandstone reservoir during ASP flooding and provide basic theory and reliable geologic data.

我国东部油田已经到了开发后期，为了稳定产量，提高采收率，科技工作者将各种驱油方法的集成形成三元复合驱。矿场实验表明，三元复合驱可以提高采收率20%。然而，在实践过程中，三元复合驱也存在着许多不足，主要是碱和岩之间的化学反应，由于储层矿物和碱发生反应，形成大量成分复杂的垢。国内外对碱和储层物质的反应做了大量的研究，在注入端和流出端发现pH值、离子浓度、孔隙度、渗透率都发生了改变，表明溶蚀与沉淀作用明显发生在三元复合驱的过程中。国内外的实验也未能确定结垢是在油层内部或者仅在井筒中。本次研究的主要目的就是采用新的实验方法，通过储层地质研究、碱-岩反应机理研究、三元复合驱体系的化学变化研究，确定储层物质的反应条件和过程，尤其是沉淀作用发生的条件和位置，易结垢部位，结垢晶出顺序，完善实验方法，建立三元复合驱过程中砂岩储层溶蚀与沉淀的反应机制，探索规律，为三元复合驱的发展提供基础理论和可靠的地质依据。