Process, mechanism and impacts of scale formation in alkaline flooding by a variable porosity and permeability model
Process, mechanism and impacts of scale formation in alkaline flooding by a variable porosity and permeability model作者机构:Key Laboratory of Mechanics in Fluid Solid Coupling Systems Institute of Mechanics Chinese Academy of Sciences
出 版 物:《Acta Mechanica Sinica》 (力学学报(英文版))
年 卷 期:2016年第32卷第3期
页 面:406-421页
核心收录:
学科分类:0820[工学-石油与天然气工程] 08[工学] 082002[工学-油气田开发工程]
基 金:supported by the National Basic Research Program of China (Grant 2005CB221300) the National Natural Science Foundation of China (Grant 11302234)
主 题:Alkali Precipitation Chemical flood Permeability Oil recovery
摘 要:In spite of the role of alkali in enhancing oil recovery(EOR), the formation of precipitation during alkaline-surfactant-polymer(ASP) flooding can severely do harm to the stratum of oil reservoirs, which has been observed in situ tests of oil fields such as scale deposits found in oil stratum and at the bottom of oil wells. On the other hand,remarkable variation of stratum parameters, e.g., pore radius,porosity, and permeability due to scale formation considerably affects seepage flow and alkaline flooding process in return. The objective of this study is to firstly examine these mutual influential phenomena and corresponding mechanisms along with EOR during alkaline flooding when the effects of precipitation are no longer negligible. The chemical kinetic theory is applied for the specific fundamental reactions to describe the process of rock dissolution in silicabased reservoirs. The solubility product principle is used to analyze the mechanism of alkali scale formation in *** a 3D alkaline flooding coupling model accounting for the variation of porosity and permeability is established to quantitatively estimate the impact of alkali scales on reservoir stratum. The reliability of the present model is verified in comparison with indoor experiments and field tests of the Daqing oil field. Then, the numerical simulations on a 1/4well group in a 5-spot pattern show that the precipitation grows with alkali concentration, temperature, and injection pressure and, thus, reduces reservoir permeability and oil recovery correspondingly. As a result, the selection of alkaliwith a weak base is preferable in ASP flooding by tradeoff strategy.