Abstract:

CO₂ flooding attracts extesive attention in recent years,it is widely used both home,especially abroad,and good effectiveness is achieved.It is studied that in the process of oil recovery by CO₂ injection,when CO₂ gets into reservoirs,the change in physical and chemical properties occures duo to the contact between CO₂ and crude oil,formation water and reservoir rocks,which makes reservoir permeability change.The compatibility study of CO₂,formation water and reservoir is conducted by using the samples of formation water in core permeability before and after CO₂ injection is tested,and the reason is analyzed.Result indicates that,in the process of CO₂ injection,no calcium carbonate precipitates to plug pore space as to decrease permeability,on the contrary,permeability is improved because CO₂ dissolves in water to form carbonic acid,which dissolves some cement of the rocks.

Key words: Carbon dioxide, formation water, permeability, compatibility, precipitation of calcium carbonate