Abstract: Many carbonate reservoir have been into high water-cut development stage. How to dig the remaining oil potential
and enhancing oil recovery further is dominant work target now. There are many problems in carbonate reservoir of R11，
such as low oil production of single well，inefficient utilization of injected water，and worsening of the water-flood efficiency.
Therefore it is necessary to find a new way to dig reservoir production potential. The EOR mechanism by Carbon dioxide
injection process in R11 is analyzed and the numerical simulation research on EOR by Carbon dioxide injection process in R11
reservoir is completed. Aimed at reservoir properties and development characteristic the three-dimensional numerical model is
set up. Based on the fitting history of water flooding，the gas injection rate，gas injection mode，gas injection position and the
gas-oil ratio control are optimized. The plan of Carbon dioxide injection is predicted for 20 years and the result shows that oil
production rise obviously and it can enhance oil recovery about 3.5% more than the current exploitation mode.

Key words: Carbon dioxide injection, carbonate reservoir, reservoir numerical simulation, EOR