Abstract:

CO₂ injection is a commonly used technique for recovering oil from mature reservoirs as it can not only greatly improve oil recovery, but also achieve the goal of greenhouse gas emission reduction. Most of the reservoirs in China are continental deposits, and the serious heterogeneity leads to serious CO₂ gas channeling, which makes the effect of CO₂ flooding worse. In this paper, the simulation experiment of continuous gas injection, WAG, intermittent gas injection and pulse injection of CO₂ is carried out by using the heterogeneous model in the layer, and the effects of the characteristics of the CO₂ flooding in the heterogeneous oil reservoir and the dynamic environment on the CO₂ gas blow-by are studied. The experimental results show that WAG injection flooding is the best, the effect of intermittent gas injection and continuous gas injection is second, and the pulse gas injection effect is the worst; CO₂ flooding has no gas and low gas oil. In the production stage, extending the production time of the two stages can improve the development effect; by changing the hydrodynamic conditions, the CO₂ gas channeling can be effectively suppressed, and the WAG injection is more capable of suppressing the gas channeling, and the disturbance effect of the pulse gas injection is intensified. The above experimental results show that WAG injection in heterogeneous reservoirs is the optimal injection mode for CO₂ flooding.

Key words: CO₂ channeling, heterogeneous reservoir, hydrodynamic method, WAG, intermittent injection, pulse gas injection