Abstract
There is still half oil remaining in the reservoir after polymer flooding. This paper has carried out the laboratory studies on multi-profile control and displacement system to enhance oil recovery after polymer flooding. First of all, the multiple system comprising a gel particle, cross-linking agent and high effective surfactant, is screened according to specific criteria. Then the profile control experiments on binary and ternary system after polymer flooding are separately carried out to verify the potential of enhanced oil recovery. The results show that the multiple injection system not only blocks the high permeable layers and channels, but also makes full use of medium and low permeability layers, finally improving the whole sweep efficiency. Owing to the surfactant injection, the displacement efficiency is simultaneously improved to some extent, and thus greatly improves the oil recovery after polymer flooding.
Highlights
Field experience has proven that polymer flooding can be an effective means to improve oil recovery after waterM
Polymer flooding, which is widely used in offshore oilfields in China, has become an important enhanced oil recovery (EOR) technique recently for offshore oilfields development (Ming et al 2006; Wei et al 2007; 2008)
The results show that the recovery factors of water and polymer flooding for cation and anion are nearly same, but the recovery factor of cationic gel particle is eight percents higher than anion after profile control displacement stage
Summary
The major focus is the effect of the system in core flooding after polymer flooding, including the water cut decline, the oil recovery improvement and the injection pressure reduction. The cation gel particle and the anion gel particle are going to be screened by the relationship between the injected PV and the recovery factor of the core profile control experiment (Shaodong and Xiangguo 2002). It can be seen that the pressure in water and polymer flooding stage is almost the same, when it turns to surfactant flooding, the pressure begins to dramatically decline and the pressure continues to reduce at the following water flooding stage This phenomenon certifies that the surfactant system can bring down the injection pressure by reducing the water–oil interfacial tension and residual oil saturation to raise the water phase relative permeability.
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