This paper shows the close relation between the displacement effects and reservoir properties in CO2 flooding for low permeability reservoirs. Low permeability reservoirs are characterized by tight matrix, strong heterogeneity and developed fractures. With the increase of CO2 injection rate, the CO2 viscous fingering gets worse in low permeability homogeneous reservoirs. While for low permeability heterogeneous reservoirs, the increase in displacement differential pressure contributes to the enhanced oil recovery in less permeable layers. The moderate increase in effective pressure is conductive to improveing the oil recovery in matrix. The displacement effect and CO2 channeling can be improved through the adjustment of injection-production parameters in CO2 flooding. Additionally, the interaction among CO2, oil and brine can improve the water-oil viscosity ratio. The gas viscous fingering can be weakened. The temporary performance of oil-water emulsion band formed in carbonate water can plug high permeability layers, and the production capacity of low permeability layers can be enhanced. The compound gel system in the sour environment of CO2 can plug large gas-channeling paths, restrict gas channeling and enlarge the sweep efficiency.
The gas consumption was the highest in both systems (0.5% Span20 +0.05% SDS) and (0.5% Span20 + 0.5% l-l), indicating that the two systems had a faster hydrate formation rate.
Summary
Phase change materials (PCMs) attached to building envelopes have been widely investigated, but there are rare studies to evaluate the influence of micro‐environments of PCMs. This paper, therefore, aims to study the action mechanism of PCMs under the micro‐environment systematically and provides the optimization of PCMs parameters, to realize a further reduction in building energy use. Simulation results indicate that a big difference in the heat transfer of envelopes appears in different orientations due to differences in solar radiation. Then, the optimal transition temperature Tp and amount of use of PCMs increase with the increase in solar radiation intensity Isr. Compared with other envelopes, the west‐facing wall and roof need higher Tp and amount of PCMs, under Isr from 400 to 1000 W/m2 the optimal Tp increases from 28 to 34°C with a difference high up to 6°C. The result also shows that the building energy‐saving of optimal PCMs parameters would rise by 16.6% compared to the fixed PCMs parameters.
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