In this paper we propose a characteristics mixed finite element method to overcome thenumerical dispersion for the 2-phase immiscible displacement. The pressure and associatedfluid velocity will be approximated by a m...In this paper we propose a characteristics mixed finite element method to overcome thenumerical dispersion for the 2-phase immiscible displacement. The pressure and associatedfluid velocity will be approximated by a mixed finite element method, and the saturationwill be treated by a backward characteristics method. The L_∞ stability and convergence forthe scheme are proved, and optimal-order error estimates in L_∞ are obtained.展开更多
深部咸水含水层具有巨大的CO_(2)封存潜力,研究致密砂岩CO_(2)-水两相驱替机制对实现高效安全的CO_(2)咸水层封存具有重要意义。对两个具有不同孔隙结构特征的低渗透砂岩开展了CO_(2)-水两相驱替试验,利用核磁共振(nuclear magnetic res...深部咸水含水层具有巨大的CO_(2)封存潜力,研究致密砂岩CO_(2)-水两相驱替机制对实现高效安全的CO_(2)咸水层封存具有重要意义。对两个具有不同孔隙结构特征的低渗透砂岩开展了CO_(2)-水两相驱替试验,利用核磁共振(nuclear magnetic resonance,NMR)和磁共振成像(magnetic resonance imaging,MRI)技术对气驱和吸水两个阶段气水两相的分布进行了定量及可视化研究,分析了岩芯孔径分布、非均质性及渗透率差异等对两相驱替特征的影响机制。研究表明在气驱阶段CO_(2)相优先被捕获在较大的孔隙中,大孔分布较多的岩芯表现出更高的CO_(2)饱和度;但在吸水阶段小孔占比更高、渗透率更低的岩芯内捕获的CO_(2)相不易被水驱走,表现出更高的CO_(2)封存效率;岩芯局部渗透率变化对最终的残余气分布影响显著,渗透率较低的区域具有更高的最终残余气饱和度和封存效率。研究可进一步完善CO_(2)咸水含水层封存项目中的储层优选、高效封存以及安全性评估等理论体系。展开更多
The performance of the single-stage anaerobic digestion of kitchen wastes was investigated in an anaerobic sequencing batch reactor(ASBR) with gas-phased absorb of CO 2. The ASBR was operated at four chemical oxygen ...The performance of the single-stage anaerobic digestion of kitchen wastes was investigated in an anaerobic sequencing batch reactor(ASBR) with gas-phased absorb of CO 2. The ASBR was operated at four chemical oxygen demand(COD) loading rates, 2.8, 5.1, 6.2 and 8.4 g/(L·d) respectively. The COD loading rate was increased with the TS concentration and HRT changing. At maximum COD loading rate of 8.4 g/(L·d), the COD, total solid(TS) removal rate and methane gas yield were 69%, 68% and 2.5 L/(L·d) respectively. The operation of the reactor with gas-phased absorb of CO 2 was stable in spite of the low pH(2.6—3.9) and high concentration of TS(142 g/L) of input mixture. The output volatile fatty acid(VFA) concentration was between 2.7—4.7 g/L and had no inhibition on the methanogenic microorganism. The reactor without gas-phased absorb of CO 2 became acidified when the total COD loading rate was increased to 5.1 g/(L·d). Stoichiometry of the methanogenesis for kitchen wastes showed a considerable amount of alkaline will be required to keep pH in the appropriate range for the methanogenic microorganism based on theoretical calculation. Gas-phased absorb of CO 2 effectively reduced the alkaline consumption, hence avoided excessive cation into the reactor.展开更多
碳捕集、利用与封存(carbon capture,utilization and storage,CCUS)技术是中国实现“双碳”目标的关键手段,CO_(2)驱油技术作为CCUS技术的重要组成部分,通过向地层注入CO_(2)以提高油气产量,而且实现部分CO_(2)封存,从而达到环境保护...碳捕集、利用与封存(carbon capture,utilization and storage,CCUS)技术是中国实现“双碳”目标的关键手段,CO_(2)驱油技术作为CCUS技术的重要组成部分,通过向地层注入CO_(2)以提高油气产量,而且实现部分CO_(2)封存,从而达到环境保护与经济效益双赢的效果。依托鄂尔多斯盆地X区块长8段低渗透油藏,探究CO_(2)驱油过程中原油与CO_(2)体系的相态特征。通过高压物性分析和原油与CO_(2)体系相态实验,获取原油的体积系数、黏度、密度和饱和压力,并从实验和模拟角度进一步探究了CO_(2)注入对其相态特征的影响。结果表明:鄂尔多斯盆地X区块长8段原油密度、体积系数和饱和压力随压力变化显著;CO_(2)的注入能改善油藏压力、降低原油黏度、改变原油与注入气体的相态行为和混相程度;孔隙尺度对CO_(2)与原油体系相态特征有显著影响,孔隙尺寸越小,孔隙内毛管力越大,对原油相态影响更显著;中值孔隙介质中,CO_(2)注入量增加使原油黏度下降明显,密度也逐渐减小,体积系数随之增大,表明CO_(2)驱油能够改善原油相态,有助于提升低渗油藏的开发效果,研究成果有望为CO_(2)提高原油采收率提供理论依据。展开更多
基金Project supported by the National Natural Science Foundation of China.
文摘In this paper we propose a characteristics mixed finite element method to overcome thenumerical dispersion for the 2-phase immiscible displacement. The pressure and associatedfluid velocity will be approximated by a mixed finite element method, and the saturationwill be treated by a backward characteristics method. The L_∞ stability and convergence forthe scheme are proved, and optimal-order error estimates in L_∞ are obtained.
文摘深部咸水含水层具有巨大的CO_(2)封存潜力,研究致密砂岩CO_(2)-水两相驱替机制对实现高效安全的CO_(2)咸水层封存具有重要意义。对两个具有不同孔隙结构特征的低渗透砂岩开展了CO_(2)-水两相驱替试验,利用核磁共振(nuclear magnetic resonance,NMR)和磁共振成像(magnetic resonance imaging,MRI)技术对气驱和吸水两个阶段气水两相的分布进行了定量及可视化研究,分析了岩芯孔径分布、非均质性及渗透率差异等对两相驱替特征的影响机制。研究表明在气驱阶段CO_(2)相优先被捕获在较大的孔隙中,大孔分布较多的岩芯表现出更高的CO_(2)饱和度;但在吸水阶段小孔占比更高、渗透率更低的岩芯内捕获的CO_(2)相不易被水驱走,表现出更高的CO_(2)封存效率;岩芯局部渗透率变化对最终的残余气分布影响显著,渗透率较低的区域具有更高的最终残余气饱和度和封存效率。研究可进一步完善CO_(2)咸水含水层封存项目中的储层优选、高效封存以及安全性评估等理论体系。
文摘The performance of the single-stage anaerobic digestion of kitchen wastes was investigated in an anaerobic sequencing batch reactor(ASBR) with gas-phased absorb of CO 2. The ASBR was operated at four chemical oxygen demand(COD) loading rates, 2.8, 5.1, 6.2 and 8.4 g/(L·d) respectively. The COD loading rate was increased with the TS concentration and HRT changing. At maximum COD loading rate of 8.4 g/(L·d), the COD, total solid(TS) removal rate and methane gas yield were 69%, 68% and 2.5 L/(L·d) respectively. The operation of the reactor with gas-phased absorb of CO 2 was stable in spite of the low pH(2.6—3.9) and high concentration of TS(142 g/L) of input mixture. The output volatile fatty acid(VFA) concentration was between 2.7—4.7 g/L and had no inhibition on the methanogenic microorganism. The reactor without gas-phased absorb of CO 2 became acidified when the total COD loading rate was increased to 5.1 g/(L·d). Stoichiometry of the methanogenesis for kitchen wastes showed a considerable amount of alkaline will be required to keep pH in the appropriate range for the methanogenic microorganism based on theoretical calculation. Gas-phased absorb of CO 2 effectively reduced the alkaline consumption, hence avoided excessive cation into the reactor.
文摘碳捕集、利用与封存(carbon capture,utilization and storage,CCUS)技术是中国实现“双碳”目标的关键手段,CO_(2)驱油技术作为CCUS技术的重要组成部分,通过向地层注入CO_(2)以提高油气产量,而且实现部分CO_(2)封存,从而达到环境保护与经济效益双赢的效果。依托鄂尔多斯盆地X区块长8段低渗透油藏,探究CO_(2)驱油过程中原油与CO_(2)体系的相态特征。通过高压物性分析和原油与CO_(2)体系相态实验,获取原油的体积系数、黏度、密度和饱和压力,并从实验和模拟角度进一步探究了CO_(2)注入对其相态特征的影响。结果表明:鄂尔多斯盆地X区块长8段原油密度、体积系数和饱和压力随压力变化显著;CO_(2)的注入能改善油藏压力、降低原油黏度、改变原油与注入气体的相态行为和混相程度;孔隙尺度对CO_(2)与原油体系相态特征有显著影响,孔隙尺寸越小,孔隙内毛管力越大,对原油相态影响更显著;中值孔隙介质中,CO_(2)注入量增加使原油黏度下降明显,密度也逐渐减小,体积系数随之增大,表明CO_(2)驱油能够改善原油相态,有助于提升低渗油藏的开发效果,研究成果有望为CO_(2)提高原油采收率提供理论依据。
