【作者】 杨芳；

【导师】 汤达祯； 白宝君；

【作者基本信息】 中国地质大学（北京） ， 矿产普查与勘探， 2010， 博士

【摘要】 二氧化碳封存于地下盐水层中可减少空气中二氧化碳含量,减缓全球变暖速度。盐水层分布广泛且可储量大,极具发展前景。研究二氧化碳在盐水层中的封存特性,可指导注入过程,并为盐水层的选取评估和相关经济评价提供可靠的地质模型和依据。本文以深部和浅部盐水层为研究对象,在广泛查阅资料、收集数据基础上,合理取值,建立模型,应用油藏数值模拟技术,结合试验设计分析方法,查明了二氧化碳在盐水层中的运移分布特征、存储量与注入能力以及封存机理类型与程度,探讨了储层物性和注入速度对二氧化碳存储量和注入能力的影响,并分析了注入井类型、水平井位置与长度、直井射孔层位和产水等优化注入方案。研究表明,二氧化碳在盐水层中主要向上运移,分布形态与储层非均质性有关。二氧化碳存储量在深部盐水层中更高,而注入能力在浅部盐水层中更高。二氧化碳在盐水层中以游离态为主,其次是束缚态、溶解态和离子态,矿化态含量极低。主要封存方式是剩余气体饱和度封存和溶解封存。储层非均质性对二氧化碳储量和注入能力的影响程度很小。相对而言,平均横向渗透率对二氧化碳存储量和注入能力的影响最大。二氧化碳存储量大致与平均横向渗透率和纵横向渗透率比值成正比,与渗透率变异系数成反比。二氧化碳注入能力则相反。相关地质与工程因素中,地层破裂压力梯度对二氧化碳存储量影响最大,而最大注入速度对二氧化碳注入能力影响最大。储层深度对二氧化碳封存影响程度一般,显示浅部盐水层存在碳封存可行性。增加储层厚度、孔隙度和最大注入速度可提高二氧化碳存储量和注入能力。水平井比直井利于二氧化碳封存,可提高二氧化碳存储量1%左右。水平井位于储层上部时,二氧化碳存储量可增加达10%。根据二氧化碳存储量和注入效率,确定模型中水平井最优长度为280米。直井射孔层段越多,越靠近储层上部,二氧化碳存储量越大。产水可大幅度提高二氧化碳存储量,且有助于二氧化碳溶解。更多还原

【Abstract】 Carbon sequestration in saline aquifers has been identified as a promising method of reducing atmospheric CO₂ in response to growing concerns over climate change. Saline aquifers are attractive for such sequestration because of their large capacity and broad distribution. Modeling CO₂ sequestration in saline aquifers is needed to direct injection, site selection, and economic evaluation. With data extracted from publications, deep and shallow saline aquifer models were built using compositional reservoir simulator CMG-GEM to investigate CO₂ transportation, distribution, CO₂ storage capacity, CO₂ injectivity, and the type and extend of sequestration mechanisms. The effect of reservoir properties and injection rate on CO₂ storage and injectivity in saline aquifers were then studied. Sensitivity analysis was carned out using design of "experiments （DOE） to determine the dominant factors. In addition, engineering aspects were discussed to optimize CO₂ storage capacity, including water withdraw and completion methods as partial perforation, well geometry, orientation, location and length.Simulation results show that CO₂ moves upward in saline aquifers and the distribution pattern is affected by reservoir heterogeneity. The storage capacity CO₂ in deep saline aquifer is high than that of shallow aquifer, but CO₂ injectivity is lower. Most CO₂ present as free gas, some are residual gas and dissolved phase, and very few CO₂ are mineralized. Two main trapping mechanisms occur in saline aquifers are residual gas trapping and solubility trapping.Generally, heterogeneity has very little effect on CO₂ storage capacity and injectivity. Relatively, mean permeability affects CO₂ storage capacity and injectivity the most. More CO₂ can be stored in the heterogeneous reservoirs with low mean permeability; however, high injectivity can be achieved in the uniform reservoirs with high mean permeability.Among all the properties discussed in the model, the fracture pressure gradient of reservoir affects CO₂ storage capacity the most, while the maximum injection rate affects CO₂ injectivity the most. Reservoir depth doesn’t affect CO₂ sequestration significantly, suggesting the possibility of CO₂ sequestration in shallow aquifers. Increasing reservoir depth, porosity, and the maximum injection rate can improve CO₂ storage capacity and injectivity.Comparing to deviated wells and vertical wells, horizontal wells are better choices for CO₂ injection in that it improves CO₂ storage capacity, especially when set in upper layers of reservoir. The optimal length can be determined according to CO₂ storage capacity and the sequestration efficiency. For the aquifer examined, the value is 280 m. Completing more layers in the upper reservoir gets more CO₂ injected. Water withdraw can improve CO₂ storage capacity greatly and benefit CO₂ dissolution.更多还原