CO_(2)地质利用与封存中碳迁移及其相态分布规律

Carbon migration and phase distribution patterns in CO_(2) geological utilization and storage

CO_(2)地质利用与封存技术是“双碳”战略下重要的碳减排手段,前人的研究多集中于地质利用方面,而对地层的碳封存潜力尤其是CO_(2)矿化潜力的定量评价存在不足。为此,通过程序开发手段,将闪蒸计算加入开源的反应溶质运移模拟软件中,利用改进后的软件建立了松辽盆地大情字井油田H59区块的三维地质模型,通过历史拟合注采过程校正模型地层参数,最后采用校正后模型量化表征了不同注入阶段及注采结束后CO_(2)迁移与相态转化的时空演化过程。研究结果表明:①在油藏CO_(2)混相驱条件下,CO_(2)在注入井端的小范围内呈现气相,在接触到油相前缘后,CO_(2)受浮力影响减弱,在垂向上逐渐趋于均匀分布,并向开采井端均匀推进;②气水同注阶段与注气阶段均有超过70%注入的CO_(2)溶解于油相,但气水同注阶段溶解于水相的CO_(2)含量明显增加;③注采结束后的相态演化特征表现为溶解水相CO_(2)逐渐转变为矿物相,而溶解油相CO_(2)存在转变为游离态气相的趋势;④注采结束后,主要矿化过程为绿泥石及铁白云石溶解产生铁、钙离子,与碳酸根离子结合构成方解石和菱铁矿等沉淀矿物(固碳矿物),而主要溶解矿物有钾长石、钙蒙脱石、铁白云石及绿泥石。结论认为,基于现场实测数据,利用嵌入闪蒸计算的CO_(2)地质利用与封存组分模拟软件,提高了对CO_(2)迁移及分布相态规律的进一步认识,研究结果对实现注CO_(2)高效提高采收率与封存具有重要指导意义。

CO_(2) geological utilization and storage(CGUS)is an important method to reduce carbon emissions in the context of“carbon peaking and carbon neutrality”goals.The previous studies mostly focused on geological utilization,but paid little attention to the quantitative evaluation of the carbon storage potential of strata,especially the potential of CO_(2) mineralization.By means of program development,this paper introduces the flash calculation into the open source software to simulate the reaction solute transport,and then establishes a 3D geological model of H59 block of Daqingzijing Oilfield in the Songliao Basin by using the improved software.In addition,the formation parameters of the model are corrected through history match of injection and production process.Finally,the spatio-temporal evolution of CO_(2) migration and phase transformation in different injection stages and after the end of injection and production is quantified with the corrected model.And the following research results are obtained.First,under the condition of miscible CO_(2) flooding in the reservoir,CO_(2) presents as gas phase in a small range at the end of injection well.And after contacting the front of oil phase,CO_(2) gets weakened by buoyancy,gradually tends to be evenly distributed in the vertical direction,and advances uniformly to the end of the production well.Second,more than 70%of the injected CO_(2) is dissolved in the oil phase in both the gas-water injection stage and the gas injection stage,but the content of CO_(2) dissolved in the water phase increases significantly in the gas-water injection stage.Third,the phase evolution after the end of injection and production is characterized by the gradual transformation of CO_(2) dissolved in water phase into mineral phase,but the transformation trend of CO_(2) dissolved in oil phase into the free gas phase.Fourth,after the end of injection and production,the main mineralization process is the dissolution of chlorite and iron dolomite to produce iron and calcium ions,which combine with carbonate ions to form precipitated minerals(carbon fixing minerals)such as calcite and siderite,and the dissolved minerals are mainly potassium feldspar,calcium montmorillonite,iron dolomite and chlorite.In conclusion,based on the field measurement data,the CO_(2) migration and phase distribution patterns are theoretically studied by using the CGUS component simulation software embedded with flash calculation,and the research results are of important significance to guide efficient CO_(2) EOR and storage.