With increasing CO_(2)concentration in the atmosphere,CO_(2)geo-aequestration has become a popular technique to counter the dangers of global warming resulting from high levels of CO_(2)in the atmosphere.This paper ex...With increasing CO_(2)concentration in the atmosphere,CO_(2)geo-aequestration has become a popular technique to counter the dangers of global warming resulting from high levels of CO_(2)in the atmosphere.This paper examins sequestration parameters such as CO_(2)plume behaviour,residual gas trapping and injectivity as a means of achieving safe and successful CO_(2)storage in saline aquifers.Mineral precipitation/dissolution rates are used to establish a relationship between these parameters and geochemical reactions in saline aquifers.To achieve this,mechanistic models(6 models with different inputs,created using CMG e GEM,2016 and WINPROP,2016)are simulated using input data from literature and studying changes in fluids and formation properties as well as mineral precipitation/dissolution rates in aquifers when subjected to different conditions in the different models.The results from the models show that high CO_(2)dissolution,which creates large CO_(2)plume,leads to high mineral dissolution/precipitation as results of increased fluid-rock interactions(geochemical reactions);whereas injectivity,although enhanced by CO_(2)-water cyclic injection,does not show much increase in bottom hole pressure when mineral trapping(thus geochemical reactions)is introduced into the model.Sensitivity study on residual gas trapping shows that high residual gas saturation leads to reduced mineral precipitation/dissolution due to the reduced amount of dissolved CO_(2)in brine.Also,rapid changes in the bottom hole pressure at high residual gas saturation means that a formation that fosters high residual gas trapping,rather than CO_(2)dissolution in brine,is more likely to experience injectivity issues during the sequestration process.展开更多
为建立基于分布滞后非线性模型(Distributed Lag Non-linear Model, DLNM)的CO_(2)诱蚊灯监测的蚊密度模型,探索不同气候条件下上海市淡色库蚊密度变化的特征,在上海市15个区,于4-11月每旬共设置229个CO_(2)诱蚊灯,监测淡色库蚊密度。以...为建立基于分布滞后非线性模型(Distributed Lag Non-linear Model, DLNM)的CO_(2)诱蚊灯监测的蚊密度模型,探索不同气候条件下上海市淡色库蚊密度变化的特征,在上海市15个区,于4-11月每旬共设置229个CO_(2)诱蚊灯,监测淡色库蚊密度。以2018-2020年的监测数据建立基于DLNM的蚊密度与气象因素的方程。以改进的赤池信息准则(QAIC)对各个气象因素、连接函数和参数组合进行评价,最终选择QAIC最小的模型。最终建模结果取类泊松模型为DLNM的连接函数,进入模型的气象因素包括每旬的日平均最高气温、平均日降雨量和平均相对湿度。结果显示,旬平均最高气温与淡色库蚊密度呈倒“U”型关系,在平均最高气温大于10℃后逐步升高,在30℃达到密度峰值,其后逐步降低。平均日降雨量与淡色库蚊密度呈“J”型关系,在日平均降雨量大于6 mm后逐步升高。旬平均相对湿度与淡色库蚊密度呈倒“U”型关系,在平均相对湿度为70%时达密度峰值。结果表明,DLNM可以解释气象因子变量对蚊虫种群密度的影响,从而预测未来蚊虫密度的变化,为开展蚊虫控制措施提供科学依据。展开更多
To accelerate the CO_(2) trapping in geological storage sites,several injection strategies have been proposed by researchers so far.However,the question remains unanswered as to which one of these injection strategies...To accelerate the CO_(2) trapping in geological storage sites,several injection strategies have been proposed by researchers so far.However,the question remains unanswered as to which one of these injection strategies is the most efficient in terms of immobilising CO_(2) and more importantly,how these strategies might be improved.In this paper,we attempt to simulate a typical geological CO_(2) storage scheme in an aquifer using the E300 compositional reservoir simulator and subsequently investigate and compare the impact of various injection strategies on CO_(2) immobilising efficiency.Secondly,the impact of adding a short period of post-brine injection on various strategies is newly investigated.Our results reveal that using a relatively short period of post-brine injection can significantly improve total CO_(2) trapping efficiency in all the strategies.In general,by using post injection of brine,more CO_(2) is spread out through the aquifer and,as a consequence,by increasing the interfacial area of the CO_(2) plume,the amount of dissolution as a result of mass transfer increases significantly.Moreover,the effect of convection can become stronger in the case of post-brine injection creating a stronger density instability and thus a more rapid initiation of convection.Furthermore,when brine is injected into the system,CO_(2) is displaced away from the well resulting in a forced imbibition process and thereby enhancing the capillary trapping efficiency.The post-injection of brine has also one more particular effect in strategies of horizontal injection and simultaneous CO_(2)/brine injection in different intervals.In this regard,postbrine injection creates a stronger downward pressure gradient that counters the tendency of the CO_(2) plume to rise and therefore retards the CO_(2) in reaching the top of the aquifer.This increases the time that the CO_(2) can be in contact with the fresh formation brine and so enhances the trapping efficiency.We envisage that the post-brine injection could enhance the total trapping efficiency of CO_(2) from 26%,30.8%,39.8%and 59.1%to 47.7%,44.2%,62%and 63.9%,when it was added into different strategies of CO_(2) continuous injection,simultaneous injection of CO_(2)/brine in the same and different intervals and a horizontal system,respectively.However,our findings show that the effectiveness of post-brine injection may be reduced in high vertical permeability values and in this respect,capillary trapping can be more affected by vertical permeability variation.Furthermore,the results show that selection of the rate and duration of post-brine injection can have considerable effects on total CO_(2) trapping efficiency.展开更多
文摘With increasing CO_(2)concentration in the atmosphere,CO_(2)geo-aequestration has become a popular technique to counter the dangers of global warming resulting from high levels of CO_(2)in the atmosphere.This paper examins sequestration parameters such as CO_(2)plume behaviour,residual gas trapping and injectivity as a means of achieving safe and successful CO_(2)storage in saline aquifers.Mineral precipitation/dissolution rates are used to establish a relationship between these parameters and geochemical reactions in saline aquifers.To achieve this,mechanistic models(6 models with different inputs,created using CMG e GEM,2016 and WINPROP,2016)are simulated using input data from literature and studying changes in fluids and formation properties as well as mineral precipitation/dissolution rates in aquifers when subjected to different conditions in the different models.The results from the models show that high CO_(2)dissolution,which creates large CO_(2)plume,leads to high mineral dissolution/precipitation as results of increased fluid-rock interactions(geochemical reactions);whereas injectivity,although enhanced by CO_(2)-water cyclic injection,does not show much increase in bottom hole pressure when mineral trapping(thus geochemical reactions)is introduced into the model.Sensitivity study on residual gas trapping shows that high residual gas saturation leads to reduced mineral precipitation/dissolution due to the reduced amount of dissolved CO_(2)in brine.Also,rapid changes in the bottom hole pressure at high residual gas saturation means that a formation that fosters high residual gas trapping,rather than CO_(2)dissolution in brine,is more likely to experience injectivity issues during the sequestration process.
文摘To accelerate the CO_(2) trapping in geological storage sites,several injection strategies have been proposed by researchers so far.However,the question remains unanswered as to which one of these injection strategies is the most efficient in terms of immobilising CO_(2) and more importantly,how these strategies might be improved.In this paper,we attempt to simulate a typical geological CO_(2) storage scheme in an aquifer using the E300 compositional reservoir simulator and subsequently investigate and compare the impact of various injection strategies on CO_(2) immobilising efficiency.Secondly,the impact of adding a short period of post-brine injection on various strategies is newly investigated.Our results reveal that using a relatively short period of post-brine injection can significantly improve total CO_(2) trapping efficiency in all the strategies.In general,by using post injection of brine,more CO_(2) is spread out through the aquifer and,as a consequence,by increasing the interfacial area of the CO_(2) plume,the amount of dissolution as a result of mass transfer increases significantly.Moreover,the effect of convection can become stronger in the case of post-brine injection creating a stronger density instability and thus a more rapid initiation of convection.Furthermore,when brine is injected into the system,CO_(2) is displaced away from the well resulting in a forced imbibition process and thereby enhancing the capillary trapping efficiency.The post-injection of brine has also one more particular effect in strategies of horizontal injection and simultaneous CO_(2)/brine injection in different intervals.In this regard,postbrine injection creates a stronger downward pressure gradient that counters the tendency of the CO_(2) plume to rise and therefore retards the CO_(2) in reaching the top of the aquifer.This increases the time that the CO_(2) can be in contact with the fresh formation brine and so enhances the trapping efficiency.We envisage that the post-brine injection could enhance the total trapping efficiency of CO_(2) from 26%,30.8%,39.8%and 59.1%to 47.7%,44.2%,62%and 63.9%,when it was added into different strategies of CO_(2) continuous injection,simultaneous injection of CO_(2)/brine in the same and different intervals and a horizontal system,respectively.However,our findings show that the effectiveness of post-brine injection may be reduced in high vertical permeability values and in this respect,capillary trapping can be more affected by vertical permeability variation.Furthermore,the results show that selection of the rate and duration of post-brine injection can have considerable effects on total CO_(2) trapping efficiency.
