An interface super molecular structure model for oil-water-surfactant mixture and calcite was established. By using a molecular dynamics method, the effects of rhamnolipid, sodium dodecyl benzene sulfonate and sodium ...An interface super molecular structure model for oil-water-surfactant mixture and calcite was established. By using a molecular dynamics method, the effects of rhamnolipid, sodium dodecyl benzene sulfonate and sodium hexadecyl sulfonate on the interface adsorption behavior of oil molecules were investigated. It was found that these three surfactants could reduce oil-calcite interface binding energy, and play a role of oil-displacing agent.展开更多
Microscopic pore structure in continental shale oil reservoirs is characterized by small pore throats and complex micro-structures.The adsorption behavior of hydrocarbons on the pore walls exhibits unique physical and...Microscopic pore structure in continental shale oil reservoirs is characterized by small pore throats and complex micro-structures.The adsorption behavior of hydrocarbons on the pore walls exhibits unique physical and chemical properties.Therefore,studying the adsorption morphology of hydrocarbon components in nanometer-sized pores and clarifying the exploitation limits of shale oil at the microscopic level are of great practical significance for the efficient development of continental shale oil.In this study,molecular dynamics simulations were employed to investigate the adsorption characteristics of various single-component shale oils in inorganic quartz fissures,and the influence of pore size and shale oil hydrocarbon composition on the adsorption properties in the pores was analyzed.The results show that different molecules have different adsorption capacities in shale oil pores,with lighter hydrocarbon components(C6H14)exhibiting stronger adsorption abilities.For the same adsorbed molecule,the adsorption amount linearly increases with the increase in pore diameter,but larger pores contribute more to shale oil adsorption.In shale pores,the thickness of the adsorption layer formed by shale oil molecules ranges from 0.4 to 0.5 nm,which is similar to the width of alkane molecules.Shale oil in the adsorbed state that is difficult to be exploited is mainly concentrated in the first adsorption layer.Among them,the volume fraction of adsorbed shale oil in 6 nm shale pores is 40.8%,while the volume fraction of shale oil that is difficult to be exploited is 16.2%.展开更多
Here we present a combined DFF and molecular dynamics study of uranyl （U（VI）） interaction mecha- nisms with the calcite （104） surface in aqueous solution. The roles of three anion ligands （CO2 , HCO3, OH ） and...Here we present a combined DFF and molecular dynamics study of uranyl （U（VI）） interaction mecha- nisms with the calcite （104） surface in aqueous solution. The roles of three anion ligands （CO2 , HCO3, OH ） and solvation effect in U（VI） interaction with calcite have been evaluated. According to our calculations, water adsorbed on the calcite （104） surface prefers to exist in molecular state rather than dis- sociative state. Energy analysis indicate that the positively charged uranyl species prefers to form surface complexes on the surface, while neutral uranyl species may bind with the surface via both surface complexing and ion exchange reactions of U（VI） → Ca（II）. In contrast, the negatively charged uranyl species prefer to interact with the surface via ion exchange reactions of U（VI）→ Ca（II）, and the one with UO2（CO3）2（H2O）^2- as the reactant becomes the most favorable one in energy. We also found that uranyl adsorption increases the hydrophilicability of the （104） surface to different extents, where the UO2（CO3）3Ca2 species contributes to the largest degree of energy changes （ 53 kcal/mol）. Our calcula- tions proved that the （104） surface also has the ability to immobilize U（VI） via either surface complexing or ion exchange mechanisms under different pH values.展开更多
生物表面活性剂为一种特定微生物代谢产生的具有表面活性的物质,通过在岩石表面的吸附来达到改变其润湿性的目的,而润湿改性机制对油藏提高采收率至关重要。通过接触角的测定、洗油砂评价、液-固界面自由能计算及分子动力学模拟等方法,...生物表面活性剂为一种特定微生物代谢产生的具有表面活性的物质,通过在岩石表面的吸附来达到改变其润湿性的目的,而润湿改性机制对油藏提高采收率至关重要。通过接触角的测定、洗油砂评价、液-固界面自由能计算及分子动力学模拟等方法,研究了鼠李糖脂表面活性剂与疏水Si O_(2)表面间的相互作用,并对其吸附特性和润湿改性机制进行了阐释。结果表明,鼠李糖脂可快速改善亲油玻片表面的润湿性。经10%鼠李糖脂溶液浸泡12 h后,亲油玻片的接触角从111.6°降至32.7°。鼠李糖脂溶液对油砂的最佳洗油有效加量为30%,洗油效率可达84.83%,原油黏附功降低了98.4%。通过液-固界面自由能计算得到去离子水与鼠李糖脂溶液作用后的亲油玻片间的自由能为-140.2 m J/m^(2),远低于去离子水与原始亲油玻片间的自由能(-52.1 m J/m^(2))。分子模拟计算结果表明,鼠李糖脂分子主要通过氢键这一强作用力吸附在亲水Si O_(2)表面,其与亲水界面的吸附结合能达到29.7 e V;而鼠李糖脂分子与疏水Si O_(2)表面的作用力为静电力和范德华力等弱作用力,导致其与疏水界面的吸附结合能仅为12.2 e V。结合液-固界面自由能和分子模拟计算结果推测,鼠李糖脂分子相较于原油极性分子具有更强的界面竞争吸附能力,从而使其易于锚定到亲水表面、最终替换油性分子,达到提高洗油效率的目的。研究结果可为构建以鼠李糖脂为主的生物润湿调控驱油体系提供理论支撑。展开更多
有机质及其相关孔隙吸附行为的研究对于揭示页岩油赋存状态与机理有重要意义。不同于以往采用石墨烯模型代替有机质的方法,研究采用真实的干酪根分子模型(Ⅱ-C型),基于GAFF(general Amber force field)力场模拟了有机孔内页岩油多组分...有机质及其相关孔隙吸附行为的研究对于揭示页岩油赋存状态与机理有重要意义。不同于以往采用石墨烯模型代替有机质的方法,研究采用真实的干酪根分子模型(Ⅱ-C型),基于GAFF(general Amber force field)力场模拟了有机孔内页岩油多组分体系下的吸附行为。结果表明:(1)与石墨烯仅能模拟壁面吸附不同,干酪根对页岩油具有吸附和吸收双重作用:壁面上存在页岩油竞争吸附,以极性和重质组分吸附为主,而骨架中则存在页岩油组分吸收现象,小分子迁移距离较远。页岩油在干酪根壁面上的吸附和在骨架中的迁移受控于页岩油与干酪根相互作用能的强弱及分子大小,重质组分表现出“强吸附-弱吸收”、轻质组分呈“弱吸附-强吸收”的特征。(2)页岩油组分的吸收使得干酪根骨架和孔隙发生变化,表现出新孔隙的形成、原有孔隙的扩大和部分塌陷。干酪根的塑性对吸收页岩油进而膨胀起重要作用,干酪根塑性较强时(干酪根成熟度低),页岩油更容易被吸收从而引发明显的干酪根骨架膨胀,反之,干酪根膨胀较弱。(3)温度增加会促进干酪根骨架吸收芳香烃分子萘和非极性分子甲酸、乙醇以及噻吩,降低干酪根壁面的吸附作用,同时有利于饱和烃类分子的脱附。压力对页岩油在干酪根中的吸附和吸收影响不明显。研究利用真实的干酪根分子模型,首次创新性地模拟了干酪根吸附和吸收页岩油组分的现象,对于客观揭示页岩油在干酪根中赋存状态及赋存机理具有重要帮助。展开更多
基金supported by the Venture Innovation Fund of PetroChina Company Limited (07-06D-01-04-02-10)CNPC Innovative Fund for Middle-aged and Youth of China (CNPC2006-2008)
文摘An interface super molecular structure model for oil-water-surfactant mixture and calcite was established. By using a molecular dynamics method, the effects of rhamnolipid, sodium dodecyl benzene sulfonate and sodium hexadecyl sulfonate on the interface adsorption behavior of oil molecules were investigated. It was found that these three surfactants could reduce oil-calcite interface binding energy, and play a role of oil-displacing agent.
文摘Microscopic pore structure in continental shale oil reservoirs is characterized by small pore throats and complex micro-structures.The adsorption behavior of hydrocarbons on the pore walls exhibits unique physical and chemical properties.Therefore,studying the adsorption morphology of hydrocarbon components in nanometer-sized pores and clarifying the exploitation limits of shale oil at the microscopic level are of great practical significance for the efficient development of continental shale oil.In this study,molecular dynamics simulations were employed to investigate the adsorption characteristics of various single-component shale oils in inorganic quartz fissures,and the influence of pore size and shale oil hydrocarbon composition on the adsorption properties in the pores was analyzed.The results show that different molecules have different adsorption capacities in shale oil pores,with lighter hydrocarbon components(C6H14)exhibiting stronger adsorption abilities.For the same adsorbed molecule,the adsorption amount linearly increases with the increase in pore diameter,but larger pores contribute more to shale oil adsorption.In shale pores,the thickness of the adsorption layer formed by shale oil molecules ranges from 0.4 to 0.5 nm,which is similar to the width of alkane molecules.Shale oil in the adsorbed state that is difficult to be exploited is mainly concentrated in the first adsorption layer.Among them,the volume fraction of adsorbed shale oil in 6 nm shale pores is 40.8%,while the volume fraction of shale oil that is difficult to be exploited is 16.2%.
基金supported by the National Natural Science Foundation of China (U1507116, 21471152, and 21477130)the Major Research Plan of Natural Science Foundation of China (91326202)The Science Challenge Project of China (JCKY2016212A504) is also acknowledged
文摘Here we present a combined DFF and molecular dynamics study of uranyl （U（VI）） interaction mecha- nisms with the calcite （104） surface in aqueous solution. The roles of three anion ligands （CO2 , HCO3, OH ） and solvation effect in U（VI） interaction with calcite have been evaluated. According to our calculations, water adsorbed on the calcite （104） surface prefers to exist in molecular state rather than dis- sociative state. Energy analysis indicate that the positively charged uranyl species prefers to form surface complexes on the surface, while neutral uranyl species may bind with the surface via both surface complexing and ion exchange reactions of U（VI） → Ca（II）. In contrast, the negatively charged uranyl species prefer to interact with the surface via ion exchange reactions of U（VI）→ Ca（II）, and the one with UO2（CO3）2（H2O）^2- as the reactant becomes the most favorable one in energy. We also found that uranyl adsorption increases the hydrophilicability of the （104） surface to different extents, where the UO2（CO3）3Ca2 species contributes to the largest degree of energy changes （ 53 kcal/mol）. Our calcula- tions proved that the （104） surface also has the ability to immobilize U（VI） via either surface complexing or ion exchange mechanisms under different pH values.
文摘生物表面活性剂为一种特定微生物代谢产生的具有表面活性的物质,通过在岩石表面的吸附来达到改变其润湿性的目的,而润湿改性机制对油藏提高采收率至关重要。通过接触角的测定、洗油砂评价、液-固界面自由能计算及分子动力学模拟等方法,研究了鼠李糖脂表面活性剂与疏水Si O_(2)表面间的相互作用,并对其吸附特性和润湿改性机制进行了阐释。结果表明,鼠李糖脂可快速改善亲油玻片表面的润湿性。经10%鼠李糖脂溶液浸泡12 h后,亲油玻片的接触角从111.6°降至32.7°。鼠李糖脂溶液对油砂的最佳洗油有效加量为30%,洗油效率可达84.83%,原油黏附功降低了98.4%。通过液-固界面自由能计算得到去离子水与鼠李糖脂溶液作用后的亲油玻片间的自由能为-140.2 m J/m^(2),远低于去离子水与原始亲油玻片间的自由能(-52.1 m J/m^(2))。分子模拟计算结果表明,鼠李糖脂分子主要通过氢键这一强作用力吸附在亲水Si O_(2)表面,其与亲水界面的吸附结合能达到29.7 e V;而鼠李糖脂分子与疏水Si O_(2)表面的作用力为静电力和范德华力等弱作用力,导致其与疏水界面的吸附结合能仅为12.2 e V。结合液-固界面自由能和分子模拟计算结果推测,鼠李糖脂分子相较于原油极性分子具有更强的界面竞争吸附能力,从而使其易于锚定到亲水表面、最终替换油性分子,达到提高洗油效率的目的。研究结果可为构建以鼠李糖脂为主的生物润湿调控驱油体系提供理论支撑。
文摘有机质及其相关孔隙吸附行为的研究对于揭示页岩油赋存状态与机理有重要意义。不同于以往采用石墨烯模型代替有机质的方法,研究采用真实的干酪根分子模型(Ⅱ-C型),基于GAFF(general Amber force field)力场模拟了有机孔内页岩油多组分体系下的吸附行为。结果表明:(1)与石墨烯仅能模拟壁面吸附不同,干酪根对页岩油具有吸附和吸收双重作用:壁面上存在页岩油竞争吸附,以极性和重质组分吸附为主,而骨架中则存在页岩油组分吸收现象,小分子迁移距离较远。页岩油在干酪根壁面上的吸附和在骨架中的迁移受控于页岩油与干酪根相互作用能的强弱及分子大小,重质组分表现出“强吸附-弱吸收”、轻质组分呈“弱吸附-强吸收”的特征。(2)页岩油组分的吸收使得干酪根骨架和孔隙发生变化,表现出新孔隙的形成、原有孔隙的扩大和部分塌陷。干酪根的塑性对吸收页岩油进而膨胀起重要作用,干酪根塑性较强时(干酪根成熟度低),页岩油更容易被吸收从而引发明显的干酪根骨架膨胀,反之,干酪根膨胀较弱。(3)温度增加会促进干酪根骨架吸收芳香烃分子萘和非极性分子甲酸、乙醇以及噻吩,降低干酪根壁面的吸附作用,同时有利于饱和烃类分子的脱附。压力对页岩油在干酪根中的吸附和吸收影响不明显。研究利用真实的干酪根分子模型,首次创新性地模拟了干酪根吸附和吸收页岩油组分的现象,对于客观揭示页岩油在干酪根中赋存状态及赋存机理具有重要帮助。
