泥质岩石纳米孔隙对孔内流体的局限效应.pdf

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1、矿物岩石地球化学通报·纳米地质学·BulletinofMineralogy，PetrologyandGeochemistryVo1．35No．1，Jan．，2016泥质岩石纳米孑L隙对孔内流体的局限效应贾新驰，陆现彩，杨侃，张立虎，徐金覃表生地球化学教育部重点实验室，南京大学地球科学与工程学院，南京210023摘要：泥页岩以孔隙丰富、孔径细小为特征，纳米孔隙对孔隙流体的局限效应决定了泥页岩中页岩气的赋存形式和扩散性质以及潜在的CO处置能力。本文在总结泥质岩石纳米孔隙表征结果的基础上，使用淬火固体密度泛函理论(QsI)FT)和分子动力学方法(MD

2、)，研究了泥质岩石中纳米孔隙内流体的密度分布、赋存形式以及活动性。结果表明，孔径较小(如1．0nm)时，因孔壁的束缚效应纳米孔隙内甲烷成单层分布，而当孔径增大至2．0lm时，除孔壁表面多层吸附的甲烷外还出现自由态甲烷。相同条件下，孔径较小的孔内吸附态甲烷密度高于孔径较大的孔内吸附态甲烷密度，有机孔内吸附态甲烷的密度高于无机孔内吸附态甲烷的密度。随着温度、压力(深度)的增大，孔隙表面的局限效应减弱，表面束缚的吸附态甲烷比例减小，自由态甲烷相对增加。关键词：泥质页岩；纳米孔隙；孔隙流体；局限效应中图分类号：P588．212．1文章编号：1007—2

3、802(2016)O1—0070—09doi：10．3969／j．issn．1007．2802．2016．O1．009ConfiningEffectsonPoreFluidsofNano-PoresofShalesJIAXin—chi，LUXian—cai，YANGKan，ZHANGLi—hu，XUJin-tanKeyLabofSurficialGeochemistry，MinistryofEducation，SchoolofEarthSciencesandEngineering，NangUniversity，Nang210023，ChinaA

4、bstract：Ithasbeenwellknownthatmudstonesandshalesarecharacterizedwithabundanttinypores．TheOccurrencestateanddiffusionfeatureofshalegasaswellastheCO2storagecapacityarecommonlycontrolledbyconfiningefectsofnano·sizedporesinshales．Basedonthesummaryofnano—porestructurecharacterist

5、icsofshales，astudyonthedensityvariation，ocau~encestate，andmobilityofporefluidsinnano—poresinshaleshasbeenca~iedoutinthispaperbyusingmethodsofthequenchedsoliddensityfunctionaltheory(QSDFT)calculationandmoleculardynamics(MD)simulation．Resuhsshowthatthemethaneisdistributedasamo

6、nolayerorbilayerinnano—poreswhicharelessthan1．0nlninsize．However，theporemethaneoccursasmultipleadsorptionlayersandevenfreemethanein2．0nmsizedpores．Underthesameconditions，thecalculateddensityofthemethaneinsmallnano-poresishigherthanthatofthemethaneinrelativelybignano—pores，an

7、dthedensityofthemethaneintheorganicporeishigherthanthatofthemethaneintheinorganicone．Withtheincreaseoftemperatureandpressure(i．e．，burieddepth)，theconfiningeffectsofnano—poresaredecreased．Thisresultedinthedecreaseoftheproportionofconfiningmethaneandtheincreaseofthefreemethane

8、increasesinnano—pores·Keywords：shale；nano-pore；porefluid；confiningefect大量研究