烃源岩中单甲基烷烃化合物分析与鉴定  

Analysis and Identification of Monomethylalkanes in Source Rocks

作　　者：钱宇[1,2] 王作栋[1] 贾冬[1,2] 雷艳[2,3] 王有孝[1] 贺永红 妥进才[1] 张婷[1,2] 

机构地区：[1]甘肃省油气资源研究重点实验室/中国科学院油气资源研究重点实验室,兰州730000 [2]中国科学院大学,北京100049 [3]中国科学院广州地球化学研究所有机地球化学国家重点实验室,广州510640 [4]陕西延长石油(集团)有限责任公司研究院,西安710075

出　　处：《沉积学报》2015年第5期1033-1042,共10页Acta Sedimentologica Sinica

基　　金：中国科学院西部行动计划(编号:KZCX2-XB3-12);国家自然科学基金(批准号:41072106,41402129);甘肃省重点实验室专项(编号:1309RTSA041)联合资助

摘　　要：对鄂尔多斯盆地中生界三叠系延长组烃源岩饱和烃进行了GC-MS分析。在吴56井长8烃源岩样品中检出碳数为C12!C31的单甲基烷烃(MMAs)系列化合物,由甲基位置为C2至中间碳原子的不同异构体组成,其出峰位置在同碳数正构烷烃之前;甲基取代基为C2和C3的MMAs相对丰度最高,C4以上甲基烷烃相对丰度较低。根据单甲基烷烃质谱图的离子碎片特征和化学键重组方式,并结合保留时间,以C22单甲基烷烃系列化合物为例,对甲基位置不同的单甲基烷烃系列化合物进行了鉴定,结果表明:C22单甲基烷烃的甲基位置为C2!C11;其质谱图与同碳数正构烷烃相似,质谱图基峰仍为m/z57或m/z71,并呈现出按碳数增长(CnH2n+1)规律相对丰度降低的特征,有明显的分子离子峰(M+)和M+-15质量碎片;与正构烷烃相比,甲基取代基在C5以上位置时,C22单甲基烷烃质谱图中存在m/z126、140、154…CnH2n等偶数离子特征碎片,被认为是鉴定单甲基烷烃的重要依据。据此,总结了单甲基烷烃系列化合物特征离子表,并利用特征离子的质量色谱图的反褶积来确定气相色谱中未被分离的单甲基烷烃的保留时间,进一步利用Kovats指数和同形性因子(Hp)对单甲基烷烃进行鉴定和预测。Saturated hydrocarbons in source rock from member 8 of Yanchang Formation（ Upper Triassic） in Ordos Basin were analyzed by GC-MS. Different isomers of monomethylalkanes（ MMAs）（ carbon number ranging from 12 to31） have been measured on a rock sample from Well Wu 56 located in Wuqi area. MMAs,with different substituted methyl ranging from the second carbon to the middle carbon,have shorter retention time than the corresponding n-alkanes with identical carbon number. 2-methylalkanes and 3-methylalkanes are the most abundant compounds among MMAs,while 4-methylalkanes and other MMAs are relatively low. The positions of the substituted methyl in the MMAs can be identified through typical fragment ions,recombination pattern for chemical bonds,and retention time by mass spectrometry. For example,it has been found that the substituted methyl positions of C22-MMAs are C2-C11.The mass spectrometry is similar to the n-alkane with the same carbon number,m / z57 or m / z 71 is their base peak.They also show a predominant M＋peak and（ M-15）＋peak,suggesting a branched methyl. Moreover,the relative abundance decreases as the total carbon increases. When the methyl position is exceeding the fifth carbon,in comparison with n-alkanes,their major characteristic fragment ions are such m / z126,140,154,as even CnH2 n,which are important to identify MMAs. Generally,a table about the characteristic fragment ions of MMAs are concluded. As well as gas chromatographic unseparated monomethylalkane isomers were resoluted by mass spectrometric deconvolution.Finally,by using of the Kovats index and the homomorphy factors for precise retention prediction and identification of the monomethylalkanes.

关 键 词：单甲基烷烃(MMAs) 烃源岩 特征离子 科瓦茨指数 同形性因子 

分 类 号：TE135[石油与天然气工程—油气勘探]