塔北地区三叠系油藏原油中性含氮化合物和烷基苯酚的运移分馏作用

Migration Fractionation of Neutral Nitrogen Compounds and Alkylphenols in Triassic Crude Oils from Tabei Field,Tarim Basin,China

塔北地区三叠系油藏原油中性含氮化合物和烷基苯酚自南向北存在着运移分馏作用 ,表现为中性含氮化合物的绝对浓度由高变低 ,屏蔽型化合物相对富集而部分屏蔽型化合物和裸露型化合物相对贫瘠 ,1,8 DMCA/1,7 DM CA ,1,8 DMCA/2 ,7 DMCA ,1,8 DMCA/部分屏蔽化合物 ,1,8 DMCA/裸露化合物的比值由小变大 ,而 [a]/[c]的比值则由大变小 ,烷基苯酚化合物 2 MPH/3 MPH和 2 ,6 DMPH/2 ,3 DMPH的比值亦由小变大。此外同一构造带中原油自西向东 ,从下而上中性含氮化合物同样存在着运移分馏效应。研究还表明塔北地区三叠系原油横向上自南向北 ,从吉拉克地区向桑塔木断垒和轮南断垒带方向运移 ,而侧向上原油从下而上 。

Tabei field is separated into Lunnan fault uplift,Sangtamu fault uplift and Jilake anticline structuere from north to sounth.Analysis of a range of Triassic crude oils in this area appears to indicate that neutral nitrogen compounds and alkylphenols has a strong migration fractionation.In addition, from the south of the field to the north,the absolute concentration of neutral nitrogen compounds has changed from large to small with relative enrichment for nitrogen shielded isomers,and parts of nitrogen shielded isomers and nitrogen exposed isomers relatively scarce in concentration.The concentrations of benzo〔a〕carbazole plus benzo〔c〕carbazole(〔a〕+〔c〕),carbazole(CA),methylcarbazoles(MCA)and dimethylcarbazoles(DMCA)of crude oils in Sangtamu fault uplift are obvious higher than those of Lunnan fault uplift.For instance,differences in the migration parameters between the LN44 well oil from Sangtamu fault uplift,and LN2 well oil from Lunnan fault uplift are very obvious,i.e.,the amounts of [a]+[c],CA,MCA,DMCA decrease from 1.80 μg/g oil,2.10 μg/g oil,6.57 μg/g oil,13.43 μg/g oil to 0.49 μg/g oil,0.93 μg/g oil,4.39 μg/g oil,1.02 μg/g oil.From south to north,the [a]/[c] ratio in Jilake structure is the highest,ranging from 2.04 to 2.22,and the ratio in Sangtamu fault uplift range from 0.98 to 1.94.However,Lunnan fault uplift is lower,ranging from 0.71 to 1.25.The ratio of o cresol,to m cresol,and of 2,6 to 2,3 dimethylphenol,i.e.,the hydroxyl group shielded isomers are relatively enriched in the oils from the north of Tabei field.In the same fault uplift,the neutral nitrogen compounds of crude oils have migration frationation from the west of the fault uplift to the east,as well as from T Ⅲ oil leg of the fault uplift to T Ⅰ oil leg.The results suggest that Triassic oils across Tabei field migrate laterally from Jilake field to Sangtamu fault uplift and Lunnan fault uplift,Trassic oils in the same fault uplift migrate and remigrate vertically from T Ⅲ oil leg to T Ⅰ oil leg and from the west of the fault to the east.