Geochemical analysis of mixed oil in the Ordovician reservoir of the Halahatang Depression,Tarim Basin,China  

作　　者：CHENG Bin WANG Tieguan CHANG Xiangchun 

机构地区：[1]State Key Laboratory of Petroleum Resources and Prospecting,China University of Petroleum [2]Shandong University of Science and Technology

出　　处：《Chinese Journal Of Geochemistry》2013年第4期347-356,共10页中国地球化学学报

基　　金：funded by the China Postdoctoral Science Foundation Funded Project(Grant No.20110490539)

摘　　要：In this study,12 crude oil samples were collected and analyzed from the Ordovician reservoir in the Halahatang Depression,Tarim Basin,China.Although the density of oil samples varies considerably,based on saturated hydrocarbon gas chromatographic(GC),saturated and aromatic hydrocarbon gas chromatographic-mass spectrometric(GC/MS) and stable carbon isotopic composition analyses,all the samples are interpreted to represent a single oil population with similar characteristics in a source bed or a source kitchen,organic facies and even in oil charge history.The co-existence of a full suite of n-alkanes and acyclic isoprenoids with UCM and 25-norhopanes in the crude oil samples indicates mixing of biodegraded oil with fresher non-biodegraded oil in the Ordovician reservoir.Moreover,according to the conversion diagram of double filling ratios for subsurface mixed crude oils,biodegraded/non-biodegraded oil ratios were determined as in the range from 58/42 to 4/96.Based on oil density and oil mix ratio,the oils can be divided into two groups:Group 1,with specific density>0.88(g/cm3) and oil mix ratio>1,occurring in the north of the Upper Ordovician Lianglitage and Sangtamu Formation pinchout lines,and Group 2,with specific density<0.88(g/cm3) and oil mix ratio<1,occurring in the south of the pinchout lines.Obviously,Group 2 oils with low densities and being dominated by non-biodegraded oils are better than Group 1 oils with respect to quality.It is suggested that more attention should be paid to the area in the south of the Upper Ordovician Lianglitage and Sangtamu Formation pinchout lines for further exploration.In this study, 12 crude oil samples were collected and analyzed from the Ordovician reservoir in the Ha- lahatang Depression, Tarim Basin, China. Although the density of oil samples varies considerably, based on saturated hydrocarbon gas chromatographic （GC）, saturated and aromatic hydrocarbon gas chromatographic-mass spectromet- ric （GC/MS） and stable carbon isotopic composition analyses, all the samples are interpreted to represent a single oil population with similar characteristics in a source bed or a source kitchen, organic facies and even in oil charge his- tory. The co-existence of a full suite of n-alkanes and acyclic isoprenoids with UCM and 25-norhopanes in the crude oil samples indicates mixing of biodegraded oil with fresher non-hiodegraded oil in the Ordovician reservoir. More- over, according to the conversion diagram of double filling ratios for subsurface mixed crude oils, biode- graded/non-biodegraded oil ratios were determined as in the range from 58/42 to 4/96. Based on oil density and oil mix ratio, the oils can be divided into two groups： Group 1, with specific density 〉0.88 （g/cm3） and oil mix ratio 〉1, occurring in the north of the Upper Ordovician Lianglitage and Sangtamu Formation pinchout lines, and Group 2, with specific density 〈0.88 （g/cm3） and oil mix ratio 〈1, occurring in the south of the pinchout lines. Obviously, Group 2 oils with low densities and being dominated by non-biodegraded oils are better than Group 1 oils with re- spect to quality. It is suggested that more attention should be paid to the area in the south of the Upper Ordovician Lianglitage and Sangtamu Formation pinchout lines for further exploration.

关 键 词：塔里木盆地 地球化学分析 奥陶系 混合油 储层 中国 生物降解油 密度变化 

分 类 号：P618.13[天文地球—矿床学]