摘要
塔中421井和塔中402井石炭系油层2个原油样和8个油砂样连续抽提组分甾烷、萜烷分布特征和正构烷烃单体碳同位素组成具有明显的差异,具有不同的来源。塔中421井上石炭统3个油砂样自由态组分、束缚态组分和油气包裹体具有伽马蜡烷和C28甾烷相对含量高、正构烷烃单体碳同位素组成重的特征,划分为Ⅰ类原油,对比认为主要来源于寒武系-下奥陶统烃源岩。塔中421井和塔中402井上石炭统的2个油样具有伽马蜡烷和C28甾烷相对含量低、并且正构烷烃单体碳同位素组成轻的特征,划分为Ⅱ类原油,其来源尚不明确。塔中402井石炭系上、中和下统的5个油砂样各类组分具有介于Ⅰ、Ⅱ类原油之间的特征,为Ⅰ和Ⅱ类原油的混合物。5个油砂样从自由态组分、束缚态组分至油气包裹体Ⅰ类原油含量依次增高,Ⅱ类原油含量依次降低。2口井8个油砂样从自由态组分、束缚态组分至油气包裹体C23三环萜烷/(C23三环萜烷+C30藿烷)和C21/(C21+ΣC29)甾烷比值都依次降低,反映了油气充注过程中,原油成熟度不断升高。塔中4井区储层油砂不同吸附态烃类分子与碳同位素的研究结果反映塔中4油田具有多种油气来源,经历长期油气充注过程,寒武系-下奥陶统烃源岩在地史上对该区具有成烃贡献。
Substantial variations have been observed in the distribution patterns of terpanes and steranes and δ^13C values of individual n-alkanes between two crude oils and oil fractions obtained by sequential extraction from eight oil sandstones collected from the Carboniferous oil columns in wells TZ421 and TZ402. The result demonstrates that these crude oils and oil fractions have different origins. All the free oil, adsorbed oil and inclusion oil obtained from the three oil sandstones from the oil columns within the Upper Carboniferous strata in well TZ421 are characterized by high relative amounts of gammaceranes and C28 steranes, and high δ^13C values of individual n-alkanes. These oil fractions are classified as type Ⅰ oils, which were derived from Cambrian-Lower Ordovician source rocks. In contrast, the two crude oils from wells TZ421 and TZ402, respectively, have low relative amounts of gammaceranes and C28 steranes, and low δ^13C values of individual n-alkanes. They are classified as type II oils, the source rocks of which are unknown so far. The oil fractions obtained from the five oil sandstones from the oil columns of the Upper, Middle and Lower Carboniferous strata in well TZ402 are mixtures of types I and II oils. From the free oil, the adsorbed oil, to the inclusion oil of these five oil sandstones, the proportion of type I oil increases while the proportion of type II oil decreases. In addition, from the free oil, the adsorbed oil, to the inclusion oil of all the eight oil sandstones from both wells TZ421 and TZ402, the ratios of C23tricyclic terpane/（C23tricyclic terpane＋C30hopane） and C21/（C21＋∑C29） steranes decrease, suggesting that the maturity of charging oil increased during filling process. The molecular and carbon isotope compositions of various hydrocarbon fractions by sequential extraction from oil sandstones demonstrate that hydrocarbons of Tazhong 4 oilfield were derived from multiple source rocks by long charging process, including the source rocks within Cambrian-Lower Ordovician strata.
出处
《地球化学》
CAS
CSCD
北大核心
2010年第5期479-490,共12页
Geochimica
基金
国家重点基础研究发展计划项目(2005CB422102)
国家自然科学基金(40673014)
有机地球化学国家重点实验室专项基金(SKLOG2008A01)
关键词
油砂连续抽提
油气包裹体
单体烃碳同位素
塔中4油田
塔里木盆地
sequential extraction on oil sandstone
oil-bearing fluid inclusion
0-3C values of individual n-alkanes
Tazhong 4 oilfield
Tarim Basin
