塔河油田奥陶系油藏成藏期次研究

Accumulation periods of Ordovician reservoirs in Tahe Oil Field

塔河油田奥陶系油藏的成藏期次长期以来争议较大,有两期、三期、多期之争,对成藏期次认识上的差异必然导致对其烃源岩层位认识上的不同,从而给油气勘探带来一定程度的不确定性。经过多年的多学科联合攻关,采用国际上最先进的单体包裹体成分分析技术,从不同期次单个油包裹体中提取出其地球化学特征信息,直接获得了塔河油田东南部两期充注原油的有机成分信息,研究表明塔河油田东南部奥陶系油藏主要为两期成藏,第一期油包裹体以发黄色—褐色荧光、芳烃组分相对饱和烃含量高、正构烷烃分布完整(nC11-nC30)、轻烃缺失等为特点,成熟度较低,为早期运移产物;第二期油包裹体以发蓝色—蓝白色荧光、饱和烃组分相对芳烃含量高、正构烷烃分布较窄(nC8-nC28)、轻烃完整等为特点,成熟度较高,为晚期轻质原油充注的特征。结合古温度、古压力模拟,混源油比例判识研究,对不同期次原油充注的时间以及贡献作了初步探讨,这对塔河油田主力烃源岩的再认识以及进一步的勘探具有重要指导意义。

How many stages of accumulation have the Ordovician reservoirs experienced in the Tahe Oil Field, 2, 3 or even more？The debate causes different understandings of source rock location, hence leads to uncertainty in oil and gas exploration. After years of multidisciplinary joint research, using the most advanced technique of mono-mer inclusion component analysis, the geochemical features of single oil inclusion during different stages have been identified. The geochemical components of crude oils charged during 2 stages in the southeast of the Tahe Oil Field have been made clear. It has been concluded that the Ordovician reservoirs in the southeast of the Tahe Oil Field have experienced 2 stages of accumulation. The oil inclusions of the 1st stage are featured by yellow-brown fluores-cence, higher aromatic component content than saturated hydrocarbon content, complete distribution of n-alkanes （nC11-nC30）, and light hydrocarbon missing. They have lower maturity and mainly generate from early migration. The oil inclusions of the 2nd stage are featured by blue-light blue fluorescence, higher saturated hydrocarbon con-tent than aromatic component content, narrow distribution of n-alkanes （ nC8-nC28 ） , and complete light hydrocar-bon. They have higher maturity, indicating for late-stage light oil charging. Combined with the simulations of paleo-pressure and paleotemperature as well as the studies of mixed oil proportion, the charging time and contribution of crude oils of different stages have been discussed, which may guide source rock studies in the Tahe Oil Field.