东海盆地西湖凹陷宝云亭气田油气成藏史——来自流体包裹体的证据

Accumulation history of BaoYunting gas field in the Xihu sag,East China Sea Basin:from evidence of fluid inclusions

对东海盆地西湖凹陷宝云亭气田平湖组储层进行包裹体岩相观察、显微荧光光谱、红外光谱、显微测温、激光共聚焦扫描显微镜和古压力模拟等流体包裹体系统测试分析,并结合原油的气相色谱,从古流体证据的角度综合研究了宝云亭气田多阶段、动态油气成藏与变迁历史。研究结果表明,储层存在均匀的橙黄色荧光、近蓝色—近黄色荧光之间的渐变色、均匀的蓝绿色荧光、近亮蓝—淡蓝色荧光之间的渐变色和均匀的亮蓝色荧光共5种不同类型荧光光谱的油包裹体,与红外光谱的测试参数CH2a/CH3a和正构烷烃直链碳数Xstd分析结果一致。结合均一温度、古压力、含油颗粒指数、埋藏史和油气地球化学特征分析,揭示了西湖凹陷宝云亭气田发生了"两期油和一期气充注,油早气晚,多期成藏,晚期为主,之间还发生了混源和气洗作用"的复杂成藏过程。

Taking reservoir of Pinghu formation of BaoYunting gas field in Xihu sag of the East China Sea Basin as an example,the multistage and dynamics history of oil and gas accumulation and evolution was studied based on petrographic observations as well as systematic test and analysis of fluid inclusion using microscopic fluorescence spectroscopy,infra-red spectroscopy,microthermometry,laser scanning confocal microscope and pressure simulation,in combination with gas chromatography and palaeo-fluid evidences.The results indicate there exist 5 different types of fluid-inclusions according to the colors of fluorescence spectra：homogeneous orange,gradient color between those close to blue and yellow,homogeneous bluish green,gradient color between those close to bright and light blue,and homogeneous bright blue,which is consistent with analysis results using the infra-red spectroscopy test parameter CH2a/CH3 aand n-alkane straight-chain carbon number Xstd.Combined with homogeneous temperature,paleo-pressure,GOI,burial history,oil and gas geochemical characteristics,the complicated accumulation process of BaoYunTing gas field was discovered and described as＂two stages of oil charging and one stage of gas charging,oil charging before gas charging,multi-stage accumulation and dominated in late stage,with the occurrence of mixed source and gas injection＂.