东营凹陷牛庄-六户洼陷沙河街组三段下亚段烃源岩排烃通道及证据

通过岩心和薄片镜下观测、包裹体荧光分析、扫描电镜、QGF-E和X-CT等技术对东营凹陷牛庄—六户洼陷沙河街组下亚段(简称沙三下)烃源岩的排烃通道进行了判识,结果表明:①源岩内部的裂缝(包括沿层理面的顺层裂缝、与层理面斜交的裂缝和成岩收缩缝)多被固体沥青所充填,且充填裂缝的方解石脉体中存在大量发亮黄色荧光的油包裹体,说明裂缝充当了源岩排烃的有效通道;②牛24、牛83等4口井的73块与烃源岩互层的薄层砂岩样品的QGF-E荧光强度值绝大多数大于120pc(约占分析样品总数的78.6%),仅少数样品的荧光强度小于40pc,说明大多数薄层砂岩充当了源岩内部烃类侧向排出的通道;③扫描电镜和高分辨率X-CT扫描结果显示,Es3下烃源岩样品中干酪根网络分布连续,按照Hunt(1967)确定的有机质中烃类含量的下限标准(2.5%~10%),高有机质丰度和转化率的Es3下烃源岩存在通过干酪根网络的排烃机制。

Primary Hydrocarbon Migration Paths and Evidence in Lower Es3 Source Rock,Niuzhuang-Liuhu Sag,Dongying Depression,China

We use thin section microscope observation, fluorescence analysis in fluid inclusions, the scanning electron microscope (SEM), quantitative grain fluorescence on extract (QGF-E), and X-ray computed tomography (X-CT) to identify and estimate the hydrocarbon primary migration paths in the lower Es3 source rock within the Niuzhuang-Liuhu sag, Dongying Depression, China. The microfractures in the oil source rock, including the microfractures paralleled layers and vertical or almost vertical microfissures are mostly filled with solid bitumen and calcite veins, and a lot of oil fluid inclusions with light-yellow fluorescence discovered in calcite veins. The QGF-E fluorescence intensity of the samples collected form Niu 24, Niu 83 in 4 wells, which are folium sandstones within lower Es3 source rock, is almost much more than 120 pc and a few less than 40 pc. The result of SEM and X-CT indicts that the kerogen network in the lower Es3 source rock is continuous. According to the lower threshold of hydrocarbon in the organic matter (2.5%~10%), the hydrocarbon expulsed from the kerogen network existed in the lower Es3 source rock. Abundant evidence indicates that the subtle migration paths, for example fracture and microfracture, folium sandstone and the organic kerogen network, are the main route for a great deal hydrocarbon expulsion.