| Multiple sets of hydrocarbon sand bodies are developed in the Lower Member of Minghuazhen Formation in Laizhouwan sag, which are widely distributed.However, the structural characteristics and genetic mechanism of sand bodies remain unclear, and the relationship between sand bodies and oil bearing is also ambiguous, which restricts the next exploration. Based on seismic, well logging, core and thin section data, the internal structural characteristics of sand bodies in research area are dissected, and the controlling factors of the sand bodies formation and their relationship with oil bearing are discussed.The results show that: (1)There are three types of internal structures of sand bodies in the study area, namely isolated type, lap type and cutting overlay type, the cutting overlay sand bodies are mainly developed in the early sedimentary stage (the V oil group in the Lower Member of Minghuazhen Formation), the lap type sand bodies mainly developed in the middle sedimentary stage (the transitional part between the IV and V oil group in the Lower Member of Minghuazhen Formation), and the isolated sand bodies are mainly developed in the late sedimentary stage(the IV oil group in the Lower Member of Minghuazhen Formation); (2)Through the systematic analysis of geological factors such as paleoclimate and provenance supply in the study area, the controlling factors of sand bodies with different structures are determined. In the early stage of the study area, the humid climate and sufficient provenance supply promoted the formation of cutting overlay sand bodies. In the late stage of the study area, the arid climate and insufficient provenance supply led to the extensive development of isolated sand bodies; (3)Combined with fluvial sedimentary dynamics and sedimentary rules, the favorable superimposed areas of isolated sand bodies in the late sedimentary stage are effectively identified, and the innovative vertical cutting-overlay hydrocarbon migration model of superimposed sand bodies is proposed. On the one hand, this research achievement enriches and improves the Neogene hydrocarbon migration theory system in the Bohai Sea and ensures the overall reserve scale of the zone. On the other hand, it has guiding significance for the development of reservoir potential in mature oil fields. |
