“富砂型”河流相沉积储层砂体精细刻画

河流相沉积的“富砂型”储层中,河道交切关系复杂,精细刻画河道末期水线对理清砂体叠置关系、单一点坝刻画具有重大意义。针对渤海海域A油田高弯度复合型河道砂体(明上段B砂体),基于高分辨率地震资料进行倾角导向滤波及90°相移转换,开展高精度小尺度相干技术研究。利用正演模型,验证了不同尺度河道在地震剖面上的响应特征,确定了利用常规相干方法不能刻画小尺度河道的结论。针对地震数据的非相干性,可以采用振幅对比的方法进行刻画,结合实钻井资料,证实了利用振幅对比方法刻画小尺度河道及点坝边部岩性边界的正确性。在此基础上,利用地震多属性融合方法将河道和砂体信息叠合,采用等间隔地层切片方法直观展示河道和砂体平面形态,从而可以清晰研究河道发育迁移过程和砂体沉积过程,再结合地震剖面,提出了新的砂体沉积模式。以此沉积模式为指导,将复合砂体拆分为三期朵体沉积砂体,统一了油水界面,为部署评价井提供了依据。该方法技术对类似复合型曲流河沉积砂体精细研究具有借鉴意义。

Sand-rich reservoirs in fluvial facies deposits present complex cross-cutting relationships with ancient river channels.The fine characterization of the streamline position of the late channel is of great significance as it allows the characterization of the spatial overlap of the sand bodies and single-point bars.In this study,a high-precision small-scale coherence technology was applied to the high camber composite channel sand in oilfield A in the Bohai Bay Basin using dip-guided filtering with a 90° phase shift.A forward model was first used to verify the effect of channels of various scales on the seismic profile and it was demonstrated that small-scale channels cannot be described by a conventional coherent method.The amplitude contrast method was thus used to depict the incoherence of the seismic data.The results were compared with actual drilling data to confirm the identification of the small-scale channels and the boundary of single-point bars.Subsequently,the seismic multi-attribute fusion method was used to superimpose the channel and sandbody information.The plane shape of the channel and sandbody can be displayed directly using the equal interval stratigraphic slice method,which can clearly characterize the development and swing process of the river channel as well as the sandbody deposition process.Using information of the seismic section facies,a new viewpoint on the sedimentary model of sandbodies was proposed.In particular,three stages of Lobe deposition were identified,and a continuous oil-water interface was defined,thereby providing a strong basis for the deployment of production wells.The proposed method could be used as a reference for the fine study of similar complex meandering river sedimentary sandbodies.

中海石油(中国)有限公司综合科研项目“渤海双高油田挖潜关键技术研究”(YXKY-2018-TJ-04)资助。