| In this paper,taking the fourth block of Gudong Oilfield as an example,the unique geological characteristics of meandering river reservoir in river sedimentary system are studied by using the method of well-seismic combination from large to small and layer by layer.Due to the frequent migration and swing of meandering river,the lateral erosion and cutting of point bar to river channel are not in the same period,and the complex contiguous development,zonal deposition and development of river channel sand body are controlled by many factors,which makes its internal structure very complex.However,the current research on the underground meandering belt is only limited to the description of the plane shape distribution.In this paper,with the help of drilling data with high vertical resolution and seismic data with high lateral resolution,the architectural structure of underground meandering belt is dissected and the distribution characteristics of its internal structural units are analyzed in order to form a systematic interpretation method of reservoir structure in meandering belt.In this paper,guided by modern sedimentation,according to the morphological characteristics and distribution location,the point bar sand body is further subdivided into the sand body at the side of the point bar(PI sand body),the sand body at the end of the point bar(PE sand body,the lower sand body of the abandoned channel)and the main sand body of the point bar,and the superposition combination of 5 sand bodies is summarized.They are : the main body of the point bar superimposes the river edge in the early stage,the sand body at the initial lateral accretion site of the point bar superimposes the abandoned river channel,the sand body at the initial lateral accretion site of the point bar superimposes the sand body at the initial lateral accretion site of the point bar,the abandoned river channel superimposes the abandoned river channel mudstone,and the abandoned river channel superimposes the sand body at the initial lateral accretion site of the point bar.The corresponding forward model is established,and the sand body configuration of the well-seismic combination guided by the forward model is carried out.In the study of seismic sedimentology in the meandering zone of the study area,the stratigraphic slice technology is used to roughly identify the evolution characteristics of the river channel in the study area,and the superposition relationship of different secondary point bars and the injection-production and tracer data are verified.Finally,the distribution of the channel body and the point bar in the meandering zone is determined.Then the internal structure of the point bar is dissected,and the parameters of the lateral accretion body and the physical properties of the lateral accretion body inside the point bar are studied.It is found that the internal grain size of the lateral accretion body inside the point bar decreases linearly from bottom to top,the clay content index increases,and the permeability decreases exponentially.The lowest value is the permeability value corresponding to the mudstone.Based on the study of the sand body structure in the meandering belt,the paper finally summarizes the control effect of the internal configuration and configuration combination of the meandering belt on the distribution of remaining oil.It is found that the remaining oil in the horizontal superposition part of the point bar is more abundant,especially in the lower part of the mudstone between the point bar.In this paper,a new set of well-seismic combined analysis method for the internal structure characteristics of meandering river reservoir is proposed,which has a good guiding significance for the study of the architectural structure of meandering river reservoir and the distribution of remaining oil in the ultra-high water cut stage of the oilfield. |
