Seismic Forward Modeling And Characteristic Response Analysis Of Fluvial Reservoirs

As the degree of oil and gas exploration continues to deepen,the difficulty is also increasing.Recently,structural oil and gas reservoirs have become increasingly scarce,the exploration and development of lithologic reservoirs has been paid more and more attention.Fluvial sand bodies are the main reservoir types in continental basins in China.Rivers,sandbanks and floodplains in river basin will change dramatically in a short historical period.Frequent breaks and diversions of rivers in the basin will constantly transform the sedimentary patterns of rivers,resulting in rivers beco ming a perplexing lithologic complex in the process of sedimentation,which makes it extremely difficult to identify and trace a channel or bar.The paper aims at the problem that the sand body of the fluvial facies reservoir is generally thin,the vertical sedimentary model is complex and variable,and the boundary of the river channel is difficult to identify.Two forward modeling methods,seismic physical modeling and numerical modeling are used to multi-stage sub-channel sand bodies.Seismic reflection characteristics and attribute recognition of multi-stage channel sand bodies are studied in detail.This paper takes Sulige area as the research target area.Firstly,based on the detailed analysis of its geological and seismic characteristics parameters of the study area,we established a representative physical model of the fluvial facies reservoir.The physical model considers the lateral swing and longitudinal superposition of different streamway,and then uses the fine form processing to ensure the preparation of fluid-bearing sediments.The three-dimensional laser scanning morphology system is used to precisely control the spatial shape of the river.Through the precise process control,we manufactured a three-dimensional physical model with five braided river sediments.Through data acquisition,processing and analysis,a set of multi-stage three-dimensional seismic physical simulation data of braided river is obtained,which provides visible analysis data for the follow-up study of fluvial reservoirs.In the process of 3D velocity volume modeling,based on the physical model morphology laser point cloud data,a two-step modeling step was proposed.The sedimentary facies control and trend surface constraint method was used to establish the fluvial facies physical model.3D using the model shape test data.A new idea of using the model shape test data to build a reservoir model is proposed.Comparing the results of seismic physics and 3D numerical modeling,analyzed the waveform profile and slice profile features of different channels,summarized the characteristics of waveforms in different river configurations.The waveform characteristics vary with sand body thickness and sand-mud ratio.When the fluid sandstone is present,there will also be amplitude changes in the profiles.The results of the two modeling methods show that the numerical simulation results are significantly better than the physical simulation without noise.The two sets of data have similarities in waveform characteristics,but the difference is very large.In field data,this problem should be more prominent,it is necessary to do noise attenuation and high resolution processing.Different slicing methods show that the slice interpretation technique based on volume interpretation is more accurate and meticulous for the depiction of river.Time window selection is not very important in the composite wave field for the seismic attribute identification channels.Through the comparison of different attributes,the amplitude attribute is better for internal characterization,and the related attribute will be more detailed for the boundary of river.