Fine Sedimentary Pattern,geological Knowledge Database And Sand Body Prediction In Dense Well Area

After more than 50 years of development and production,the distribution of underground remaining oil in the oilfields of Songliao Basin in eastern China is more complex.Due to serious water flooding,imbalance of injection-production relationship,serious decline of oil and gas production,it is more difficult to find alternative production,and the distribution characteristics of sand body and remaining oil are not clear.The average well spacing in the study area is less than 60 m,which belongs to the extremely dense well pattern type.The unique well pattern conditions provide a solid foundation for the fine study of the distribution of underground microfacies sand body and the extraction of relevant geological knowledge.This study takes the fluvial-delta reservoir developed in the typical dense well pattern area of Yaojia formation in Songliao Basin as the research object.Firstly,based on the traditional "facies controlled cycle correlation",combined with high-resolution sequence correlation technology,the high-precision isochronal stratigraphic framework of the study area was constructed.The fine correlation and division of 58 layers in the whole area are completed in the framework,and the vertical sedimentary evolution law and sedimentary system evolution pattern of Sapu oil layer were discussed.Secondly,the braided river,meandering river,shallow water delta plain and front sediments in the study area are taken as the research objects to finely depict the spatial distribution pattern of underground sand body under the condition of high-density well pattern.On this basis,combined with the data of the field outcrop and the modern sedimentation,the combination forms of different types of sand body were discussed,and the fluvial-delta sedimentary pattern with high resolution have also been discussed.Based on the dense well pattern data of the study area,combined with the comparable field outcrops and modern sedimentary data,and guided by the theory of quantitative geology,the geological information with guiding significance for reservoir stochastic simulation in this area has been extracted,and the relevant geological knowledge database were established,so as to enrich and improve the quantitative geological knowledge of fluvial-delta sedimentary system.Based on the above geological knowledge,the fine three-dimensional sedimentary microfacies and sand-mudstone distribution model in the study area were established by using the PETREL software.A modeling method based on surface and architecture elements has been explored.This method adopts multi-level surface constraints and non-uniform grid upscaling technology,which can characterize the three-dimensional structure of architectural level interlayer with less grids,and was successfully applied to point bar,middle channel bar,distributary channel,beach bar,estuary bar and other types of the reservoir.Based on the principle of stochastic modeling method,this paper analyzes the advantages and disadvantages of different modeling methods(based on object,two-point statistics,multi-point statistics,etc.)in different types of reservoir prediction research;combined with sedimentary pattern,river type,quantitative geological knowledge,different modeling methods are used to carry out sand body prediction research for different sedimentary types of thinning well pattern,and sand body prediction is carried out.The results show that the multi-point geostatistics method has the best prediction effect.Finally,on the basis of determining the best prediction method for different river types,the effective prediction well spacing range under the control of dense well pattern is studied,and the limit prediction well spacing is determined by comparing the control degree of well pattern under different well spacing.The results show that with the continuous thinning of well pattern,the control degree of channel sand body will gradually weaken.There is a positive correlation between the channel control index and the proportion of channel sand body area.The well pattern density of braided river,meandering river,delta plain,delta inner front and delta outer front will decrease in turn.