Prediction And Three-dimensional Characterization Of Well-seismic Integration Parameters Of Shale Gas Reservoirs In M Production Area

M production area is located in Weiyuan shale gas demonstration area of Sichuan Basin.At present,the basic geological knowledge is relatively weak,the prediction method of shale gas reservoir parameters needs to be improved,and a reliable three-dimensional geological model has not yet been established.Therefore,on the basis of understanding the shale tectonic sedimentary background of Wufeng formation-Longmaxi formation in M production area,combined with geological,seismic,logging and other data,the structural details of this area have been implemented,and the fine division of the structure and tectonics of shale gas layer is carried out,and the prediction method of attribute parameters of shale gas layer based on well-seismic combination is put forward according to the target layer,and the analysis and modeling of sedimentary facies and lithofacies are further carried out,then the heterogeneity of the attribute parameters under phase control in three-dimensional space is characterized,in this paper.The main achievements and new cognitions are as follows:1)The fine division of shale gas layer structure and tectonics has been carried out.The target layer is deep-water shelf facies deposition with stable formation distribution.According to seismic interpretation and logging curve data,the data set of boundary mark high points of 14 long horizontal wells has been obtained by using visualization contrast method of horizontal well layer structure.The detailed division and three-dimensional modeling of six small-layer structures are completed.The structure model shows the characteristics of obvious longitudinal variation and good plane inheritance,which lays a foundation for the prediction and representation of attribute parameters.2)The prediction method of shale gas reservoir attribute parameters based on well-seismic combination is proposed.Based on the reliable interpretation data of core calibration and field authentication of the evaluation well,the interpretation method of organic carbon content based on natural gamma energy spectrum,and the porosity prediction method based on compensated neutron,and the mineral content prediction method based on the whole component volume model are proposed;According to the seismic multi-attribute analysis method,constrained by the single-well parameters of log interpretation,a neural network model for predicting organic carbon content with relative acoustic impedance and RMS amplitude,a neural network model for predicting porosity with instantaneous bandwidth and RMS amplitude,a neural network model for predicting mud content by RMS amplitude,instantaneous amplitude and second derivative,and a neural network model for predicting silicon content by instantaneous amplitude and second derivative,domination frequency and instantaneous frequency,and a quadratic regression model for predicting calcium content with instantaneous amplitude and phase cosine is established,and the reliability of the model is verified by near well prediction.3)The shale sedimentary facies,lithofacies analysis and 3D modeling are completed.According to outcrop survey,core description and sediment characteristics of each layer,there are three sedimentary microfacies in the study area:siliceous shelf,sandy shelf and mixed shelf.which have the characteristics of stratified distribution.Based on the predicted organic carbon content and mineral content,the lithofacies of 15 wells in the study area have been divided,and 22 kinds of lithofacies have been identified,in which the dominant lithofacies are carbon-rich calcium-bearing muddy siliceous shale and carbon-rich mixed shale.The statistical characteristics show that the sedimentary relative lithofacies has the ability of stratification constraint.The stratabound lithofacies probability modeling strategy is adopted and the truncated Gaussian simulation is used to establish the three-dimensional lithofacies model.It lays a foundation for modeling the parameters of phased-controlled attributes.4)The heterogeneity of attribute parameters in three-dimensional space is characterized.Taking the attribute model of seismic prediction as the plane trend and the single point parameter value of logging prediction as the main constraint,the three-dimensional model of attribute parameters in this area is established by sequential Gaussian simulation method with lithofacies constraint and stratification constraints of sedimentary facies,and its heterogeneity was characterized.According to the characteristics of spatial distribution,the organic carbon content in this area increases downward as a whole,the porosity changes little,mostly between 5%and 7%,and the mineral content is more siliceous,calcareous and less muddy.The above achievements and understandings provide the basic and important geological results for the division of shale gas enrichment areas in M production area and similar reservoir,the development design of horizontal well groups and reservoir reconstruction.