Application Study Of Rock Physical Analysis In Thin Interbed Reservoir Prediction In The LD Area

While the seismic exploration targets have changed from structural hydrocarbon reservoir in the past into structural lithologic or lithologic reservoir,the seismic interpretation is changing from qualitative analysis into quantitative interpretation.And seismic prestack inversion based on petrophysical modeling and analysis plays an important role in the process of quantitative interpretation.The petrophysical analysis is the communication link reservoir with the seismic information.The research area is located on lithologic reservoir,which is highly heterogeneous,and its sandstone bodies are spread in a small area with a rapid horizontal variation,and overlapped vertically.According to these characteristics of thin interbed reservoir in this area,rock physical analysis has been done in the paper,combining the geological condition,seismic data,and log information with the characteristics of reservoir.The main work includes:(1)By the given log information,empirical formula,theoretical calculation based on rock physics modeling,and comprehensive calculation which combine empirical formula with theoretical calculation have been applied to estimate shear velocity,so as to overcome the difficulties of lacking shear velocity information.(2)According to a quantitative method of calculation,we selected the elastic parameters and AVO attributes parameters of the target block,which are sensitive in lithologic distinguish and pore fluid identification,so that we can analyze the feature of different rock physical parameters,establish the relationship between petrophysical with the characteristic of the thin interbed reservoir,and apply it to predict the reservoir.(3)The research of forward modeling of sand and shale thin interbed layers has been done.By changing the parameters of sandstone reservoirs,including the thickness of reservoir,the thickness of shale interlayer,the combination of internal structure,and the total thickness of internal structure;and the frequency and phase of the wavelet,we analyze seismic reflection characteristic and the affecting factors of seismic resolution in thin interbed to predict the reservoir by seismic attributes.Based on rock physical modeling research,we set up the geologic model of different rock physical parameters,study on fluid replacement and the influence of porosity,water saturation and shale content on P-wave velocity,S-wave velocity and density.Single well AVO modeling and analysis of reservoir have been done in E2d25 layer of Y38,to analyze seismic reflection characteristic and AVO attributes parameters,to analyze the differences and changes between effective and non-reservoir,and to determine the sensitive AVO attributes to lithology and physical property.The research can reduce the diverse solution of seismic inverse,improve the reliability of reservoir prediction and interpretation,and as well as guide us to interpret seismic prestack inversion result in the research area.