Research On AVO Inversion Based On Rock-physics Modeling And Structural Interpretation And Analysis Of Nova Scotia Basin

Amplitude versus offset,also known as AVO inversion,provides exploration geophysicist an additional tool to extract information from the stacked seismic data regarding the earth elastic parameters.Amplitude versus offset is not useful when used individually to interpret the seismic.It is necessary to use other seismic attributes as well.This research employs the AVO and its characteristics,such as intercept gradient,elastic impedance,and extended elastic impedance attributes.3D pre and post stack seismic reflection and wireline log data of well L-30 and B-41 of Penobscot area located in the vicinity of Sable Basin is used for this purpose.The reservoir rock in the study area is early Cretaceous Mississauga Formation,which mainly composed of sandstones with interbedded shales.To interpret the 3D seismic data of Penobscot Nova Scotia Canada,elastic impedance(EI)itself is an attribute of AVO is handy in the delineation of the subsurface.A review of existing EI formulas in its general form is described along with AVO evolution.The P and S-wave velocity and density,which are lithologically sensitive and help in the identification of sandstone and mudstone.It also helps in reservoir characterization and fluid identification.In this study,seismic structural interpretation is carried out to study the subsurface structural interpretation of 3D seismic data from Penobscot Nova Scotia.Mississauga formation is approximately 3500 meters in the Sable Sub-basin with 30 to 50% sandstone/siltstone present consists of thick sands deposits,which is used as the target zone.Moreover,the application of seismic attributes analysis and Elastic impedance seismic inversion is successfully applied to the study area to predict new prospects,thin sand beds detection,direct hydrocarbon indicators,and for better reservoir characterizations.Enhancement tools such as automated fault interpretation have made fault delineation more time efficient and effective.The primary purpose of current research is to understand the subsurface faults network of the Penobscot area within the Scotian Basin using similar advanced tools.Use of advanced interpretation tools provides improved results and confidence for fault analysis;therefore,it is essential for predicting structural traps for the hydrocarbons.Elastic impedance inversion constant K,which is S-wave to P-wave ratio of the nth layer and n+1 layer across the interface,it must be changed accordingly.The importance of the value of K for a particular Amplitude Variation with Offset AVO type(I-IV)is studied using different Elastic Impedance Equations.When K Calculated is used,AVO type I and Type II shows a good match at near,mid and far offsets.Type III does not change due to the changing value of K.Type IV gives good agreement at near and intermediate offsets.This variation in curves,with the change in the value of K,indicates that it is a significant factor of interpretation using elastic impedance.It is helpful to resolve severe errors in the interpretation due to the constant value of K.Maximum a Posteriori(MAP)estimate of Bayesian Statistic is used to recover the porosity,and water saturation Grid Maps of inverted porosities and Bayesian inversion showed that Fatti two-term and Connolly-EI match with those of Zoeppritz,but the use of Fatti three-term and Shear Elastic Impedance fails to recover porosities.The analysis reveals that performing fluid saturation modeling and using those logs in Elastic impedance inversion it delineates and separates the reservoir from non-reservoir rocks.Intercept versus Gradient,LMR,cross-plots analysis,help in the delineation of hydrocarbon anomaly showing the apparent deviation from background geology.Similarly,Poisson's reflectivity versus intercept works very well and discriminate the hydrocarbon and non-hydrocarbon fluids.The application of a change in the value of K and its effects in the inversion results have been studied and applied.The results show to prove that there is a visible change in choice of constant K.Intercept and gradient analysis have been performed.Our analysis shows that cross-plotsfrom pre-stack seismic and log data at pay sand five intervals in intercept,particularly in comparison with gradient followed the same trend.Hydrocarbon anomaly has a clear difference from the background geology in these cross-plots.Hydrocarbon fall into II quadrant in the intercept versus the gradient cross plot.Intercept / gradient analysis demonstrates the behavior of class IV as a hydrocarbon anomaly.