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Wireline log data for well 01 showing markers (gray colour) and suite of logs (red colour)

Wireline log data for well 01 showing markers (gray colour) and suite of logs (red colour)

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Amplitude variation with offset (AVO) analysis was carried out on Konga oil field, an onshore oil field in the Niger Delta, Southeastern Nigeria. The study consisted of forward modeling from rock parameters measured from well logs and AVO analysis of events on pre-stack time migrated 3D seismic gathers. Forward modeling predicted specific AVO behav...

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... In recent days, AVO analysis has been widely applied in hydrocarbon exploration studies [18][19][20][21][22] . In the Niger Delta, AVO techniques have been used to determine anomalous and gas zones in wells [23][24][25][26][27] , detect hydrocarbon reservoirs on pre-stack time seismic data [28] , and identify hydrocarbon-charged reservoirs using Rock physics modeling and Lamda-Mu-Rho (LMR) seismic inversion [28] . The focus of the research has primarily been on conducting AVO Inversion analysis on pre-stack seismic data and well information to reveal geologic structures and impedance contrasts within lithology. ...
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... Pre-stack inversion delivers a breakthrough in the analysis and interpretation of seismic amplitude data by extracting both compression and shear wave properties information (Goodway et al. 1997;Ohaegbuchu and Igboekwe 2016). Various studies prove that given the same geologically accurate information, pre-stack simultaneous inversion constraints with rock physics analysis provide more value to the interpreter to estimate reservoir petrophysical properties and lithofacies (Durrani et al. 2020b;Yi et al. 2018;Jiang and Spikes 2016;Shuangquan et al. 2009;Ma 2002). ...
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... The log data were subjected to some quality checks after loading to improve upon their quality to obtain desirable results. Some of the quality Castagna's empirical relationship [9], that relate P-wave and S-wave velocity for unconsolidated and moderately consolidated sand was applied first to estimate the correct shearwave velocity for the layers across the well at 100% Sw; i.e. for shales and brine filled sands [19], of the entire depth of the well. The equation is given in equation (1) (2) and ( 3)} required to estimate P-wave for the brine filled scenario [21]. ...
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Shear wave logs are one of the key data required for most Amplitude Versus Offset (AVO) studies and quantitative seismic interpretation. Despite its overwhelming importance, it is hardly available in most wells due to its very high cost of acquisition. In the absence of shear wave logs in the field, the Castagna’s empirical relationship that relates P-wave and S-wave velocities and Biot-Gassman’s Fluid substitution equations were adopted for its estimation. The results obtained revealed that Castagna’s empirical relationship underestimated the Shear wave log in the field, even after Biot-Gassman’s Fluid substitution model was applied to define P-wave of the brine filled scenario. A cross plot of Mu-Rho versus Lambda-Rho presented low values for Mu-Rho due to the underestimated shear wave used. To correct for the underestimation, a modified form of the Castagna’s Equation constants were establish. This was achieved by generating several linear regression equations that defines the relationship between P and S-wave for brine sands in the field. The cross plot of Mu-Rho versus Lambda-Rho done with the modified shear wave gave very good results as expected for both fluid and lithology discrimination. KeyWords; Shear Wave, Castagna’s Equation, Biot-Gassman’s Equation, Rock Physics, Cross plots