Elastic Inversion Using Partial Stack Seismic Data: Case Histories in China

Outline Introduction Work Flow Case Histories Conclusions Introduction

Background of Elastic Parameter Inversion

Comparison of elastic impedance and acoustic impedance on recognizing of reservoir lithology (According to Connolly.Patrick,1999)

Background of Elastic Parameter Inversion Result of Acoustic Impedance Inversion Result of Elastic Impedance Inversion (According to Connolly. Patrick,1999) Oil-bearing reservoir Unidentified Oil-bearing reservoir identified clearly

Outline Introduction Work Flow Case Histories Conclusions

Seismic data processing Petrophysical modeling Elastic impedance generation Wavelet estimation and horizon calibration AVA Constrained Sparse Spike Inversion Work Flow of Elastic Parameter Inversion

Seismic Data Processing Flow INPUT COMMON-SHOT GATHERS Amplitude Recovery Filtering Spiking Deconvolution Bandpass Filter CMP Sorting Residual Statics Velocity Analysis Kirchhoff Pre-stack Time Migration Common-angle Gather Extraction Limited-angle Stacking OUTPUT MIGRATED COMMON-ANGLE DATA 3-D Random Noise Attenuation

0-10 deg10-20 deg Full stack20-30 deg Seismic Data Volume of Partial Angle Gather Stack

Shale volumeTotal porosityTemperature, pressure, fluid type & density Vp&Vs modeling of brine-bearing reservoirs Vp&Vs modeling of oil & gas-bearing reservoirs Cross-plot analysis of elastic parameters of lithologies & fluids Petrophysical model ： Xu&White (DEM) & SCA Petrophysical Modeling Calculation of elastic parameters Guide to identifying reservoirs & fluids

Petrophysical Modeling A plot of petrophysical modeling of borehole logging data VshDensityM-PVpSwM-PVs Shear modulus LambdaPoisson’s ratio Vp/VsS-impP-imp Total porosity

Cross-plot Analysis of Elastic Parameters sh Sw Sand Shale Oil sand Brine sand Oil sand S-impedance P-impedance Lambda Vp / Vs P-impedance Vp / Vs S-impedanceP-impedanceVp / VsSwTotal-ProVsh

Wavelet & synthetic seismogram (0-10deg angle gathers stack) Wavelet Estimation and Horizon Calibration Various wavelets are extracted from near, middle and far offset angle gather stack seismic data using elastic impedance curves corresponding with angle series of seismic data. Wavelet & synthetic seismogram (10-20deg angle gathers stack) Wavelet & synthetic seismogram (20-30deg angle gathers stack)

Wavelet analysis of different angle gathers 0-10deg 10-20deg 20-30deg Wavelet Estimation and Horizon Calibration Interpolated wavelet & interpolation weights Wavelet amplitude spectrum, phase spectrum, and time-frequency analysis

Outline Introduction Work Flow Case Histories Conclusions Case Histories

0-10 deg deg deg Case 1. Changqing Oilfield Coal bed

S-impedance P-impedance Case 1. Changqing Oilfield Gas sandstone Sandstone existence

Case 1. Changqing Oilfield Lambda Gas sandstone Well BWell A Gas sandstone Vp/Vs

0-12deg 12-24deg fullstack 24-36deg Case 2. Zhunger Oilfield

P-impedance of post-stack acoustic inversion Case 2. Zhunger Oilfield P-impedance of pre-stack elastic inversion

Poisson’s ratio Case 2. Zhunger Oilfield S-impedance

Vp/Vs S-impedance Case 2. Zhunger Oilfield

Red and yellow colors show the favorable distribution of oil-bearing reservoirs Favorable area : 40 Km 2 Dry well Oil well Proposed well

Outline Introduction Work Flow Case Histories Conclusions

Elastic inversion is more powerful than conventional post-stack acoustic inversion, which provides more petro-physical parameters used in identifying lithology and fluid distribution in a reservoir. Our elastic inversion result fits very well with drilling results. Elastic inversion obviously is a major direction in reservoir characterization. Conclusions

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