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AAPG Asia Pacific Technical Symposium

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Seismic AVO Previous HitAnisotropyNext Hit VTI Modeling and Mechanical Properties of Kerogen in Gas Shale

Abstract

Geology and Geophysics risk uncertainty of shale gas reservoir development could be reduced by understanding the Kerogen fraction, mechanical properties of mineralogy in shale, and seismic amplitude response. Mechanical properties of rocks mineralogy and fraction of kerogen in shale are among the key factors for developing shale gas which may or may not be present as sweet spot on seismic data. The goal of this study is generating mechanical model for predicting seismic sweet spot and selecting mechanical criteria for target fracturing zones of shale gas reservoir. Mechanical properties of shale on surface depend on mineralogy, porosity and fraction of kerogen. Rock strength (UCS) will decrease gradually by increasing fraction of kerogen, quartz + carbonate and porosity. Rock strength will be used for estimate fracturing pressure at certain depth. Modulus Young properties of shale will increase by increasing fraction of quartz and carbonate, while Poisson ratio will decrease by increasing kerogen. The result of this mechanical modeling study is proposing a method to select fracturing zones targeting. Selecting criteria for shale fraccability are low rock strength, low poisson ratio and higher modulus Young. Seismic amplitude response of layering shale can be quantified through physical process using seismic P and S wave velocity measurement. Seismic amplitude response of kerogen fractions in shale can be generated through modeling based on AVO VTI Previous HitanisotropyTop method by using Thomsen parameter. The result of amplitude modeling using Bakken shale data shows that the response of fraction kerogen in gas shale has negative amplitude reflection and decreasing with offset. Based on this result, it is recommended to use the intercept and gradient method for predicting kerogen sweet spot by using common mid point seismic gather data.