Rock physics model for velocity–pressure relations and its application to shale pore pressure estimation

查看全文 作　　者：GUO [1]Jingyi;LI [1,2]Min;ZHUANG [3]Mingwei;SUN [1]Yuefeng

机构地区：[1]Department of Geology&Geophysics,Texas A&M University,College Station,77843,United States;[2]Southwest Geophysical Research Institute,BGP,CNPC,Chengdu 610213,China;[3]Institute of Electromagnetics and Acoustics,Xiamen University,Xiamen 361005,China

出　　处：《Petroleum Exploration and Development》索引2023年第50卷第2期,共15页

基　　金：Supported by the TAMU (M1803964)。 摘　　要：Acoustic wave velocity has been commonly utilized to predict subsurface geopressure using empirical relations.Acoustic wave velocity is, however, affected by many factors. To estimate pore pressure accurately, we here propose to use elastic rock physics models to understand and analyze quantitatively the various contributions from these different factors affecting wave velocity. We report a closed-form relationship between the frame flexibility factor(γ) in a rock physics model and differential pressure, which presents the major control of pressure on elastic properties such as bulk modulus and compressional wave velocity. For a gas-bearing shale with abundant micro-cracks and fractures, its bulk modulus is much lower at abnormally high pore pressure(high γ values) where thin cracks and flat pores are open than that at normal hydrostatic pressure(low γ values) where pores are more rounded on average. The developed relations between bulk modulus and differential pressure have been successfully applied to the Upper Ordovician Wufeng and Lower Silurian Longmaxi formations in the Dingshan area of the Sichuan Basin to map the three-dimensional spatial distribution of pore pressure in the shale, integrating core, log and seismic data. The estimated results agree well with field measurements. Pressure coefficient is positively correlated to gas content. The relations and methods reported here could be useful for hydrocarbon exploration, production, and drilling safety in both unconventional and conventional fields. 关键词：pore pressure pressure coefficient acoustic velocity bulk modulus pore structure shale gas Upper Ordovician Wufeng Formation Lower Silurian Longmaxi Formation Sichuan Basin

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Rock physics model for velocity–pressure relations and its application to shale pore pressure estimation

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