Influence of Silt and Organic Matter Contents on Elastic Properties of Shaly Formations
M. Pervukhina, P. Rasolofosaon and V. Mikhaltsevitch
Event name: 80th EAGE Conference and Exhibition 2018
Session: Rock Physics III - Shales and Source Rocks
Publication date: 11 June 2018
Info: Extended abstract, PDF ( 684.51Kb )
Price: € 20
A simple rock physics model is proposed for describing the elastic property of silty organic-rich shale. A classical result is that the presence of organic component tends to soften the rock and to increase the anisotropy strength. The presence of silt component contributes to stiffen the rock and to reduce the anisotropy strength. The combined effect of the presence of silt and organic components tends to reduce the possible values of anisotropy coefficients ε and γ. Furthermore, given an estimation of the silt and organic content we generalize recent Rock Physics templates for straightforwardly quantifying the Orientation Distribution Function of the clay crystallite alignment in shale from the measurement of seismic anisotropy parameters. Lastly, by statistically analyzing the most comprehensive state-of-the-art collection data on shales (typically more than 800 samples) we discriminate the elastic properties of organic-lean shale and organic-rich shale. A new result is the rough correlation between anisotropy parameters ε and γ and the ratio Vp/Vs observed only in organic-rich shale. More detailed analysis of the link between “geometry” (slash distribution) of organic matter and Vp/Vs and the anisotropy parameters can be further used to estimate a reservoir thermal maturity from Poisson’s ratio and P- and S-wave anisotropy.