Effect of Fluid Saturation on Dynamic Shear Modulus of Tight Sandstones
D.Q. Li, J.X. Wei, B.R. Di, P.B. Ding, S.Y. Qin and M. Wang
Event name: 79th EAGE Conference and Exhibition 2017
Session: Rock Physics A - Fluid Saturation and Pore Geometry
Publication date: 12 June 2017
Info: Extended abstract, PDF ( 1.77Mb )
Price: € 20
Tight sandstone oil and gas have become important unconventional resources. The influence of fluid on the elastic parameters of rock has become a key issue in seismic exploration. However, there is a lack of research on the influence of fluid on the elastic parameters of tight sandstone, especially the effect of fluid on shear modulus, which is directly related to the application of Gassmann’ theory in tight sandstone. In this paper, 24 samples of tight sandstone are selected to study the effect of fluid saturation on shear modulus. It is found that the shear modulus of most samples increases when the rock is saturated with water, the maximum increase rate reaches 20%, two samples show a decrease and only two samples show no change in the shear modulus, these results violates the constant shear modulus derivation from Gassmann’s theory. The theoretical analysis shows that the main mechanism behind the increase of shear modulus is the dispersion caused by squirt flow effect. The dispersion is not limited to high frequencies, therefore, our study on the changes of shear modulus under high frequency conditions is advantageous to the application of Gassmann’ theory at both high frequencies and low frequencies.