Himalayan Geology, Vol. 42 (2), 2021, pp. 256-262, Printed in India
An improved Rock Physics Modeling approach to estimate attenuation and dispersion for three phase medium to delineate methane hydrates reserves
MUHAMMAD IRFAN EHSAN1,2*, YONG HONG ZHAO1#, PERVEIZ KHALID2, TAHIR AZEEM3,
NAVEED AKRAM4, SOHAIL AKRAM2, SHAHID ALI2, ANDONG XU1, ZHANG QI1
1School of Earth and Space Science, Peking University, Beijing, 100871, China
2Institute of Geology, University of the Punjab, Lahore, 54590, Pakistan
3Department of Earth Sciences, Quaid-I-Azam University Islamabad, Pakistan
4School of Earth and Space Science University of Science and Technology, Anhui Heifei, China
Email: *irfan_opq@yahoo.com; #zhaoyh@pku.edu.cn
Abstract: Seismic attenuation and velocity dispersion are vital attributes to identify hydrocarbon reserves. Now a day's seismic attenuation attribute is intensively used to explore unconventional energy resources, especially gas hydrates. Recently Seismic attenuation response is discussed comprehensively with the reference of two-phase medium (Gas hydrates and water), its response for three phase medium (gas hydrates, water and free gas) is still not investigated properly to mark bottom simulating reflector when temperature and pressure conditions are variable due to tectonic activity. Seismic attenuation and velocity dispersion phenomena are elaborated by using wave-induced fluid flow technique for the partially saturated reservoir which contains gas hydrates, water and free gas. The numerical simulation procedure is adopted by taking into account the mesoscopic heterogeneities, interconnected spatially variations within fluid properties. The link between seismic and elastic properties is estimated by considering the increasing trend of free gas saturation in a three-phase medium. The results show that seismic velocities response for homogenous and patchy distribution formation pattern gives an impressive variation with the inclusion of free gas in multiphase medium (gas hydrates, water). Bulk modulus as a function of frequency is sorted out for a three-phase medium at different gas saturation. Velocity dispersion and attenuation phenomena are observed by considering high, medium and low saturation of gas hydrates with primary influence free gas saturation by taking saturation of water constant. It is depicted that velocity dispersion and attenuation are increased with the increase of free gas saturation in a three-phase medium.
Keywords: Gas Hydrates, Exploration geophysics, Rock Physics, Waves and wave analysis
