Investigation Of Relationship Among Rock Physics Parameters And Seismic Wave Attenuation Coefficient Of Unconsolidated Sandstone Sediments

In this paper, we modeled the absorption and attenuation factor of unconsolidated sediments as a function of porosity, permeability and methane hydrate saturation. We studied t, the relationship between interval velocity and porosity, along with depth. We also set up a relation among permeability, porosity, saturation and grain size. Using wave velocity, we tried to invert the porosity and water- statured sentiments, then, obtain the permeability of hydrate formation through absorption and attenuation factor. This whole process is aimed to establish the new method for hydrate recognition. The law of stratigraphic absorption and attenuation are not understood clearly so far , however , researcher always cite three theories, including Biot bi-phase medium theory, jet flow mechanism (jets mechanism) and BISQ theory. Generally, the porosity is higher than 30% in and grain particles do not cement each other in unconsolidated sentiments. Besides, the frequency of seismic waves is much lower than that of sound waves and ultrasonic wave (less than 200Hz). According to the initial conditions of South China Sea, we analyzed the impact of petrophysical properties on absorption and attenuation factor through all of the three theories, draw the relation curves and found the rules among them. In the numerical simulation of the absorption and attenuation the curve of the porosity as a function of depth derives from reported volume modulus model. Porosity is an important parameter in petrophysics and seismic exploration field. Based on it, we can compute the elastic modulus, p-wave velocity and s-wave velocity, which is helpful for hydrate recognition and reserve estimates. Nevertheless, it is difficult to acquire the porosity in marine without drill log. According to some model, porosity shows an exceptional decline with depth in various sentiments. Then, two problems follow with the model. The one is if this decline is exceptional ,the other is how to chose the parameter in the model.In this paper, we studied the trend of porosity from a different perspective. we found the behavior of porosity in each layer through the compressibility of sea floor one and another and the results show that simulation data close to data from well log or seismic inversion .