Identification of gas hydrate based on velocity cross plot analysis

Abstract

Gas hydrate is regarded as a kind of important energy resource in the recent decades. The identification of gas hydrate is a hot issue for researchers all over the world in order to exploration and exploitation. Previous research shows some methods to identify gas hydrate, but these methods also have shortcomings in different actual conditions. It is still a difficult problem to distinguish gas hydrate accurately from marine sediments. Here we propose a cross plot analysis of velocity to identify gas hydrate. Firstly, we simulate different minerals bearing sediments by rock physics models to obtain different physical properties. After a series of experiments, the results show that there are obvious differences between gas hydrate bearing sediments and other minerals bearing sediments in P-wave and S-wave velocity. Therefore, the cross plot of velocity can be used to distinguish gas hydrate qualitatively. Finally, we verify the cross plot method using the data in the Ocean Drilling Program (ODP) Leg 204 expedition of the Hydrate Ridge along the Oregon continental margin, where gas hydrate is confirmed via logging. The hydrate identification results of actual velocity data by cross plot analysis are generally in keeping with the results of core samples. Moreover, using the cross plot method also can estimate gas hydrate saturation range, which is in accordance with the measurement of chloride (Cl−) concentration in most cases.