Potential evaluation of methane hydrate as a future energy resource by seismic method.

Methane hydrate is considered to be one of the expecting non-conventional natural gas resources in the next century because the abundant amount of methane hydrate has been found.It is necessary，therefore，to survey the distribution of methane hydrate by seismic survey.BSR(Bottom Simulating Reflector)phenomenon is one of the guidelines of the hydrate distribution。But quantitatively it is not clear the behavior of seismic waves in and around the methane hydrate。So it is important to establish the method of evaluating the resource amount from the various characteristics of seismic data.This study aims to roughly clarify the amplitude and velocity of relation between hydrate amount and wave velocities in hydrate layers.We measured elastic wave amount the 3-Phase pseudo hydrate model，which simulates the 3-phase model in hydrate layers.It is ideal if we can use the actual samples of methane hydrate to analyze the characteristics of wave propagation，but it is very difficult to actu…More ally synthesize the methane hydrate in sample。Thus we assume that the condition of methane hydrate is similar to that of frozen or partly frozen water-saturated samples。Consolidated and non-consolidated samples are used to analyze the wave propagation characteristics.In the experiments，the wave velocity of samples under various conditions are intensively measured becourse the velocity variation can be considered as on of the most important indices for exploration like BSR in the seismic records.To consider the physical characteristics of these samples，we introduced the numerical models of Laclaire et al.(1994)，known as Extension Biot‘s theory，as well as experimentally provided’sonic transit time-to-porosity tramsform‘。As the results the fo11 owin concluding remarks are obtained.·Usefullness of two or three phase models are demonstrated.·Wyllie or Raymer‘s formula can be applied to consolidated samples，but not applied to unconsolidated samples。·Extension Biot‘s theory will be useful to evaluate the total amount of methane hydrate，but not a few parameters are required to apply this theory to the unconsolidated samples。Less：Less

Methane hydrate is considered to be one of the expecting non-conventional natural gas resources in the next century because the abundant amount of methane hydrate has been found. It is necessary, therefore, to survey the distribution of methane hydrate by seismic survey. BSR (Bottom Simulating Reflector) phenomenon is one of the guidelines of the hydrate distribution. But quantitatively it is not clear the behavior of seismic waves in and around the methane hydrate. So it is important to establish the method of evaluating the resource amount from the various characteristics of seismic data.This study aims to roughly clarify the amplitude and velocity of relation between hydrate amount and wave velocities in hydrate layers. We measured elastic wave amount the 3-Phase pseudo hydrate model, which simulates the 3-phase model in hydrate layers. It is ideal if we can use the actual samples of methane hydrate to analyze the characteristics of wave propagation, but it is very difficult to actu … More ally synthesize the methane hydrate in sample. Thus we assume that the condition of methane hydrate is similar to that of frozen or partly frozen water-saturated samples. Consolidated and non-consolidated samples are used to analyze the wave propagation characteristics. In the experiments, the wave velocity of samples under various conditions are intensively measured becourse the velocity variation can be considered as on of the most important indices for exploration like BSR in the seismic records. To consider the physical characteristics of these samples, we introduced the numerical models of Laclaire et al. (1994), known as Extension Biot's theory, as well as experimentally provided 'sonic transit time-to-porosity tramsform'. As the results the fo11owin concluding remarks are obtained.・ Usefullness of two or three phase models are demonstrated.・ Wyllie or Raymer's formula can be applied to consolidated samples, but not applied to unconsolidated samples.・ Extension Biot's theory will be useful to evaluate the total amount of methane hydrate, but not a few parameters are required to apply this theory to the unconsolidated samples. Less