Zijian Zhang

Quantitative interpretation for gas hydrate accumulation in the eastern Green Canyon Area, Gulf of Mexico using seismic inversion and rock physics transform

Gas hydrate can be interpreted from seismic data through observation of bottom simulating reflector (BSR). It is a challenge to interpret gas hydrate without BSR. Three-dimensional qualitative and quantitative seismic interpretations were used to characterize gas hydrate distribution and concentration in the eastern Green Canyon area of the Gulf of Mexico, where BSR is absent. The combination of qualitative and quantitative interpretation reduces ambiguities in the estimation and identification of gas hydrate. Sandy deposition and faults are qualitatively interpreted from amplitude data. The 3D acoustic impedance volume was interpreted in terms of high P-impedance hydrate zones and low P-impedance free gas zones. Gas hydrate saturation derived from P-impedance is estimated by a rock physics transform. We interpreted gas hydrate in the sand-prone sediments with a maximum saturation of approximately 50% of the pore space. Sheet-like and some bright spot gas hydrate accumulations are interpreted. The interpr...

Seismic interpretation of gas hydrate based on physical properties of sediments

This paper analyzes amplitude behavior of gas hydrate from stacked seismic data, based on rock physics properties of hydrate-saturated sediments, gas saturated sediments, and water saturated sediments. Gas hydrate is likely to occur in suitable gas hydrate occurrence environment. Velocity of hydrate saturated sediments increases as gas hydrate replaces water in pore space of the sediment. In contrast, velocity of gas filling sediment decreases. The different patterns that consist of low concentrated gas hydrate, high concentrated gas hydrate, water and/or gas produce Dim out and Bright spots. The two gas hydrate indicators are illustrated in a 3D seismic data from the Green Canyon area of the Gulf of Mexico.

A Rock Physics Model For Hydrates Bearing Sediments of Near Surface

Gas hydrates presented as form of segregated bodies have been observed on shallow subsurface sediments. However, most gas hydrate physics models describe that hydrates occur in pore space in deep subsurface sediment. A new model considers gas hydrate as segregated bodies to derive elastic properties of hydrates bearing sediments and gas hydrate saturation. The predicted elastic properties based on the model are coincided with measurements of well logs in site 1327 of Integrated Ocean Drilling Program (IODP). The results show the model can be used to estimate gas hydrate saturation from seismic data of near surface.