Numerical simulation of elastic properties of hydrate-bearing sediments with digital rock technology

Abstract

The elastic properties are crucial rock physics properties in the exploration and reserve evaluation of hydrate reservoirs. However, accurately describing the evolution of these properties is a complex task due to the influence of numerous factors, such as particle properties, matrix components, sediments framework, and the distribution of natural gas hydrates within the pores. Existing empirical models often exhibit limitations in adequately capturing the effect of these factors, hindering a comprehensive understanding of the elastic behavior of hydrate-bearing sediments. In this study, the digital rock method was applied to analyze the impact of four factors, which include porosity, particle size, clay components, and the hydrate distribution morphology, on the elastic properties of sediments. The applicability of three theoretical models, namely the time-averaging equation, cementation theory, and three-phase Biot equation, in characterizing the effects of these factors was evaluated. Finally, the numerical simulation results were used to offer a comprehensive characterization of the range of variation in sediment elastic properties under each category of influencing factors. The results indicate that the applicability of the uncemented-sand model is dependent on the initial porosity of the sample, while the cemented-sand model is not a reliable predictor of the shear modulus. On the other hand, the simplified three-phase Biot equation exhibits good coverage of the simulated data at hydrate saturations exceeding 30%. Moreover, the distribution of hydrates can be effectively determined by adjusting the model parameters. The findings from this study contribute to a better understanding of the impact of these factors on sediment elastic properties and have important implications for the exploration and assessment of hydrate reservoirs.