A review of rock physical models for elastic properties characterization of gas hydrate bearing sediments

Gas hydrate is mainly explored through seismic methods, which, however, are bedeviled by the problem of uncertainty due to lack of constraints. Rock physics model links the physical parameters with elastic properties and can serve as constraint for seismic methods. A number of models were proposed to simulate the elastic properties of gas hydrate bearing sediments, addressing different mechanisms and applications. However, they are generally miscellaneous, making it difficult to choose the proper model in a specific scenario. Besides, since the simulation usually involves multiple sub-models and steps, determining the uncertainty sources is troublesome. We summarize the previous models and classify them into five categories according to different principles, which include hydrate morphology, frame structure, research purpose, hydrate generation stage, and lithology. We also analyze the advantages and disadvantages of different models and explain the application scenarios. Moreover, we also generalize the modeling workflow, enumerate the feasible models in each step, and indicate the possible uncertainty sources. In the end, we summarize the problems in the current modeling and suggest multiple research directions. This work provides a clear perspective of the models, related uncertainties, and simulation workflow of gas hydrate bearing sediments; it also offers some implications for future research, which may be helpful for seismic characterization of hydrate reservoirs.