Modeling deepwater oil/gas blowouts with hydrate formation and decomposition.

摘要

When gas is spilled in deepwater, the high pressure and low temperature can convert the gases into hydrates. The hydrates formed from natural gases are buoyant. As these hydrates travel upwards they will encounter regions of lower pressure. The hydrates can decompose into free gas under these conditions. The presence or absence of hydrates has a significant impact on the behavior of the jet/plume due to the alteration of the buoyancy. The free gas may dissolve in water.; This thesis describes a computer model developed to simulate the behavior of oil and gas released from deepwater locations in the ocean. The model integrates the hydrodynamics of the jet/plume, thermodynamics of the jet/plume, thermodynamics and kinetics of hydrate formation and decomposition, dissolution of gases. The possibility of gas separation from the main plume is modeled.; An integrated formulation to calculate the buoyant velocity of bubbles/droplets of various sizes and shapes developed by Zheng and Yapa (2000) is used. This formulation can be applied to solids, liquid, or gases. An improved method from Zheng and Yapa (2002) is used to compute dissolution from gas bubbles in ultra-deep water plumes, where the non-ideal nature of gasses under high pressures is taken into account. Both methods (Zheng and Yapa, 2000, 2002) account for non-spherical shapes of gas bubbles, and the computed results show a good match compared with previously conducted lab experiments.; The comprehensive model is used to simulate the Deepspill experiments. The simulations compare well with Echo sounder data from the Deepspill experiments for both vertical profiles and the Bird's eye view. A series of parametric analysis is made to show the effect on the behavior of the jet/plume due to variations in key input parameters. Scenario simulations are presented to show the behavior of oil/gas under different deepwater conditions.