摘要：The dissociation of natural gas hydrate produces a large amount of methane gas and causes volume expansion to the pore, further leading to the sharp pore pressure increase of stratum around the w ell and possibly the damage of cement sheath or the collapse of large-dimension surface casing, causing significant risk to the drilling and exploitation. The sediment volume expansion model caused by hydrate dissociation is derived based on the universal gas law of thermodynamics and the phase state models of hydrate before and after the dissociation, and then the excess pore pressure calculation model of hydrate dissociation is concluded referring to relevant theoretical models proposed in studies in frozen soil mechanics. Besides, the influence of different factors on the excess pore pressure produced due to hydrate dissociation is also discussed on with the deep well of a stratum containing natural gas hydrate in the South China Sea as a case for calculation.
关键词：Natural gas hydrate;dissociation;excess pore pressure;example calculation;deepwater well
