Tham khảo tài liệu 'natural gas part 5', kỹ thuật - công nghệ, cơ khí - chế tạo máy phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | 152 Natural Gas Numerical studies Moridis et al. 2008 report rather comprehensive numerical studies that assess the hydrate production potential for the tree classes of hydrate deposits with the three production options. They found that Class 1 deposits appear to be the most promising target due to the thermodynamic proximity to the hydrate stability zone. That is the boundary between the free gas zone and the hydrate layer forms the equilibrium line and hence only small changes in temperature or pressures will induce dissociation of hydrate. In addition the free gas zone will secure gas production regardless of the hydrate gas contribution. They found Class 1G to be a more desirable target within Class 1 due to less water production and more evenly distributed pressure fields. Class 2 may attain high rates but are burdened with long lead times with little initial gas production. Class 3 may supply gas earlier but with lower rates. Moridis et al. 2008 concluded that depressurisation is the favourable production option for all three classes meaning that the deposit is not a desirable target if depressurisation appears to be ineffective. It is however very important to stress that numerical simulations of hydrate exploitation scenarios are still in an early stage with corresponding challenges at the fundamental level as well as in the parameterisation. Field example the Mackenzie River Delta The Mackenzie River Delta of Canada was explored mainly for conventional petroleum reserves but a total of 25 drilled wells have identified possible gas hydrate sites. The gas hydrate research well JAPEX JNOC GSC Mallik 2L-38 drilled in 1998 was designed to investigate the nature of in situ hydrates in the Mallik area to explore the presence of subpermafrost gas hydrate. A major objective was to investigate the gas hydrate zones obtained by well logs in 1972 in a nearby well which was believed to have encountered at least ten significant gas-hydrate stratigrapic units. .
