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基于野外气体地球化学调查研究,以及前人有关冻土表层温度、冻土层内地温梯度、冻土层下地温梯度等的资料,对青藏高原多年冻土区天然气水合物的形成条件开展了模拟研究.结果显示:研究区冻土条件能够满足天然气水合物形成的基本要求;气体组成、冻土特征(如冻土厚度或冻土表层温度、冻土层内地温梯度、冻土层下地温梯度等)是影响研究区天然气水合物稳定带厚度的最重要因素,其在不同点位上的差异性可能导致天然气水合物分布的不均匀性的主要原因;研究区最可能的天然气水合物为甲烷与重烃(乙烷和丙烷)的混合气体型天然气水合物;在天然气水合物分布的区域,其产出的上临界点深度在几十至一百多米间,下临界点深度在几百至近一千米间,厚度可达到几百米.与CanadianMallik三角洲多年冻土区相比,青藏高原多年冻土区除了冻土厚度小些外,其他条件,如冻土层内地温梯度、冻土层下地温梯度、气体组成等条件较为相近,具有一定的可比性,预示着良好的天然气水合物潜力.
Based on the investigation of field gas geochemistry and the predecessors’ information about the surface temperature of permafrost, the geothermal gradient in permafrost and the geothermal gradient under permafrost, the formation conditions of gas hydrate in the permafrost region of Qinghai-Tibet Plateau are simulated The results show that the permafrost conditions in the study area can meet the basic requirements of natural gas hydrate formation. The gas composition, frozen soil characteristics (such as permafrost thickness or permafrost surface temperature, geotemperature gradient in permafrost layer, Etc.) is the most important factor affecting the thickness of the gas hydrate stability zone in the study area. The differences at different sites may lead to the inhomogeneity of the gas hydrate distribution. The most likely gas hydrate in the study area is methane And heavy hydrocarbon (ethane and propane) mixed gas type gas hydrate; in the region where the gas hydrate is distributed, the output of the upper critical point depth in the tens to a hundred meters, the depth of the lower critical point in the hundreds To nearly one kilometer, the thickness can reach a few hundred meters.Compared with the CanadianMallik delta permafrost, permafrost in Qinghai-Tibet Plateau in addition to the thickness of frozen soil smaller, the other As permafrost interior temperature gradients, temperature gradients G1, G2, and other conditions more similar to the composition of the gas, with some comparable, indicating good potential for gas hydrate.