塔里木盆地和田河气田水溶气成藏过程

塔里木盆地和田河气田的天然气具备水溶气成藏地球化学特征和理想的水溶气成藏条件。喜马拉雅运动晚期和田河气田圈闭形成，巴楚断隆以南的西南坳陷寒武系高一过成熟烃源岩生成的天然气在深部高温、高压条件下大量溶解于水中。随着断裂的开启，在异常压力驱使下，水溶气沿断裂从深部寒武系运移至气田东部的奥陶系和石炭系圈闭中，由于压力和温度降低，水溶气释放形成游离气气顶，气水界面下部的水体继续自气田东部高压区向西部低压区沿不整合面长距离运移，运移过程中压力不断降低。导致水溶气不断释放，变成游离相天然气，在运移路径上成藏，形成条带状、串珠状分布的和田河气田。由此造成气田西部井区天然气偏干、甲烷碳同位素组成偏重、CO2含量明显偏高，一系列的水溶气运移参数自东部井区向西部明显增大。图6参27

Water-soluble gas accumulation process of Hetianhe gas field in Tarim Basin,NW China

The Hetianhe gas field of Tarim Basin has excellent geological conditions for water-soluble gas accumulation. The gases exhibit very good water-soluble characteristics. The traps were formed during the Late Himalaya orogeny,when the gases generated by highly mature Cambrian source rock were largely dissolved in water. Subsequent faulting allowed the gas charged water to migrate towards Ordovician and Carboniferous traps in the eastern part of the field. As the pressure and temperature decreased, some gases were released from water and gas reservoirs were formed. The water beneath the gas-water interface subsequently migrated along the unconformity for a long distance from the eastern high-pressure part towards the western low-pressure part of the field. During the horizontal migration, the gases were gradually released as pressure decreased. A chain-like cluster of gas pools was formed. The migration history has made the migration parameters of the water soluble gases increase significantly from west