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以克拉 2气田为例 ,讨论了天然气在地层水中溶解—释放作用对气藏形成的影响 ,估算了因地层抬升所导致的水溶气释放为游离气的量 ,分析了影响水溶气与气藏中游离气组分分馏的主要因素。研究表明 ,天然气在地层水中的溶解—释放作用对克拉 2气田天然气组分分馏起重要的作用 ,主要表现为 :①在地层沉降和抬升过程中 ,由于地层温度、压力的变化 ,地层水选择性溶解和释放天然气组分 ;②在大规模水平挤压过程中 ,C2 + 烃类气体随着边底水的迁移而流失 ;③地层异常高压导致大量C2+ 烃类溶解于地层水中 ,致使气藏中甲烷相对富集。此外 ,水溶气释放对克拉 2气田异常高压的形成也有一定的贡献作用。文章还通过天然气在水中溶解—释放模拟试验 ,分析了甲烷气体在地层水中因压力变化而释放的过程中碳同位素分馏状况。总结了克拉 2气藏水溶气成藏过程及其成藏模式。
Taking Kela-2 gas field as an example, the effects of dissolution-release of gas on formation of gas reservoirs in formation water are discussed. The amount of release of water-soluble gas due to formation uplift is estimated as the amount of free gas. Fractionation of free gas components of the main factors. The results show that the dissolved-release effect of natural gas plays an important role in the fractionation of natural gas components in the Kela-2 gas field. The main features are as follows: (1) During the process of subsidence and uplift of the strata, due to the change of formation temperature and pressure, Dissolve and release natural gas components; (2) During the large-scale horizontal extrusion, C2 + hydrocarbon gas will be lost with the migration of edge water; (3) abnormally high formation pressure will cause a large amount of C2 + hydrocarbons to dissolve into the formation water, Methane is relatively concentrated. In addition, the release of water-soluble gas also has a certain contribution to the formation of abnormal high pressure in the Kela-2 gas field. In this paper, through natural gas dissolution-release simulation experiment in water, the situation of carbon isotope fractionation during the release of methane gas due to pressure changes in formation water is analyzed. The process and model of water-soluble gas accumulation in Kela-2 gas pool are summarized.