鄂尔多斯盆地东胜气田氦气分布规律及特大型富氦气田的发现

Helium distribution of Dongsheng gas field in Ordos Basin and discovery of a super large helium-rich gas field

近年来,随着鄂尔多斯盆地北缘杭锦旗地区东胜气田勘探开发进程的逐步推进,发现在该地区天然气中普遍伴生具有工业价值的氦气。通过对东胜气田166口井天然气样品分析发现,氦气含量为0.045%~0.487%,达到含氦-富氦气田标准。气田中部独贵加汗区带及北部什股壕区带2个基底断裂发育区氦气含量较高,平均含量大于0.1%,具有较大的氦气勘探开发潜力。纵向上从下(盒1段)到上(盒3段)氦气含量依次降低,盒1段和盒2段氦气含量较高,均大于0.1%,为主要的氦气勘探开发层系。根据氦气同位素组成发现,东胜气田氦气为典型的壳源成因,主要来源于基底的太古宇—元古宇变质岩—花岗岩系,氦气分布受基底岩相和深大断裂双重控制,高值区主要沿泊尔江海子等通基底断裂两侧分布,在二级断裂的通氦源断裂与四级断裂的输导体系交汇处和太古宇—元古宇变质岩—花岗岩系基底发育区富集。通过对东胜气田重点天然气井中短期内氦气含量随气井生产动态的变化特征研究,发现天然气在较长的开发时期内氦气含量保持稳定;按照体积法计算,其氦气探明储量为2.444×10^(8)m^(3),三级储量为8.304×10^(8)m^(3),是目前我国第一大特大型含氦—富氦气田,资源潜力巨大。建议选取东胜气田作为氦气资源开发利用的先导试验区,加快论证建设氦气战略储备基地的可行性;同时加强主要含油气盆地天然气中氦气成藏规律、资源潜力评价以及氦气等伴生资源的综合利用研究,指导氦气资源勘探开发和综合利用。

With the developments of exploration and production of natural gas in the Dongsheng gas field of Hangjinqi area,northern part of Ordos Basin,industrial valued helium has been discovered in this area.Natural gases from 166 wells in the Dongsheng gas field were analyzed in this study and results show that the helium contents of these gases range from 0.045%to 0.487%,with an average value of 0.118%,indicating industrial value for the helium resource.Two basement-faults developed zones of Duguijiahan and Shiguhao in the center of the gas field have relative higher content of helium,with an average value higher than 0.1%,indicating a great exploration potential.The average helium contents decrease from the lower stratum(the first member of Xiashihezi Formation,P_(1)x_(1))to the upper stratum(the third member of Xiashihezi Formation,P_(1)x_(3)),indicating that the P_(1)x_(1)and P_(1)x_(2) are potential targets for helium exploration and development.According to helium isotopic compositions,helium in the Dongsheng gas field has of a typical crust source,mainly from Archean-Proterozoic metamorphic rock-granite series in the basement.It is clear that helium distribution in the Dongsheng gas field was controlled by both basement lithofacies and deep fractures.Helium is enriched mainly along deep basement fractures such as Borjianghaizi and Wulanjilinmiao,and at the intersection of second-level fractures communicating helium source and fourth-level faults being migration pathways,and in the areas of Archean-Proterozoic metamorphic rock-granite series basement distribution.The variation of helium content with gas well production performance in short and medium term of key natural gas wells in the Dongsheng gas field showed that the helium contents in natural gases are stable in a relatively long term.The proved helium reserves are 244.4×10^(6) m^(3) and the 3P reserves are approaching 830.4×10^(6) m^(3) by volume method.Thus,the Dongsheng gas field is considered as the first supergiant helium-rich gas field in China.It is suggested that the Dongsheng gas field in the Ordos Basin should be regarded as a pilot test area for the development and utilization of helium resources,and the feasibility of building helium strategic reserve base should be accelerated.The research on helium accumulation mechanism,resource potential evaluation and comprehensive utilization of helium and other associated resources in natural gas should be strengthened in major oil and gas bearing basins,in order to guide the exploration,development and comprehensive utilization of helium resources.