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

Abstract

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, P1x1) to the upper stratum (the third member of Xiashihezi Formation, P1x3), indicating that the P1x1 and P1x2 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 244.4×106 m3 and the 3P reserves are approaching 830.4×106 m3 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.

Keywords

• helium content
• proved helium reserves
• supergiant helium-rich gas field
• dongsheng gas field
• hangjinqi area
• ordos basin