苏北盆地黄桥地区盐城组氦气成藏地质条件及富集规律

Geological conditions and enrichment patterns of helium reservoir in Yancheng Formation, Huangqiao area, Subei Basin

姚红生 陈兴明 周韬

YAO Hongsheng CHEN Xingming ZHOU Tao

中国石化 华东油气分公司, 南京 210011

SINOPEC East China Oil & Gas Company, Nanjing, Jiangsu 210011, China

苏北盆地黄桥地区新近系盐城组天然气中He含量介于1.05%～1.40%，普遍高于工业品位，为壳—幔复合型氦气资源。目前，对于这种来源的氦气富集主控因素以及勘探目标评价的研究较为薄弱，为此，系统剖析了黄桥地区典型富氦气藏氦气成因、来源及圈闭特征，重点分析了幔源断裂对富氦气藏输导作用、盐城组圈闭条件的影响，提出了黄桥地区盐城组富氦气藏富集模式。结果表明：(1)黄桥地区南新街深大断裂在盐城组沉积时期持续活动，导致幔源物质上涌，伴随着火山活动及CO2、N2以及氦气沿断裂运移至浅层；(2)黄桥地区盐城组埋深为370～400 m,盐城组底部砂岩厚度约为40 m，上覆10～40 m泥岩，储盖组合有利,富氦气层由东往西尖灭；(3)黄桥地区盐城组整体为单斜构造，盐城组底部界面与下伏地层呈角度不整合，通过地震标定及解释，刻画出了富氦气层岩性—地层复合圈闭面积。黄桥地区盐城组富氦气藏具有断裂沟通地幔输导、砂岩储集、泥岩作为盖层、岩性—地层复合圈闭富集等特征，该认识对黄桥地区氦气有利目标评价具有重要意义。

The helium (He) content in the natural gas of the Neogene Yancheng Formation in the Huangqiao area of Subei Basin ranges from 1.05% to 1.40%, which is generally higher than the industrial grade, indicating a crust and mantle composite type of helium resource. However, current research on the main controlling factors of helium enrichment and the evaluation of exploration targets from this source is relatively weak. Therefore, the study systematically analyzed the helium genesis, source, and trapping characteristics of typical helium-rich gas reservoirs in the Huangqiao area. It focused on the influence of mantle-derived faults on the transport and accumulation of helium-rich gas reservoirs and the trapping conditions within the Yancheng Formation. An enrichment model for helium-rich gas reservoirs in the Yancheng Formation of the Huangqiao area was proposed. The results show that: (1) The Nanxinjie deep fault in the Huangqiao area was active during the sedimentation of the Yancheng Formation, resulting in upwelling of mantle-derived materials, accompanied by volcanic activities and migration of CO2, N2, and helium along the fault to shallow layers. (2) The burial depth of the Yancheng Formation in the Huangqiao area ranges from 370 to 400 m. The thickness of the bottom sandstone of the Yancheng Formation is about 40 m, capped with 10 to 40 m of mudstone. The reservoir and cap combination is favorable for enrichment, and the helium-rich layers pinch out from east to west. (3) The Yancheng Formation in the Huangqiao area exhibits a monoclinal structure as a whole, with the bottom interface displaying angular unconformity with the underlying strata. Through seismic calibration and interpretation, the lithological and stratigraphic composite trap area of the helium-rich gas layer was outlined. The helium-rich gas reservoir of the Yancheng Formation in the Huangqiao area is characterized by fault-communicated mantle transport, sandstone reservoirs, mudstone cap layers, as well as lithological and stratigraphic composite traps for enrichment. This understanding is significant for the evaluation of favorable helium exploration targets in the Huangqiao area.

中国石化先导项目(YTBXD-FCZY-2024-1-07-001)资助。

https://doi.org/10.11781/sysydz202405906