Commercial helium systems have been found to date as a serendipitous by-product of petroleum exploration. There are nevertheless significant differences in the source and migration properties of helium compared with petroleum. An understanding of these differences enables prospects for helium gas accumulations to be identified in regions where petroleum exploration would not be tenable. Here we show how the basic petroleum exploration playbook (source, primary migration from the source rock, secondary longer distance migration, trapping) can be modified to identify helium plays. Plays are the areas occupied by a prospective reservoir and overlying seal associated with a mature helium source. This is the first step in identifying the detail of helium prospects (discrete pools of trapped helium). We show how these principles, adapted for helium, can be applied using the Rukwa Basin in the Tanzanian section of the East African Rift as a case study. A thermal hiatus caused by rifting of the continental basement has resulted in a surface expression of deep crustal gas release in the form of high-nitrogen gas seeps containing up to 10% ⁴He. We calculate the total likely regional source-rock helium generative capacity, identify the role of the Rungwe volcanic province in releasing the accumulated crustal helium and show the spatial control of helium concentration dilution by the associated volcanic CO₂. Nitrogen, both dissolved and as a free-gas phase, plays a key role in the primary and secondary migration of crustal helium and its accumulation into what might become a commercially viable gas pool. This too is examined. We identify and discuss evidence that structures and seals suitable for trapping hydrocarbon and CO₂ gases will likely also be efficient for helium accumulation on the timescale of the Rukwa Basin activity. The Rukwa Basin prospective recoverable P₅₀ resources of helium have been independently estimated to be about 138 BSCF (billion standard cubic ft: 2.78 x 10⁹ m³ at STP). If this volume is confirmed it would represent about 25% of the current global helium reserve. Two exploration wells, Tai 1 and Tai 2, completed by August 2021 have proved the presence of seal and reservoir horizons with the reservoirs containing significant helium shows.

This article is part of the Energy Geoscience Series available at https://www.lyellcollection.org/cc/energy-geoscience-series

迄今为止，已发现商业氦气系统是石油勘探的偶然副产品。然而，与石油相比，氦的来源和迁移性质存在显着差异。对这些差异的了解可以在石油勘探不可行的地区确定氦气聚集的前景。在这里，我们展示了如何修改基本的石油勘探手册（源、来自源岩的初级迁移、二次长距离迁移、圈闭）以识别氦气区。储层是预期储层和与成熟氦源相关的上覆密封所占据的区域。这是确定氦远景（被困氦的离散池）细节的第一步。我们展示了这些适用于氦气的原理，可以使用东非裂谷坦桑尼亚部分的鲁夸盆地作为案例研究。大陆基底裂陷造成的热中断导致地壳深层气体释放的地表表现形式为高氮气体渗漏，含氮量高达 10%⁴他。我们计算了可能的区域烃源岩总氦生成能力，确定了 Rungwe 火山区在释放积累的地壳氦中的作用，并展示了相关火山 CO ₂对氦浓度稀释的空间控制。溶解的和作为自由气相的氮在地壳氦的初级和次级迁移及其积累到可能成为商业上可行的气藏的过程中起着关键作用。这也被审查。我们确定并讨论了适用于捕获碳氢化合物和 CO ₂气体的结构和密封件的证据，这些证据可能也有助于在 Rukwa 盆地活动的时间尺度上有效地积累氦气。Rukwa 盆地预期可采 P ₅₀氦资源独立估计约为 138 BSCF（十亿标准立方英尺：2.78 x 10 ⁹  m ³在 STP）。如果这一数量得到确认，它将占当前全球氦储量的 25% 左右。2021 年 8 月完成的两口探井 Tai 1 和 Tai 2 已证明存在密封层和储层层位，储层中含有大量氦气显示。

本文是能源地球科学系列的一部分，可在 https://www.lyellcollection.org/cc/energy-geoscience-series