Geological storage of gases will be necessary in the push to net zero and the energy transition to reduce carbon emissions to atmosphere. These include CO₂ geological storage in suitable sandstone reservoirs. Understanding groundwater flow, connectivity and hydrogeochemical processes in aquifer and storage systems is vital to prevent risk and protect important water resources, such as the Great Artesian Basin. Here, we provide a ‘tool-box’ of geochemical assessment methods to provide information on flow patterns through the basin's aquifers (changes in chemistry along flow path), stagnant versus flowing conditions (cosmogenic isotopes and noble gases), inter-aquifer connectivity and seal properties (major ions, Sr and stable isotopes), water quality (major ions and metals) and general assessments on residence times of groundwater (cosmogenic isotopes and noble gases). This information can be used with reservoir and groundwater models to inform on possible changes in the above-mentioned processes and serve as input parameters for CO₂ injection impact modelling. We demonstrate the use and interpretation on an example of a potential CO₂ storage geological sequestration site in the Surat Basin, part of the Great Artesian Basin, and the aquifers that overly the reservoir. The stable water isotopes are depleted compared to average rainfall and most likely indicate greater contributions from monsoonal rain events from the northern monsoonal troughs, where amount and rainout effects lead to the depletion rather than colder recharge climates. This is supported by the modern recharge temperatures from noble gases. Inter-aquifer mixing between the Precipice Sandstone reservoir and the Hutton Sandstone aquifer seems unlikely as the Sr isotope ratios are distinctly different suggesting that the Evergreen Formation is a seal in the locations sampled. Mixing, however, occurs on the edges of the basin, especially in the south-east and east where the Surat Basin transitions into the Clarence-Moreton Basin. Groundwater flow appears to be to the south in the Precipice Sandstone, with a component of flow east to the Clarence-Morton Basin. The cosmogenic isotopes and noble gases strongly indicate very long residence times of groundwater in the central south Precipice Sandstone around a proposed storage site. ¹⁴C values below analytical uncertainty, R³⁶Cl ratios at secular equilibrium as well as high He concentrations and high ⁴⁰Ar/³⁶Ar ratios support the argument that groundwater flow in this area is extremely slow or groundwater is stagnant. The results of this study reflect the geological and hydrogeological complexities of sedimentary basins and that baseline studies, such as this one, are paramount for management strategies.

为了推动净零排放和减少大气碳排放的能源转型，气体地质储存是必要的。其中包括在合适的砂岩储层中进行CO ₂地质封存。了解含水层和储存系统中的地下水流量、连通性和水文地球化学过程对于预防风险和保护重要水资源（例如大自流盆地）至关重要。在这里，我们提供了地球化学评估方法的“工具箱”，以提供有关流域含水层的流动模式（沿流动路径的化学变化）、停滞与流动条件（宇宙成因同位素和稀有气体）、含水层间连通性和密封特性（主要离子、锶和稳定同位素）、水质（主要离子和金属）以及地下水停留时间的一般评估（宇宙成因同位素和稀有气体）。该信息可与水库和地下水模型一起使用，以告知上述过程中可能发生的变化，并用作CO ₂注入影响建模的输入参数。我们以苏拉特盆地（大自流盆地的一部分）和水库上方的含水层为例，展示了潜在的 CO _{2封存地质封存地点的使用和解释。}与平均降雨量相比，稳定水同位素已耗尽，很可能表明来自北部季风槽的季风降雨事件的贡献更大，其中水量和降雨效应导致了水的耗尽，而不是较冷的补给气候。惰性气体的现代补给温度支持了这一点。Precipice 砂岩储层和 Hutton 砂岩含水层之间的含水层间混合似乎不太可能，因为 Sr 同位素比率明显不同，这表明 Evergreen 地层是采样位置的密封层。然而，混合发生在盆地边缘，特别是在苏拉特盆地过渡到克拉伦斯-莫顿盆地的东南部和东部。地下水流似乎流向悬崖砂岩的南部，其中一部分流向东部的克拉伦斯-莫顿盆地。宇宙成因同位素和稀有气体强烈表明地下水在拟议储存地点周围的中南部悬崖砂岩中的停留时间非常长。^{低于分析不确定度的14} C 值、处于长期平衡的 R ³⁶ Cl 比率以及高 He 浓度和高⁴⁰ Ar/ ³⁶ Ar 比率支持该地区地下水流极其缓慢或地下水停滞的论点。这项研究的结果反映了沉积盆地的地质和水文地质复杂性，并且像这样的基线研究对于管理策略至关重要。