Injecting CO₂ into aquifer pore fluid (high salinity brine) in deep saline aquifers during the sequestration process causes the chemico-mineral structure to be altered through complex chemically-coupled mechanical deformations. This is as yet poorly understood in the field. The authors conducted a series of tri-axial strength tests on Hawkesbury sandstone under in-situ stress and temperature conditions to characterise the behaviour of reservoir rock upon exposure to super-critical CO₂ (ScCO₂₎ to determine this chemically-coupled mechanical behaviour.

According to the findings, injection of CO₂ into a brine-saturated reservoir rock mass may cause a considerable strength reduction, probably due to the rock’s mineralogical alteration-induced mechanical weakening of grain contacts. This was confirmed by SEM analysis, according to which the mineral dissolution process upon exposure to ScCO₂ is significant, and considerable quartz and calcite dissolution were noticed in the tested samples. Importantly, this rock mineral dissolution may alter the reservoir’s natural pore geometry. This eventually affects the effective stress patterns acting on the rock matrix. In addition, the slip tendency of brine+CO₂-reacted reservoir rock is increased with increasing injection pressure, revealing the fate of the resulting pore pressure-dominant effective stress field through the CO₂ injection process. The results were then incorporated in the effective stress field model. This model can be used to predict the possibility of mechanical failure of reservoir rock upon CO₂ injection into saline aquifers.

在螯合过程中，将CO ₂注入深层盐水含水层的含水层孔隙流体（高盐度盐水）中，会导致化学-矿物结构通过复杂的化学耦合机械变形而发生变化。在本领域中，这还为人所知。作者在原位应力和温度条件下对霍克斯伯里砂岩进行了一系列三轴强度测试，以表征储层岩石在暴露于超临界CO ₂（ScCO _2）后的行为，从而确定这种化学耦合的机械行为。

根据发现，将CO ₂注入盐水饱和的储层岩体中可能会导致强度显着降低，这可能是由于岩石的矿物学变化引起的颗粒接触机械弱化所致。通过SEM分析证实了这一点，根据该分析，暴露于ScCO ₂时的矿物溶解过程是显着的，并且在测试样品中注意到大量的石英和方解石溶解。重要的是，这种岩石矿物溶解可能会改变储层的天然孔隙几何形状。这最终会影响作用在岩石基质上的有效应力模式。另外，盐水+ CO ₂的滑移趋势随注入压力的增加，反应堆中的储层岩石增加，揭示了通过CO ₂注入过程产生的以孔隙压力为主的有效应力场的命运。然后将结果合并到有效应力场模型中。该模型可用于预测将CO ₂注入盐水层后储层岩石机械破坏的可能性。