Kalyoncu Pakkaner Gülce, Cnudde Veerle, Derluyn Hannelore, Bultreys Tom
PProGRess, Department of Geology, Ghent University, Ghent, Belgium.
UGCT, Department of Physics, Ghent University, Ghent, Belgium.
Adv Water Resour. 2025 Jul;201:104984. doi: 10.1016/j.advwatres.2025.104984.
Porous geological formations play an important role as storage media for CO and H. Brine in these formations can evaporate during gas injection, leading to salt precipitation. Estimating how and where salt precipitates is important to understand its influence on injectivity. So far, studies on gas injection scenarios primarily focused on formation dry-out inside the pore space. However, salt precipitation on external rock surfaces exposed to dry-out (e.g., the wellbore interface) can strongly influence drying dynamics as well. The occurrence of salt precipitation on these surfaces and its relation to the internal precipitation dynamics remain unclear. Therefore, we conducted experiments injecting dry gas into Bentheimer sandstone at two flow rates in the advective regime and for two different brine salinities. We tracked precipitation on both the gas injection surface and in the pores via μCT imaging. Salt precipitation on the surface occurred for all cases, and precipitation within the pores exhibited heterogeneous distribution, with higher salt accumulation at higher salinities and lower flow rates. Porosity decreased by less than 3 % for all cases, nevertheless accompanied by up to 20 % reduction in permeability. Our experiments suggest a strong correlation in time between precipitation dynamics within the pores and on the injection surface. We discovered a sudden decrease in brine concentration inside the pores during dry-out, with a simultaneous increase in the rate of precipitated salt volume on the surface, highlighting a previously unrecognized interaction. This work provides insight into complex drying and precipitation dynamics during gas injection, which carries important implications for well injectivity impairment in field operations.
多孔地质构造作为二氧化碳和氢气的储存介质发挥着重要作用。在这些构造中注入气体时，盐水会蒸发，导致盐分沉淀。估算盐分如何以及在何处沉淀对于了解其对注入能力的影响很重要。到目前为止，关于注气情况的研究主要集中在孔隙空间内的地层干涸上。然而，暴露于干涸状态的外部岩石表面（例如井筒界面）上的盐分沉淀也会强烈影响干燥动力学。这些表面上盐分沉淀的发生及其与内部沉淀动力学的关系仍不清楚。因此，我们进行了实验，在平流状态下以两种流速向本特海默砂岩中注入干气，并针对两种不同的盐水盐度进行实验。我们通过μCT成像跟踪了注气表面和孔隙内的沉淀情况。在所有情况下，表面都会发生盐分沉淀，孔隙内的沉淀呈现出不均匀分布，在较高盐度和较低流速下盐分积累更多。所有情况下孔隙度下降均小于3%，但渗透率最多降低20%。我们的实验表明，孔隙内和注入表面的沉淀动力学在时间上有很强的相关性。我们发现干涸过程中孔隙内盐水浓度突然下降，同时表面沉淀盐体积的速率增加，这突出了一种以前未被认识到的相互作用。这项工作深入了解了注气过程中复杂的干燥和沉淀动力学，这对现场作业中的井筒注入能力损害具有重要意义。
