Koulidis Alexis, Grubben Tessel M, van der Schans Martin L, Bloemendal Martin, Vardon Philip J
Faculty of Civil Engineering and Geosciences, Delft University of Technology, Delft, The Netherlands.
KWR Water Research Institute, Nieuwegein, The Netherlands.
Ground Water. 2025 Mar-Apr;63(2):231-247. doi: 10.1111/gwat.13455. Epub 2024 Dec 19.
Drilling wells in unconsolidated formations is commonly undertaken to extract drinking water and other applications, such as aquifer thermal energy storage (ATES). To increase the efficiency of an ATES system, the drilling campaigns are targeting greater depths and enlarging the wellbore diameter in the production section to enhance the flow rates. In these cases, wells are more susceptible to collapse. Drilling fluids for shallow formations often have little strengthening properties and, due to single-string well design, come into contact with both the aquifer and the overburden. Drilling fluids and additives are experimentally investigated to be used to improve wellbore stability in conditions simulating field conditions in unconsolidated aquifers with a hydraulic conductivity of around 10 m/d. The impact on wellbore stability is evaluated using a new experimental setup in which the filtration rate is measured, followed by the use of a fall cone penetrometer augmented with an accelerometer to directly test the wellbore strengthening, and imaging with a scanning electron microscope (SEM) to investigate the (micro)structure of the filter cakes produced. Twelve drilling fluids are investigated with different concentrations of bentonite, polyanionic cellulose (PAC), Xanthan Gum, calcium carbonate (CaCO), and aluminum chloride hexahydrate ([Al(HO)]Cl). The filtration results indicate that calcium carbonate, average d <20 μm, provides pore throat bridging and filter cake formation after approximately 2 min, compared to almost instantaneous discharge when using conventional drilling fluids. The drilling fluid containing 2% [Al(HO)]Cl forms a thick (4 mm) yet permeable filter cake, resulting in high filtration losses. The fall cone results show a decrease of cone penetration depth up to 20.78%, and a 40.27% increase in deceleration time while penetrating the sample with CaCO compared with conventional drilling fluid containing bentonite and PAC, indicating a significant strengthening effect. The drilling fluids that contain CaCO, therefore, show high promise for field implementation.
在松散地层中钻井通常用于获取饮用水及其他用途，如含水层热能储存（ATES）。为提高ATES系统的效率，钻井作业的目标深度更大，且生产段的井筒直径不断扩大以提高流速。在这些情况下，井更容易坍塌。浅地层钻井液通常强化性能较差，并且由于单管井设计，会与含水层和覆盖层接触。针对水力传导率约为10米/天的松散含水层，在模拟现场条件下对钻井液和添加剂进行了实验研究，以用于改善井筒稳定性。使用一种新的实验装置评估对井筒稳定性的影响，该装置先测量过滤速率，然后使用配备加速度计的落锥贯入仪直接测试井筒强化效果，并通过扫描电子显微镜（SEM）成像来研究所形成滤饼的（微观）结构。研究了十二种含有不同浓度膨润土、聚阴离子纤维素（PAC）、黄原胶、碳酸钙（CaCO）和六水合氯化铝（[Al(H₂O)₆]Cl）的钻井液。过滤结果表明，平均粒径d<20μm的碳酸钙在约2分钟后提供孔隙喉道桥接并形成滤饼，而使用传统钻井液时几乎是瞬间排放。含有2%[Al(H₂O)₆]Cl的钻井液形成了厚（4毫米）但可渗透的滤饼，导致高滤失量。落锥试验结果表明，与含有膨润土和PAC的传统钻井液相比，使用CaCO穿透样品时，锥入深度降低了20.78%，减速时间增加了40.27%，表明有显著的强化效果。因此，含有CaCO的钻井液在现场应用方面具有很大潜力。
