Experimental Investigation of Mechanical Properties of Black Shales after CO₂-Water-Rock Interaction.
Experimental Investigation of Mechanical Properties of Black Shales after CO₂-Water-Rock Interaction.
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DOI：
10.3390/ma9080663
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发表时间：
2016-08-06
期刊：
影响因子：
--
通讯作者：
Ji B
中科院分区：
文献类型：
--
作者：
Lyu Q;Ranjith PG;Long X;Ji B
CO2-水-岩石相互作用对页岩力学性质的影响对于估计页岩储层中封存CO2的可能性至关重要。通过单轴抗压强度试验、声发射系统、SEM和EDS分析，研究了不同饱和时间（10 d、20 d和30 d）的黑色页岩在气态/超临界CO2溶解水中的力学性能和微观结构变化。实验结果表明，在含气态/超临界CO2的水中，随着饱和时间的增加，UCS、杨氏模量和脆性指数逐渐减小。与未饱和的样品相比，30天饱和导致气体饱和样品的UCS和杨氏模量分别降低56.43%和54.21%，而超临界饱和样品的UCS和杨氏模量分别降低66.05%和56.32%。脆性指数也急剧下降，从84.3%的样品没有饱和到50.9%的样品在水中饱和的气态CO2，到47.9%的样品在水中饱和的超临界二氧化碳（SC-CO2）。SC-CO2导致页岩的机械性能的更大降低。声发射系统的裂纹扩展结果表明，较长的饱和时间产生较高的峰值累积声发射能量。SEM图像显示，当页岩样品在含有气态/超临界CO2的水中饱和时，会出现许多孔隙。EDS结果表明，CO2-水-岩石相互作用增加了饱和样品表面C和Fe的百分比，降低了Al和K的百分比。
The effects of CO2-water-rock interactions on the mechanical properties of shale are essential for estimating the possibility of sequestrating CO2 in shale reservoirs. In this study, uniaxial compressive strength (UCS) tests together with an acoustic emission (AE) system and SEM and EDS analysis were performed to investigate the mechanical properties and microstructural changes of black shales with different saturation times (10 days, 20 days and 30 days) in water dissoluted with gaseous/super-critical CO2. According to the experimental results, the values of UCS, Young’s modulus and brittleness index decrease gradually with increasing saturation time in water with gaseous/super-critical CO2. Compared to samples without saturation, 30-day saturation causes reductions of 56.43% in UCS and 54.21% in Young’s modulus for gaseous saturated samples, and 66.05% in UCS and 56.32% in Young’s modulus for super-critical saturated samples, respectively. The brittleness index also decreases drastically from 84.3% for samples without saturation to 50.9% for samples saturated in water with gaseous CO2, to 47.9% for samples saturated in water with super-critical carbon dioxide (SC-CO2). SC-CO2 causes a greater reduction of shale’s mechanical properties. The crack propagation results obtained from the AE system show that longer saturation time produces higher peak cumulative AE energy. SEM images show that many pores occur when shale samples are saturated in water with gaseous/super-critical CO2. The EDS results show that CO2-water-rock interactions increase the percentages of C and Fe and decrease the percentages of Al and K on the surface of saturated samples when compared to samples without saturation.