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Experimental study on the softening effect and mechanism of anthracite with CO2 injection
International Journal of Rock Mechanics and Mining Sciences ( IF 7.0 ) Pub Date : 2021-01-14 , DOI: 10.1016/j.ijrmms.2021.104614
Qinghe Niu , Liwen Cao , Shuxun Sang , Wei Wang , Xiaozhi Zhou , Wei Yuan , Zhongmin Ji , Jiangfang Chang , Mengyang Li

The injection of supercritical CO2 into coal seam alters the mechanical properties of the coal, which should be paid close attention when considering security issues during CO2-Enhanced CoalBed Methane recovery (CO2-ECBM). In this study, the Qinshui Basin is considered as the research object, and mechanical parameters, such as the peak strength, elastic modulus, and Poisson's ratio of anthracites under the coupled influences of CO2 saturation pressure, CO2 saturation time, and water content were investigated. The results indicate a decrease in the peak strength and elastic modulus and an increase in the Poisson's ratio of the CO2-saturated coal. Increasing the CO2 saturation pressure, extending the CO2 saturation time, and increasing the water content contributes to the softening of the coal. The modified Langmuir equation and stretched exponential (SE) equation are used to accurately predict the peak strength and elastic modulus reduction with CO2 saturation pressure and CO2 saturation time, respectively. The failure patterns change from brittle shear failure for natural coal and transitional shear failure for supercritical CO2-saturated coal to the ductile non-dilatant barreling for the supercritical CO2+water-saturated coal. The softening effect of coal can be attributed to the chemical and physical reactions between coal and CO2, including the surface energy reduction of CO2-bearing coal, extraction and plasticization reactions, differential adsorption swelling and swelling stress, and dissolution of carbonate solution for the mineral filling pore/fracture. In view of the geo-mechanical changes caused by CO2 to coal, the optimization of the targeted reservoir is pivotal for the successful implementation of CO2-ECBM.



中文翻译:

注入CO 2的无烟煤软化效果及机理的实验研究

将超临界CO 2注入煤层会改变煤的机械性能,在考虑CO 2增强煤层气回收(CO 2 -ECBM)期间的安全性问题时应密切注意。本研究以沁水盆地为研究对象,在CO 2饱和压力,CO 2饱和时间和含水量的共同影响下,无烟煤的峰值强度,弹性模量和泊松比等力学参数为研究对象。被调查了。结果表明,CO 2饱和煤的峰值强度和弹性模量降低,泊松比增加。增加CO 2饱和压力,延长CO 2饱和时间并增加水含量有助于煤的软化。修改后的Langmuir方程和拉伸指数(SE)方程分别用于精确预测随CO 2饱和压力和CO 2饱和时间的峰值强度和弹性模量降低。破坏模式从天然煤的脆性剪切破坏和超临界CO 2饱和煤的过渡剪切破坏变为超临界CO 2 +水饱和煤的延性非膨胀桶状破坏。煤的软化作用可以归因于煤与CO 2之间的化学和物理反应包括降低含CO 2的煤的表面能,萃取和增塑反应,不同的吸附溶胀和溶胀应力,以及用于填充矿物/孔隙的碳酸盐溶液的溶解。考虑到CO 2对煤造成的地质力学变化,目标油藏的优化对于成功实施CO 2 -ECBM至关重要。

更新日期:2021-01-14
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