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Geochemically induced shear slip in artificially fractured dolomite- and clay-cemented sandstone
International Journal of Greenhouse Gas Control ( IF 4.6 ) Pub Date : 2021-09-15 , DOI: 10.1016/j.ijggc.2021.103448
Samantha J. Fuchs 1 , Dustin Crandall 2 , Johnathan E. Moore 2 , Mayandi Sivaguru 3 , Bruce W. Fouke 3, 4 , D. Nicolas Espinoza 5 , Ange-Therese Akono 6 , Charles J. Werth 1
Affiliation  

Geologic carbon sequestration in deep saline aquifers results in a low pH brine plume that pushes into subsurface storage reservoirs and can access pre-existing or induced microfractures. This work investigates the effect of acidic brine on displacement of an artificial fracture under stress in the dolomite- and clay-cemented Bandera Gray sandstone. Samples were held under stress in a custom flow cell housed within an industrial CT scanner, and either acidic (pH 4) or reservoir-simulated (pH 8.3) brine was flowed through the artificial fracture for seven days. CT imaging shows that acidic brine resulted in greater shear slip than reservoir-simulated brine, with 0.379 ± 0.022 mm shear slip after pH 4 flow and only 0.213 ± 0.011 mm slip after pH 8.3 flow. Fracture surfaces exposed to acidic brine had rougher surfaces and lower fracture toughness, respectively, than those exposed to reservoir-simulated brine. SEM images of fracture surfaces indicate a loss by area of Fe-dolomite cementing crystals (6.05 ± 1.37% to 3.78 ± 0.73%) after exposure with the acidic brine, as well as a corresponding porosity increase (24.6 ± 1.1% to 26.1 ± 1.1%). These results indicate dissolution and weakening of the dolomite cements by acidic brine frees individual grains at the fracture surface to move, resulting in geochemically-induced stress release. Acidic brine created from geological carbon sequestration can dissolve sandstone cements and lead to increased shear slip at fracture interfaces, but further work at larger scales and with more realistic fracture conditions is needed.



中文翻译:

人工压裂白云岩和粘土胶结砂岩中地球化学诱发的剪切滑移

深部咸水层中的地质碳封存导致低 pH 盐水羽流进入地下储层,并可以进入预先存在或诱发的微裂缝。这项工作研究了酸性盐水对白云石和粘土胶结的班德拉灰色砂岩中应力作用下人工裂缝位移的影响。样品在工业 CT 扫描仪内的定制流通池中保持压力,酸性 (pH 4) 或水库模拟 (pH 8.3) 盐水流过人工裂缝 7 天。CT 成像显示酸性盐水比储层模拟盐水导致更大的剪切滑移,pH 4 流动后剪切滑动为 0.379 ± 0.022 mm,pH 8.3 流动后剪切滑动仅为 0.213 ± 0.011 mm。暴露在酸性盐水中的断裂表面具有更粗糙的表面和更低的断裂韧性,分别比暴露于油藏模拟盐水的那些。断口的 SEM 图像表明,暴露于酸性盐水后,铁白云石胶结晶体的面积损失(6.05±1.37% 至 3.78±0.73%),以及相应的孔隙率增加(24.6±1.1% 至 26.1±1.1) %)。这些结果表明,酸性盐水对白云石胶结物的溶解和弱化使裂缝表面的单个颗粒自由移动,从而导致地球化学诱导的应力释放。地质固碳产生的酸性盐水可以溶解砂岩胶结物并导致裂缝界面处的剪切滑移增加,但需要在更大规模和更现实的裂缝条件下进行进一步研究。断口的 SEM 图像表明,暴露于酸性盐水后,铁白云石胶结晶体的面积损失(6.05±1.37% 至 3.78±0.73%),以及相应的孔隙率增加(24.6±1.1% 至 26.1±1.1) %)。这些结果表明,酸性盐水对白云石胶结物的溶解和弱化使裂缝表面的单个颗粒自由移动,从而导致地球化学诱导的应力释放。地质固碳产生的酸性盐水可以溶解砂岩胶结物并导致裂缝界面处的剪切滑移增加,但需要在更大规模和更现实的裂缝条件下进行进一步研究。断口的 SEM 图像表明,暴露于酸性盐水后,铁白云石胶结晶体的面积损失(6.05±1.37% 至 3.78±0.73%),以及相应的孔隙率增加(24.6±1.1% 至 26.1±1.1) %)。这些结果表明,酸性盐水对白云石胶结物的溶解和弱化使裂缝表面的单个颗粒自由移动,从而导致地球化学诱导的应力释放。地质固碳产生的酸性盐水可以溶解砂岩胶结物并导致裂缝界面处的剪切滑移增加,但需要在更大规模和更现实的裂缝条件下进行进一步研究。这些结果表明,酸性盐水对白云石胶结物的溶解和弱化使裂缝表面的单个颗粒自由移动,从而导致地球化学诱导的应力释放。地质固碳产生的酸性盐水可以溶解砂岩胶结物并导致裂缝界面处的剪切滑移增加,但需要在更大规模和更现实的裂缝条件下进行进一步研究。这些结果表明,酸性盐水对白云石胶结物的溶解和弱化使裂缝表面的单个颗粒自由移动,从而导致地球化学诱导的应力释放。地质固碳产生的酸性盐水可以溶解砂岩胶结物并导致裂缝界面处的剪切滑移增加,但需要在更大规模和更现实的裂缝条件下进行进一步研究。

更新日期:2021-09-16
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