超临界CO_(2)注入煤层对顶板岩石纵波速度及力学响应特征研究  

Study on P-wave velocity and mechanical response characteristic of rock in coal seam roof with supercritical CO_(2) injection

作　　者：陈晨[1] 何邢益 牛庆合 于洪旭 解翔宇 CHEN Chen;HE Xingyi;NIU Qinghe;YU Hongxu;XIE Xiangyu(Key Laboratory of Roads and Railway Engineering Safety Control,Ministry of Education,Shijiazhuang Tiedao University,Shijiazhuang 050043,China;Hebei Province Technical Innovation Center of Safe and Effective Mining of Metal Mines,Shijiazhuang 050043,China)

机构地区：[1]石家庄铁道大学道路与铁道工程安全保障省部共建教育部重点实验室,河北石家庄050043 [2]河北省金属矿山安全高效开采技术创新中心,河北石家庄050043

出　　处：《煤田地质与勘探》2021年第5期98-104,共7页Coal Geology & Exploration

基　　金：国家自然科学基金项目(U1967208);河北省高等学校科学技术研究项目(QN2021129);石家庄铁道大学大学生创新创业训练计划项目(S202010107082)。

摘　　要：深部煤层CO_(2)地质封存与CH4强化开采(CO_(2)–ECBM)技术在提高煤层气采收率的同时可实现碳减排,具有能源和环境双重效益。超临界CO_(2)(ScCO_(2))、水和煤层顶板之间的地球化学反应可改变其物理力学性质,增加CO_(2)泄漏的风险。以沁水盆地胡底煤矿3号煤层顶板岩石为研究对象,开展"ScCO_(2)–水–岩"地球化学反应模拟实验,探讨CO_(2)煤层封存条件下ScCO_(2)–水–顶板岩样地球化学反应过程及其对岩石纵波速度和力学性质的影响。结果表明:ScCO_(2)–水–岩之间化学溶蚀反应造成岩样Ca、Mg元素显著降低,促使岩样表面形成孤立状溶蚀孔,并随着反应时间的持续,进而形成大量的"溶蚀坑"和"溶蚀缝";增加了岩样结构不连续性,使得声波传播路径增大、能量损失加剧,导致纵波波速降低;ScCO_(2)–水–岩反应后岩样的峰值强度和弹性模量降低,泊松比升高,且三者之间的变化率与反应时间之间呈现Logistic函数的变化关系。对于胡底煤矿而言,ScCO_(2)–水–岩反应过程中顶板力学性质的弱化不足以造成盖层的破裂和CO_(2)泄漏,但在评价煤层CO_(2)封存安全性时,还应考虑煤层吸附膨胀应力对顶板的影响。Deep coal seam CO_(2) geological sequestration and enhanced CH_(4) recovery(CO_(2)-ECBM) can both increase CBM recovery and achieve carbon emission reduction,possessing dual benefits of energy and environment.The geochemical reactions between supercritical CO_(2)(ScCO_(2)),water and coal seam roof can change its physical-mechanical properties and increase the risk of CO_(2) leakage.In this paper,taking the roof rock of No.3 coal seam in Hudi Mine from Qinshui Basin as the research area,the ScCO_(2)-water-rock geochemical reaction simulation experiment was carried out to explore the geochemical reaction process of ScCO_(2)-water-roof under the condition of CO_(2) coal seam storage and its influence on P-wave velocity and mechanical properties of rock.Results show that the chemical dissolution reaction between ScCO_(2),water and rock results in the significant decrease of Ca and Mg elements in the rock samples,which promotes the formation of isolated dissolution pores.And extensive"corrosion pits"and"corrosion fractures"are developed as the reaction time goes on.ScCO_(2)-water-rock reaction raises the discontinuity of internal structure of rock samples,increases the propagation path and energy loss of acoustic wave,and reduces the P-wave velocity.After ScCO_(2)-water-rock reaction,the peak strength and elastic modulus of rock samples decrease,while the Poisson’s ratio increases.There is a logistic function relationship between peak strength change rate,elastic modulus change rate and Poisson’s ratio change rate with reaction time.For this study area,the change of roof mechanical properties in the process of ScCO_(2)-water-rock reaction is not enough to cause cap rock fractures and CO_(2) leakage,while the influence of adsorption swelling stress should also be emphasized when evaluating the security of CO_(2) geological storage in a coal seam.

关 键 词：CO_(2)地质封存 地球化学反应 纵波速度 力学性质 安全性 

分 类 号：P618.11[天文地球—矿床学]