摘要
超临界CO_2由于诸多的优良特性,在非常规天然气资源的开采上具有经济技术优势。为了定量研究CO_2与超临界CO_2对致密砂岩气储层裂隙结构与力学性质的影响,采用声发射与低场核磁共振技术研究了在CO_2与超临界CO_2作用下15 d砂岩的损伤行为。结果表明:CO_2组和超临界CO_2组单轴强度均降低,且超临界CO_2组降低明显。超临界CO_2组在弹性阶段就产生大量声发射信号;CO_2组与超临界CO_2组的累计声发射计数曲线上升点(裂隙闭合与裂隙发育分界点)均出现在更小的应变阶段;所有试件的声发射能量概率密度P(E)都较好地满足幂定律,CO_2与超临界CO_2浸泡并不改变砂岩声发射能量的尺度不变性。超临界CO_2组拥有更为倾斜的概率密度曲线,反映其小能量声发射信号所占比例增加;超临界CO_2组核磁T2波谱波形改变,其孔隙率与氢质子核磁信号均有明显增加。
Considering the excellent properties of supercritical CO2 has economic and technological advantages on the development of unconventional gas resources. This study aims to investigate the quantitative effects of CO2 and supercritical CO2 on the structure and mechanical properties of sandstone. Hence, acoustic emission（AE） and low-field nuclear magnetic resonance tests are carried out to analyse the damage of sandstone by soaking with CO2 and supercritical CO2 for 15 days. The results show that uniaxial strengths of samples under these two conditions decrease, and the results under supercritical CO2 soaking condition are even lower. In addition, samples subjected to supercritical CO2 soaking produce a large number of AE signals in the elastic stage. The growth points of accumulated AE curve（the cut-off between the crack closure and crack initiation） for all samples appeare in smaller strain stages. The AE energy probability densities P（E） of all samples satisfy the power law well, CO2 and supercritical CO2 soaking conditions do not change the scale invariance of AE energy for sandstone. The probability density curve is more inclined under the supercritical CO2 soaking condition, which reflects an increase in the proportion of small AE energy signals. The nuclear magnetic T2 waveforms of samples soaked with supercritical CO2 represent more developed porosity, internal microstructures and higher proton NMR signals.
作者
蒋翔
钱昆
王小书
高思娴
谢凯楠
姜德义
JIANG Xiang;QIAN Kun;WANG Xiao-shu;GAO Si-xian;XIE Kai-nan;JIANG De-yi(State Key Laboratory for the Coal Mine Disaster Dynamics and Controls, Chongqing University, Chongqing 400044, China;Department of Earth Sciences, University of Cambridge, Cambridge CB2 3EQ, United Kingdom)
出处
《岩土力学》
EI
CAS
CSCD
北大核心
2018年第4期1355-1361,共7页
Rock and Soil Mechanics
基金
国家自然科学基金(No.51304256
No.5154048)
中国博士后科学基金(No.2015T80857)~~
关键词
砂岩
超临界CO2
单轴压缩
声发射
核磁共振
sandstone
supercritical carbon dioxide
uniaxial compression
acoustic emission
nuclear magnetic resonance （NMR）
