摘要
急剧冷却作用下花岗岩物理力学及渗透性的研究,对深入认识干热岩开发中储层的改造及演化具有重要意义。以20℃~600℃急剧冷却处理后花岗岩为研究对象,开展不同温度急剧冷却后物理力学性质的测试,采用压力脉冲衰减法测试圆柱体试样的渗透率。得到以下结论:(1)随着经历温度的升高,急剧冷却后试样的密度、纵波速度、抗压强度、弹性模量及抗拉强度均单调下降,渗透率先缓慢后急剧增加。这是由于缓慢升温及保温阶段,花岗岩由于矿物颗粒的热膨胀不匹配和热膨胀各向异性,产生热破裂;急剧冷却时,沿试件径向产生的温度梯度应力诱发了更多的裂纹,最终导致花岗岩物理力学性质的劣化及渗透性的增强。(2)急剧冷却条件下,花岗岩的脆延性转化温度为500℃~600℃,低于此温度,花岗岩主要表现为脆性破坏;高于此温度,花岗岩向延性转化。(3)自由状态缓慢升温急剧冷却条件下,花岗岩渗透率变化的阈值温度为400℃。(4)基于弹性模量的损伤因子能较准确地反应花岗岩力学性质的劣化,而基于纵波速度的损伤因子会夸大力学性质的劣化程度。
The study on physico-mechanical and transport properties of granite under the rapid cooling is of great significance for understanding the variation of reservoirs of hot dry rock. The rapid cooled granite from 20 ℃ to 600 ℃ was tested to investigate the physico-mechanical properties of the samples rapid cooled from different temperatures. The permeability of the cylindrical samples was measured with the pressure pulse decay method. With the temperature increasing,the density,longitudinal wave velocity,compressive strength,elastic modulus and tensile strength of the rapid cooled samples decrease monotonously,and the permeability increases initially slowly and then sharply. This is because that the inhomogeneous and anisotropic thermal expansion of the mineral grains leads to the thermal cracking of the granite at the slow heating and heat preservation stage. Upon the rapid cooling,the temperature gradients generate the stress along the radial direction of sample and induces more cracks,which ultimately leads to the deterioration of the physic-mechanical properties and the enhancement of permeability. Under the rapid cooling,the brittle-ductile transition temperature of granite is between 500 ℃ and 600 ℃,below and above which the granite exhibits mainly the brittle failure and the ductile failure respectively. Under slow heating,rapid cooling and unconfined condition,the threshold temperature for the variation of permeability of granite is 400 ℃. The damage factor based on the elastic modulus reflect accurately the deterioration of the mechanical properties of granite,while the damage factor based on the longitudinal wave velocity overestimates it.
作者
靳佩桦
胡耀青
邵继喜
赵国凯
朱小舟
李春
JIN Peihua;HU Yaoqing;SHAO Jixi;ZHAO Guokai;ZHU Xiaozhou;LI Chun(Institute of Mining Technology,Taiyuan University of Technology,Taiyuan,Shanxi 030024,China;Key Laboratory of ln-situ Property-improvingMiningofMinistryofEducation,Taiyuan University of Technology,Taiyuan,Shanxi030024,China)
出处
《岩石力学与工程学报》
EI
CAS
CSCD
北大核心
2018年第11期2556-2564,共9页
Chinese Journal of Rock Mechanics and Engineering
基金
国家自然科学基金资助项目(51574173)
山西省研究生教育创新计划资助项目(2016BY046)~~
关键词
岩石力学
急剧冷却
热开裂
力学性质
渗透率
rock mechanics
rapid cooling
thermal cracking
mechanical property
permeability
