冻融对煤体损伤及瓦斯放散影响实验研究
发布时间：2019-06-08 07:03
【摘要】：低温致裂技术是一种潜在改造煤储层,促进煤层气增产的有效方法。低温致裂技术通常是指在煤层中注入液氮、液态二氧化碳等低温介质改造煤储层,提高煤层渗透性。1998年Mc Daniel B W等人在美国肯塔基州采用液氮作为压裂液对4口煤层气井和1口致密砂岩气井进行了重复压裂施工,获得了良好的增产效果。目前国内外对于煤层低温致裂的研究集中于低温流体注入煤层气井后的地应力、温度场、裂隙分布等模拟研究,对煤体本身的冻融损伤破坏研究较少。对于冻融作用下的煤体破坏、孔隙结构、渗透性能的研究,还不尽完善。冻融损伤后与煤层气产出密切相关的煤体瓦斯放散特性还未有人开展相关的研究。针对上述问题,文本采用理论分析和实验相结合的方法测量了冻融损伤对煤体的孔隙结构、力学性能和瓦斯放散能力等煤体特性的影响。首先以低温致裂技术为研究背景,冻融损伤为研究切入点,笔者在查阅相关资料的基础上,分析了冻融作用下煤体损伤破坏机制,形成了煤体冻融破坏机理,以此来指导后续的研究内容和实验设计。同时限制了以下若干实验条件:含水量,煤体均为饱和试样;冻融温度,范围为-20℃-20℃。本文采用焦煤和贫煤两种煤体主要考察了冻融次数的影响。开展了冻融作用对煤体宏观破坏的研究。文中分析了不同冻融循环次数后的煤体表面破坏特征,采用单轴压缩和声发射技术测量了煤体抗压强度和声发射信号的形式特征。此外,我们通过室内超生波波速的测量计算,获得了不同冻融循环次数煤体的泊松比、杨氏模量等动力学参数变化。开展了冻融作用对煤体孔渗特性的研究。实验中主要采用核磁共振和扫描电镜技术对焦煤和贫煤两种煤体的孔渗特征开展了相关研究。主要测试了煤体总孔隙度、可动孔隙度(PP)、束缚孔隙度(IP)、渗透率、以及煤体内吸附孔和渗流孔的比例变化。这些测试有助于深入讨论冻融损伤对煤体微观结构的改变。最后,开展了冻融对煤体瓦斯放散特性影响的研究,分析了冻融前后煤体的瓦斯放散参数(放散量、放散速度、放散系数)的变化。结果表明煤体冻融损伤有助于简化煤的孔隙结构,减少扩散阻力,增扩煤体的渗流通道,减少渗流阻力,有利于瓦斯(煤层气)从煤层中运移出来。
[Abstract]:Low temperature fracturing technology is an effective method to potentially transform coal reservoir and promote coalbed methane production. Low temperature cracking technology usually refers to the injection of liquid nitrogen, liquid carbon dioxide and other low temperature media into coal seams to transform coal reservoirs. Improve the permeability of coal seam. In 1998, Mc Daniel B W et al used liquid nitrogen as fracturing fluid to repeatedly fracturing 4 coal seam gas wells and 1 tight sandstone gas well in Kentucky, USA, and achieved good results of increasing production. At present, the research on low temperature cracking of coal seam at home and abroad focuses on the simulation of ground stress, temperature field and fracture distribution after low temperature fluid injection into coal seam gas well, but the research on freeze-thaw damage and failure of coal body itself is less. The research on coal failure, pore structure and permeability under freeze-thaw is not perfect. The gas emission characteristics of coal body which are closely related to the production of coalbed methane after freeze-thaw damage have not been studied. In order to solve the above problems, the effects of freeze-thaw damage on the pore structure, mechanical properties and gas release capacity of coal are measured by means of theoretical analysis and experiment. First of all, taking the low temperature cracking technology as the research background and freeze-thaw damage as the starting point, the author analyzes the damage and failure mechanism of coal body under freeze-thaw action on the basis of consulting the relevant data, and forms the freeze-thaw failure mechanism of coal body. To guide the follow-up research content and experimental design. At the same time, the following experimental conditions are limited: water content, coal is saturated sample, freeze-thaw temperature, range of-20 鈩，
本文编号：2495094
[Abstract]:Low temperature fracturing technology is an effective method to potentially transform coal reservoir and promote coalbed methane production. Low temperature cracking technology usually refers to the injection of liquid nitrogen, liquid carbon dioxide and other low temperature media into coal seams to transform coal reservoirs. Improve the permeability of coal seam. In 1998, Mc Daniel B W et al used liquid nitrogen as fracturing fluid to repeatedly fracturing 4 coal seam gas wells and 1 tight sandstone gas well in Kentucky, USA, and achieved good results of increasing production. At present, the research on low temperature cracking of coal seam at home and abroad focuses on the simulation of ground stress, temperature field and fracture distribution after low temperature fluid injection into coal seam gas well, but the research on freeze-thaw damage and failure of coal body itself is less. The research on coal failure, pore structure and permeability under freeze-thaw is not perfect. The gas emission characteristics of coal body which are closely related to the production of coalbed methane after freeze-thaw damage have not been studied. In order to solve the above problems, the effects of freeze-thaw damage on the pore structure, mechanical properties and gas release capacity of coal are measured by means of theoretical analysis and experiment. First of all, taking the low temperature cracking technology as the research background and freeze-thaw damage as the starting point, the author analyzes the damage and failure mechanism of coal body under freeze-thaw action on the basis of consulting the relevant data, and forms the freeze-thaw failure mechanism of coal body. To guide the follow-up research content and experimental design. At the same time, the following experimental conditions are limited: water content, coal is saturated sample, freeze-thaw temperature, range of-20 鈩，
本文编号：2495094
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