摘要
煤层气开采过程中,经常出现井壁坍塌、渗透率降低等问题。超临界二氧化碳(SC-CO_(2))钻井技术的提出为煤层气钻井提供了新的技术支撑,但较高的破煤门限压力和高能耗,仍是限制SC-CO_(2)推广应用的关键。射流形式是影响射流能量转化效率的重要因素之一,目前SC-CO_(2)射流的相关研究均基于连续射流。相较于连续射流,脉冲射流冲击压力大、具有更高的破煤岩效率,其中自激振荡脉冲射流是与工程相结合的最现实的一种脉冲射流形式。目前关于自激振荡脉冲射流的研究多是基于水射流开展的,但由于SC-CO_(2)与水的流体性质存在较大差异,自激振荡脉冲水射流喷嘴的相关结构参数是否适用于SC-CO_(2)尚未可知,仍需进一步开展相关研究。因此,为进一步提升SC-CO_(2)的破煤效率,提出自激振荡脉冲SC-CO_(2)射流。在传统Helmholtz共振腔的基础上,结合可压缩流体理论,明确了SC-CO_(2)的自激振荡脉冲发生机制,确定了适用于SC-CO_(2)的自激振荡喷嘴结构;通过大涡模拟分析了SC-CO_(2)的自激振荡发生过程,并开展了SC-CO_(2)连续射流与脉冲射流破煤对比实验,验证了自激振荡脉冲SC-CO_(2)射流的破煤效率。结果表明:SC-CO_(2)射流的自激振荡脉冲机理与水射流的自激振荡脉冲机理存在本质上的差异;SC-CO_(2)湍流的脉动主要由涡模态、声模态和熵模态组成,其运动中的剪切过程决定了涡结构的形成与放大,是形成自激振荡扰动的根本,膨胀压缩过程和热力学过程决定了扰动的反馈以及扰动频率,是完成自激振荡的关键。并且涡模态、声模态和熵模态之间相互耦合,共同作用;发现自激振荡脉冲SC-CO_(2)射流喷嘴的设计关键是找到合适的振荡腔结构;自激振荡脉冲SC-CO_(2)射流相较于连续射流而言,射流能量转化率更高,冲蚀破坏效果更好。综上所述,该研究创新性提出了自激振荡脉冲SC-CO_(2)射流,
Problems such as collapsed well walls and reduced permeability often occur during the extraction of coalbed methane.The proposed supercritical carbon dioxide(SC-CO_(2))drilling technology provides a new technical support for coal bed methane drilling.However,the high coal breakage threshold pressure and the high energy consumption are still the keys to limiting the application of SC-CO_(2).The form of the jet is one of the most important factors affecting the energy conversion efficiency of the jet,and the current studies on SC-CO_(2)jet are based on a continuous jet.The pulsed jet has higher impact pressure and higher rock breakage efficiency than a continuous jet.Among them,the self-excited oscillation pulsed jet is the most realistic form of pulsed jet combined with engineering.Current research on the self-excited oscillation pulsed jet is mostly based on water jets.However,as the fluid properties of SC-CO_(2)and water are very different,the applicability of the structural parameters of the self-excited oscillation pulsed water jet nozzle to SC-CO_(2)is not yet known,and a further research is needed.Therefore,to further enhance the coal breakage efficiency of SC-CO_(2),a self-excited oscillation pulsed SC-CO_(2)jet was proposed in this paper.On the basis of the conventional Helmholtz resonance cavity,the self-excited oscillation pulsed generation mechanism of SC-CO_(2)was clarified in conjunction with compressible fluid theory,and the self-excited oscillation nozzle structure applicable to SC-CO_(2)was determined.The process of self-excited oscillation of SC-CO_(2)was analyzed by large eddy simulation,and a comparison experiment of coal breakage between continuous and pulsed SC-CO_(2)jets was carried out.The coal breakage efficiency of the self-excited oscillation pulsed SC-CO_(2)jet was also verified.The results show that the self-excited oscillation pulsed mechanism of the SC-CO_(2)jet is fundamentally different from that of the water jet.The pulsation of SC-CO_(2)turbulence consists mainly of vortex,acousti
作者
刘勇
崔家玮
魏建平
张宏图
徐向宇
LIU Yong;CUI Jiawei;WEI Jianping;ZHANG Hongtu;XU Xiangyu(State Key Laboratory Cultivation Base for Gas Geology and Gas Control,Henan Polytechnic University,Jiaozuo 454000,China;State Collaborative Innovation Center of Coal Work Safety and Clean-efficiency Utilization,Jiaozuo 454000,China)
出处
《煤炭学报》
EI
CAS
CSCD
北大核心
2022年第7期2643-2655,共13页
Journal of China Coal Society
基金
国家自然科学基金资助项目(52174170)
中原千人-中原领军人才资助项目(ZYQR201912036)
河南省高校科技创新人才资助项目(21HASTIT009)。
关键词
煤层气钻井
破煤效率
超临界二氧化碳
自激振荡
脉冲射流
大涡模拟
coalbed methane drilling
coal breakage efficiency
supercritical carbon dioxide
self-excited oscillation
pulse jet
large eddy simulation
