围压对超临界二氧化碳射流冲击力与冲蚀射孔的影响  

Effects of ambient pressure on the impinging pressure and rock erosion performance of supercritical CO_2 jet

作　　者：贺振国[1,2] 李根生[1] 石李保[2] 王海柱[1] 沈忠厚[1] 王友文[1] 

机构地区：[1]中国石油大学(北京)油气资源与探测国家重点实验室,北京102249 [2]中国石油勘探开发研究院,北京100083

出　　处：《振动与冲击》2017年第2期65-71,116,共8页Journal of Vibration and Shock

基　　金：国家重点基础研究发展计划(973计划)项目(2014CB239203);国家自然科学基金国际合作项目(51210006);国家自然科学基金青年基金项目(51304226);国家自然科学基金石油化工联合基金重点基金项目(U1562212)

摘　　要：与水射流相比,超临界二氧化碳射流破岩具有所需能量少、效率高,以及不产生储层渗透性伤害等优点。将其应用于非常规油气资源的径向井钻井与喷射压裂作业中已引起广泛关注。井底压力环境对水力能量具有严重影响,而超临界二氧化碳流体性质易随环境压力改变而显著变化,是否具有良好射流作业效率仍亟待研究。通过数值模拟与室内测试实验方法,研究了模拟围压对流场速度分布、射流冲击力以及冲蚀破岩效率的影响。结果表明:喷射压力恒定时,射流冲击力和射孔深度均随围压增大而显著减小,二氧化碳临界压力处变化明显;喷射压差恒定时,随着围压的增大,射流冲击力几乎不发生变化,而射孔深度先较稳定或轻微增长然后明显减小,在临界压力时达到最大。分析认为,围压升高引起喷嘴外流场二氧化碳由气态相变为超临界态,射流形式由非淹没射流转变为淹没射流,是超临界二氧化碳射流与水射流冲蚀射孔规律显著不同的主要原因。Compared to water jet, supercritical carbon dioxide (CO2) jet can break rocks more efficiently at lower pressure, without causing permeability damage on reservoir. Its potential applications in radial drilling and well stimulation for unconventional resources have been attracted much attention. The unique properties of supercritical CO2fluid as well as the jet impingement and rock-breaking performance can be affected by ambient pressure, especially under complex bottom-hole conditions. Corresponding numerical simulations and lab experiments were carried out. The results show that, at constant inlet jet pressure, the jet impinging pressure and depth of eroded hole both decrease notably with the increase of ambient pressure. Under constant pressure difference, as the ambient pressure increases, the jet impinging pressure almost keeps no change, while the eroded depth increases slightly, then tends to decrease at a moderate rate and is bounded by the critical pressure of CO2. The different rock-breaking performance against water jet is attributed to the unique fluid properties of supercritical CO2. Increased ambient pressure makes CO2change from gaseous to supercritical phase, and causes a non-submerged supercritical CO2jet to a submerged one. © 2017, Editorial Office of Journal of Vibration and Shock. All right reserved.

关 键 词：超临界二氧化碳 围压 射流冲击力 冲蚀射孔 非淹没射流 

分 类 号：TE248[石油与天然气工程—油气井工程]