基于高压微流控芯片的水合物相变与气泡演化研究  

AN INVESTIGATION ON CH4 HYDRATE TRANSITION AND GAS BUBBLE EVOLUTION ON A MICROFLUIDIC CHIP

作　　者：张吉东 殷振元 李清平 李淑霞[4] 焦红梅 刘晓惠 Zhang Jidong;Yin Zhenyuan;Li Qingping;Li Shuxia;Jiao Hongmei;Liu Xiaohui(National Key Laboratory of Marine Natural Gas Hydrates,Beijing 100028,China;Shenzhen International Graduate School,Tsinghua University,Shenzhen 518055,Guangdong,China;Huairou Laboratory,Beijing 101499,China;School of Petroleum Engineering,China University of Petroleum(East China),Qingdao 266580,Shandong,China)

机构地区：[1]海洋天然气水合物全国重点实验室,北京100028 [2]清华大学深圳国际研究生院,广东深圳518055 [3]北京怀柔实验室,北京101499 [4]中国石油大学(华东)石油工程学院,山东青岛266580

出　　处：《力学学报》2024年第6期1615-1623,共9页Chinese Journal of Theoretical and Applied Mechanics

基　　金：天然气水合物国家重点实验室开放基金(2022-FKJJ-SHW);国家自然科学基金(52306254);广东省珠江人才计划(2021QN02H836)资助项目。

摘　　要：天然气水合物因其巨大的资源量与高能量密度而被视为一种前景广阔的能源.理解孔隙尺度下天然气水合物生成与分解动力学及气-水-水合物三相分布对优化天然气水合物开采工艺至关重要.文章设计了一种新型的高压微流控可视化实验装置(最高耐压19.0 MPa),可实现孔隙尺度下气体水合物生成和分解相变的直接观测.首先,观测并分析了南海神狐海域温压条件下(压力15.5 MPa)甲烷水合物的成核与生长过程.通过图像识别算法分析了热激法下3种升温速率(0.5,2.0和8.0 K/h)对甲烷水合物分解动力学与气泡演化规律.实验结果表明,孔隙中存在两种不同的甲烷水合物生成机制:(1)甲烷气泡主导生成的气-水-水合物三相共存的疏松多孔型水合物;(2)水中溶解相甲烷主导生成的致密单晶型水合物.其中,单晶型水合物包裹在多孔型水合物周围并呈树突状生长,在接触甲烷气泡时会诱导多孔型水合物的快速成核与生长.水合物分解过程中,气-水-水合物三相共存的多孔型水合物优先分解,单晶型水合物相对稳定,其分解温度高于多孔型水合物约0.3 K.孔隙内水合物分解后产生明显的气泡聚集与融合现象,气泡平均直径为60~100μm.提高升温速率显著加快了水合物分解速率,更有利于气泡融合,造成较大气泡在孔隙内分布.本研究为甲烷水合物在孔隙尺度下生成、分解与微米级气泡演化提供直接实时观测证据,研究结果对深入理解水合物分解动力学与水合物沉积物两相渗流理论提供基础支撑.Methane hydrate(MH)have been considered the future energy source due to its vast resource volume and high energy density.Understanding the pore-scale MH formation and dissociation behavior and gas-liquid-MH distribution at pores,and its effect on gas-liquid flow is significant for designing effective production strategies and safe exploiting of MH reservoirs.In this study,we employed a novel microfluidic chip technology(Pmax=19.0 MPa)that is capable of directly observation of pore-scale MH formation and dissociation behavior.Firstly,we observed the MH nucleation and growth behaviors under same conditions with Shenhu Sea,South China Sea(P=15.5 MPa,T=276.2 K).In addition,the MH dissociation behavior and gas bubble evolution via thermal stimulation with three heating rates(0.5,2.0 and 8.0 K/h)were examined.Our experimental results reveal that two types MH formation mechanisms co-exist in pores:(a)porous-type MH with gas-liquid-hydrate co-exist formed from CH4 gas bubbles;and(b)crystal-type MH formed from dissolved CH4 gas.The crystal-type MH is wrapped around the porous-type MH with dendritic shape.The growth of crystal-type MH can trigger the nucleation of porous-type MH.In addition,the gas-liquid-hydrate coexistence of porous-type MH preferential dissociation under thermal stimulation.Crystal-type MH is relatively stable and its dissociation temperature is higher than that of porous-type MH about 0.3 K.MH dissociation in the pores produce obvious gas bubble aggregation and coalescence,and the average diameter of gas bubbles is 60~100μm.Increasing the heating rate significantly enhanced the MH dissociation rate,which was more favorable for gas bubble aggregation and coalescence,resulting in the distribution of larger gas bubbles within the pores.The results provide direct pore scale observation of MH formation and dissociation behavior,gas bubble evolution,which provide fundamental understanding of MH transition phase kinetic and gas-liquid seepage in natural gas hydrate-bearing sediments.

关 键 词：甲烷水合物 高压微流控 水合物形貌 气泡演化 相变动力学 多孔介质 

分 类 号：TE312[石油与天然气工程—油气田开发工程]