天然气水合物降压开采过程井周水合物的二次形成  

Secondary hydrate formation in gas hydrate production by depressurization

作　　者：马超 秦绪文 孙金声 余路 李胜利[4] 王金堂 毛文静 边航 陆程 MA Chao;QIN Xuwen;SUN Jinsheng;YU Lu;LI Shengli;WANG Jintang;MAO Wenjing;BIAN Hang;LU Cheng(Southern Marine Science and Engineering Guangdong Laboratory(Guangzhou),Guangzhou 511458,China;National Engineering Research Center for Gas Hydrate Exploration and Development,Guangzhou Marine Geological Survey,Guangzhou 511458,China;School of Petroleum Engineering in China University of Petroleum(East China),Qingdao 266580,China;College of Construction Engineering,Jilin University,Changchun 130061,China;School of Energy Resources in China University of Geosciences(Beijing),Beijing 100083,China;Oil and Gas Resources Survey,China Geological Survey,Beijing 100083,China)

机构地区：[1]南方海洋科学与工程广东省实验室(广州),广东广州511458 [2]广州海洋地质调查局天然气水合物勘查开发国家工程研究中心,广东广州511458 [3]中国石油大学(华东)石油工程学院,山东青岛266580 [4]吉林大学建设工程学院,吉林长春130061 [5]中国地质大学(北京)能源学院,北京100083 [6]中国地质调查局油气资源调查中心,北京100083

出　　处：《中国石油大学学报（自然科学版）》2022年第6期21-30,共10页Journal of China University of Petroleum(Edition of Natural Science)

基　　金：国家自然科学基金重大项目(51991365);南方海洋科学与工程广东省实验室(广州)人才团队引进重大专项(GML2019ZD0105);广东省海洋经济发展(海洋六大产业)专项(粤自然资合[2021]56号);地质调查项目(DD20211350);冷泉系统研究装置前期研究项目。

摘　　要：采用降压法开采天然气水合物,受分解吸热效应影响,地层温度降低区域的范围不断扩大。同时,生产井周水合物分解区受气体节流膨胀效应影响,温度降低现象更加显著,在一定的温、压条件下会出现水合物或冰形成,导致该区域内储层有效渗流通道被堵塞,渗流阻力升高,影响水合物分解气体的产出。通过自主研发的水合物分解区逆相变形成演化试验装置,模拟不同生产压差下水合物分解产出气体从分解前缘渗流至生产井筒这一过程,采集和计算试验过程中的储层温度、压力、饱和度等参数变化,探究分解区内影响冰与水合物二次形成的主控因素。结果表明:水合物分解气体在较大生产压差作用下受气体节流膨胀效应影响,会在生产井周5 m内引起温度下降,导致水合物二次形成;压差越大水合物二次形成的范围越向井壁缩小,且温度易降至0℃,形成冰堵,抑制气体产出;小压差情况下分解气供给小,造成分解前缘前部水合物二次形成区域范围大,但水合物二次形成量小;低渗透水合物储层气体流速低,气体节流膨胀效应减弱,水合物二次形成带窄。Due to the effect of dissociation and endothermic effect,the area of hydrate reservoir temperature reduction is expanded continuously when gas hydrate is extracted by depressurization production.Meanwhile,the gas hydrate dissociation zone around the production well is influenced by the gas throttling expansion effect,and the temperature decrease phenomenon is more significant.Under certain temperature and pressure conditions,the formation of secondary hydrate or ice will occur,which leads to the blockage of effective seepage channels in the reservoir and the increase of seepage resistance.This would affect the production of gas hydrate dissociation.Through the self-developed experimental device for the formation and evolution of reverse phase transition in the hydrate dissociation zone,the process of gas produced by hydrate decomposition from the dissociation front to the production wellbore under different production pressure differences was simulated.The changes of reservoir temperature,pressure,saturation and other parameters during the experiment were collected and calculated.The main controlling factors affecting the secondary formation of ice and hydrate in the decomposition zone were investigated.The results show that under the action of large production pressure difference,the gas hydrate dissociation gas is affected by gas throttling expansion effect,which will cause temperature drop within 5 m around the production well,resulting in the formation of secondary hydrate.The greater the pressure difference,the smaller the scope of the secondary formation of hydrate,and the temperature is easy to drop to 0℃,forming ice block and inhibiting gas production.Under the condition of small pressure difference,the gas supply from hydrate dissociation is small,resulting in a large area of hydrate secondary formation in the front of the dissociation front,but the amount of hydrate secondary formation is small.The gas flow rate of low permeability hydrate reservoir is low,the gas throttling expansion effect is weaken

关 键 词：降压开采 试验模拟 水合物分解 水合物二次形成 节流膨胀 

分 类 号：TE357[石油与天然气工程—油气田开发工程]