深水气井测试条件下井筒水合物生成及浅层水合物分解的环空保护液导热系数  

Influence of thermal conductivity of annular protective fluids on wellbore hydrate formation and hydrate decomposition in shallow formation during deep-water drilling and well testing

作　　者：步玉环 景韶瑞[1,2] 杨恒 郭胜来 柳华杰 刘合兴[3] BU Yuhuan;JING Shaorui;YANG Heng;GUO Shenglai;LIU Huajie;LIU Hexing(Key Laboratory of Unconventional Oil&Gas Development(China University of Petroleum(East China)),Ministry of Education,Qingdao 266580,China;School of Petroleum Engineering in China University of Petroleum(East China),Qingdao 266580,China;CNOOC China Limited,Zhanjiang Branch,Zhanjiang 524057,China)

机构地区：[1]非常规油气开发教育部重点实验室(中国石油大学(华东)),山东青岛266580 [2]中国石油大学(华东)石油工程学院,山东青岛266580 [3]中海石油(中国)有限公司湛江分公司,广东湛江524057

出　　处：《中国石油大学学报（自然科学版）》2023年第1期81-88,共8页Journal of China University of Petroleum(Edition of Natural Science)

基　　金：国家自然科学基金项目(51974355)。

摘　　要：针对南海海域可能钻遇浅层水合物,且在深水井测试过程中井筒生成天然气水合物造成井筒堵塞的难题,从环空保护液的角度出发,以南海某深水气井为例,采用数值模拟方法,研究深水气井测试时不同产量下不同环空保护液导热系数对井筒生成水合物和浅层水合物分解的影响。结果表明:环空保护液导热系数越低,井筒生成水合物的临界测试产量越低,当环空保护液导热系数低至0.10 W/(m·℃)时,可满足产量5×10^(4)m^(3)/d,井筒内不生成水合物;随着环空保护液导热系数降低,井筒外缘温度随之降低,浅层水合物越不容易发生分解;现场测试产量下的井口温度与模拟结果误差均小于5%,验证了计算模型的可行性。During deep-water drilling of hydrate bearing formations, natural gas hydrates in near wellbore formation can decompose, and in well testing or production of deep-water oil and gas reservoirs, hydrates can be formed in wellbore, causing blockage. Special annular protective fluids can be used to mitigate those problems.In this study, taking a deep-water gas well in the South China Sea as an example, a numerical simulation method was used to study the influence of the thermal conductivity of annular protective fluids on wellbore hydrate formation and shallow hydrate decomposition under different drilling and well test conditions. The simulation results indicate that the lower the thermal conductivity of the annular protective fluid, the lower the critical gas production rate for hydrate generation in wellbore. When the thermal conductivity of the annular protective fluid is as low as 0.10 W/(m·℃),the critical gas rate for no hydrate generation in wellbore can be reduced to 5×10^(4) m^(3)/d. Low thermal conductivity of the annular protective fluid is also beneficial to reduce heat transfer between wellbore and nearby rock formation, which can inhibit hydrate decomposition during drilling when drilling fluid with higher temperature is used. The accuracy of the simulation model has been verified by comparing the wellhead temperature measured during field gas production testing with the simulation results, with errors being less than 5%.

关 键 词：深水气井 环空保护液 井筒生成水合物 浅层水合物分解 

分 类 号：TE256[石油与天然气工程—油气井工程]