Safety impact analysis of dynamic evolution of gas compositions on heavy-oil thermal recovery wells with nitrogen injection

doi:10.3969/j.issn.1006-6535.2026.04.008

Abstract

Abstract: During heavy-oil development operations with nitrogen injection,downhole explosion hazards may still exist during field operations even when the purity of injected nitrogen meets industry standards.With a typical field downhole explosion accident as the research object,this study systematically analyzed the dynamic evolution mechanism of explosion-inducing factors in nitrogen-injection thermal-recovery wellbores from four dimensions:crude-oil properties,combustible formation,oxidant conditions,and ignition sources.The results show that hydrocarbon components in formation crude oil undergo cracking and volatilization reactions in high-temperature,high-pressure wellbore environments,continuously generating combustible hydrocarbon gases such as methane.Dissolution and dissipation of nitrogen in the wellbore lead to imbalance in gas composition,causing the oxygen volume fraction in the system to gradually increase.The mixed-gas parameters enter the methane explosion-limit range,ultimately forming a highly hazardous explosive gas mixture.During steam-injection operations,mechanical collision of the tubing string,string friction,and fluid electrostatic accumulation can all generate energetic ignition sources,satisfying all conditions required for an explosion.Field measured data and comparative tests from adjacent wells in the same horizon verified the dynamic evolution pattern of gas compositions in the wellbore and the formation mechanism of explosive gas mixtures,clarifying the root cause of downhole explosion accidents.Based on the explosion-triangle theory,a risk prevention and control system for heavy-oil development with nitrogen injection was constructed,providing theoretical support for safety-risk identification and hazard prevention and control in heavy-oil nitrogen-injection thermal recovery.Targeted technical recommendations were also proposed for key links,including optimization of the nitrogen-injection process,real-time monitoring of wellbore gas,and source control of ignition sources,providing a scientific reference for field safety management.

Key words: safety risk, nitrogen-injection thermal recovery, wellbore explosion, dynamic evolution, heavy oil

CLC Number:

TE357

Zhang Ruyun, Zhang Laibin, Dong Shaohua. Safety impact analysis of dynamic evolution of gas compositions on heavy-oil thermal recovery wells with nitrogen injection[J]. Special Oil & Gas Reservoirs, 2026, 33(4): 59-65.

References

[1] 李睿姗,何建华,唐银明,等.稠油油藏氮气辅助蒸汽增产机理试验研究[J].石油天然气学报,2006,28(1):72-75.
Li Ruishan,He Jianhua,Tang Yinming,et al.Experiment on the mechanism of nitrogen-assisted steam stimulation in heavy oil reservoirs[J].Journal of Oil and Gas Technology,2006,28(1):72-75.
[2] 张学萍.热氮气辅助蒸汽热采机理研究[D].山东:中国石油大学(华东),2019:8-10.
Zhang Xueping.Study on thermal recovery mechanism of thermal nitrogen assisted steam[D].Qingdao:China University of Petroleum(East China),2019:8-10.
[3] 孙德浩.油井注氮气增产技术的研究与应用[J].断块油气田,2003,10(5):61-62.
Sun Dehao.Study and application of injection nitrogen into wells for increasing oil production technology[J].Fault-Block Oil & Gas Field,2003,10(5):61-62.
[4] 章启成,张跃林.一起注氮施工时发生的油管爆炸事故[J].工业安全与环保,1991,21(6):30-31.
Zhang Qicheng,Zhang Yuelin.A tubing explosion accident during nitrogen injection operations[J].Industrial Safety and Environmental Protection,1991,21(6):30-31.
[5] 肖丰浦,董海,王鑫,等.注氮辅助蒸汽吞吐工艺过程井筒爆炸事故分析方法[J].安全与环境学报,2021,21(5):1985-1991.
Xiao Fengpu,Dong Hai,Wang Xin,et al.Analysis method of explosion accident in the wellbore during nitrogen injection assisted steam stimulation process[J].Journal of Safety and Environment,2021,21(5):1985-1991.
[6] 刘慧卿,东晓虎.稠油热复合开发提高采收率技术现状与趋势[J].石油科学通报,2022,7(2):174-184.
Liu Huiqing,Dong Xiaohu.Current status and future trends of hybrid thermal EOR processes in heavy oil reservoirs[J].Petroleum Science Bulletin,2022,7(2):174-184.
[7] 孙焕泉,刘慧卿,王海涛,等.中国稠油热采开发技术与发展方向[J].石油学报,2022,43(11):1664-1674.
Sun Huanquan,Liu Huiqing,Wang Haitao,et al.Development technology and direction of thermal recovery of heavy oil in China[J].Acta Petrolei Sinica,2022,43(11):1664-1674.
[8] 蒋琪,游红娟,潘竟军,等.稠油开采技术现状与发展方向初步探讨[J].特种油气藏,2020,27(6):30-39.
Jiang Qi,You Hongjuan,Pan Jingjun,et al.Preliminary discussion on current status and development direction of heavy oil recovery technologies[J].Special Oil & Gas Reservoirs,2020,27(6):30-39.
[9] 方吉超,李晓琦,计秉玉,等.中国稠油蒸汽吞吐后提高采收率接替技术前景[J].断块油气田,2022,29(3):378-382.
Fang Jichao,Li Xiaoqi,Ji Bingyu,et al.Prospect of replacement technology for enhanced oil recovery after cyclic steam stimulation of heavy oil in China[J].Fault-Block Oil & Gas Field,2022,29(3):378-382.
[10] 王正茂,廖广志,蒲万芬,等.注空气开发中地层原油氧化反应特征[J].石油学报,2018,39(3):314-319.
Wang Zhengmao,Liao Guangzhi,Pu Wanfen,et al.Oxidation reaction features of formation crude oil in air injection development[J].Acta Petrolei Sinica,2018,39(3):314-319.
[11] 江丙友,张念超,张延水,等.爆炸三角形的原理及应用[J].能源技术与管理,2008,33(5):34-36.
Jiang Bingyou,Zhang Nianchao,Zhang Yanshui,et al.Principle and application of the explosion triangle[J].Energy Technology and Management,2008,33(5):34-36.
[12] 王学忠,王金铸,乔明全.水平井、氮气及降黏剂辅助蒸汽吞吐技术——以准噶尔盆地春风油田浅薄层超稠油为例[J].石油勘探与开发,2013,40(1):97-102.
Wang Xuezhong,Wang Jinzhu,Qiao Mingquan.Horizontal well,nitrogen and viscosity reducer assisted steam huff and puff technology:taking super heavy oil in shallow and thin beds,Chunfeng Oilfield,Junggar Basin,NW China,as an example[J].Petroleum Exploration and Development,2013,40(1):97-102.
[13] 刘尧文,刘建仪.氮气的溶解及抽提效应对原油性质的影响[J].西安石油大学学报(自然科学版),2004,19(5):28-30,55.
Liu Yaowen,Liu Jianyi.Effects of nitrogen dissolution and separating-out on the property of crude oil in nitrogen displacement[J].Journal of Xi'an Shiyou University(Natural Science Edition),2004,19(5):28-30,55.
[14] 万成略.焦炉煤气含氧量安全限值的分析[C]//2003中国钢铁年会论文集.北京:冶金工业出版社,2003:1139-1142.
Wan Chenglue.Analysis on threshold of oxygen concentration in coke oven gas[C]//CSM 2003 Annual Meeting Proceedings.Beijing:Metallurgical Industry Press,2003:1139-1142.
[15] 冯长根,卜晓颖,刘振翼,等.高温高压水蒸气射流静电场强度规律试验研究[J].安全与环境学报,2022,22(5):2395-2403.
Feng Changgen,Bu Xiaoying,Liu Zhenyi,et al.Experimental study on the law of electrostatic field strength of water vapor jet with high temperature and high pressure[J].Journal of Safety and Environment,2022,22(5):2395-2403.
[16] 何明俊,韩兆辉,吴秀敏.石油化工企业蒸汽静电危险分析[J].河北大学学报(自然科学版),2007,27(增刊):177-179.
He Mingjun,Han Zhaohui,Wu Xiumin.Analysis of the hazard of steam static in petrochemical enterprise[J].Journal of Hebei University(Natural Science Edition),2007,27(S):177-179.
[17] 薛海涛,卢双舫,付晓泰.甲烷、二氧化碳和氮气在油相中溶解度的预测模型[J].石油与天然气地质,2005,26(4):444-449.
Xue Haitao,Lu Shuangfang,Fu Xiaotai.Forecasting model of solubility of CH₄,CO₂ and N₂ in crude oil[J].Oil & Gas Geology,2005,26(4):444-449.
[18] 李继梅.低压环境下不同油体内氮气和氧气溶解度的实验研究[D].合肥:中国科学技术大学,2012:14-15.
Li Jimei.Experimental study on the solubility of nitrogen and oxygen in different oils under low-pressure conditions[D].Hefei:University of Science and Technology of China,2012:14-15.
[19] 于超.低渗透油藏减氧空气驱原油低温氧化机理研究[D].北京:中国石油大学(北京),2019:9-11.
Yu Chao.Low temperature oxidation of crude oil and characteristics of its components change in low permeability reservoir[D].Beijing:China University of Petroleum(Beijing),2019:9-11.
[20] 张莉,祝仰文,王友启.稠油热采新技术研究现状及展望[J].钻采工艺,2023,46(4):64-70.
Zhang Li,Zhu Yangwen,Wang Youqi.Research status and prospects of new technology of heavy oil thermal recovery[J].Drilling & Production Technology,2023,46(4):64-70.