深层煤层气井下管柱腐蚀结垢原因分析及缓蚀阻垢剂应用  

Analysis on the causes of corrosion and scaling of downhole tubing in deep coalbed methane wells and the application of corrosion and scale inhibitor

作　　者：袁洋 王玉斌 刘印华 徐万勇 YUAN Yang;WANG Yubin;LIU Yinhua;XU Wanyong(Engineering Technology Research Institute,PetroChina Coalbed Methane Company Limited,Xi’an 710082,China;China United Coalbed Methane National Engineering Research Center,Beijing 100089,China)

机构地区：[1]中石油煤层气有限责任公司工程技术研究院,西安710082 [2]中联煤层气国家工程研究中心有限责任公司,北京100089

出　　处：《中国科技论文》2024年第4期506-512,共7页China Sciencepaper

基　　金：中国石油股份公司前瞻性、基础性科技项目(2021DJ2304);中石油煤层气有限责任公司“研发一代”科技项目(2021-KJ-04)。

摘　　要：针对大宁-吉县区块深层煤层气井下管柱腐蚀结垢现象严重的问题,在采出气、采出水及腐蚀结垢产物组成测试的基础上,开展了腐蚀结垢原因分析,并优选出了一种复合缓蚀阻垢剂。结果表明:深层煤层气井采出水中Ca^(2+)质量浓度高(4069.88~56667.51 mg·L^(-1)),易与HCO_(3)^(-)生成CaCO_(3);气藏开发过程中,地层压力逐渐降低,导致生成CaCO_(3)时产生的CO_(2)不断从水中析出,促进CaCO_(3)生成;此外,随着地层压力的降低,井筒内采出水加速蒸发,促进可溶性盐析出。采出气中CO_(2)分压较高(0.16~0.99 MPa),导致井下管柱表面难以形成有效的FeCO_(3)腐蚀钝化膜;此外,垢层下的金属离子难以扩散,促使采出水中的Cl^(-)迁入垢层中以保持电荷平衡,造成管柱加速腐蚀。优选得到的复合缓蚀阻垢剂效果良好,在70℃条件下,质量浓度为300 mg·L^(-1)时,阻垢率为91.39%,静态腐蚀速率为0.058 mm·a^(-1),动态缓蚀率>90%。应用井注入复合缓蚀阻垢剂后,采出水无明显结垢现象且Fe^(3+)质量浓度由281.93~378.60 mg·L^(-1)降至33.90 mg·L^(-1),检泵周期由139 d延长至327 d。In view of the serious problem of corrosion and scaling of downhole tubing in deep coalbed methane wells in the Daning-Jixian block,the cause analysis of corrosion and scaling were carried out based on the composition tests of produced gas,produced water,and corrosion and scale formation products.Morevoer,a composite corrosion and scale inhibitor was selected based on the corresponding mechanism astudy.The results show that the Ca^(2+)mass concentration in the produced water of deep coalbed methane wells is high(4069.88-56667.51 mg·L^(-1)),which favors the formation of CaCO_(3)with HCO_(3)^(-).In the process of gas reservoir devel⁃opment,the formation pressure gradually decreases,resulting in the continuous release of CO_(2)from the water during the generation of CaCO_(3),which promotes the generation of CaCO_(3).In addition,the reduced formation pressure leads to accelerated evaporation of the produced water in the wellbore,facilitating soluble salt extraction.The high partial pressure of CO_(2)in produced gas(0.16-0.99 MPa)makes it difficult to form effective FeCO_(3)corrosion passivation film on the surface of downhole tubing.In addition,the diffusion of metal ions under the scale layer is difficult,promoting Cl^(-)in the produced water to migrate into the scale layer to maintain charge bal⁃ance and resulting in accelerated corrosion of downhole tubing.The selected composite corrosion and scale inhibitor exhibits high perfor⁃mance.Under the condition of 70℃,when the mass concentration is 300 mg·L^(-1),the scale inhibition rate is 91.39%,the static corro⁃sion rate is 0.058 mm·a^(-1),and the dynamic corrosion inhibition rate is greater than 90%.After injecting the composite corrosion and scale inhibitor,no obvious scaling phenomenon is observed in the produced water of the test well,and the Fe^(3+)mass concentration decreases from 281.93-378.60 mg·L^(-1)to 33.90 mg·L^(-1).The pump inspection cycle is extended from 139 d to 327 d.

关 键 词：深层煤层气 鄂尔多斯盆地东缘 腐蚀结垢 缓蚀阻垢剂 

分 类 号：TE358[石油与天然气工程—油气田开发工程]