文中建立了一套酸性气田用内涂层油管耐腐蚀性能评价方法,此方法先考察了内涂层油管在氯离子、氢离子、凝析油、H2S/CO2等介质环境的耐渗透性能,再考察了内涂层油管在高温高压高酸性条件下的耐腐蚀性能,配套制定的相关指标,可用于指导内涂层油管应用.结果表明:酚醛环氧内涂层油管具有较好的耐渗透性能,酸性条件下并不改变涂层耐渗透性能;而随着温度的升高及硫化氢分压的升高,涂层失效由阴极剥离失效转变为鼓泡失效.

Due to complicated operating conditions and various corrosion environments, different forms of material failure may appear in service gas pipelines and other equipment, such as pipeline rupture, downhole tubing perforation and valve leakage.In order to solve these problems, the reasons of pipeline and equipment material failure were analyzed and the measures were proposed accordingly, which can provide technical support for corrosion control on the scene.This paper focuses on the evaluation methods on material failure in sour gas field, and researches the different typical cases of material failure on pipelines and equipment.In the end, the assessment technique of material failure of gas pipelines and irrelevant equipment is formed.

天然气中硫含量超过一定温度、压力条件下的溶解度会导致气井中发生硫沉积,当元素硫大量沉积时,会堵塞流体通道,导致关井停产以及采输系统的严重腐蚀.为此,采用电化学极化测试、电化学阻抗测试和失重腐蚀及应力腐蚀测试的组合体系,全面系统地开展了元素硫存在条件下碳钢的腐蚀性能试验,进而模拟了元素硫在现场可能出现的沉积方式,弄清了元素硫沉积量、沉积方式对碳钢腐蚀性能的影响及腐蚀垢物的组成.结果表明:①元素硫与试样的接触程度和堆积形式对碳钢的腐蚀行为有重要影响:②元素硫的存在促进了碳钢的阴极反应;③硫的加入会改变腐蚀产物膜的结构,降低膜的电阻,增大腐蚀速率.最后结合电化学及失重腐蚀测试结果,明确了碳钢在含氯化物湿硫化氢环境中的腐蚀机理,为元素硫沉积工况下的材质选择、缓蚀剂应用、腐蚀监测及控制提供了技术支撑.

The main reasons for corrosion failure of pipeline in sour gas field have been proposed based on the analysis techniques of Optical Microscopy (OM), Scanning Electron Microscope (SEM), Energy Dispersive Spectrometer (EDS) and X-ray Diffraction (XRD). The results show that the leakage happened caused by pit corrosion in the test samples. Pit corrosion occurs under the condition of wet H2S corrosion, while fouling and Cl-do promotion. Test pipe material properties meet the conditions requirements of China. According to the condition of pipeline corrosion, it is suggested that the raw gas should process gas-water separation before transportation, and the filter unit should be added to reduce the sand and gravel content.

The optical microscope was used to research microstructure of Titanium alloy and its welds , then corrosion weight loss method , NACE TM0177 A method (Standard Tensile Test) and standard Bent-Beam test method were used to research corrosion resistance perform-ance of electrochemistry and environmental cracking in high sour environment . The results showed that the microstructure of TA2 was singleαphase ,welds were big α+αphase or blockα+flaky α+αphase ,and microstructure of heat affected zone was tinier than welds .Titanium al-loy had good corrosion resistance in high sour environment .

In view of liquid deposit and corrosion in some gathering pipelines in the Longgang Sour Gasfield,OLGA software was used to simulate two typical low flowrate pipelines and 001-6# gas production pipeline under different flow conditions to analyze the flow pattern,liquid holdup and variation in shear stress between fluid and pipe wall along the pipeline and study how flow will influence fluid characteristic parameters in 001-6# gas production pipeline.The results show that the pressure drop and temperature drop of the two gas production pipelines simulated by OLGA software are consistent with the actual production data,which means that the result of simulation is reliable.In the downhill pipelines,liquid holdup is less than 0.05 and shear stress between fluid and pipe wall is less than 20 Pa,while in the uphill pipelines,liquid holdup is from 0.3 to 0.4 and the maximum shear stress between fluid and pipe wall is from 80 to 270 Pa,which indicates that liquid deposit and corrosion are especially serious in the uphill pipelines.Flow of gas has a great impact on the fluid characteristic parameters in Longgang 001-6# gas production pipeline with low flowrate,further reduction of gas flow will cause drastic increase in liquid holdup and shear stress between fluid and pipe wall,which then will aggravate liquid deposit and corrosion.When the gas flow increases to 97.5×104m3/d,the liquid holdup and shear stress between fluid and pipe wall are both very low,and the liquid deposit and corrosion will be relieved.

The elemental sulfur deposition often occurs in the exploitation of high sour gas field.The presence of elemental sulfur has been long known to corrode carbon steel extremely and may block the gathering lines.It will influence the normal production of gas fields.This paper introduces the source and damage of elemental sulfur(S) in sour gas field.Based on this information the corrosion evaluation method is stated in detail,while the application range of each corrosion evaluation method and their characteristics are analyzed,as well as the mechanism of elemental sulfur corrosion.In the end,the detailed understandings and suggestions according to the current situation in China are proposed.

在高酸性气田的开发过程中,由于H2S、CO2、Cl-以及元素硫等介质的存在,对井下管柱、地面管线和设备的腐蚀有很大的影响,如何了解和控制高酸性环境下的腐蚀就显得尤为重要.针对川东北地区飞仙关组鲕滩气藏高舍H2S和CO2的特殊情况,研制出高酸性气田在线腐蚀试验装置,并利用该装置在天东5-1井进行现场试验.现场试验进一步证实了水中Cl-是影响腐蚀的主要因素,评价了目前常用/拟采用材料的腐蚀情况、缓蚀剂的防护效果以及不同腐蚀监测方法的适应性.现场试验结果为川东北高酸性气田防腐措施的制定提供了现场试验数据,具有重要的意义.

With high temperature and pressure condensate autoclave simulating,the wet gas pipeline environment,the influences of the temperature of wet gas and the state of thin liquid film on CO2 corrosion of X65 pipeline steel were studied.The corrosion rate increased with the temperature increment of wet gas.The temperature of wet gas and environment out of pipe affected the thickness of the condensate film,the condensation rate,and the film temperature.When the temperature of wet gas or condensate film is relatively low,the corrosion is mainly controlled by the electrochemical reaction with low corrosion rate.With the temperature increased,corrosion rate became higher due to increase of film thickness and condensation rate.However,when temperature of wet gas is higher or the liquid film is thicker,corrosion scale would deposit and protect the steel.

The corrosion behavior of L245NB steel in the presence of CO2 with various partial pressure and Cl with various concentrations was evaluated using indoor static coupon test in high-pressure autoclave and inductance-type spot-corrosion test.The protective action of CO2 corrosion inhibitor CT2-7 for the steel was examined.Results showed that the corrosion rate of the steel increased with increasing partial pressure of CO2 and concentration of Cl-in the aqueous solution.Besides,gas-phase pit occurred at a temperature of 40 ℃,Cl-concentration of over 5%,total pressure of 9.0 MPa,and CO2 partial pressure of over 1.0 MPa.

Elemental sulfur and produced water would deposit in the gathering lines of sour gas, and led to serious corrosion of the gathering lines. Based on these phenomena, research on the electrochemical corrosion of the gathering lines were carried out. The laboratory results showed that the corrosion rate of L245 metal was 0.0937mm/a when the elemental sulfur was suspended in the water. It increased to 23.068mm/a when L245 was immerged in the elemental sulfur, and the corrosion type was localized corrosion. The corrosion rate of L360 was 1.267 mm/a when the velocity was very low (for example, 0 m/s) in the field because produced water and elemental sulfur would deposit. The corrosion rate of L360 were 0.177 mm/a and 0.362 mm/a when the velocity of the sour gas was 2.25m/s and 4.0m/s respectively, which were much lower than the corrosion rate in the low velocity (such as 0). The corrosion rate of the materials would accelerate when Cl-content in the water increased. Deposition of elemental and produced water would have a great influence on the corrosion of the gathering lines based on the results. Therefore, inhibition methods should be considered.

在高酸性天然气的集输过程中,元素硫和凝析水/地层水很有可能沉积在集输管线的底部,导致管线的严重腐蚀.针对这种现象,开展了地面集输管线材料的电化学腐蚀研究.室内研究结果表明,当元素硫悬浮在试验介质中时,L245的腐蚀速率为0.0937 mm/a;而试验材料浸没在元素硫中时,L245的腐蚀速率为23.068 mm/a,且以局部腐蚀为主.在现场试验条件下,天然气流速为0 m/s时,会出现凝析水/模拟盐水以及元素硫的沉积,导致L360的腐蚀特别严重(1.267 mm/a),在较高的流速(2.25 m/s和4.0 m/s)下,随着流速的增大,L360的腐蚀速率有所上升(分别为0.177 mm/a和0.362 mm/a),但比流速为0时要小;增加水中Cl-含量会加剧材料的腐蚀.研究结果表明,元素硫和地层水/凝析水的沉积对管线腐蚀的影响特别大,应重视其防护方法.

Field and laboratory tests were carried out based on the corrosion problems of the sour gas fields. The results showed that the corrosion of the medium in the field was not serious at present, the corrosion rate of the materials were lower than 0.1mm/a, and the corrosion represented as pitting corrosion. The content of the Cl~- in the water had greater effects on the corrosion according to the laboratory tests. High Cl~- content ground water or elemental sulfur maybe appear during the course of production and their influences on the corrosion as well as inhibition methods should be considered.

Because of the high downhole pressure environment in the Chuandongbei gas field (8 to 17% [v/v] of hydrogen sulfide [H2S]content and 5 to 10% [v/v] of carbon dioxide[CO2])la study was made of the behavior of corrosion-influencing factors on AC80 steel used for downhole tubing. The results show that AC80 is corroded severely by the downhole environment, with a corrosion rate of 0.273 to 2.677 mm/y. The H2S and CO2 partial pressure, the Cl- content in the water, and the presence of sulfur are the main factors that affect the corrosion of the steel. The corrosion rate reaches its maximum when the temperature is 40 degrees C, but changes slightly when the temperature is 60 and 120 degrees C. The corrosion rate increases gradually with increasing Cl- content in the water, or from the partial pressure of H2S and CO2. The presence of elemental sulfur will accelerate the general and pitting corrosion of AC80 and the maximum pitting corrosion depth is 41.4 mm/y. The corrosion products are ferrous sulfide (FeS) and FeS0.9.

Given the high pressure and corrosion environment with 8%-16% of H2S content and 5%-10% of CO 2 content in the gathering line for a domestic gas field with high sulfur content, the possible corrosion factors are analyzed. And with static high temperature autoclave, the acting law of different corrosion factors, such as H 2S, CO 2, temperature, Cl, and elemental sulfur, etc, on the steel 20# is investigated. The results show the steel 20# is corroded severely in the experimental scope. The corrosion rate is at 0. 348 - 2. 559 mm/a. But the temperature, Cl content in water and elemental sulfur are the main factors of the steel 20# corrosion. The higher the Cl content is, the faster the corrosion rate is. The corrosion rate of the steel 20# is bigger relatively at 40 ̊C of temperature. The weight-loss corrosion and pitting corrosion will be speeded since the elemental sulfur existing. The maximum pitting corrosion depth is 4. 867 mm/a. Based on the in-house study, it is suggested the proper measures should be taken to remove the elemental sulfur deposited in the gathering line and keep out of temper ature about 40 ̊C for the pipeline operation to reduce the corrosion. Also, the corrosion control should be enhanced for the gathering line where the formation water with high Cl content converges.

讨论了一套适合于油气井的缓蚀剂评选程序,该程序遵循简便、快速、经济、可靠的原则,为现场筛选经济有效的缓蚀剂提供了一种方法.采用该程序筛选出的缓蚀剂在大港千米桥气田现场防腐试验中进行了验证.结果表明,室内筛选的缓蚀剂在现场得到成功应用,说明制订的缓蚀剂评选程序是合理、有效的.

根据在测定酸化废水COD值重复再现性几率较小,跳跃幅度较大的特点,通过大量的实验研究,探讨了油田酸化废水COD测定中的4个影响因素及消除办法.实验结果表明,Cl-含量对COD值的影响最大,其次为石油类含量,而加热回流时间和悬浮物含量对测定结果的影响不大.这些影响因素不仅存在于油田废水的COD测定中,而且在其它类型的废水处理中也存在类似的问题,此方法亦可作为借鉴.

本文介绍了CT2-15缓蚀剂在四川气田、大港油田的应用情况.结果表明:CT2-15缓蚀剂具有优良的气相和液相综合防腐效果,其气、液两相缓蚀率均大于90%,可将现场的腐蚀速率控制在0.125 mm/a以下,对抑制油套管的局部腐蚀具有突出的效果.适用于以H2S为主的腐蚀环境及H2S和CO2的混合腐蚀环境的腐蚀防护,同时对于以CO2为主的腐蚀环境和高温(＜160 ℃ )油气井也具有一定的缓蚀作用,使用方便,技术经济合理.