长庆油田户外可更换深井阳极套管阴极保护试验

针对黄土高原地区单井或二口井井组的油水井套管外腐蚀问题,在长庆油田开展了户外深井可更换阳极的阴极保护试验。MMO阳极与硅铸铁复合运行的阴极保护系统运行电压≤16 V,在阳极井井深≥200 m下可实现MMO阳极更换,套管的保护深度达1400 m以上。该项技术为类似黄土高原地区已完井的单井或二口井井组的套管保护提供了经济适用的解决方案。     

Analysis of different factors affecting cathodic protection for deep well casings

This paper introduces a comparative theoretical investigation of the conventional cathodic protection (CP) and the pulse cathodic protection (PCP) systems to show how both of them behave under different operating conditions. The effectiveness of the PCP system is also highlighted for a typical large‐scale configuration as well as some field measurements have been carried out. The performance of PCP system has been analyzed in the light of getting better protection‐current distribution along the protected well casing at reduced anode current together with reducing the stray current (corrosion) at any nearby unprotected structure(s). Many factors have been investigated to show their effects on the performance of the CP system, namely, soil resistivity, voltage pulse waveform and frequency, and multi‐layer soil. In addition, the performance of both the conventional CP and the PCP systems has been compared to that when utilizing unused/abandoned well casing as anode energized by the conventional CP system. The PCP system shows better performance than that of the conventional CP, and a similar performance at high soil resistivity to that when using unused/abandoned well casing. On the other hand, the utilization of the unused/abandoned well casing gives superior performance, especially at low soil resistivities, where the protection‐current profiles of both the conventional CP and the PCP systems decay sharply.     

海上热采井套管热应力强度衰减与高温腐蚀叠加条件下的管材优选研究

目的探究不同材质套管在高温腐蚀环境下的适用性。方法采用高温高压釜,以渤海某稠油油田岩心、地层水样为腐蚀介质,对不同材质的套管进行模拟评价。结果利用气相色谱技术分析确定了该油田的腐蚀环境:CO2分压最高值为0.2 MPa,H2S分压最高值为0.0023 MPa。用最高的腐蚀气体分压进行了腐蚀模拟实验,测定出不同钢材在此腐蚀环境下的腐蚀速率,并建立了长期腐蚀速率预测模型,得到100H、80-1Cr、110-3Cr的长期腐蚀速率分别为0.24、0.20、0.05 mm/a。综合腐蚀实验结果和稠油热采套管强度衰减规律,对热采套管进行了强度设计,80-1Cr、100H、110-3Cr的安全寿命分别为3.8、6.5、11.2 a。结论高温会引起套管强度衰减,且腐蚀会导致套管径厚比变化,而多轮次注蒸汽会加速腐蚀进程,降低套管的使用寿命。研究结果对腐蚀环境中稠油热采套管的选材具有重大指导意义。     

套管磨损分析技术在油气井建井工程中的应用

套管磨损是一个系统性问题,科学地分析套管磨损原因是解决套管磨损问题的核心;当前的套管磨损分析技术可以科学有效地评估钻井过程中的套管磨损情况;油田应在钻井设计、钻井过程中应用套管磨损预测分析技术优化钻井方案,并在完钻后分析套管磨损状况,重新评估套管的剩余强度及管柱的安全性。介绍了CWEAR软件应用于酒东油田套管磨损情况的分析实例。     

Simulation and inversion of ultrasonic pitch-catch through-tubing well logging with an array of receivers

Current methods for ultrasonic pitch-catch well logging use two receivers to log the bonded material outside a single casing. For two casings separated by a fluid, we find by simulation that increasing the number of receivers provides a better picture of the effect of the bonded material outside the second casing. Inverting simulated measurements with five receivers, using a simulated annealing algorithm and a simple forward model, we find for a subset of simulations that we can estimate the impedance of the material outside the outer casing.     

油井套管井T阴极保护电位计算方法研究

提出了一种利用阴极保护地面测量参数和油井套管完井数据来计算油井套管井下阴极保护电位分布的新方法.将这种方法应用到美国得克萨斯A井的结果表明,计算值和实测值非常吻合,最大相对误差小于2%.     

Effects of SRB on cathodic protection of Q235 steel in soils

The effects of sulfate reducing bacteria (SRB) on cathodic protection (CP) of the Q235 steel in the soils have been studied by bacterial analyses, electrochemical impedance spectroscopy (EIS), scanning electron microscopy (SEM) and energy‐dispersive X‐ray analysis (EDX). The results showed that the pH value of the soil around the steel gradually increased, the number of SRB and the corrosion rate of the steel decreased, and the CP efficiency increased with the increasing of applied cathodic potential. At the cathodic polarization potential of ?1050 mV, SRB still survived in the soils. At the same potential, the CP efficiency in the soil without SRB was higher than that with SRB, and the corrosion rate of the steel in the soil with SRB was much higher than that without SRB. The cathodic current density applied for the steel in the soil with SRB was bigger than that without SRB at the same cathodic potential.     

经济型抗CO2、H2S腐蚀油套管的开发

简述了油井管在油田的CO2腐蚀原理和特点以及低Cr油套管的研制和开发过程。重点介绍了经济型抗CO2、H2S腐蚀大生产成品管的力学性能,抗CO2、H2S腐蚀开裂性能。运用SEM扫描电镜、X光电子能谱仪、X射线衍射仪、体视显微镜等设备分析了经济型钢管经CO2腐蚀后的表面腐蚀产物的组成以及抗CO2腐蚀的机理。     

脉冲电流阴极保护技术在油井套管上的应用

油井套管外腐蚀是套管失效的最主要形式,严重制约了油田的作业和开发。阴极保护技术已广泛应用于油井套管系统的防腐蚀保护。实践证明,该技术是目前使用最广泛、最有效的油井套管防腐蚀技术。然而,基于脉冲电流的阴极保护技术在油井套管中还没有相关应用。理论研究和模拟实验证明,脉冲电流阴极保护技术具有电流分布更均匀,总电流需求更低,保护深度更深,耗能更低等诸多优点。通过介绍脉冲电流阴极保护技术的历史、研究进展、应用条件等,对油井套管阴极保护技术进行了综述;探讨了油井套管脉冲电流阴极保护基本参数的影响规律;总结了对该技术保护效果的评价,并对其保护效果进行了展望。     

注水开发井套管的选择

分析了注水开发井套管损坏的特点;提出了解决注水开发井套管损坏的主要途径,即开发并合理选用高抗挤套管。选择高抗挤套管的具体方案是：对于2000m以内的浅井,既可以考虑在油层井段、注水裂缝地层段和油层以上的上覆岩层压力地层段使用抗挤油层套管,也可以考虑通井使用;对于3000～4500m的中深井,分为油层套管井段和各种岩层的封固段两种情况进行选择;对于5000-8000m的深井、超深井,分为油层套管井段、各种复杂地层的封固段、尾管段以及超深井多层套管柱4种情况进行选择。     

全井段套管磨损量预测与磨损后抗挤强度计算方法研究

在钻井过程中,由于钻具和套管相互摩擦,造成套管内壁磨损导致强度降低,直接影响后期安全作业。阐述了套管磨损的机理和影响因素,研究得出基于实钻井眼轨迹管柱摩阻扭矩分析的全井段套管磨损量预测方法。应用该方法对某井全井段套管可能产生的磨损量进行了预测。提出一种磨损后套管抗挤强度的计算方法。研究表明,运用该方法计算出的结果接近试验值,计算精度满足工程要求,可为磨损套管柱强度评估和后期作业强度设计提供理论依据。     

On‐site corrosion rate measurements: 3D simulation and representative values

The corrosion of reinforcement can be detected and its evolution quantified through the polarization resistance, R_p, which enables to calculate the instantaneous corrosion rate. In large structures, the determination of the R_p method uses a small counter electrode and the current applied attenuates with the distance, which makes unknown the area polarized. Two main solutions have been applied to overcome this limitation: to use a guard ring (GR) to confine the current to a prefixed area or to measure the bar length polarized by the current. In present work, a 3D numerical simulation is presented using the program COMSOL Multiphysics. Three cases are studied: no confinement, non‐modulated confinement, and modulated confinement of the current. In the results, it is illustrated that only when the GR is correctly modulated, the correct homogeneous distribution is achieved and the critical length is well confined in the area below the circle passing underneath the “confinement controller electrodes”. In a second part, the paper presented the manner to obtain an annual representative value of the corrosion rate through the integration of the instantaneous I_corr values.     

大庆油田油水井套管侧挂串状阳极防腐模拟实验研究

针对大庆油田油水井浅表层套管腐蚀外漏逐年加剧的问题,对于正常生产的油水井套管的防腐保护提出套管外壁侧埋深井牺牲阳极串的防腐蚀技术.通过室内模拟实验,发现在水电阻率和阴-阳极面积比近似相同的情况下,深埋阳极对套管的保护效果明显优于浅埋阳极,阳极以串、并联组合方式连接有较大的电流输出和较好的电位分布.结果表明,阳极以深埋方式为宜,阳极埋入深度在3000 cm～5000 cm左右为最佳位置,阴阳极间最佳距离为900 cm.     

油井套管脉冲电流阴极保护监控系统设计

目的设计油井套管脉冲电流阴极保护远程监控系统,确保脉冲电流阴极保护系统安全运行状态,实现集约化、数字化管理。方法基于二次逆变及GPRS无线通信技术,设计采用C8051F020单片机为控制核心的脉冲电源系统,并通过HAR306模块实现GPRS无线数据传输,结合远程监控中心对油井套管脉冲电流阴极保护过程进行实时监控。结果该系统具有投入成本低、组网方便、数据传输稳定可靠、人机界面友好、功能强大等优点,可以实现油井套管脉冲电流阴极保护的集约化、数字化、智能化管理。结论采用二次逆变方法设计油井套管脉冲电流阴极保护专用电源主电路,在此基础上应用GPRS技术设计脉冲电流阴极保护远程无线监控系统的方案是可行的。     

套管阴极保护的一种新计算方法及其应用

胜利油田调查表明,腐蚀导致大量油井套管损坏,于 是在一些油井上采用了阴极保护来防止套管腐蚀,但是面临着如何原位地评价井下阴极保护 水平的问题.用美国腐蚀工程师协会标准中的Schremp等人的方法对胜利油田南8-82井进行 计算的结果大部分偏离实测结果10%以上,最大误差接近20%.在本工作中,我们将已建立的 一种原位计算油井套管井下阴极保护电位分布的新方法应用到南8-82井上,所得计算结果与 实测结果的误差均小于6%,从而证实了这种方法的可行性.     

Effect of alternating current on cathodic protection on pipelines

In this work, the effects of alternating current (AC) on the performance of cathodic protection (CP) and the CP potential readings were investigated on a 16Mn pipeline steel in a simulated soil solution. The presence of AC interference decreases the CP effectiveness to protect the steel from corrosion. Only when CP potential is sufficiently negative, the steel is under a complete protection even when the AC current density is 400 A/m². Moreover, the AC would shift CP potential from the designed value. The effect of AC on the CP performance depends on the cathodic potential applied on the steel.     

超高强度抗挤套管的开发

中原油田东濮凹陷地区发育相当成熟的岩层要求套管单轴抗挤强度不低于103MPa,以抵御恶劣的地质条件。为了能和上下管柱设计使用的API标准规格的Φ177.8mm×10.36mm以及Φ177.8mm×11.51mm套管方便地连接,设计了非API标准规格的Φ180mm×11.51mm套管。采用纯净钢技术制造了这种规格的BG160TT超高强度抗挤套管。试制结果表明:该套管屈服强度不低于1210MPa,冲击功不小于110J,抗挤强度不低于110MPa。该超高强度抗挤套管已在中原油田东濮凹陷地区成功下井使用。     

套管穿越处的阴极保护

套管作为管道穿越处的保护管，在穿越时能对管道的防蚀层超到很好的保护作用。但在管道的运行过程中，由于套管的屏蔽作用，套管内的管段处于线路阴极保护系统的屏蔽区，随极保护电流不能对其起保护作用，使其成为线路防蚀的薄弱环节。针对这一情况，介绍了一种在套管内管段上补加特殊开头的牺牲阳极的方法，解决了这一特殊环境中的腐蚀问题。     

Effect of cathodic protection on macrocell currents: A viable method to monitor and control the efficiency of CP?

Corrosion protection of steel reinforcement in concrete structures by cathodic protection (CP) is a cost effective, reliable, and widely accepted method to stop and prevent the corrosion of the steel reinforcement. The efficiency of CP is usually monitored by the “24 h, 100 mV depolarization criterion,” a purely empirical criterion whose implementation is cost and labor intensive and that does not allow online control of CP. Within an extended research project on CP applied to concrete members of a highway bridge exposed to penetrating moisture, three sets of macrocells (MC), each composed of five MC sensors, were installed in conjunction with concrete resistance sensors and silver/silver chloride reference cells. Chloride profiles were determined from the cored or drilled powder originating from the installation of sensors and from drilling cores. Corrosion currents, steel potentials, and concrete resistance were monitored over a period of 1 year before, after installing the CP systems (which remained switched off for half a year for evaluating the effect of the conductive coating), and after start-up of the CP systems. The CP systems applied consist of a moisture resistant conductive coating. As expected CP has a pronounced effect on local MC currents: Anodic MC currents were reduced or changed into cathodic currents, whereas cathodic currents were only weakly influenced. By adjusting the applied protection current all anodic MC currents may be changed into cathodic MC currents. Results indicate that the 100 mV depolarization criterion is a conservative criterion in atmospherically exposed concrete; it is not reliable in strongly wetted concrete. There was no consistent correlation between the CP induced changes in the local MC currents and 24 h depolarization values indicating that large potential shifts induced by CP do not necessarily imply overprotection. Results show that monitoring MC currents before, during, and after CP operation allows to demonstrate in a transparent way the effect of CP on the corrosion of the steel reinforcement. Online monitoring of MC currents is proposed as a viable and comprehensible method to monitor and control the efficiency of CP.     

中原油田文10—1井套管腐蚀原因分析

通过现场检测和腐蚀产物Ｘ衍射分析，对文１０－１井套管的腐蚀原因进行了探讨，检测结果表明是以内壁腐蚀为主，套管上部腐蚀严重，下部腐蚀轻微，两者腐蚀产物中铁的硫化物不同，室内试验研究了温度对硫酸盐还原菌（ＳＲＢ）生长的影响，以及ＳＲＢ对套管钢的腐蚀作用，文１０－１井套管严重腐蚀部位的腐蚀产物为疏松的Ｆｅ９Ｓ８。而腐蚀轻微处主要是较致密的ＦｅＳ。