Stress corrosion cracking behavior of buried oil and gas pipeline steel under the coexistence of magnetic field and sulfate-reducing bacteria

Magnetic field and microorganisms are important factors influencing the stress corrosion cracking(SCC)of buried oil and gas pipelines. Once SCC occurs in buried pipelines, it will cause serious hazards to the soil environment. The SCC behavior of X80 pipeline steel under the magnetic field and sulfate-reducing bacteria(SRB) environment was investigated by immersion tests, electrochemical tests, and slow strain rate tensile(SSRT) tests. The results showed that the corrosion and SCC sensitivity of X80 steel decreased with increasing the magnetic field strength in the sterile environment. The SCC sensitivity was higher in the biotic environment inoculated with SRB, but it also decreased with increasing magnetic field strength, which was due to the magnetic field reduces microbial activity and promotes the formation of dense film layer. This work provided theoretical guidance on the prevention of SCC in pipeline steel under magnetic field and SRB coexistence.

Use of Corrosion Inhibitor in Solid Form to Prevent Internal Corrosion of Pipelines and Acidification Process

Use of corrosion inhibitors in solid form promotes the development of a new technique for internal corrosion protection of oil & gas pipelines and operations of oil wells acidification, because the controlled dissolution of the corrosion inhibitor forms a surface on metallic parts, a protective film that prevents or minimizes undesirable reactions to corrosion. In addition, this technique has important social and environmental benefits, ensures the operator has a lower risk of contamination when handling the product, changes the type of industrial packing, facilitates transportation, reduces solvent use and consequently reduces the waste that normally results from the use of inhibitors. The purpose of this article is to present a class of solid corrosion inhibitor tested in the laboratory and offer proposals for its application in industrial pipes such as gas and oil pipelines.

Risk analysis and maintenance decision making of natural gas pipelines with external corrosion based on Bayesian network

Buried natural gas pipelines are vulnerable to external corrosion because they are encased in a soil environment for a long time.Identifying the causes of external corrosion and taking specific maintenance measures is essential.In this work,a risk analysis and maintenance decision-making model for natural gas pipelines with external corrosion is proposed based on a Bayesian network.A fault tree model is first employed to identify the causes of external corrosion.The Bayesian network for risk analysis is determined accordingly.The maintenance strategies are then inserted into the Bayesian network to show a reduction of the risk.The costs of maintenance strategies and the reduced risk after maintenance are combined in an optimization function to build a decision-making model.Because of the limitations of historical data,some of the parameters in the Bayesian network are obtained from a probabilistic estimation model,which combines expert experience and fuzzy set theory.Finally,a case study is carried out to verify the feasibility of the maintenance decision model.This indicates that the method proposed in this work can be used to provide effective maintenance schemes for different pipeline external corrosion scenarios and to reduce the possible losses caused by external corrosion.

Prediction on Failure Pressure of Pipeline Containing Corrosion Defects Based on ISSA-BPNNModel

Oil and gas pipelines are affected by many factors,such as pipe wall thinning and pipeline rupture.Accurate prediction of failure pressure of oil and gas pipelines can provide technical support for pipeline safety management.Aiming at the shortcomings of the BP Neural Network(BPNN)model,such as low learning efficiency,sensitivity to initial weights,and easy falling into a local optimal state,an Improved Sparrow Search Algorithm(ISSA)is adopted to optimize the initial weights and thresholds of BPNN,and an ISSA-BPNN failure pressure prediction model for corroded pipelines is established.Taking 61 sets of pipelines blasting test data as an example,the prediction model was built and predicted by MATLAB software,and compared with the BPNN model,GA-BPNN model,and SSA-BPNN model.The results show that the MAPE of the ISSA-BPNN model is 3.4177%,and the R2 is 0.9880,both of which are superior to its comparison model.Using the ISSA-BPNN model has high prediction accuracy and stability,and can provide support for pipeline inspection and maintenance.

Combating Corrosion in Transmission Pipelines in Marine Environment Using Vernomia Amydalina as Inhibitor

Pipelines are system of pipes designed to transport liquids, gases or solid/ liquid mixtures over long distances. Some are used for domestic, household and sewage purposes. Others are buried underground or submerged in water for transportation of natural oil and gas (O & G) products. In this work, the specimens had to be kept in a workable state and steps were taken to prepare each specimen: all cuts and sheared edges were ground out to prevent them from becoming sites for preferential attack. The finishing of the specimen surface with grit abrasive paper (sand paper) and rinsing of the specimens in distilled water were done. Then degreasing of specimen in acetone and air-dried were carried out. Upon drying, the specimens were immediately weighed to obtain their initial weights. Twelve specimens were used for the test as follows: 6 Aluminum (Al);and 6 mild steel (MS) samples. With a 2 M concentration of Vernomia Amydalina (VA) extract solution, the MS and Al samples were immersed in different plastic containers containing 400 ml of seawater with pH value of 7.25 with no (0%) inhibitor added to it. A 5% (400 ml) of the VA solution was poured into the measuring cylinder for each sample-Al and MS. The specimens were suspended by the strings and completely immersed in the different percentage test media. The same procedure was carried out for each of the different percentages, 10%, 15%, 20%, and 25% and a total of 12 solutions were set up. The experimental procedure used was that seawater of 7.25 pH was obtained from Abonnema water front of Rivers State. At the end of every week (168 hours), the specimens were removed from the corrosive media. Observation and recording of appearance of the specimen noting sites were done. Cleanings of specimen with white handkerchief or tissue paper were carried out and washing of specimen with distilled water, scrubbing of specimen with a soft brush and dipping the specimen into acetone after washing, it was removed to air-dry and weighed. It is observed that optimum inhibition of coupons was obtained between 15% - 25% of VA solution during the first four weeks of testing. At the fifth week the inhibitor was gradually losing its effectiveness. This means that more inhibitor need be added at regular intervals to sustain the effectiveness of the inhibitor.

Environmental boundary and formation mechanism of different types of H2S corrosion products on pipeline steel

To establish an adequate thermodynamic model for the mechanism of formation of hydrogen sulfide (H2S) corrosion products, theoretical and experimental studies were combined in this work. The corrosion products of API X60 pipeline steel formed under different H2S corrosion conditions were analyzed by scanning electron microscopy, energy-dispersive X-ray spectroscopy, and X-ray diffraction. A thermodynamic model was developed to clarify the environmental boundaries for the formation and transformation of different products. Presumably, a dividing line with a negative slope existed between mackinawite and pyrrhotite. Using experimental data presented in this study combined with previously published results, we validated the model to predict the formation of mackinawite and pyrrhotite on the basis of the laws of thermodynamics. The established relationship is expected to support the investigation of the H2S corrosion mechanism in the oil and gas industry. © 2017, University of Science and Technology Beijing and Springer-Verlag Berlin Heidelberg.

Local corrosion characteristics of a graphene-oxide-modified inner coating

Pencil hardness testing,electrochemical impedance spectroscopy,scanning electron microscopy,and scanning Kelvin probe microscopy were used to study the local corrosion characteristics of a graphene-oxide-modified inner coating.The effect of chloride concentration on the corrosion of the damaged inner coating was studied.The effects of chloride ions on damaged internal coatings and graphene-oxide-modified internal coatings were investigated.It was proposed to add graphene oxide into the epoxy coating to effectively inhibit the metal corrosion at the breakage.Because of the existence of graphene oxide(GO),the modified coating had a better physical property and had the effective infiltration of H2O and Cl^- into the coating.The results showed that graphene oxide coatings can give X80 steel better corrosion resistance in sodium chloride solution.

An experimental study on the internal corrosion of a subsea multiphase pipeline

Based on the actual operational parameters of a subsea multiphase pipeline,an experimental study on the internal corrosion of a subsea multiphase pipeline was conducted in a dynamic,hightemperature autoclave,which had a similar environment to an actual field environment,using the partial pressure of CO2(PCO2),velocity of the corrosion medium,temperature,corrosion time,and corrosion inhibitor as variables.The results show that CO2 resulted in severe localized corrosion and that the corrosion rate increased as the PCO2 and velocity increased;the corrosion rate first increased and then decreased with increasing temperature.The corrosion rate peaked at approximately 65
C and then decreased continuously afterwards;the corrosion rate decreased as the duration of the experimental period increased.Under the operational conditions of the selected subsea pipeline,localized corrosion caused by CO2 was still the primary corrosion risk.Several types of corrosion inhibitors could inhibit the occurrence of localized corrosion for a short time period;however,most corrosion inhibitors could not completely inhibit localized corrosion.

减氧空气驱集输管道抗氧缓蚀剂优选与评价

目前抗氧缓蚀剂存在种类稀少、单一种类缓蚀剂的性能不够好以及经济成本较高等一系列问题。为此,结合国内某减氧空气驱集输管道实际工况特点,通过对氧腐蚀机理研究,选取了3种现已研发的油田常用抗氧缓蚀剂EQI、HTT和TCT,对其进行了动态腐蚀评价试验和表面形貌分析,通过分子动力学模拟其在Fe表面的吸附情况,得到缓蚀剂分子在水溶液环境下对Fe基体表面的吸附能大小,结合对比分析模拟和试验的结果,筛选出缓蚀性能最佳的缓蚀剂。试验和模拟结果均表明:水溶液中3种缓蚀剂分子在Fe基体表面的吸附能大小从高到低依次为TCT>EQI>HTT,缓蚀剂分子吸附能越大,缓蚀性能越佳。所得结论可为减氧空气驱集输系统的腐蚀防护工作提供理论指导。

油田集输管道腐蚀特性及防腐技术研究

为了保障油田集输管道的安全正常运行,延长其使用寿命,对西部某油田集输管道的腐蚀特性进行了研究,考察了实验温度、腐蚀介质p H值、CO_(2)含量、H_(2)S含量以及Cl-含量对集输管道钢材腐蚀速率的影响,并开展了投加缓蚀剂防腐蚀技术措施研究。结果表明,随着实验温度的不断升高以及腐蚀介质中CO_(2)、H_(2)S和Cl-含量的不断增大,钢片的腐蚀速率逐渐增大,而随着腐蚀介质p H值的逐渐升高,钢片的腐蚀速率则逐渐减小。缓蚀剂HXR-1的加入能够有效降低目标油田集输管道钢材的腐蚀速率,当其加量为80mg·L^(-1)时,钢片的腐蚀速率可由未添加缓蚀剂时的0.672mm·a^(-1)降低至0.022mm·a^(-1),腐蚀速率降低率达到了96.73%。研究结果表明,目标油田集输管道腐蚀较为严重,添加缓蚀剂HXR-1能够起到良好的防腐蚀效果。

气田集输管道缓蚀剂加注有效性问题的综述

在气田的快速发展过程中,随着采出水的逐渐增加和集输管线服役年限的延长,腐蚀问题层出不穷,尤其是刺漏穿孔频次呈逐年上升趋势。针对内腐蚀严重的问题,目前国内外主要采用“定期清管、缓蚀剂预膜及喷注”的方法进行防治。但是目前还未建立合理的集输管道缓蚀剂加药制度,相关的工艺技术流程大多依赖工程经验,其技术体系还缺乏相应的理论指导和评估标准,导致缓蚀剂加注存在适应性差、耗剂量大、膜质量控制难等技术难题。因此亟需开展缓蚀剂加注方案的优化工作,逐步完善缓蚀剂加注技术体系,形成适合现场工况的缓蚀剂加注方案和技术规程,降低气田集输管道内腐蚀程度和刺漏穿孔频次,从而实现缓蚀剂应用与管理的提质增效。为此,总结了缓蚀剂的加注工艺、缓蚀效率评价技术、缓蚀剂现场加注有效性存在的问题以及未来发展趋势,以为气田集输管道缓蚀剂加注技术提供一定的参考。

某油田污水管道腐蚀现状及防腐蚀措施研究

西部某油田污水管道腐蚀较为严重,采用涂抹防腐涂层的措施效果较差,因此,在分析了污水水质和管道腐蚀现状的基础上,开展了添加缓蚀剂防腐蚀措施研究。结果表明,目标油田污水中Cl-以及成垢离子的含量均较高,并且污水呈弱酸性,其中酸性气体CO_(2)的含量也较高,容易引起污水管道的腐蚀。现场腐蚀监测点中W-1和W-4处的腐蚀速率均在1.5mm·a^(-1)以上,其余两处监测点的腐蚀速率也能达到1.0mm·a^(-1)左右,管道腐蚀现象比较严重。随着实验温度的升高、污水pH值的降低以及污水中CO_(2)含量的增多,腐蚀速率逐渐增大。缓蚀剂HSR-1对污水管道的防腐蚀效果较好,当缓蚀剂HSR-1的加量达到60mg·L^(-1)时,能使污水对管道钢材的腐蚀速率控制在0.076mm·a^(-1)以下,起到了良好的防腐蚀效果。

管线钢硫化氢腐蚀影响因素分析及防护措施研究

为了明确硫化氢对油气集输用管线钢的腐蚀规律,并针对性地提出腐蚀防护措施,采用高温高压动态腐蚀实验装置评价了管线钢材在硫化氢存在时的腐蚀情况,考察了包括硫化氢分压在内的不同因素对腐蚀速率的影响,并提出了针对性的腐蚀防护措施。结果表明:随着硫化氢分压和实验温度的增高,挂片的腐蚀速率先增大后减小;腐蚀介质pH越大,腐蚀速率越小;实验流速和含水率越大,腐蚀速率就越大;硫化氢的存在对目标油田集输用X65管线钢的腐蚀影响较大,当硫化氢分压为0.1 MPa时,腐蚀速率达到最大。在相同的实验条件下,缓蚀剂MHS-5对管线钢的腐蚀防护效果最好,缓蚀剂MHS-5的加入能够大大降低挂片的腐蚀速率,当其质量分数为0.05%时,缓蚀效率可以达到92.8%,挂片腐蚀速率小于0.1 mm·a^(-1),能够满足行业标准的要求。

减氧空气驱油集输管线缓蚀剂防腐评价研究

减氧空气驱能有效提高低渗透油藏的采收率,但氧气的存在也必然造成下游的集输管线氧腐蚀和CO_(2)腐蚀,从而限制了减氧空气驱的推广应用。针对国内某应用减氧空气驱油田集输管线,开展了缓蚀剂防腐研究。在模拟现场集输管道工况条件下,采用挂片动态失重法,选取了6种抗CO_(2)缓蚀剂和6种抗氧缓蚀剂对20钢材的缓蚀作用进行评价筛选。实验初选了两种抗氧缓蚀剂KY-12和KY-17以及一种抗CO_(2)缓蚀剂A,三者的缓蚀率分别达到了83.67%、91.49%和78.44%。通过对初选的3种缓蚀剂在不同温度(25、40和55℃)和不同浓度(400、500、800、1000和2000 mg/L)条件下的实验评价,优选出在不同温度情况下稳定性最佳的KY-17缓蚀剂,且在不同浓度时缓蚀效果最好,缓释率最高达到92.7%。该结论对于减氧空气驱油田下游集输管线缓蚀剂的选型和加剂量有较好的参考意义。

聚合物缓蚀剂在油气管道腐蚀防护中的研究进展

油气集输管道因各种因素的影响极易发生腐蚀,在油气管道中加入缓蚀剂是预防管道腐蚀最直接有效的办法。本文对油气管道产生化学和电化学腐蚀的机理进行简要分析,阐述了含氮、含磷、乙烯基等聚合物缓蚀剂在油气管道防腐工作中的最新研究进展,分析了聚合物缓蚀剂所存在的问题,并对其发展趋势进行了展望,以期为油气管道防腐工作提供参考。

缓蚀剂对气田海底管道的保护性能模拟研究

某新建海上气田A井油藏测试临时改变了物流海底管道,导致物流介质及物流环境产生变化,有必要研究缓蚀剂对气田海底管道的保护性能。通过实验表明:高水气比和地层水工况下,腐蚀速率较高,缓蚀剂无法满足高水气比工况;正常水气比和冷凝水工况下,未添加缓蚀剂,随着流量的增加,腐蚀速率呈现上升趋势,随着缓蚀剂加注浓度的增加,腐蚀速率呈现下降趋势。缓蚀剂加注浓度500 ppm条件下,当输气量控制在58万方/天以内时,腐蚀速率可控制0.71 mm/a。实验结果为油藏测试提供了参考依据。

页岩气集输管道腐蚀原因及控制措施

南川页岩气田管道腐蚀问题逐渐凸显。从管道输送介质和腐蚀产物等方面分析了管道腐蚀的原因,并通过杀菌剂和缓蚀剂室内优选试验和配伍性试验,提出了相关的腐蚀防护措施。结果表明:气质中含有CO_(2),采出水中高含SRB和Cl^(-),腐蚀产物主要由铁、氧、碳等元素组成,CO_(2)、SRB和Cl^(-)的协同作用是造成集输管道腐蚀的主要原因;TK-S01杀菌剂的杀菌效果最好,最佳加注量为100 mg/L,此时其杀菌率达到99.99%;KY-2缓蚀剂的缓蚀效果最好,在最佳加注量150 mg/L条件下,其缓蚀率达到90%;TK-S01杀菌剂和KY-2缓蚀剂的配伍性较好,药剂效果互不影响。

高含硫天然气埋地管道冲刷腐蚀特性研究

合成了2种苯二氮卓衍生物的有机缓蚀剂,分别为BS和BT。通过标准电化学和重量法深入研究了这2种有机缓蚀剂在硫化氢模拟酸中对含硫天然气低碳钢(MS)管道的防腐蚀性能。同时,采用紫外可见光谱对钢材表面和腐蚀溶液进行了分析。结果表明:2种有机化合物在酸性介质中都表现出良好的低碳钢腐蚀缓蚀效果,并且属于混合型缓蚀剂。热力学参数揭示,2种化合物以Langmuir吸附等温线的方式吸附在金属表面。紫外可见光谱结果显示,添加这2种化合物降低了腐蚀溶液中铁离子的溶解,并在钢表面形成了一层保护性膜。

天然气输送管道用新型缓蚀剂的制备及性能研究

为有效降低天然气输送管道的腐蚀速率,提高管道的运行效率,以植物油酸、多乙烯多胺和尿素为原料,通过两步法制备了一种天然气集输管道用新型缓蚀剂XHT-1。以合成产物产率为评价指标,对中间产物X和最终产物XHT-1的合成工艺进行了优化,并以缓蚀率为评价指标,对新型缓蚀剂XHT-1的腐蚀防护效果进行了评价。结果表明,当植物油酸和多乙烯多胺的单体摩尔比为1∶1.2、反应温度为130℃、反应时间为3h时,中间产物X的产率最大(90.6%);当中间产物X和尿素单体摩尔比为1∶0.8、反应温度为140℃、反应时间为4h时,新型缓蚀剂XHT-1的产率最大(98.2%)。新型缓蚀剂XHT-1的浓度越大,缓蚀率相对就越大,当XHT-1的浓度为300mg·L^(-1)时,缓蚀率可达到95.8%,缓蚀效果较好。研究结果认为,新型缓蚀剂XHT-1能够用于目标天然气输送管道的腐蚀防护中。

集输管线钢硫化氢腐蚀及防护措施研究

含硫油气资源集输用管线钢容易受到H_(2)S的腐蚀损害,为了找出H_(2)S存在条件下集输管线钢材的腐蚀规律,采用高温高压动态腐蚀实验装置评价了H_(2)S分压等不同因素对X65管线钢材腐蚀速率的影响,并提出了具体的腐蚀防护措施。结果表明,H_(2)S的存在对目标油田集输用X65管线钢的腐蚀影响较大,H_(2)S的分压升高,挂片的腐蚀速率先增大后减小;腐蚀介质pH值越大,腐蚀速率越小;实验温度越高、实验流速以及腐蚀介质的含水率越大,腐蚀速率相对就越大。咪唑啉类复合缓蚀剂HSR-1的加入能够显著降低挂片的H_(2)S腐蚀速率,当HSR-1的质量分数为0.05%时,其对挂片的缓蚀效率可达95%以上,使腐蚀速率降低至0.038mm·a^(-1),起到了良好的腐蚀防护效果。