探析抽油杆断脱原因及防治措施.doc

/ /探析抽油杆断脱原因及防治措施摘要:抽油杆的断脱是影响油田正常生产的主要因素之一。本文结合抽油杆断脱资料,对引起抽油杆断脱的主要原因进行了全面剖析,认为疲劳破坏、机械磨损、腐蚀损坏是导致抽油杆断脱的三大主要因素,提出了治理抽油杆断脱的措施。Abstract: the sucker rod break off is one of the main factors that affect the normal oilfield production. Based on sucker rod break off materials, the main cause of sucker rod break off has carried on the thorough analysis, the fatigue damage, mechanical wear, corrosion damage is lead to three main factors of sucker rod break off, put forward the measures of governance sucker rod break off.关键词:抽油杆;断脱;磨损;腐蚀;措施Key words: sucker rod; Break off; Wear and tear; Corrosion; measures1、引言1, the introduction近几年,随着油田挖潜力度的不断加大,油井泵深不断增大,而老油田抽油杆老化、斜井偏磨、腐蚀等问题日益严重,使得抽油杆断脱井次不断增加,不仅困扰着油井的正常生产,而且增加了采油成本,近几年这一矛盾表现得更加突出。Rising in recent years, with the strength of oilfield exploration, the well pump depth increasing, the old oil fields in the rod ageing, inclined eccentric wear and corrosion problems are increasingly serious, makes the sucker rod break off Wells increasing, not only affects normal production of oil Wells, and increases the production cost, the contradictions appear more prominent in recent years.2、抽油杆断脱原因分析2, sucker rod break off cause analysis抽油杆柱由于长期受交变载荷和油、气、水以及腐蚀介质的共同作用,再加之定向井的偏磨,使其成为机械采油中可靠性最低的设备,很容易发生断脱。导致抽油杆柱断脱的原因是多方面的,影响因素也错综复杂,主要应从以下三个方面进行剖析。Rod string because of the long-term cyclic loading and oil, gas, water, and the common role of corrosive medium, plus partial grinding of directional well, making it the lowest reliability in mechanical oil recovery equipment, it is easy to break off. The causes of rod string breaks are various, influence factors are complicated, mainly analyzes from the following three aspects.2.1疲劳破坏2.1 fatigue damage2.1.1抽油杆工作条件2.1.1 rod working conditions抽油杆在工作过程中,承受不对称循环载荷的作用,上部光杆承受的载荷包括:抽油杆柱的载荷,液柱载荷,抽油杆柱、油管柱和液柱的惯性载荷,抽油杆柱在运动中受的摩擦阻力,抽油管柱和油管柱的弹性引起的振动载荷,由液击引起的冲击载荷,由井斜变化、螺纹不同心、悬绳器摆动等因素造成的扭力等七方面的力。而抽油杆柱承受的载荷随深度有所变化,如抽油杆柱载荷越往下越小,加上下部抽油杆柱所承受的上顶力的作用,在中和点以下抽油杆柱由承受张应力变成压应力,迫使抽油杆弯曲,增大了扭力和摩擦力,使得下部抽油杆工作条件更加恶劣。因此,抽油杆柱承受的不是简单的不对称循环载荷,而实际上中和点以下的抽油杆承受的是不对称拉压循环载荷,加上抽油杆柱本身未加工面积达85%以上,不可避免地会有疲劳源存在,从而产生疲劳断裂。Sucker rod in the process of work, bear the action of asymmetrical cyclic load, the upper part of polished rod load including: under a load of sucker rod string, fluid column load of sucker rod string, tubing string and fluid column of the inertial load, and the movement of the rod string by the frictional resistance of sucker string and tubing string caused by elastic vibration load, impact load caused by liquid impact, is a variation of the drift, thread to factors such as different heart, swing beam hanger of seven aspects, such as torque force. With depth and rod string on the load changes, such as the sucker rod string load down more and more small, along with the lower rod string on the role of jacking force, in the neutral point of rod string below from bear tensile stress to compressive stress, and bending force rod, increase the torque and friction, making the lower rod working conditions worse. Sucker rod string, therefore, bear is not a simple asymmetric cyclic load, and actually below the neutral point of rod is asymmetry of pressure under cycle load, coupled with the sucker rod string itself unprocessed area of more than 85%, the fatigue source will inevitably exist, resulting in fatigue fracture.2.1.2负荷变化引起的疲劳破坏分析2.1.2 load changes caused by fatigue damage analysis光杆负荷在上下冲程中是不相同的,在保证产量的前提下,长冲程和小冲次可以使负荷变化最小,负荷的变化主要与光杆的冲程和抽油机悬点负荷有关。由于泵阀的作用,上冲程时抽油杆承受着液柱重量,下冲程时液柱的重量便作用在油管上。因此,上冲程开始时,举升的液柱重量会使抽油杆的负荷发生突然变化,冲次愈高负荷愈大,这种负荷的突变愈强烈。由于负荷反复变化的冲击,疲劳破坏是抽油杆所有损坏形式的基本特点,疲劳破坏往往是由于弹性极限的交变压力造成的,弹性极限是不使金属产生永久变形的最大负荷。抽油杆因反复拉伸作用而产生裂纹,则属于应力疲劳破坏。The polished rod load is not the same in the up and down stroke, on the premise of guarantee the production, long stroke and small flush times can minimize the load changes, load changes mainly with polished rod stroke associated with the pumping unit suspension point load. Due to the role of the pump valve, stroke on sucker rod under the weight of liquid column, stroke under the weight of the liquid column he effect on the tubing. Accordingly, at the start of the stroke, the lifting of the liquid column weight will make rod load changes suddenly, the greater the speed the higher the load, the stronger the load mutation. Due to the impact of the load changed repeatedly, fatigue damage is the basic characteristics of sucker rod all forms of damage, the fatigue damage is often due to the elastic limit of the alternating stress, the elastic limit is the maximum load do not make metal produce permanent deformation. Sucker rod crack due to repeated stretching, belong to stress fatigue destruction.2.2抽油杆机械磨损2.2 rod mechanical wear2.2.1底部受压弯曲致使杆管偏磨2.2.1 eccentric wear compression bending the rod at the bottom of the tube直井抽油杆弯曲产生于下冲程。在下冲程时,抽油杆带着柱塞下行,固定阀关闭,排出阀打开,液柱作用在油管上,使油管伸直。而抽油杆柱承受在液柱中的重力,杆柱与液体之间的摩擦力,采出液体通过排出阀的液流阻力所产生的向上作用力,下行时特别是在活塞游动凡尔打开前的瞬间,由于泵内液体及泵筒内壁对活塞的阻力,加之以上力的作用,导致使整个杆柱下部受压上部受拉,拉压之间存在一既不受拉又不受压的中和点,中和点以下,杆柱受压失稳弯曲,弯曲的杆柱与油管内壁接触,相对运动造成杆管磨损。通过计算发现,随泵径加大,泵深增加,中和点以下长度在杆柱全长中所占比例增加,相应地杆柱弯曲越严重。现场发现下行磨损均有且较严重,说明下行杆柱受压弯曲是偏磨的主要原因。Vertical Wells rod bending next stroke. The next stroke, the sucker rod with a plunger downward, fixed valve closed, open the discharge valve, liquid column on the tubing, straight out of tubing. And rod string and liquid column in the gravity, the friction force between rod string and liquid, extraction liquid through the discharge valve of the liquid flow resistance produced by the upward force, especially when downward in the moments before swimming piston valve to open, it is due to the liquid in the pump and the pump barrel inside of piston resistance, combined with the above, the action of forces in the whole rod upper lower stressed in tension, the tension and compression between the both in tension and compression of neutral point, below the neutral point of rod string compression instability bending, bending of the rod string and tubing wall contact, caused by relative motion rod tube abrasion. Found by calculation, with the pump diameter, depth of pump, on the rod string below the neutral point length length increase, the proportion of rod string bending the more serious accordingly. Downward wear are found at the scene and more serious, explain downward compression bending pole is a major cause of eccentric wear.2.2.2井斜引起的机械磨损2.2.2 deviation caused by mechanical wear由于井斜,使油管产生弯曲,在抽油井生产时,抽油杆的综合拉力或综合重力产生了一个水平分力。在水平分力的作用下,油管和抽油杆相互接触产生摩擦。上冲程时,使抽油杆与油管内壁的一侧产生磨损,下冲程时,抽油杆弯曲与油管内壁的另一侧面产生摩损。弯曲度越大,磨损越严重,不仅抽油杆接箍与油管内壁产生磨损,而且抽油杆本体也与油管内壁产生磨损。Due to drift, buckling of tubing in oil well production, integrated pull rod or the comprehensive level of gravity produces a force component. In under the action of horizontal component of the tubing and sucker rod friction contact each other. On stroke, the sucker rod and tubing wall on one side of the wear and tear down stroke, sucker rod and tubing wall of another side friction losses. Curvature is bigger, the more serious wear and tear, and sucker rod coupling and the tubing wall not only result in the wear and tear, ontology and sucker rod and tubing wall also produce wear.2.2.3含水升高,杆管磨损加剧2.2.3 water cut rise, rod pipe wear当杆与管相接触发生滑动摩擦时,磨损速度与它们之间的润滑状态有关,而水的摩擦系数远远大于油的摩擦系数,另外通过计算发现,含水升高,抽油杆下行时,使抽油杆的中和点下移,加剧抽油杆弯曲。When the rod and tube in contact when the sliding friction, the wear rate is related to the lubricating state between them, and water than oil, the friction coefficient of friction coefficient, and through calculation, found that water cut increases, sucker rod downward, the neutral point of rod down, fuel rod bending.2.3抽油杆腐蚀破坏2.3 rod corrosion damage绝大多数油井,在开发中后期产出液都会含水,而产出水中又含有各种腐蚀介质,腐蚀性微生物等,伴生气中也会有CO2、H2S 等腐蚀气体,由于存在这些腐蚀介质,加上抽油杆承受的是不对称循环载荷,所以腐蚀损坏便成为油杆断裂的又一主要原因。Most of oil Wells, the middle produced fluid will be water cut development, and output water contains a variety of corrosive medium, the corrosive microorganism, associated gas in there will be corrosion gas such as CO2, H2S, because of the corrosive medium, and sucker rod is asymmetric under cycle load, so the corrosion damage becomes another main rod fracture reasons.2.3.1 二氧化碳的影响2.3.1 the influence of carbon dioxide地层水中含有大量的CO2,它是由地球的地质化学过程产生的,当水中有游离的CO2存在时,水呈酸性反应,由于水中H+离子的量增多,就会产生氢去极化腐蚀,所以游离的CO2腐蚀,从腐蚀电化学的观点看,就是含有酸性物质而引起的氢去极化腐蚀。CO2溶于水呈弱酸性,因为弱酸只有一部分电离,所以随着腐蚀过程的进行,消耗掉的氢离子会被弱酸的继续电离所补充。钢材受游离CO2腐蚀而生成的腐蚀产物都是易溶的,在金属表面不易形成保护膜。CO2腐蚀坑通常是圆底,侧面很陡,连成一片,产生虫蛀效应。Formation water containing large amounts of CO2, it is produced by the earths geological chemical processes, when there is free of CO2 is dissolved in the water, the water acidic reaction, because of the amount of H + ions in water, can produce hydrogen depolarization corrosion, so free CO2 corrosion and electrochemical corrosion from the point of view, is containing the acid corrosion caused by hydrogen depolarization. Because CO2 is dissolved in water in weak acid, weak acid ionization only part of, so as the corrosion process, consume hydrogen ions will be added by the continuation of weak acid ionization. Steel corrosion products generated by dissociation of CO2 corrosion are soluble, difficult to form a protective film on metal surface. CO2 corrosion pit is usually a round bottom, side is very steep, unbroken expanse, bug eat by moth effect is produced.2.3.2 硫化氢的影响2.3.2 the influence of hydrogen sulfide含硫油田中与油水共生的水往往含有硫化氢,碳钢的阳极产物铁离子与水中硫离子相结合生产硫化铁。硫化铁的溶度积很小,是一类难溶沉淀物,它常以黑色粉末或垢的形式附着在油杆表面。含H2S的水对金属材料的腐蚀破坏还有两种类型:一是氢脆,电化学腐蚀产生的氢渗入钢材内部,使材料韧性变差,引起微裂缝,使钢材变脆。二是硫化物应力腐蚀,在拉应力和残余应力作用下钢材氢脆裂纹发展,致使钢材破裂。以上两种腐蚀可能在没有任何征兆的情况下,在短时间突然发生,这应是预防的重点。H2S腐蚀坑是随机排列的,呈圆锥形,侧面较陡,坑的边缘圆滑,坑之间不相连,腐蚀物呈黑色,较粘,有硫化氢味。Sulfur symbiosis with oil and water in oil field water, often containing hydrogen sulfide, carbon anode product of iron iron sulfide and sulfur ions in water production. Iron sulfide solubility product is small, is a kind of refractory sediment, it is often in the form of black powder or scale attached to the surface of rod. Water containing H2S corrosion damage of metal materials has two types: one is the hydrogen embrittlement, electrochemical corrosion of hydrogen into steel inside, make the material toughness is poor, cause microfracture, make steel brittle. Second, sulfide stress corrosion, the steel tensile stress and residual stress under the action of hydrogen embrittlement crack development, the steel break. The above two kinds of may without any signs of corrosion, suddenly in a short time, this should be the focus of prevention. H2S corrosion pit is random and is conical, flank is steep, round the edge of the pit, the pit is not connected, between corrosion, in black ink, the glue, the smell of hydrogen sulfide.3、抽油杆断脱综合防治措施3, sucker rod break off comprehensive prevention and control measures3.1强化抽油杆老化分析,预防断裂事故的发生。3.1 strengthening rod ageing analysis, prevent the happening of the fracture accident.根据统计,抽油杆故障发生有两个高峰,一是2-3年内,故障率在15%左右,另一高峰在7年以后,故障率高达32-47%。第一高峰是抽油杆质量导致,全井抽油杆中个别质量不合格问题暴露。第二高峰是操作造成,以后便是各种原因疲劳老化造成,因此要做好下井前检验、规范使用、后期损伤检测、更换四个过程的控制。Sucker rod failure according to one estimate, there are two peaks, one is 2-3 years, the failure rate is around 15%, another peak after seven years, up to 32-47% failure rate. Quality in the first peak is sucker rod, all well sucker rod in the individual exposure substandard problem. The second peak is caused by operation, so it is fatigue aging caused by various reasons, so to the well before inspection, specification use, damage detection, replace the four process control.3.2引进高强度抽油杆3.2 introduce the high strength sucker rod3.2.1玻璃钢抽油杆3.2.1 the reinforced plastic fiberglass sucker rod玻璃钢抽油杆具有强度高,重量轻,弹性好和耐腐蚀的特点,其强度和同规格的D级钢杆相近,但重量只约为钢杆的1/3,弹性模量约为钢杆的1/4-1/5,降低了抽油机的悬点负荷,以最大限度提高抽油杆的使用寿命。Reinforced plastic fiberglass sucker rod has high strength, light weight, good elasticity and the characteristics of corrosion resistance, its strength and D steel rod with specifications close, but the weight is only about 1/3 of the steel rod, modulus of elasticity is about 1/4 to 1/5 of the steel bar, reduce the pumping unit of the polished rod load, in order to maximize the service life of sucker rod.3.2.2高强度H级杆3.2.2 class H high strength bar用强度H级抽油杆代替同规格D级抽油杆,由于H级抽油杆比同规格D级抽油杆的强度高30%,在相同载荷条件下,疲劳寿命高两倍。Class H sucker rod instead of the same specification with strength grade D sucker rod, because the class H sucker rod than the same specification of grade D sucker rod with high intensity, 30% in the same load conditions, the fatigue life twice as high.3.3采用防腐技术,减少腐蚀影响3.3 the anti-corrosion technology, reduce corrosion effects目前,油井加入缓蚀剂是解决油井井筒腐蚀的一种常用有效方法。其原理是通过缓蚀剂与金属表面的化学吸附,在金属表面形成牢固的表面反应膜,隔离腐蚀介质,达到保护金属,防止腐蚀发生的目的。At present, the oil well join corrosion inhibitor is a common and effective wa