發(fā)布時(shí)間：2018-05-18 00:20

  本文選題：臨界剩余壁厚 + 腐蝕套管　； 參考：《東北石油大學(xué)》2015年碩士論文

【摘要】：在石油開(kāi)采過(guò)程中套管是地上與地下物質(zhì)的重要交換通道。套管的服役條件非常苛刻,由于多種驅(qū)油方法的聯(lián)合使用使得采出液成分十分復(fù)雜,正是這種理化環(huán)境復(fù)雜性使得套管失效現(xiàn)象頻頻出現(xiàn),給油田的安全生產(chǎn)帶來(lái)極大影響。本文針對(duì)大慶油田實(shí)際生產(chǎn)情況,對(duì)三元復(fù)合驅(qū)采出井的腐蝕損傷套管進(jìn)行失效分析。通過(guò)對(duì)失效管段的宏觀分析和微觀分析發(fā)現(xiàn)腐蝕以?xún)?nèi)壁為主,附著有較厚的垢,垢下形成較多密集分布的腐蝕坑。嚴(yán)重的局部腐蝕特別是垢下腐蝕是套管失效的主要原因。通過(guò)對(duì)腐蝕介質(zhì)的電導(dǎo)率、pH值及化學(xué)成分分析,了解了防垢劑及酸洗液可以加速腐蝕過(guò)程。最終確定套管的腐蝕機(jī)理為服役前期發(fā)生吸氧腐蝕,服役過(guò)程中管壁結(jié)垢發(fā)生嚴(yán)重的垢下腐蝕直至穿孔,在腐蝕過(guò)程中,酸洗液中的H+、Cl-及防垢劑直接加速了腐蝕。結(jié)合腐蝕機(jī)理及局部腐蝕的失效形式,利用ANSYS有限元軟件重點(diǎn)模擬了平底方形、平底長(zhǎng)圓形、橢圓形、圓形蝕坑及組合腐蝕缺陷的幾何尺寸及內(nèi)壓對(duì)失效的影響,其中腐蝕深度和內(nèi)壓對(duì)臨界剩余壁厚的影響最大,缺陷長(zhǎng)度及缺陷寬度的影響依次降低。對(duì)于圓形點(diǎn)蝕坑,當(dāng)深度超過(guò)7mm時(shí),等效應(yīng)力最大值會(huì)出現(xiàn)明顯的激增。對(duì)于雙點(diǎn)腐蝕而言,本文分別模擬了平底方形及長(zhǎng)圓形腐蝕缺陷,并得到兩類(lèi)缺陷相互干涉距離分別為90mm和115mm。此外,通過(guò)對(duì)含腐蝕缺陷套管的室內(nèi)模擬打壓實(shí)驗(yàn),并將實(shí)驗(yàn)數(shù)據(jù)與ANSYS軟件模擬數(shù)據(jù)進(jìn)行對(duì)比,得到兩者的最大誤差為7.75%,符合工程應(yīng)用中小于10%的要求,驗(yàn)證了有限元分析方法的準(zhǔn)確性。最后,結(jié)合Ansys Workbench軟件中的優(yōu)化設(shè)計(jì)模塊,進(jìn)行了二次開(kāi)發(fā),進(jìn)而更方便的計(jì)算腐蝕套管臨界剩余壁厚,為剩余壽命的預(yù)測(cè)奠定基礎(chǔ)。
[Abstract]:In the process of oil production, casing is an important exchange channel between ground and underground material. The service conditions of casing are very harsh, because of the combined use of many oil displacement methods, the composition of produced liquid is very complex. It is precisely this kind of physical and chemical environment complexity that makes casing failure frequently appear, which has a great impact on the safe production of oil field. According to the actual production situation in Daqing Oilfield, the failure analysis of corrosion damaged casing in ASP flooding production wells is carried out. Through the macroscopic and microscopic analysis of the failure pipe section, it is found that the corrosion is mainly on the inner wall, and there is thicker scale attached to it, and more dense corrosion pits are formed under the scale. Serious local corrosion, especially scale corrosion, is the main cause of casing failure. Through the analysis of pH value and chemical composition of the corrosion medium, it is understood that the corrosion process can be accelerated by the scale inhibitor and acid lotion. Finally, it is determined that the corrosion mechanism of the casing is oxygen absorption corrosion in the pre-service period, serious corrosion under the scale of the pipe wall and even perforation in the service process. In the process of corrosion, the H _ (+) Cl- and anti-scaling agent in the acid washing liquid directly accelerates the corrosion. Combined with the mechanism of corrosion and the failure form of local corrosion, the effects of geometric dimension and internal pressure of square, oblong, elliptical, circular pits and combined corrosion defects on the failure are simulated by ANSYS finite element software. The influence of corrosion depth and internal pressure on critical residual wall thickness is the greatest, and the influence of defect length and defect width decreases in turn. For circular pitting pits, the maximum equivalent stress increases significantly when the depth exceeds 7mm. For double point corrosion, the square and long circle corrosion defects with flat bottom are simulated, and the interference distance between the two kinds of defects is 90mm and 115 mm respectively. In addition, by comparing the experimental data with the simulation data of ANSYS software, the maximum error is 7.75, which accords with the requirement of less than 10% in engineering application. The accuracy of the finite element analysis method is verified. Finally, combined with the optimization design module in Ansys Workbench software, the secondary development is carried out, and the critical residual wall thickness of corroded casing is calculated more conveniently, which lays a foundation for the prediction of residual life.
【學(xué)位授予單位】：東北石油大學(xué)
【學(xué)位級(jí)別】：碩士
【學(xué)位授予年份】：2015
【分類(lèi)號(hào)】：TE983

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本文編號(hào)：1903531