水泥环缺陷对套管承载能力的影响研究

发布时间：2018-01-20 23:22

本文关键词： 水泥环缺陷承载能力仿真模拟外挤力 Von Mises等效应力　出处：《西南石油大学》2015年硕士论文　论文类型：学位论文

【摘要】：水泥环缺陷会直接影响到套管的受力状态,并且往往会造成套管出现应力集中现象,严重时甚至会导致套管损坏。然而,目前国内外针对水泥环缺陷对套管承载能力影响的相关研究还比较少,并且所建立的水泥环缺陷模型比较单一理想化,与实际并不十分相符。为此,本文首先在弹塑性力学的基础上,建立了水泥环完好且受均匀地应力作用的套管最大等效应力计算模型；然后根据现场资料与室内实验数据,建立了不同类型的水泥环缺陷模型；最后利用有限元软件对不同水泥环缺陷时的套管等效应力进行了模拟研究,得出水泥环缺陷对套管承载能力的影响规律。取得了如下主要认识： (1)偏心环空水泥环缺失往往出现在环空窄间隙处,并且套管承载能力会随着缺失面积的增加先急剧降低再迅速回升,并且回升幅度逐渐降低,最终接近但低于水泥环完好时的套管承载能力； (2)气侵通道面积越大、通道位置离套管壁越近,套管的承载能力越低；气侵通道对称分布时,通道数量越少,套管承载能力也会越低；当存在两条气侵通道时,两通道相隔越远,套管承载能力越低。当套管偏心时,气侵通道位置离环空窄间隙越近,套管承载能力也会越低,并且此时气侵通道数量对套管承载能力几乎无任何影响； (3)微环隙缺失宽度的增加,虽然可以提高套管的承载能力,但同时会降低水泥环密封性,影响固井质量,甚至导致一系列严重后果；当微环隙不为完整圆形时,随着微环隙缺失长度的增加,套管承载能力会急剧降低再逐渐缓慢回升,根据微环隙位置与宽度的不同,套管承载能力的降低与上升幅度也会不同； (4)水泥环的半月形缺失对套管承载能力的影响与气侵通道的影响规律类似,但相同缺失程度情况下,半月形缺失导致的套管承载能力降低幅度更大； (5)套管承载能力随着水泥石弹性模量的增加而快速降低接着再缓慢回升,随着水泥石泊松比的增加而降低,但降幅很小,几乎可以忽略不计。通过本文的研究,为进一步深入认识水泥环缺陷对套管承载能力影响奠定了良好的基础。
[Abstract]:Cement sheath defects will directly affect the stress state of the casing, and often lead to casing stress concentration phenomenon, and even lead to casing damage. At present, there are few researches on the influence of cement sheath defect on casing bearing capacity, and the cement ring defect model is single and idealized, which is not very consistent with the actual situation. On the basis of elastoplastic mechanics, a model for calculating the maximum equivalent stress of casing with intact cement sheath and subjected to uniform in-situ stress is established in this paper. Then, according to the field data and laboratory data, different types of cement ring defect models are established. Finally, the equivalent stress of casing with different cement sheath defects is simulated by using finite element software, and the influence of cement sheath defect on casing bearing capacity is obtained. The main results are as follows: 1) the loss of eccentric annulus cement ring often appears in the narrow gap of annulus, and the bearing capacity of casing decreases sharply with the increase of missing area, and then increases rapidly, and the range of recovery decreases gradually. The bearing capacity of casing is close to but lower than that of cement sheath. 2) the larger the area of the gas invasion channel, the closer the location of the passage from the sleeve wall, the lower the bearing capacity of the casing; When the gas invasion channel is distributed symmetrically, the smaller the number of channels, the lower the bearing capacity of casing. When there are two gas invasion channels, the longer the two channels are separated, the lower the casing bearing capacity is, and when the casing is eccentric, the closer the gas invasion channel is to the narrow gap between annulus and annulus, the lower the casing bearing capacity will be. At this time, the number of gas invasion channels has little effect on the bearing capacity of casing. 3) the increase of the missing width of microannulus can improve the bearing capacity of casing, but at the same time, it will reduce the sealing ability of cement ring, affect the cementing quality, and even lead to a series of serious consequences. When the microannular gap is not round, with the increase of the missing length of the microannular gap, the bearing capacity of the casing decreases sharply and then rises slowly, according to the difference of the position and width of the microannular gap. The decrease of bearing capacity of casing is different from that of rising. (4) the influence of semilunar loss of cement sheath on casing bearing capacity is similar to that of gas invasion channel. The bearing capacity of casing decreases rapidly with the increase of elastic modulus of cement stone and then rises slowly, and decreases with the increase of the ratio of cement stone to stone, but the decrease is very small and can be ignored. The research in this paper lays a good foundation for further understanding the influence of cement sheath defects on casing bearing capacity.
【学位授予单位】：西南石油大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：TE256

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