盐穴储气库运行对水泥环结构完整性的影响研究

发布时间：2018-10-21 15:03

【摘要】：储气库井筒在运行期间受到极限压力和交变压力的影响,压力的过高和循环周期频繁都会造成井筒完整性失效,然而国内外的研究针对水泥环的研究比较少,并且建立的模型大部分都是二维模型。因此本文在弹塑性力学的基础上,根据得到的大量储气库岩石力学性质,水泥环材料数据,建立了三维多地层井筒模型,通过ABAQUS软件分析水泥环井筒在极限压力下,水泥环在不同工况下的受力情况以及在交变压力下,水泥环胶结面分离情况和疲劳情况。获得如下认识:在理想状态下,储气库应选用低弹性模量、高泊松比的水泥浆体系,而不是增加水泥环厚度。这主要是因为水泥环应力随着弹性模量的增加和泊松比的减小而逐渐增加,增加的幅度较大,而随着水泥环厚度的增加,水泥环应力增加的幅度较少;在理想状态下,水泥环不会发生强度破坏。当水泥环在较低的椭圆度,低套管偏心,低水泥环缺失情况下,水泥环受力比较接近理想情况;但是在较高的椭圆度,套管偏心,水泥环缺失情况下,水泥环受力远远大于理想情况,水泥环整体不均匀性变大;同时较高的套管偏心以及水泥环缺失情况下,水泥环会在偏心处和缺失面积附近处,发生强度破坏。在理想状态下,无论弹性模量、泊松比、厚度的变化,水泥环的一、二界面始终保持紧密接触;在非理想状态下,椭圆度的变化,不会导致水泥环发生接触失效,水泥环一界面和二界面始终保持接触。但是,在较大的水泥环缺失和套管偏心下,水泥环整体非均匀性的增加,水泥环的一界面开始分离,开始分离的时间逐渐提前。因此在非理想状态下,过高的偏心度和水泥环缺失,可能导致天然气从一界面出泄漏。通过疲劳分析,在理想状态下和非理想状态下,水泥环疲劳次数远大于50次,均能满足盐穴储气库50年运行要求。通过以上分析,本文认为,低弹性模量,高泊松比的水泥浆体系更适合储气库的要求;同时,保持井壁稳定,套管居中能保证储气库后期稳定的运行。
[Abstract]:The wellbore of gas storage is affected by the limit pressure and alternating pressure during operation. The high pressure and frequent cycle will cause the wellbore integrity failure. However, there is little research on cement ring at home and abroad. And most of the models established are two-dimensional models. On the basis of elastoplastic mechanics, according to the rock mechanical properties of gas storage reservoir and the material data of cement ring, a three-dimensional multi-formation wellbore model is established in this paper. The ABAQUS software is used to analyze the cement-ring wellbore under the limit pressure. The stress of cement ring under different working conditions and the separation and fatigue of cement ring cementing surface under alternating pressure. Under the ideal condition the cement slurry with low elastic modulus and high Poisson ratio should be used instead of increasing the thickness of cement ring. This is mainly because the stress of cement ring increases gradually with the increase of elastic modulus and the decrease of Poisson's ratio, but with the increase of cement ring thickness, the stress of cement ring increases by less. Cement ring will not occur strength damage. Under the condition of low ellipticity, low casing eccentricity and low cement sheath missing, the stress of cement sheath is close to the ideal condition, but in the case of higher ellipticity, casing eccentricity and missing cement sheath, The stress of cement ring is far greater than that of ideal condition, and the overall inhomogeneity of cement ring becomes larger. At the same time, when the casing eccentricity is high and the cement ring is missing, the strength of cement ring will be destroyed at the eccentricity and near the missing area. Under ideal conditions, the first and second interfaces of the cement ring remain in close contact regardless of the change of elastic modulus, Poisson's ratio, thickness, and the ellipticity of the cement ring does not cause contact failure in the non-ideal state. The first and second interfaces of the cement ring are always in contact with each other. However, under the condition of large cement sheath missing and casing eccentricity, the overall inhomogeneity of cement sheath increases, the interface of cement sheath begins to separate, and the time of separation begins to advance gradually. Therefore, high eccentricity and lack of cement ring may lead to gas leakage from an interface in non-ideal state. Through fatigue analysis, the fatigue times of cement ring are far more than 50 times under ideal and non-ideal conditions, which can meet the requirements of 50 years operation of salt cavern gas storage. Through the above analysis, it is concluded that the cement slurry system with low elastic modulus and high Poisson ratio is more suitable for the requirement of gas storage, and at the same time, keeping the sidewall stable and casing in the middle can ensure the stable operation of the gas storage in the later stage.
【学位授予单位】：西南石油大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TE972

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