非均匀地应力下井壁Von Mises应力及稳定性分析
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摘要
为分析非均匀地应力作用下井壁Von Mises(米塞斯)应力及其对井壁稳定性的影响,建立了非均匀地应力作用下井壁附近岩石的力学分析模型。根据弹性力学中应力与应力函数之间的关系,应用叠加原理,导出了非均匀地应力下井壁径向应力、环向应力和剪切应力计算公式,分析了非均匀地应力对井壁稳定性的影响,确定了以钻井液密度为自变量的井壁Von Mises应力的二次拟合公式。采用拟合公式计算的井壁Von Mises应力误差小于2.5%,利用该公式可以确定井壁岩石不会破裂的钻井液密度。
In order to analyze the influence of Von Mises stress on the borehole wall under non-uniform insitu stress and its effect on the stability of the borehole wall, a mechanical analysis model of the rock near the wellbore wall under non-uniform in-situ stress was established. According to the relationship between stress and stress function in elastic mechanics, based on the superposition principles, the formulas of radial stress,circumferential stress and shear stress are derived, the influence of non-uniform in-situ stress on wellbore wall stability is analyzed, the quadratic fitting formula of the Von Mises stress on the wellbore wall with the density of drilling fluid as the independent variable is determined. The error of Von Mises stress calculated by the fitting formula is less than 2.5%, and this formula can be used to determine the density of drilling fluid in the wellbore wall rock without fractures.
In order to analyze the influence of Von Mises stress on the borehole wall under non-uniform insitu stress and its effect on the stability of the borehole wall, a mechanical analysis model of the rock near the wellbore wall under non-uniform in-situ stress was established. According to the relationship between stress and stress function in elastic mechanics, based on the superposition principles, the formulas of radial stress,circumferential stress and shear stress are derived, the influence of non-uniform in-situ stress on wellbore wall stability is analyzed, the quadratic fitting formula of the Von Mises stress on the wellbore wall with the density of drilling fluid as the independent variable is determined. The error of Von Mises stress calculated by the fitting formula is less than 2.5%, and this formula can be used to determine the density of drilling fluid in the wellbore wall rock without fractures.
引文
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[2]蒋晓红,刘其明,衡俊鹏.川西大邑地区气体钻井井壁稳定性评价研究[J].石油地质与工程,2011,25(2):95–97.
[3]周国庆,程锡禄.特殊地层中的井壁应力计算问题[J].中国矿业大学学报,1995,24(4):24–25.
[4]姚直书,李瑞君.考虑竖向附加力时井壁应力计算方法[J].东北煤炭技术,1997,4:3–4.
[5]李军,柳贡慧,陈勉.正交各向异性地层井壁围岩应力新模型[J].岩石力学与工程学报,2011,30(12):2 481–2 482.
[6]王建军,林凯,王新虎,等.易坍塌地层椭圆形井眼内套管应力的有限元分析[J].石油大学学报,2004,28(2):45–46.
[7]冉小丰,王越之,贾善坡,等.基于渗流–应力–损伤耦合模型的泥页岩井壁稳定性研究[J].中国科技论文,2015,10(3):370–374.
[8]光新军,陈曾伟,刘修善,等.三向应力状态下层理性泥页岩地层井壁稳定性研究[J].科学技术与工程,2015,15(5):54–57.
[9]何朋立,郭力,王在泉.深厚表土层井壁温度竖向附加应力分析[J].金属矿山,2015,(4):119–122.
[10]欧焕农.应力状态对井壁失稳安全性的影响分析[J].科学技术与工程,2013,14(6):1 588–1 591.
[11]郭莉霞,蒋晓红,黄振华.完整性与非完整性井壁应力模拟分析研究[J].钻采工艺,2011,34(5):10–12.
[12]王渭明,路林海.正交各向异性复合井壁应力变形分析与应用[J].力学与实践,2009,31(1):52–56.