The internal pressure strength of tubing and casing often cannot satisfy the design requirements in high pressure, high temperature and high H2S gas wells. Also, the practical safety coefficient of some wells is lower than the design standard according to the current API 5C3 standard, which brings some perplexity to the design. The ISO 10400: 2007 provides the model which can calculate the burst strength of tubing and casing better than API 5C3 standard, but the calculation accuracy is not desirable because about 50 percent predictive values are remarkably higher than real burst values. So, for the sake of improving strength design of tubing and casing, this paper deduces the plastic limit pressure of tubing and casing under internal pressure by applying the twin shear unified strength theory. According to the research of the influence rule of yield-to-tensile strength ratio and mechanical properties on the burst strength of tubing and casing, the more precise calculation model of tubing-casing's burst strength has been established with material hardening and intermediate principal stress. Numerical and experimental comparisons show that the new burst strength model is much closer to the real burst values than that of other models. The research results provide an important reference to optimize the tubing and casing design of deep and ultra-deep wells.
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机译:在高压,高温和高H2S气井中,管道和套管的内部压力强度通常不能满足设计要求。而且,一些井的实际安全系数低于根据当前API 5C3标准的设计标准,这给设计带来了一些困惑。 ISO 10400:2007提供的模型可以比API 5C3标准更好地计算油管和套管的爆裂强度,但是计算精度并不理想,因为约50%的预测值明显高于实际爆裂值。因此,为了提高油管和套管的强度设计,本文采用双剪统一强度理论推导了油管和套管在内部压力下的塑性极限压力。根据屈服抗拉强度比和力学性能对油管和套管破裂强度影响规律的研究,建立了具有材料硬化和中间主应力的更精确的油管破裂强度计算模型。数值和实验比较表明,新的爆裂强度模型比其他模型更接近真实的爆裂值。研究结果为优化深井和超深井的油管和套管设计提供了重要参考。
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