【作者】 董雪林； 高德利； 段之殷；

【Author】 Xuelin Dong;Deli Gao;Zhiyin Duan;Key Laboratory of Petroleum Engineering, China University of Petroleum;Beijing University of Civil Engineering and Architecture;

【机构】 中国石油大学(北京)石油工程教育部重点实验室； 北京建筑大学；

【摘要】 油气管柱是石油天然气工程中的重要组成部分,在钻井、采油和储运各个环节中均发挥重要作用。井筒完整性是确保油气管柱正常、安全、稳定和可靠运行的关键因素。套管-水泥环-地层构成典型的地下井筒组合,在复杂的施工条件和恶劣的地质环境作用下,井筒完整性受到严重的威胁。其中,水泥环是井筒整体中最为薄弱的环节,水泥环完整性受到破坏,将导致油气产量下降、地下物质窜层并对环境造成污染。因此,对水泥环完整性的科学评价与安全分析,是油气管柱完整性管理的重要部分。本文针对水泥环中存在径向裂纹时的裂纹扩展行为进行分析,在非均匀地应力和套管内压作用下计算裂纹尖端应力强度因子。利用弹性力学原理给出载荷作用下水泥环中的环向应力分布,基于权函数法和格林函数计算水泥环中径向裂纹尖端的应力强度因子,结合有限元模拟验证理论模型。更多还原

【Abstract】 Pipings, casings and strings play an important role during drilling, exploration and transmission in oil and gas industry. Particularly well integrity is crucial to safety, stability and reliability of a hydrocarbon well. For instance, casing-cement-stratum is a typical system which is subjected to extreme operations and rigorous downhole conditions. In general, cement sheath is the most vulnerable component, and its failure would reduce the productivity, lose the zonal isolation and contaminate the environment. Therefore, assessment of the cement sheath integrity is essential to the well integrity. This paper focus on the calculation of the stress intensity factor at the crack tip, which generates in the cement sheath and propagates along the radial direction under non-uniform crustal stresses and inner pressure on the casing surface. The hoop stress in the cement is obtained from linear elasticity theory, and the stress intensity factor is derived based on weight function and Green function. Finally, a finite element simulation is carried out to validate the theoretical analysis.更多还原