| 摘要: |
| 针对套管内压变化影响井筒完整性问题，将套管、水泥环和地层视为弹塑性材料，从微间隙的形成及水泥环周向拉伸破坏两方面综合分析井筒的完整性，采用有限元方法模拟研究水泥环和地层机械参数变化对井筒完整性的影响。结果表明：水泥环弹性模量越大，越易形成微间隙和发生水泥环拉伸破坏；水泥环泊松比越小，形成的微间隙尺寸越大，越易发生水泥环拉伸破坏，但泊松比的影响程度较弹性模量小。地层弹性模量越小，越易形成微间隙且间隙尺寸较大，越易发生水泥环拉伸破坏；地层泊松比越大，形成的微间隙尺寸越大，但其影响程度较弹性模量小；地层泊松比变化对水泥环拉伸破坏的影响较小。在形成微间隙之前就可能会发生水泥周向环拉伸破坏。 |
| 关键词: 变内压 井筒完整性 弹塑性 微间隙 周向拉伸破坏 |
| DOI：10.3969/j.issn.1673-5005.2018.03.008 |
| 分类号:TE21 |
| 文献标识码:A |
| 基金项目:国家自然科学基金项目（51704325，51704321）；国家"973"重点基础研究发展计划项目（2015CB251202）；中央高校基本科研业务费专项（18CX02103A） |
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| Elastoplastic analysis of wellbore integrity under varying internal casing pressure |
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GUO Xinyang1, WU Yongquan2, BU Yuhuan1, LI Qiang3, GUO Shenglai1
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(1.School of Petroleum Engineering in China University of Petroleum(East China), Qingdao 266580, China;2.Kelgary International Oil ＆ Gas Technology Company Limited, Beijing 100123, China;3.No.2 Cementing Company of Bohai Drilling Engineering Company Limited, Tianjin 300280, China)
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| Abstract: |
| In order to study the wellbore integrity under varying internal casing pressure, casing, cement sheath and near wellbore rock formation were considered as elastoplastic materials. The failure modes of the wellbore include the formation of micro-fractures and circumferential tensile damage of the cement sheath. A finite element method was used to simulate the effect of different cement and formation parameters on wellbore integrity. The results show that the larger of the cement sheath elasticity modulus, the higher possibility for the micro-fractures and circumferential tensile damages to occur. As the cement Poisson's ratio decreases, the size of the micro-fracture increases and the circumferential tensile damage is more readily to occur. However, the influence of the cement Poisson's ratio is less than that of the cement elasticity modulus. The smaller of the formation elasticity modulus, the higher possibility for micro-fractures to appear with larger sizes, and more possible for the circumferential tensile damage to occur. The size of micro-fractures increases as the formation Poisson's ratio increases. The effect of formation Poisson's ratio is less than that of formation elasticity modulus, while the effect of Poisson's ratio on the circumferential tensile damage is not significant. The circumferential tensile damage can occur before the micro-fractures form. |
| Key words: internal casing pressure change wellbore integrity elastoplastic micro-fracture circumferential tensile damage |
