Numerical investigation of casing shear deformation due to fracture/fault slip during hydraulic fracturing,Energy Science & Engineering

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Numerical investigation of casing shear deformation due to fracture/fault slip during hydraulic fracturing
Energy Science & Engineering ( IF 3.5 ) Pub Date : 2020-06-17 , DOI: 10.1002/ese3.766
Hu Meng ₁ , Hongkui Ge ₁ , Dengwei Fu ₂ , Xiaoqiong Wang ₁ , Yinghao Shen ₁ , Zhenxin Jiang ₂ , Jianbo Wang ₁

Affiliation

The frequent occurrence of casing failure has significantly affected the development of shale gas in the Sichuan Basin. Based on engineering and geology analyses, natural fracture/fault slip leads to casing shear deformation during hydraulic fracturing. Hence, natural fracture/fault slip and casing‐cement sheath‐formation assembly finite element models were established to quantitatively examine the characteristics of natural fracture/fault slip and mechanisms of casing shear deformation. Many factors, such as formation elastic property, in situ stress, natural fracture/fault geometry property, fluid pressure, casing elastic property, cement sheath elastic property, and well trajectory, were considered. The simulated results were in good agreement with the field data. The results indicated that natural fracture/fault slip leads to a sharp increase in casing deformation and stress in the adjacent region. Furthermore, factor sensitivity analysis results showed that a higher fluid pressure, larger fracture length, larger fracture dip angle, higher in situ stress difference, lower formation Young's modulus, and shorter distance from the wellbore to the center of the slip surface lead to severe casing stress and deformation. The countermeasures for preventing casing shear deformation involve decreasing the fracturing treatment pressure, reducing the crossing angle between the wellbore and natural fracture/fault, maintaining a safe distance from the wellbore to the large fracture/fault center, and adopting “balanced stress” fracturing operation. Hence, this study proposes a reasonable method to evaluate casing shear damage under hydraulic fracturing.

中文翻译：

水力压裂过程中裂缝/断层滑动引起套管剪切变形的数值研究

频繁发生的套管破裂严重影响了四川盆地页岩气的发育。基于工程和地质分析，自然裂缝/断层滑动会导致水力压裂过程中套管剪切变形。因此，建立了天然裂缝/断层滑动和套管-水泥鞘-地层组合有限元模型，以定量检查天然裂缝/断层滑动的特征和套管剪切变形的机理。考虑了许多因素，例如地层弹性，原地应力，自然裂缝/断层几何性质，流体压力，套管弹性，水泥鞘弹性和井眼轨迹。模拟结果与现场数据吻合良好。结果表明，自然的裂缝/断层滑动导致邻近区域的套管变形和应力急剧增加。此外，因子敏感性分析结果表明，较高的流体压力，较大的裂缝长度，较大的裂缝倾角，较高的原地应力差，较低的地层杨氏模量以及从井眼到滑移面中心的距离较短，会导致严重的套管应力和变形。防止套管剪切变形的对策包括降低压裂处理压力，减小井眼与自然裂缝/断层之间的交角，保持井眼到大裂缝/断层中心的安全距离以及采取“平衡应力”压裂作业。。因此，

更新日期：2020-06-17

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