Analysis of the External Pressure on Casings Induced by Salt-Gypsum Creep in Build-up Sections for Horizontal Wells

Ge, W. F.; Chen, Mian; Jin, Yan; Zhang, Fuxiang; Lu, Yunhu; Yang, Peng; Ding, Jihui; Zeng, Hao

doi:10.1007/s00603-011-0162-5

Cited by 15 publications

(6 citation statements)

References 8 publications

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“…e goafs of a gypsum mine created by the room pillar method often remain intact for several years or even decades before collapse. Under long-term stress, the stability and lag collapse of a gypsum mine goaf depend to a large extent on the ultimate support capacity of the gypsum ore pillars over time [42][43][44][45][46][47].…”

Section: Experimental Design and Process Of Time Effectsmentioning

confidence: 99%

Influencing Factors for the Instability and Collapse Mode of the Goaf Structure in a Gypsum Mine

Zhi-he

et al. 2021

Advances in Civil Engineering

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Large-area goafs in a gypsum mine tend to collapse after 10 or more years, but the influencing factors are still unclear, and the effects of multiple factors have not been comprehensively considered. In this study, the failure mechanism and collapse mode of the room-pillar goaf structure were analyzed, and the uniaxial compressive strength tests of the pillars under different conditions were carried out in a laboratory. The influences of water, temperature, and time on the strength of the gypsum rock were considered. These three factors weakened the gypsum rock in different degrees. After 120 days of immersion, water had the greatest effect with a strength-weakening rate of 52.61%. After 20 temperature cycles, changes in temperature had little effect with a strength-weakening rate of 12.60%. After 25 years of aging, the strength-weakening rate of time was 25.13%. These results show how different factors affect the instability and collapse of the goaf structure, which are of great significance for predicting and preventing this from happening.

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Section: Experimental Design and Process Of Time Effectsmentioning

confidence: 99%

Influencing Factors for the Instability and Collapse Mode of the Goaf Structure in a Gypsum Mine

Zhi-he

et al. 2021

Advances in Civil Engineering

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“…is the max horizontal stress in situ; ℎ is the max horizontal stress in situ; is casing axial tensile force; BHST is bottom hole standard temperature; BHST is bottom hole circulating temperature; and is drilling mud pressure. [1,6,13,18,19]; despite the complexity of the behavior of salt creep, many scholars agree on several main features of the steady-state creep of salt rock.…”

Section: The Mechanical Modelmentioning

confidence: 99%

Application of Multiphysics Coupling FEM on Open Wellbore Shrinkage and Casing Remaining Strength in an Incomplete Borehole in Deep Salt Formation

Tong

Guo

Zhu

2015

Mathematical Problems in Engineering

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Drilling and completing wells in deep salt stratum are technically challenging and costing, as when serving in an incomplete borehole in deep salt formation, well casing runs a high risk of collapse. To quantitatively calculate casing remaining strength under this harsh condition, a three-dimensional mechanical model is developed; then a computational model coupled with interbed salt rock-defective cement-casing and HPHT (high pressure and high temperature) is established and analyzed using multiphysics coupling FEM (finite element method); furthermore, open wellbore shrinkage and casing remaining strength under varying differential conditions in deep salt formation are discussed. The result demonstrates that the most serious shrinkage occurs at the middle of salt rock, and the combination action of salt rock creep, cement defect, and HPHT substantially lessens casing remaining strength; meanwhile, cement defect level should be taken into consideration when designing casing strength in deep salt formation, and apart from the consideration of temperature on casing the effect of temperature on cement properties also cannot be ignored. This study not only provides a theoretical basis for revealing the failure mechanism of well casing in deep complicated salt formation, but also acts as a new perspective of novel engineering applications of the multiphysics coupling FEM.

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Section: Numerical Calculations Of Well Casings Under Salt Creep Condmentioning

confidence: 99%

“…The wellbore mainly experiences the steady creep stage of salt formation during the service life of the oil and gas wells. Many laboratory works have been devoted to the creep of rock salt, 3,12,17 a large number of constitutive models for salt creep have been put forward by authors, but the steady-state creep described as a Norton–Hoff model is generally accepted, a widely applied formula can be written as follows where ɛ·cr is the steady-state creep rate, (h −1 ); Q is the activation energy (J/mol); R is the universal gas constant (J/mol); σ* is the deviatoric stress (MPa); T is the thermodynamic temperature (K); A , n is constant, which can be determined through laboratory experiments. According to the creep experiments performed on XT-01 HTHP Rheometer, 19 a group of test data is listed in Table 1.…”

Section: Numerical Calculations Of Well Casings Under Salt Creep Condmentioning

confidence: 99%

“…In recent years, with more and more field data demonstrates that well casings designed by API bulletin 5C3 occur failure under salt creep conditions though their designed safety factors are greater than 1. 8,9 Some authors 3,8–13 begin to turn their sights on the cement and formation, which closely connected with the safety of well casings, in summary, their studies indicated that cement missing or deboning changes the stress distribution of the casing, resulting in well casings bearing nonuniform loading; the flowing of salt formation changes the existing local stress field and displacement field, resulting in the time-dependent nonuniform loading on well casings. Previous studies given us enlightenment that formation, cement and casing are an inextricably linked system when it comes to casing failure.…”

Section: Introductionmentioning

confidence: 99%

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Research on a probabilistic assessment criterion of casing deformation in an incomplete borehole in deep salt formation

Tong

Guo

Zhu

2015

Proceedings of the Institution of Mechanical Engineers, Part E:

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Drilling and completing wells through complex salt formation is technically challenging and costing. Field data demonstrates that well casings designed by traditional safety coefficient criterion occurring failure in deep salt formation though their safety factors are greater than 1. To reveal the failure mechanism, a probabilistic computational model coupled with salt formation, defective cement and worn casing is established and analyzed using Monte Carlo simulation method. On the basis of reliability theory, the results calculated by 5000 times simulations show that the traditional safety coefficient criterion has been unable to adapt to the safety assessment of well casings under salt creep conditions. To gain a sophisticated evaluation, a new assessment criterion is established and applied to assess the security of well casings under salt creep conditions. This study provides a new perspective for revealing the failure mechanism and solutions of evaluation on well casings under salt creep conditions, which may be an alternative method to study and predict the life of well casings in deep complicated formation.

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Analysis of the External Pressure on Casings Induced by Salt-Gypsum Creep in Build-up Sections for Horizontal Wells

Cited by 15 publications

References 8 publications

Influencing Factors for the Instability and Collapse Mode of the Goaf Structure in a Gypsum Mine

Influencing Factors for the Instability and Collapse Mode of the Goaf Structure in a Gypsum Mine

Application of Multiphysics Coupling FEM on Open Wellbore Shrinkage and Casing Remaining Strength in an Incomplete Borehole in Deep Salt Formation

Research on a probabilistic assessment criterion of casing deformation in an incomplete borehole in deep salt formation

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