Prediction of Mud Pressures for the Stability of Wellbores Drilled in Transversely Isotropic Rocks

Deangeli, Chiara; Omwanghe, Omoruyi Omoman

doi:10.3390/en11081944

Cited by 16 publications

(27 citation statements)

References 49 publications

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“…Insitu stress and bedding plane orientations should therefore be correctly accounted for to assess the wellbore stability. Note that wellbore orientation c is similar to one of cases considered in Deangeli and Omwanghe (2018). Although the elastic anisotropy and initial undrained pore pressure response are not considered by them, the failure regions predicted for the wellbore orientation are consistent with their results.…”

Section: )supporting

confidence: 70%

“…For example, a horizontal well drilled in the maximum horizontal stress direction (orientation g) does not show bedding plane failures, while other two horizontal wells (orientations c and e) show noticeable failures. Inclination of the bedding planes also affects the failure region (e.g., Deangeli and Omwanghe 2018). Insitu stress and bedding plane orientations should therefore be correctly accounted for to assess the wellbore stability.…”

Section: )mentioning

confidence: 99%

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Anisotropic Wellbore Stability Analysis: Impact on Failure Prediction

Asaka

Holt

2020

Rock Mech Rock Eng

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Shale formations are the main source of borehole stability problems during drilling operations. Suboptimal predictions of borehole failure may partly be caused by neglecting the anisotropic nature of shales: Conventional wellbore stability analysis is based on borehole stresses computed from isotropic linear elasticity (Kirsch solution) with the assumption of no induced pore pressure. This is very convenient for a practical implementation but does not always work for shales. Here, anisotropic wellbore stability analysis was performed targeting an offshore gas field to investigate in particular the impact of elastic anisotropy on borehole failure predictions. Stress concentration around a circular borehole in anisotropic shale was calculated by the Amadei solutions, and induced pore pressure was obtained from the Skempton parameters based on anisotropic poroelasticity. Borehole failure regions and modes were then predicted using the effective stresses and those are apparently consistent with observations. A comparison with the conventional approach suggests the importance of accounting for elastic anisotropy: Predicted failure regions, modes, and also the associated mud weight limits can be completely different. This observation may have significant implications for other fields since shale often show strong elastic anisotropy.

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Section: )supporting

confidence: 70%

Section: )mentioning

confidence: 99%

Anisotropic Wellbore Stability Analysis: Impact on Failure Prediction

Asaka

Holt

2020

Rock Mech Rock Eng

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“…Based on the process of offshore gas reservoir production, the wellbore pressure distribution model in the process of producing water-bearing natural gas is established [43][44][45]:…”

Section: Wellbore Pressure Modelmentioning

confidence: 99%

Hydrate Formation and Decomposition Regularities in Offshore Gas Reservoir Production Pipelines

et al. 2020

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In recent years, the exploitation and utilization of offshore oil and gas resources have attracted more attention. In offshore gas reservoir production, wellbore temperature and pressure change continuously when water-bearing natural gas flows upward. The wellbore temperature is also affected by the low-temperature sea water. The combination of temperatures and pressures controlled by the upward flow, and cooling from the surrounding seawater frequently leads to the conditions of temperature and pressure for hydrate formation. This can lead to pipeline blockage and other safety accidents. In this study, we utilize mathematical models of hydrate phase equilibrium, wellbore temperature, wellbore pressure to study hydrate formation and decomposition in offshore gas reservoir production. Numerical solution algorithms are developed and numerical solutions are validated. The sensitivity influence of different parameters on the regions and regularities of hydrate formation and decomposition in wellbores are obtained through numerical simulations. It is found that increased daily gas production, water content, or geothermal gradient in offshore gas reservoir production pipelines results in less hydrate formation in the wellbores. Accordingly, the risk of wellbore blockage decreases and production safety is maintained. Decreased tubing head pressure or seawater depth results in similar effects. The result of this study establishes a set of prediction methods for hydrate formation and decomposition that can be used in the development of guidelines for safe construction design.

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“…Another researcher established a weak plane model and discovered that it is effective in predicting stratigraphic wellbore failure, except for obvious loose or plastic formations [21]. Therefore, it is determined that the direction of the weak plane is closely related to wellbore failure [22]. As a result, the isotropic wellbore stress distribution model is established [23,24], and it is found that Poisson's ratio has little influence on borehole stability in shale formation [25,26].…”

Section: Introductionmentioning

confidence: 99%

Influence of the Weakening Effect of Drilling Fluid on Wellbore Stability in Anisotropic Shale Formation

et al. 2021

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For horizontal wells in Longmaxi Formation, oil-based drilling fluid that soaks for a long time is more likely to cause a wellbore collapse. Therefore, in this paper, the downhole core method of shale formation, in Longmaxi Formation, was adopted. First, rock samples were selected from different sampling angles and soaked with field drilling fluid. Second, a triaxial mechanics experiment was carried out. Based on the anisotropic wellbore stress distribution model, the stability of shale wellbore was calculated and analyzed. The results show that the compressive strength and cohesion of the shale are reduced after soaking in the drilling fluid. Hence, the reduction range of various sampling angles obviously differs as well. Shear failure occurs in vertical stratification; shear slip failure occurs along the weak plane, showing strong anisotropy. Combined with the experimental results, the collapse pressure is calculated, and it is found that the weakening effect of drilling fluid makes the overall collapse pressure rise by about 0.2 g/cm3. Finally, the shale bedding dip and dip direction have a great influence on the collapse pressure. The lower critical mud weight always takes the minimum value when the borehole axis is perpendicular to the bedding.

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Prediction of Mud Pressures for the Stability of Wellbores Drilled in Transversely Isotropic Rocks

Cited by 16 publications

References 49 publications

Anisotropic Wellbore Stability Analysis: Impact on Failure Prediction

Anisotropic Wellbore Stability Analysis: Impact on Failure Prediction

Hydrate Formation and Decomposition Regularities in Offshore Gas Reservoir Production Pipelines

Influence of the Weakening Effect of Drilling Fluid on Wellbore Stability in Anisotropic Shale Formation

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