Discrete Element Approach for the Wellbore Instability of Laminated and Fissured Rocks

Yamamoto, Koji; Shioya, Y.; Uryu, N.

doi:10.2118/78181-ms

Cited by 17 publications

(2 citation statements)

References 5 publications

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“…Although this assumption is considered satisfactory for modeling stability of isotropic rocks, it is not valid while drilling through high angle wells (sub-parallel to bedding) through laminated (anisotropic) shale because the bedding layers serve as weak planes that result in strength anisotropy [39][40][41][42][43][44][45][46][47][48][49] . Chenevert (1965) studied the mechanical anisotropies of laminated sedimentary rocks experimentally 39 and determined that the formation compressive strength can vary significantly as the angle between the direction of the axial load and bedding planes vary.…”

Section: Wellbore Stability Modelingmentioning

confidence: 99%

Wellbore Stability Considerations for Drilling High-Angle Wells Through Finely Laminated Shale: A Case Study From Terra Nova

Gallant

Zhang²,

Wolfe

et al. 2007

Proceedings of SPE Annual Technical Conference and Exhibition

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fax 01-972-952-9435. AbstractHigh angle wells drilled into finely laminated shale are often found to be less stable than comparable wells drilled into nonlaminated rock. This can be attributed to a variety of factors including, but not limited to, well trajectory, the in-situ stress field, rock strength anisotropy, shale reactivity issues, chemical imbalances between the drilling fluid and shale pore fluid, and many others. However, due to the lack of available data some of these mechanisms are difficult to quantify and therefore are typically not accounted for during well planning. This can result in significant wellbore instability issues that substantially elevate drilling operation costs.In this paper, a comprehensive approach to account for many of these wellbore instability mechanisms is outlined. A plane-of-weakness model is utilized to account for the effects of weak bedding planes and other discontinuities. The model uses parameters that are obtained by curve fitting triaxial strength test results conducted at various angles with respect to bedding. Additionally, traditional mechanical and chemical effects were also addressed and incorporated into the pre-drill model to assist in well planning. The model was then implemented at the Terra Nova field for the case of a highly deviated wellbore drilled through finely laminated shale nearly parallel to bedding.Real-time monitoring of measurement and logging while drilling data was key to identifying the unstable sections so that the root cause of instability could be diagnosed. The appropriate remedial action was then applied and wellbore instability problems were mitigated.Both mechanical and chemical borehole instability models were applied in a case history to evaluate the potential for wellbore instability. In particular, bedding-plane related and chemically-induced instability were addressed and overcome through comprehensive modeling and the deployment of modified operational procedures.

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Section: Wellbore Stability Modelingmentioning

confidence: 99%

Wellbore Stability Considerations for Drilling High-Angle Wells Through Finely Laminated Shale: A Case Study From Terra Nova

Gallant

Zhang²,

Wolfe

et al. 2007

Proceedings of SPE Annual Technical Conference and Exhibition

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“…This mechanism is qualitatively explained using DEM (discrete element method) by authors 5,6 . This mechanism is qualitatively explained using DEM (discrete element method) by authors 5,6 .…”

Section: Optimization Of Mud Weightmentioning

confidence: 99%

Historical Review and Rock Mechanics Approach to Improve the Wellbore Stability in Nahr Umr Shale Formation

Yamamoto¹,

Waragai²,

Kikuchi³

et al. 2004

Proceedings of Abu Dhabi International Conference and Exhibition

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TX 75083-3836, U.S.A., fax 01-972-952-9435. AbstractIn this paper, the historical review for the drilling troubles encountered in the Nahr Umr (N.Umr) shale formation and the rock mechanics approach to improve the wellbore stability are described. An integrated approach is adopted for this study including the historical review for the actual drilling practices implemented to date, the studies of geomechanics, rock mechanics and chemistry for the N. Umr shale formation.The historical review is performed based on the actual drilling data from year 1991 to March 2004.The geomechanics model is determined with the data from the N. Umr shale formation and adjacent reservoirs. Logging data and collected formation sample data i.e. cores, cuttings are utilized to measure the properties of the formation. Numerical models considering the anisotropy and poroelastic nature of the shale lead the quantification of the failure mechanism.Laboratory testings are conducted to analyze the basic chemical properties of the shale, and the interaction between the shale and mud. A newly produced testing apparatus is applied to determine the shear strength change of the shale under saturated condition with mud. Scanning Electron Microscope is utilized to ensure the failure mechanism and evaluate the validity of the shale inhibitors.In this paper, the outline of the approaches is shown with some details of the testing and analysis methods.

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Oil-based critical mud weight window analyses in HTHP fractured tight formation

Liu

Jin

et al. 2015

Journal of Petroleum Science and Engineering

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Discrete Element Approach for the Wellbore Instability of Laminated and Fissured Rocks

Cited by 17 publications

References 5 publications

Wellbore Stability Considerations for Drilling High-Angle Wells Through Finely Laminated Shale: A Case Study From Terra Nova

Wellbore Stability Considerations for Drilling High-Angle Wells Through Finely Laminated Shale: A Case Study From Terra Nova

Historical Review and Rock Mechanics Approach to Improve the Wellbore Stability in Nahr Umr Shale Formation

Oil-based critical mud weight window analyses in HTHP fractured tight formation

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