Modeling progressive breakouts in deviated wellbores

Li, Xiaorong; Mohtar, Chadi Said El

doi:10.1016/j.petrol.2019.01.007

Cited by 21 publications

(7 citation statements)

References 23 publications

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“…According to the above models, it is feasible to perform the modeling steps and calculations with the aid of the Abaqus finite element software. Abaqus, a finite element software specifically used in geomechanics, exhibits an extremely strong capacity to process nonlinear problems and has been extensively applied to investigate various geomechanical problems such as those associated with petroleum exploration, civil engineering, tunnel construction, and landslides. − Additionally, Abaqus provides many subroutine modules for secondary user development to explore special geological problems. The USDFLD user subroutine is applied to explore the influence of changes in the formation temperature and pore pressure on the hydrate saturation.…”

Section: Establishment Of the Numerical Modelmentioning

confidence: 99%

Stratum Settlement during Depressurization of Horizontal Wells in Gas Hydrate Reservoirs

Cheng

Yan

et al. 2021

Energy Fuels

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The shallow burial of gas hydrates results in stratum settlement owing to pore pressure reduction and hydrate dissociation during depressurization. To understand this behavior in hydrate-bearing stratum, a numerical model for determining the nonlinear mechanical constitutive relation of hydrate-bearing sediments was developed based on the physical and mechanical properties of hydrate-bearing sediments. The model was compared with an ideal elastic–plastic model on the core scale. Furthermore, a model for stratum settlement during depressurization in horizontal wells in hydrate-bearing strata was also established. Variance and range analyses were conducted using an orthogonal design to explore the influences of various factors on the stratum settlement. The results show that when compared with the ideal elastic–plastic model, the established numerical model presents a higher accuracy when characterizing the deformation behaviors of hydrate-bearing sediments at different stress states. During exploitation from vertical wells, the stratum settlement center corresponds to the wellhead. However, in the horizontal well design, the upper strata of horizontal well sections also settle apart from the zones around the wellhead. The wellhead settlement of horizontal wells is attributed to the load-bearing effect of the upper strata and the compaction effect of the middle strata. The load on the wellhead decisively influences the wellhead settlement, which is positively correlated with the drawdown pressure, production time, and build angle rate but shows no obvious correlation with the length of horizontal wells. The drawdown pressure exerts the greatest influence on the settlement of the upper strata in horizontal well sections, and the influences of the production time and the length of the horizontal wells successively follow this.

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Section: Establishment Of the Numerical Modelmentioning

confidence: 99%

Stratum Settlement during Depressurization of Horizontal Wells in Gas Hydrate Reservoirs

Cheng

Yan

et al. 2021

Energy Fuels

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“…where ω is the half of the tolerable breakout width, ( • ). In general, the breakout occurs as a series of successive spalls along the direction of the minimum principal horizontal stress and results from shear failure subparallel to the free wall of the borehole [2,6,28,[32][33][34][35][36][37]. As shown in Figure 5, where 1 , 2 and 3 represent the breakout zones during deepening.…”

Section: Breakout Width Modelmentioning

confidence: 99%

“…The design of mud weight should follow the following principle: safe mud weight should higher than the lowest safe mud weight and lower than the highest safe mud weight. In general, the lowest safe mud weight needs to determine by using the pore pressure and collapse pressure, while the highest safe mud weight needs to determine by using the fracture pressure, and the SMWW can be determined by [5]: max{EMWPP, EMWCP}< SMWW < min{EMWFP} (37) where SMWW is the safe mud weight window, g/cm 3 . Thus, in order to quantitatively assess the reliability of SMWW, we also should determine the reliability of the lowest safe mud weight by integrating the reliability between EMWPP and EMWCP, and the reliability of the highest safe mud weight is just determined by EMWFP.…”

Section: Smww Modelmentioning

confidence: 99%

Uncertainty Evaluation of Safe Mud Weight Window Utilizing the Reliability Assessment Method

Tang

Chen

et al. 2019

Energies

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Due to the uncertainty of formation properties and improper wellbore stability analysis methods, the input parameters are often uncertain and the required mud weight to prevent wellbore collapse is too large, which might cause an incorrect result. However, the uncertainty evaluation of input parameters and their influence on safe mud weight window (SMWW) is seldom investigated. Therefore, the present paper aims to propose an uncertain evaluation method to evaluate the uncertainty of SMWW. The reliability assessment theory was introduced, and the uncertain SMWW model was proposed by involving the tolerable breakout, the Mogi-Coulomb (MG-C) criterion and the reliability assessment theory. The influence of uncertain parameters on wellbore collapse, wellbore fracture and SMWW were systematically simulated and investigated by utilizing Monte Carlo simulation. Finally, the field observation of well SC-101X was reported and discussed. The results indicated that the MG-C criterion and tolerable breakout is recommended for wellbore stability analysis. The higher the coefficient of variance is, the higher the level of uncertainty is, the larger the impact on SMWW will be, and the higher the risk of well kick, wellbore collapse and fracture will be. The uncertainty of basic parameters has a very significant impact on SMWW, and it cannot be ignored. For well SC-101X, the SMWW predicted by analytical solution is 0.9921–1.6020 g/cm3, compared to the SMWW estimated by the reliability assessment method, the reliability assessment method tends to give a very narrow SMWW of 1.0756–1.0935 g/cm3 and its probability is only 80%, and the field observation for well kick and wellbore fracture verified the analysis results. For narrow SMWW formation drilling, some kinds of advanced technology, such as the underbalanced drilling (UBD), managed pressure drilling (MPD), micro-flow drilling (MFD) and wider the SMWW, can be utilized to maintain drilling safety.

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“…For example, Shen et al [19] used the numerical method of boundary element to predict the dog eared failure area for various breakout failure mechanisms, taking into account the different ratios of in situ stress and fluid pressure; they observed that in many cases, the shear failure mechanism plays a role in the final formation of the breakout and the tensile failure mechanism alone cannot cause the formation of the breakout. Li et al [31,32] examined breakout in oblique boreholes and observed that breakout occurs on the plane with minor horizontal stress direction. Rahmati et al [33] used a discrete element method to simulate breakout and investigate the effect of microstructure on failure geometry; according to their results, several factors such as particle stiffness, cementation between particles, and porosity, lead to the formation of fracture-like breakout.…”

Section: Introductionmentioning

confidence: 99%

Sensitivity Analysis of Effective Parameters in Borehole Failure, Using Neural Network

Jolfaei

Lakirouhani

2022

Advances in Civil Engineering

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After drilling a borehole in the ground and in a rocky environment, the materials around the borehole are crushed and separated in layers from the borehole wall; this causes the borehole cross section to lose its original circular shape, which redistributes stresses and further failure. This type of episodic failure, which occurs symmetrically and V-shaped on both sides of the borehole and along the minor principal stress, is called breakout. The dimensions of breakout, i.e., its depth and width, are two important indicators that have recently been used in estimating in situ stresses; however, the dimensions of the breakout area depend on the in situ stresses and mechanical properties of the rock, which have not been well addressed so far. This paper presents a comprehensive investigation of breakout dimensions using finite element numerical analysis. The proposed numerical model is based on the equations governing the two-dimensional breakout phenomenon under nonisotropic in situ stresses and plane strain condition. According to the results, increasing the failure function of the area around the breakout tip causes the breakout to expand, until the failure function is less than 1 for all points around the breakout tip, at which point the breakout expansion is stopped and breakout reaches stability. In the other part of the article, using 121 datasets obtained from numerical analysis, an artificial neural network is trained to predict breakout dimensions based on the input parameters of the problem. The main finding of this section is a model that shows that among the parameters affecting the borehole breakout, the internal friction angle of the rock has the greatest impact on the dimensions of the breakout.

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Modeling progressive breakouts in deviated wellbores

Cited by 21 publications

References 23 publications

Stratum Settlement during Depressurization of Horizontal Wells in Gas Hydrate Reservoirs

Stratum Settlement during Depressurization of Horizontal Wells in Gas Hydrate Reservoirs

Uncertainty Evaluation of Safe Mud Weight Window Utilizing the Reliability Assessment Method

Sensitivity Analysis of Effective Parameters in Borehole Failure, Using Neural Network

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