Probabilistic wellbore collapse analysis

Al-Ajmi, A.; Al-Harthy, Mansoor H.

doi:10.1016/j.petrol.2010.09.001

Cited by 32 publications

(8 citation statements)

References 12 publications

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“…In the fields, the case where σ θ ≥ σ z ≥ σ r is the most commonly encountered stress state corresponding to borehole collapse [19]. Substituting σ 1 = σ θ , σ 2 = σ z and σ 3 = σ r into Equations (18)- (20), the collapse pressure model with a tolerable breakout width can be expressed as:…”

Section: Collapse Pressurementioning

confidence: 99%

“…However, due to the uncertainty of formation lithology, the uncertainty of formation pressure, the uncertainty of mechanical properties of rocks, and the unstable wellbore pressure, the input parameters of wellbore stability analysis never can be known precisely. In other words, the input parameters are often uncertain, which might cause an incorrect result [14][15][16][17][18][19][20][21][22][23][24][25][26][27][28][29][30]. In order to quantify the influence of uncertain parameters on wellbore stability and SMWW, it's necessary to utilize reliability assessment method.…”

Section: Introductionmentioning

confidence: 99%

“…Sheng et al [19] indicated that because of uncertainty in some key influential parameters, these can lead to uncertainty of wellbore stability, a Monte Carlo uncertainty analysis technique was combined with a numerical geomechanical modelling method to develop a geostatistical approach to determine the uncertainty of wellbore stability. Al-Ajmi and Al-Harthy [20] calculated the value of drilling fluid pressure as a probability distribution by utilizing a probabilistic approach captures uncertainty in input variables through running a Monte Carlo simulation. Aadnøy [21], Aadnoy and Looyeh [4] also utilized QRA to assess the effects of the errors or uncertainties associated with the key data on the instability analysis.…”

Section: Introductionmentioning

confidence: 99%

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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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Section: Collapse Pressurementioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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

Tang

Chen

et al. 2019

Energies

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“…The commonly used criteria are the Mohr‐Coulomb model, the Drucker‐Prager model, and the Hoek‐Brown model. Based on different constitutive models and failure criteria, many finite element models are proposed . Recently, a discontinuity‐based method has been utilized to simulate borehole breakouts .…”

Section: Introductionmentioning

confidence: 99%

Mesoscale numerical study on the evolution of borehole breakout in heterogeneous rocks

et al. 2020

Num Anal Meth Geomechanics

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Inherent heterogeneity of a rock strongly affects its mechanical behavior. We numerically study the mechanisms governing the initiation, propagation, and ultimate pattern of borehole breakouts in heterogeneous rocks. A twodimensional finite element model incorporating material heterogeneity is established to systematically examine the effects of several key factors on borehole failure, including borehole diameter, far-field stress, and rock heterogeneity. The inherent heterogeneity of a rock is explicitly characterized by prescribing the rock mechanical properties of mesoscale elements statistically obeying the Weibull distribution. Elastic damage mechanics is used to represent the constitutive law of the mesoscale element. We find that borehole diameter reduction remarkably changes the crack failure from tensile to shear and elevates the critical hydrostatic pressure. Far-field stress anisotropy strongly affects the shape of the borehole breakout. Rock heterogeneity dictates the location of the preferred crack under the hydrostatic stress, which leads to local stress concentration, and determines the types of breakouts around the borehole. Our findings facilitate in-depth understanding of the classic borehole stability problems in heterogeneous rocks. K E Y W O R D Sborehole breakout, borehole diameter, rock heterogeneity, Weibull distribution

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“…In the process of drilling, the economic loss caused by bore hole instability reaches more than one billion dollar every year, and the lost time is accounting for over 40% of all drilling related nonproductive time [4]. Especially in shallow sediments, because of a very low fracture pressure, drilling accidents are easy to occur [5], Traditional models of borehole stability evaluation are mainly based on elastic mechanics [6][7][8], but in many cases the borehole remains stable even if the stress concentration around the borehole exceeds the formation strength. Especially in shallow sediments, because of a very low fracture pressure, drilling accidents are easy to occur [5], Traditional models of borehole stability evaluation are mainly based on elastic mechanics [6][7][8], but in many cases the borehole remains stable even if the stress concentration around the borehole exceeds the formation strength.…”

Section: Introductionmentioning

confidence: 99%

Borehole Stability Analysis in Deepwater Shallow Sediments

Yan

Deng

Lai

et al. 2014

Journal of Energy Resources Technology

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Borehole Stability Analysis in Deepwater Shallow SedimentsDeepwater shallow sediment is less-consolidated, with a rock mechanical behavior simi lar to saturated soil. It is prone to borehole shrinkage and downhole leakage. Assume the deepwater shallow sediments are homogeneous, isotropic, and ideally elastoplastic mate rials, and formation around the borehole is divided into elastic and plastic zone. The the ories o f small deformation and large deformation are, respectively, adopted in the elastic and plastic zone. In the plastic zone, Mohr-Coulomb strength criterion is selected. The stress and deformation distributions in these two zones, and the radius o f plastic zone are derived. The collapse pressure calculation formula o f deepwater shallow sediments under the control o f different shrinkage rates is obtained. With the introduction o f excess pore pressure theory in soil mechanics, the distribution rule o f excess pore pressure in these two zones is obtained. Combined with hydraulic fracturing theory, the fracture mecha nism o f shallow sediments is analyzed and the theoretical formula o f fracture pressure is given. The calculation results are quite close to the practically measured results. So the reliability o f the theory is confirmed.

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Probabilistic wellbore collapse analysis

Cited by 32 publications

References 12 publications

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

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

Mesoscale numerical study on the evolution of borehole breakout in heterogeneous rocks

Borehole Stability Analysis in Deepwater Shallow Sediments

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