### Abstract

In studying wellbore instability, it is generally assumed that inputs are certain and average values are used. In practice, however, there are uncertainties that exist in each one of the input variables. To overcome this deficiency a probabilistic wellbore stability model is developed for vertical wells and optimum borehole trajectory determination. The adopted probabilistic approach captures uncertainty in input variables through running a Monte Carlo simulation to calculate the value of drilling fluid pressure as a probability distribution. As a result, the impact of the in situ stresses and rock strength parameters on wellbore stability analysis is captured. It has been found that the maximum horizontal stress, cohesion and friction angle of the rock formation are the most critical factors in wellbore stability analysis under all in situ stress regimes. In addition, the optimum well path is studied and again the maximum horizontal stress followed by minimum horizontal stress impacted well path the most. The suggested probabilistic approach has the ability to systematically quantify the impact of uncertainty which aids more insight in wellbore stability decisions. This approach can be used as a supplement to the current available tools in designing drilling operations.

Original language | English |
---|---|

Pages (from-to) | 171-177 |

Number of pages | 7 |

Journal | Journal of Petroleum Science and Engineering |

Volume | 74 |

Issue number | 3-4 |

DOIs | |

Publication status | Published - Nov 2010 |

### Fingerprint

### Keywords

- Decision under uncertainties
- Drilling
- Mogi-Coulomb criterion
- Risk analysis
- Well path
- Wellbore stability

### ASJC Scopus subject areas

- Geotechnical Engineering and Engineering Geology
- Fuel Technology

### Cite this

*Journal of Petroleum Science and Engineering*,

*74*(3-4), 171-177. https://doi.org/10.1016/j.petrol.2010.09.001

**Probabilistic wellbore collapse analysis.** / Al-Ajmi, Adel M.; Al-Harthy, Mansoor H.

Research output: Contribution to journal › Article

*Journal of Petroleum Science and Engineering*, vol. 74, no. 3-4, pp. 171-177. https://doi.org/10.1016/j.petrol.2010.09.001

}

TY - JOUR

T1 - Probabilistic wellbore collapse analysis

AU - Al-Ajmi, Adel M.

AU - Al-Harthy, Mansoor H.

PY - 2010/11

Y1 - 2010/11

N2 - In studying wellbore instability, it is generally assumed that inputs are certain and average values are used. In practice, however, there are uncertainties that exist in each one of the input variables. To overcome this deficiency a probabilistic wellbore stability model is developed for vertical wells and optimum borehole trajectory determination. The adopted probabilistic approach captures uncertainty in input variables through running a Monte Carlo simulation to calculate the value of drilling fluid pressure as a probability distribution. As a result, the impact of the in situ stresses and rock strength parameters on wellbore stability analysis is captured. It has been found that the maximum horizontal stress, cohesion and friction angle of the rock formation are the most critical factors in wellbore stability analysis under all in situ stress regimes. In addition, the optimum well path is studied and again the maximum horizontal stress followed by minimum horizontal stress impacted well path the most. The suggested probabilistic approach has the ability to systematically quantify the impact of uncertainty which aids more insight in wellbore stability decisions. This approach can be used as a supplement to the current available tools in designing drilling operations.

AB - In studying wellbore instability, it is generally assumed that inputs are certain and average values are used. In practice, however, there are uncertainties that exist in each one of the input variables. To overcome this deficiency a probabilistic wellbore stability model is developed for vertical wells and optimum borehole trajectory determination. The adopted probabilistic approach captures uncertainty in input variables through running a Monte Carlo simulation to calculate the value of drilling fluid pressure as a probability distribution. As a result, the impact of the in situ stresses and rock strength parameters on wellbore stability analysis is captured. It has been found that the maximum horizontal stress, cohesion and friction angle of the rock formation are the most critical factors in wellbore stability analysis under all in situ stress regimes. In addition, the optimum well path is studied and again the maximum horizontal stress followed by minimum horizontal stress impacted well path the most. The suggested probabilistic approach has the ability to systematically quantify the impact of uncertainty which aids more insight in wellbore stability decisions. This approach can be used as a supplement to the current available tools in designing drilling operations.

KW - Decision under uncertainties

KW - Drilling

KW - Mogi-Coulomb criterion

KW - Risk analysis

KW - Well path

KW - Wellbore stability

UR - http://www.scopus.com/inward/record.url?scp=78049489643&partnerID=8YFLogxK

UR - http://www.scopus.com/inward/citedby.url?scp=78049489643&partnerID=8YFLogxK

U2 - 10.1016/j.petrol.2010.09.001

DO - 10.1016/j.petrol.2010.09.001

M3 - Article

AN - SCOPUS:78049489643

VL - 74

SP - 171

EP - 177

JO - Journal of Petroleum Science and Engineering

JF - Journal of Petroleum Science and Engineering

SN - 0920-4105

IS - 3-4

ER -