Monte Carlo Simulation of Bottomhole Coordinates in Directional Drilling

ENGLISH/ANGLAIS] Affiliations: Department of Mechanical Engineering, University of Nigeria, Nsukka, NIGERIA Address for Correspondence/ Adresse pour la Correspondanc e: ekeochaj@yahoo. com Accepted/Accepté : December, 2013 Citation: Ekeocha RJO. Monte Carlo Simulation of Bottomhole Coordinates in Directional Drilling. World Journal of Engineering and Pure and Applied Sciences 2013;3(1): Increasing interest is now focused on directional survey and on the uncertainty inherent in the calculation of the bottom hole coordinates because many wells are drilled from offshore platforms and urban drill sites. These uncertainties may result from errors due to the limitation on instrument accuracy, unconcentric positioning of the tools with the borehole and may include reading errors. It is therefore necessary to develop methods for determining the cumulative effect of these errors on the bottomhole coordinates and reducing such effects. In this study, Monte Carlo simulation method is adopted as a technique of achieving this objective. The inclination angle, Ii and the azimuthal angle, Ai are treated as random variables with their associated probability density function P(Ii) and P(Ai) respectively. These represent the distributions of the potential survey measurements in a given well. The parameter Si which represents the linear segment constituting the curvilinear axis of the wellbore is treated deterministically since its values can be measured accurately. Treating Ii and Ai as random variables in a wellbore model is justified by the fact that both of them, though deterministic, can hardly ever be measured accurately in any subsurface survey. The results of the study show that the probability of the estimated bottomhole positions being true is nearly unity for vertical well and slightly less for directional well.