The current paper presents three analytical methods for evaluating the influence of parameter uncertainties in the wellbore failure process: FOSM (First Order Second Moment), FORM (First Order Reliability Model) and SEAM (Statistical Error Analysis Method). Results generated by Monte Carlo method are used as reference. These methods evaluate the probability of failure based upon reliability indexes. The paper also presents the results of a sensitivity study to establish the most important parameters that control wellbore instability. This is necessary in order to limit the number of calculations before establishing the probability of failure. The results demonstrate the importance of reducing uncertainties associated with the relevant parameters by means of careful testing procedures.

Keywords:
failure mode, upstream oil & gas, standard deviation, wellbore integrity, internal pressure, spe isrm 78179, model output, probability, probabilistic analysis, equation
Subjects:
Wellbore Design, Hydraulic Fracturing, Reservoir Characterization, Wellbore integrity, Reservoir geomechanics
Copyright 2002, Society of Petroleum Engineers
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