Risk assessment of packed holeassemblies for rotary well drilling

Abstract

The main elements of the statistical model of packed hole assemblies (PHA) design for drilling holding sections in the conditions of information uncertainty have been formalized and described. Сonstraints ystem has been given for angle maintain conditions of wellbore direction and dynamic stability of bottom hole assembly (BHA) lateral vibrations. The influence of information uncertainty of some factors (angle, parameters of the drilling practice, presence of local caverns, etc.) on risk indicators has been analyzed according to the results of numerical calculations. It has been specified that the risks of angle maintenance disturbance are significantly influenced by the angle and the weight on the bit (WOB), and dynamic stability conditions, such as angle and rotation frequency. Risks of multi-supported BHAs which have been designed for conditions of bit side force minimizing, dynamic stability and include 4 – 6 stabilizers.