Eric Maidla

An example of the drilling analysis process for extended reach wells

Between 90 to 95 percent of all operational and engineering activities are directed at the active part of drilling the well. Planning and analysis for wells are passive activities which precede and follow the well respectively. Planning could account for 5 to 8% of the activities per well, and analysis of a well might be (at best) 2 to 4%. Usually analysis is not done at all. This paper presents two new major concepts. The first is the Drilling Learn Curve Management (LCM) system for doing drilling. And the second is the drilling analysis process that supports better well planning, learning faster to improve performance and how to achieve better overall drilling performance. The value added of drilling analysis is demonstrated by an example learn curve and time versus depth analysis for three long departure offshore wells. It is shown how, starting with a high level macro learn curve analysis down to the detached time versus depth analysis, major improvements could be made for the drilling of future extended reach wells in this area. The authors believe the time has come for drilling analysis to be developed as a major tool to improve drilling performance. Accepting and practising the drilling analysis concept could eventually help reduce overall drilling costs by 10 to 25% (conservative estimate).

BHA Design Algorithm for Extended Reach Wells

A design criterion is developed to select the optimum bottomhole rotary assembly configuration (drill collar size and stabilizer positions). This allows maximum correction in the hole inclination by changing the weight on the bit while drilling a section of a hole. A computer algorithm is written in FORTRAN code to optimize the bottomhole assembly configuration. This algorithm can be used with any BHA model that calculates forces at the bit under static or dynamic conditions. A case study is presented to explain the design algorithm.