Simulation and Optimization of Multiple Bit Runs to minimize cost per foot

weight on bit , rotary speed , bit hydraulics and more importantly bit types , are the most important parameters affecting rate of penetration and consequently the economics of drilling . Pulling a worn bit is necessary to make the drilling operations more efficient. cost per foot calculation is a popular criterion used to predict when to pull a bit.simulation is a powerful tool to enhance drilling performance and thereby reducing total drilling cost. in this paper the first 3 thousands feet of a reservoir lithology including four bit runs are simulated so that factors affecting penetration rate are optimized and the lowest possible well cost is achieved. the effects of using other bit types , weight on bit , rotary speed and bit hydraulics are simulated in an attempt to determine the optimized parameters , which result in the lowest drilling cost. overall it was found that in bit runs 2,3 and 4 a lower cost per foot can be achieved using milled tooth bits instead of tungsten carbide types.