Oil well drilling is a highly complex process that leads to routine drilling operational problems. A drilling problem is any occurrence or condition that stands in the way of well objectives. It could involve anything from weather to transportation delays to blowouts. This paper concentrate on problems that occur as part of the drilling process itself and possible way to reduce such problems. A comprehensive, thoroughly researched well plan is our best defense against drilling problems. In order to minimise some of these problems, an extensive study was carried out on different drilling problems cases. An important problem in drilling is hole cleaning, in which a high number of observed parameters and other features are involved. This paper aimed to determine the basic problem associated with the drilling process of poor hole cleaning and create a simplified way based on drilling literature to optimize the drilling process acording to the total drilling costs for a set of given conditions and moreover, to identify the optimal controlled variables for the drilling process. Drilling optimization involves using available resources to minimize overall cost, subject to safety and well completion requirements. Part of this, of course, entails preventing or successfully solving hole problems. Conclusively, after an extensive literature search was performed, covering the drilling process and the challenges involved. The optimization of the drilling process was analyzed separately for the active drilling operations and pipe connections and drilling trips. The result shows that many parameters are involved in the drilling process, and deviation of one factor may lead to hole cleaning issues and other problematic situations, the time spent during pipe connection- and drilling trip procedures is identified as an important factor in the optimization of the drilling process. The constraints on the bottom hole pressure and mud circulation rate were active at the optimum but removed from further analysis when the bottom hole pressure was controlled by the choke pressure, while the main mud pump flow rate was kept constant. For single measurement controlled variables, the results show that it is optimal to control the topdrive power by manipulating the drill string rotational speed, and keep the weight on bit (WOB) constant. Combination of several measurements will give a minimum loss, with an increase in the complexity of the control structure.