In today's drilling industry, all considerations are involved to reduce drilling operation expenditure. In several cases, the drilling optimization is the key point to make a drilling operation economically satisfied. Appropriate bit selection and optimum operating condition can lower the drilling expenditure, effectively. Drilling models are drilling simulators, which can evaluate the effect of different operating conditions on the drilling rate of penetration and drilling expenditure, quantitatively.

The model constants are required to start the optimization process. The model constants are bit constants and formation rock strength. They can be determined from either laboratory tests or the drilling information of offset wells. When model constants are calculated from field data, it is beneficial to use pattern recognition and statistical tools to eliminate the noises and out of range data.

When the drilling model is developed, the optimum operating condition for each bit is calculated. Then, subsequent cost analysis is carried out to determine the cost per foot value of bits in their optimum drilling condition. Consequently, bit runs are compared based on their cost per foot values. Moreover, bit run with minimum cost per foot value along with its optimum drilling condition is selected for drilling of formation under investigation.

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