The rising application of Positive Displacement Motors (PDM) and Polycrystalline Diamond Compact (PDC) drilling bits in directional and horizontal drilling operations creates a demand for a simulator tool which enables the drilling engineer to simulate these operations in a pre-planning mode. Therefore, a new approach to model the motor/bit integration was developed in this study which can be used to simulate drilling operations with a PDM and a PDC bit. The method can also be used to determine an optimum set of operational parameters in terms of weight on bit and surface rotary speed to reach the highest average rate of penetration for a given formation or depth interval.;A background is established for the method by literature review of PDMs and PDC bits; their design and geometrical definitions and models developed to predict their performance. The PDM model considers the design and geometry of the motor and links the differential pressure and mud flow rate across the motor to its output torque and RPM. The PDC bit model predicts bit performance while integrating the effect of bit wear. The PDC bit model estimates ROP and torque for a set of applied operational parameters. The model was developed using single cutter test data from Sandia National Laboratories and full scale laboratory drilling data from BP-Amoco research center. The model also predicts bit wear rates dependent on the applied operational parameters and formation properties and estimates cumulative bit wear as drilled depth increases.;The simulation method applied to the integrated models is based on dicretizing drilling interval into meter by meter sub-intervals and estimating ROP in each sub-interval while considering the PDM output parameters. The method is verified by using the inverted ROP model to predict a confined rock strength log based on drilling data for a previously drilled well in Alberta. This meter by meter strength log is compared to a confined rock strength log generated by a commercially available drilling simulator package. Also, the PDM differential pressure log is generated and compared to field recorded on bottom motor differential pressure values supplied by Husky Energy. Two applications of this method are illustrated by examples. First, a case study is done in a drilling interval of a well in Alberta, by simulating the performance of three different PDMs, to show how improper PDM selection can affect drilling operation results. Secondly, optimization is done for three PDMs in that interval by means of the method to determine an optimum set of operational parameters, i.e. WOB and surface RPM, for maximum ROP and lowest cost.
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