Performance, simulation and field application modeling of rollercone bits

• A new ROP model is developed for rollercone bits from single cutter–rock interaction.
• Single cutter performance was integrated over the bit area to develop the ROP model.
• The ROP model integrates the effects of operational, bit wear, and design parameters.
• The ROP model estimates both ROP values and rock strength logs with known parameters.
• A systematic simulation method is introduced for drilling optimization studies.

Drilling simulation technology has been used extensively to optimize drilling operations so as to minimize the associated costs and risks. Optimum bit types and designs with corresponding drilling parameters can be recommended utilizing a simulator with rate of penetration (ROP) models. There have been several attempts to develop ROP models that can deliver the most reliable outputs, required for the pre-planning and post analysis applications, using various sets of drilling parameters. However, due to the existing modeling complexities, these attempts have not been successful. In this study, a new ROP model is developed for the rollercone bits, which properly integrates the effect of main drilling parameters as well as cutting structure of the bit. The model is mathematically derived based on the mechanism of single cutter–rock interaction, and calibrated utilizing sets of full scale laboratory data. Also, the bit wear effect for simulating accurate rock strength and ROP values is included in the analysis using a previously published model. One of the most important features of the newly introduced ROP model is that it can be easily inverted to generate accurate rock strength values using offset and/or real-time field data. This unique characteristic of the ROP model makes it a valuable candidate for drilling simulation studies to optimize drilling operations in the most cost effective manner. The verification of the introduced ROP model is performed through series of simulation analysis and comparing the generated rock strength logs to the outputs of a commercially available drilling simulator. The comparison of the results obtained from the simulator and the ROP model as well as field data has been quite encouraging which signifies the application of the developed model in determining the best case scenario for planning and/or drilling of future wells with lowest possible expenditures.

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