Design and Analysis of a Test Rig for Modeling the Bit/Formation Interface in Petroleum Drilling Applications



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Equipment failure and well deviations are prevailing contributors to production delays within the petroleum industry. Particular monetary focus is given to the drilling operations of wells to overcome these deficits, in order to extract natural resources as efficiently, and as safely, as possible. The research presented here focuses on minimizing vibrations of the drill string near the bottom-hole assembly (BHA) by identifying the cause of external forcing on the drillstring in vertical and horizontal wells and measuring the effects of various factors on the stability of perturbations on the system. A test rig concept has been developed to accurately measure the interaction forces and torques between the bit, formation and fluids during drilling in order to clearly define a bit/formation interface law (BFIL) for the purpose vibrational analysis. As a secondary function, the rig will be able to measure the potential inputs to a drilling simulation code that can be used to model drillstring vibrations. All notable quantities will be measured including torque on bit (TOB), weight on bit (WOB), lateral impact loads (LIL), formation stiffness, bit specific properties, fluid damping coefficients and rate of penetration (ROP). The conceptual design has been analyzed and refined, in detail, to verify its operational integrity and range of measurement error. The operational envelope of the rig is such that a drill bit of up to 8 ? inches in diameter can be effectively tested at desired operational parameters (WOB: 0-55,000 lbf, RPM: 60-200) with various rock formations and multiple fluid types. Future use and design possibilities are also discussed to enhance the functionality of the rig and the potential for further research in the area of oil and gas drilling and vibrational modeling.