Similarity evaluation of stratum anti-drilling ability and a new method of drill bit selection

Abstract Considering the stratum anti-drilling ability, drill bit working conditions, drill bit application effect and drill bit economic benefits, the similarity of stratum anti-drilling ability was evaluated by grey relational analysis theory to screen out candidate drill bits with reference values. A new comprehensive performance evaluation model of drill bit was established by constructing the absolute ideal solution, changing the relative distance measurement method, and introducing entropy weight to work out the closeness between the candidate drill bits and ideal drill bits and select the reasonable drill bit. Through the construction of absolute ideal solution, improvement of relative distance measurement method and introduction of entropy weight, the inherent defects of TOPSIS decision analysis method, such as non-absolute order, reverse order and unreasonable weight setting, can be overcome. Simple in calculation and easy to understand, the new bit selection method has good adaptability to drill bit selection using dynamic change drill bit database. Field application has proved that the drill bits selected by the new drill bit selection method had significant increase in average rate of penetration, low wear rate, and good compatibility with the drilled formations in actual drilling. This new method of drill bit selection can be used as a technical means to select drill bits with high efficiency, long life and good economics in oilfields.