Research on drill bit selection method based on VSI

Optimizing drill bit type is one of the most direct and effective method to improve the drilling speed and reduce drilling cost. Through the comprehensive consideration of the influence of weight on bit, rotary speed, torque and hydraulic parameters on rock fragmentation efficiency, and according to the theorem of energy conservation, a virtual intensity index （VSI） model is established. The model is used to calculate the VSI of different drill bits, and considering drilling footage and cost, effective index is used to quantitatively evaluating the bit use effect, and furthermore to eliminate the affecting of human factors in the process of bit type selection, which provides a scientific basis for bit type selection. The method is applied in Jiudong field of Yumen Oilfield, and according to the value of the efficiency index, different drill bit types are optimized to fit for wellbores with diameter of 311 mm and 216 mm. Field applications show that ROP is increased by 1.94 times and 2.77 times respectively, and a significant speed-up effect is achieved, which sets up a foundation for further improving drilling speed and accelerating the process of exploration and development in Jiudong field.