Bit Selection for Drilling of Jurassic in Kekeya Block in Tuha Basin

Proper bits can not only obviously improve the rate of penetration(ROP) and drilling quality,reduce drilling cost,but also decrease the complex cases of downhole.The main lithology of Kekeya structure in Tuha basin is dominated by conglomerate and mudstone-sandstone mixing layer and characterized by dense,grinding resistance and low drillability,causing low ROP and drilling efficiency.By means of drillability profile,combined with the principal component analysis and mathematical statistics methods,this paper selected the optimal bits for the lithology.Practices indicate that the cone bits and PDC bits selected by the synthetical methods can increase the ROP and decreases the complex cases,thus shorten the drilling cycle and save the cost,being meaningful to bits selection of neighbor wells and blocks in this area.