Bit optimization and application of deep shale gas wells in Weirong gas field of southern Sichuan basin

Weirong gas field has complex geological conditions, old strata and poor drill-ability. Based on the analysis of the application effect and existing problems of drill bits in the early stage, combined with the established strata rock drill-ability profile, the design theory of drill bits is applied to optimize the suitable type of drill bits and determine the key technology of drill bits suitable for this block. The five-blade steel PDC(poly-crystalline diamond composite) bits suitable for the formations of Kaishaximiao formation and Xintiangou formation, and the wear-resisting bits are recommended for the continental formations. The 6-blade matrix PDC bits with strong performances are mainly 6-blade steel PDC bits used in marine strata, and mixed bits are used in some high abrasive strata; 6-blade and short diameter-preserving directional PDC bits are used in the third construction slope section to improve tool surface stability; 5-blade and long diameterpreserving PDC bits are used in the horizontal section. Field application shows that the penetration rate is increased by more than one-fold compared with the previous average index.