Bit selection in geological formations

Drill Bits are used to dig wells by breaking or scraping rocks with the power of rotational motion and weight applied from top to bottom. Connected to the bottom of the drill string, it is rotated from the surface together with a rotary table, top drive, or a motor that provides the rotational movement with the hydraulic power of the drilling mud. Generally, a drilling bit consists of three main parts, the shank that provides the connection to the drilling string, the main body, and the excavator structure that does the drilling work. Before reaching the drilling site, the production and joining processes of these parts of the drill bit, reach astronomical levels in terms of cost. For this reason, a drilling bit is expected to show superior performance during drilling activity. To achieve this condition, it is of great importance to choose the appropriate drill bit for lithology. In the drilling of alternating-complex formations with a heterogeneous structure in terms of lithology bands, it can be difficult to choose the suitable drill bit for the formation and to provide predictions in this direction. In this thesis study, the Karadut Complex, which is located in the Southeastern Anatolia Region, contains complex lithologies and consists of allochthonous structures that cannot be predicted from which quantity and what kind of lithology is discussed. In the study, the drilling parameters of 3 PDC's, 6 Roller Cones, and 3 Hybrid drill bits used in 12 ¼" well drilling of 2 wells where the Karadut Complex is located have been graphed. The oil field data of 12 drill bits were evaluated based on ROP (Rate of penetration) and the optimum drill bit selection was tried to be made under/by the Karadut Complex. As a result of the study, it was understood that the use of Hybrid bits for drilling activities in formations such as Karadut Complex, which has complex lithology in terms of hardness and abrasion capability, is more suitable in terms of ROP.