A Brief Introduction to the Technology of Tricone Bit

At present, the market of cone bit has become standardized and orderly. The competition in roller cone bit market is developing in the direction of product differentiation, brand and after-sales service. As one of the two cornerstones of market competitiveness, the role of tricone bit technical service will be more and more obvious.

1. Stratum lithology

Because of the different lithology, hardness and rock breaking mechanism, the failure forms of roller cone bit are different. The physical and mechanical properties of formation lithology, which is common in drilling in various oilfields in China, have been measured. According to the formation lithology and record of drilling time per meter collected on site, the hardness, plasticity, brittleness, abrasiveness and drillability of formation rock are analyzed. The failure forms of tricone bit are compared to confirm whether the selection and use of roller cone bit are reasonable.

2. Well location

The mechanical properties of rocks in different positions in the crust vary greatly. The deep buried rock is in the state of multi-directional compressive stress, which makes the porosity decrease and the strength increase. Generally, the rock in the upper section is loose cemented and soft, with high bit speed and low bit pressure. Generally, the rock in the lower section is hard and abrasive, and the rotary bit has low speed, high WOB and long service time. According to the collected well location and record of drilling time  per meter, the characteristics of hardness, plasticity, brittleness, abrasiveness and drillability of formation rock are analyzed, and the failure forms of cone bits are compared to confirm whether the selection and use of cone bits are reasonable.

3. Well structure

Different wellbore structures have special requirements for the size, type and use of cone bits. For example, the inclining cone bit is required to have trimming teeth or gauge structure, and the use requires high speed and low weight on bit. The data of wellbore structure, tricone bit selection and operational parameters are collected to confirm whether the selection and use of cone bit are reasonable according to the failure form of cone bit.

4. Drilling parameters

The determination of weight on bit and rotation speed not only determines the efficiency of rock breaking, but also affects the wear of the teeth and bearings. In shallow wells and soft formations, the cone bit shears, and generally adopts high speed and low drilling pressure. In medium-hard formations, the cone bit has the comprehensive action of shearing, impact and crushing, and generally uses medium speed and medium and high weight-on-bit. In deep wells and hard formations, cone bits are mainly used for crushing and impact, generally with high weight-on-bit and low rotation speed. The reasonable selection of drilling parameters largely determines the failure mode of cone bits. The shift report and weight indicator are collected to analyze the drilling parameters and their changes, and determine the fairness of use according to the failure mode of the roller cone bit.