Working Load Characteristics of the PDC-Cone Composite Bit under Impact and Scraping

Kuilin Huang,Haitao Ren,Chunxiao Zhou,Yingxin Yang,Qingzhi Niu

doi:10.1155/2020/7540519

Abstract

The PDC-roller hybrid bit combines the cutting structure of a tricone bit with a PDC bit. It can achieve good results, breaking rock in directional drilling, drilling in inhomogeneous formations, and drilling in formations with high levels of hardness, and it can achieve the engineering goals of increasing speed and efficiency. First, we analyzed the rock-breaking mechanism of the composite bit and the principles of cushioning, torsion reduction, and prebreaking of the cone teeth during the breaking of rock. Second, cutting load models of the cone teeth and PDC teeth were established through unit experiments and through the calculation methods of the axial force, lateral force and torque, and lateral bending moment of the composite bit. Third, the digital simulation and analysis system was improved to include the function of calculating the working load of the composite bit. Taking an 8-1/2 inch, 2 + 4 type composite bit as an example, the working load characteristics of three cutting structures (cone, blade, and composite) were analyzed and compared. The analysis shows that the composite bit has high drilling efficiency, obvious deviation advantages, and good working stability under specific formation conditions. This paper provides technical support for the performance analysis, formation adaptability evaluation, and cutting structure design optimization of the PDC-cone bit.

Highlights

A PDC-cone composite bit, known as a “cone-PDC hybrid bit,” is a drilling tool used mainly for rock cutting that has PDC teeth on a cutting structure of three-cone bits. e composite drill bit was first proposed by Scott in 1930 [1]
The fixed cutting structure was in the form of a scraper blade, which was limited by that era’s material technology limitations, and was not popularized and applied
With the improvement of the performance index of superhard materials, the possibility of applying a composite drill bit in complicated and difficult-to-drill formations has been reconsidered by technicians

Summary

Introduction

A PDC-cone composite bit, known as a “cone-PDC hybrid bit,” is a drilling tool used mainly for rock cutting that has PDC (polycrystalline diamond compact) teeth on a cutting structure of three-cone bits. e composite drill bit was first proposed by Scott in 1930 [1]. Is paper provides effective technical means for studying the mechanical rules, cutting structure design, analysis, and individual new product development of the PDC-cone composite drill bit. 2. Analysis of Rock-Breaking Mechanism of a PDC-Cone Composite Bit under Impact and Scraping. With the cone-shaped cutting structure of a composite bit, the cone can absorb the drilling pressure and limit the penetration depth of the PDC teeth, so as to protect the PDC teeth and improve the overall impact resistance of the bit. Under the condition of inclined drilling with a conventional PDC bit, the depth of the inner cutting teeth invading the rock is greater than that on the outside, so a great transverse force and lateral bending moment is produced that causes lateral drift of the PDC bit, worsening the stability of the tool surface. Overall working torque amplitude of the bit, and simultaneously avoids the excessive invasion depth of the inner side of the drill bit, reducing the lateral drift of the bit under the condition of inclined drilling

Modeling of the Cutting Mechanics of a PDCCone Composite Bit

A PDC cutter

Findings

Conclusions