Abstract

Drill bits manufactured using the powder forge (PF) process rather than conventional welded hard metal are setting new standards for soft formation drilling. The PF process provides unique advantages in hardmetal placement and metallurgical design thus allowing cutting structures capable of drilling a variety of formations from IADC 11 to 41 and fixed cutter type applications with superior performance. This paper will:

• Explain the PF manufacturing process, highlighting lessons learned in the development learning curve.

• Review the benefits of producing bits using this process.

• Examine actual field results showing the cost savings available through application of cutting edge technologies.

• Discuss the improved wear characteristics of PF bits that has led to changes in operational variables such as weight on bit, rpm, hydraulic horsepower and monitoring drilling progress based on changes in rate of penetration.

Introduction

In 1984, ReedHycalog began to explore a distinctly new manufacturing process that led to PF cutter technology. Experiments with an advanced forging method that formed and “densified” cutters allowed the creation of cutting structures that were unachievable with conventional closed-die forging and machining.

Full-scale tests were conducted in 1991 with prototype bits that duplicated the cutting structure and materials used in standard IADC 11 type cutters. The following year a unique manufacturing facility was built and in 1993 testing began with 9 7/8-in experimental bits featuring advanced profile designs.

Two key observations were made following these runs: the bits showed a significant improvement in durability over conventional bits and wear was also very consistent between bits. The similarity of dull conditions was attributed to the inherent consistency of the manufacturing process. These observations are discussed in SPE 26344.

R&D efforts slowed in the late 1990s but after 2000, as the business climate improved, these early successes led to a renewed emphasis on commercialization of the technology. Since then, significant advances have been made in the PF process, including geometric control and process automation. The resulting product consistency led to development of an IADC 117 product line with 7 7/8-in (200 mm), 8 _-in. (216 mm) and 8 _-in. (222 mm) sizes, and plans were made for production of 9 7/8-in. (251 mm) and 12 _-in. (311 mm) bits featuring PF cutter technology.

In field applications around the world the unique characteristics afforded by the PF process have improved bit performance compared to offset wells drilled with conventionally manufactured bits. These improvements include footage, ROP and bearing life.

For instance, directional and vertical footage compared to offsets nearly doubled with the use of PF bits in Louisiana. In West Texas, an average cost per foot savings of 16% has been achieved while increasing footage and setting a new field ROP record. In Russia, bearing failures that occurred in 80% or more of conventional bits were eliminated, while footage improved 25.6% and ROP was 15.9% faster.

PF Manufacturing Process

The PF manufacturing process begins with creation of a solid cutter structure or form referred to as a “pattern.” Its shape, which only remotely resembles the final form the cutter design will take, is determined by a mathematical model that anticipates the high degree of asymmetric compression which occurs later during densification. This pattern is used to create a flexible mold. (See Figure 1)

In a separate step, hardmetal tooth coatings or “caps” are formed by an injection molding process. The hardmetal to be injected is prepared as a pliable material consisting of precisely mixed metals such as tungsten carbide pellets, steel powder and binders.