Abstract

While the emphasis in diamond bit technology has increasingly shifted toward PDC and TSP technology, two recent innovations, detailed in the paper, are directly applicable to the improvement of natural diamond bits.

Use of numerically controlled milling machines, in conjunction with computerized bit design, allows a reduction in the number of diamonds used on a bit, thus increasing penetration rates through increased diamond loading. The development and use of diamond coating techniques, which offers the possibility of improving the bit-to-matrix bond, allows increased diamond exposure on the face of the bit. When these enhanced bits are coupled with a medium speed, medium torque drilling motor, significant performance increases are realized.

The paper provides analysis of bit runs employing a significant number of enhanced diamond bits in a variety of sizes, hole intervals and well applications, primarily in western Oklahoma's Red Fork formation, which is typically a medium to hard alternating sand/shale sequence. These runs are compared to more than 100 conventional natural diamond bit motor and rotary runs.

In addition, operating limitations and recommendations are outlined for the use of enhanced natural diamond bits, which is shown to have resulted in savings of two to three days per well versus conventional diamond bit motor applications.

INTRODUCTION

Natural diamond drill bits first became popular in the oil and gas industry in the late 1940s. Since that time, a series of improvements has been made to this type of drill bit.

However, in the last several years more dramatic improvements have been made in the use of polycrystalline and thermally stable materials, synthetic or manmade materials with different crystalline structures than natural diamonds. These impressive design enhancements have tended to overshadow the gradual design improvements that have occurred with natural diamond bits.

Recently, new materials research and introduction of computer aided design and manufacturing (CAD/CAM) processes have resulted in new natural diamond drill bit designs which have proved very effective, particularly when such designs are run in combination with the latest version of positive displacement motor. The use of new technology in the design and manufacture of natural diamond drill bits has led in turn, to significant performance improvements, particularly when combined with a bit development program specific to a given application.

A multiwell drilling project incorporating the new drill bit design concepts illustrates the advantages of the new technology. A conventional natural diamond bit design was enhanced using computer-aided design techniques to meet the operator's specific drilling requirements in the Red Fork formation located in western Oklahoma, USA (Figure 1). The operator's drilling requirements are detailed and discussed with respect to their impact on the design process. Over the course of several years and more than 20 wells, the operator was able to realize a significant decrease in drilling days and costs using these new processes.

A comparison of offset performance of more than 100 natural diamond bit/motor runs is also documented and discussed. Operating recommendations resulting from analysis of more than 50 bit runs and the case history of bit development, are presented. Performance results illustrate the effects of the new technology on natural diamond drill bit performance.

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