From the magazine

A history of drill tooling

Humble beginnings
The story of drill tooling begins with the development of horizontal directional drilling (HDD) in the early 1970s. The technology was originally used for drilling exploration and various projects in the oil and gas industry.

It wasn’t until the 1990s that HDD was considered a suitable method for underground utility installation. However, the limited capacity of drill tooling meant that HDD was unable to tackle many hard rock formations. The industry responded to this challenge by making significant developments to HDD techniques and drill tooling capabilities throughout the decade.

From compact drill units to hydraulic mud motors
Early on the compact drill units were most commonly used on utility projects, including the installation of underground pipes and cables. These units were able to penetrate most soil types and soft to medium rock formations but were unsuitable for solid rock.

Compact drill units had a slant face downhole bore head, meaning that operators were unable to change the path of the bore head. To solve this problem operators had to alter the position of the slant face and push the drill string forward to create friction against the surrounding soil. While this process worked well on soft ground conditions, it was unsuccessful when used on rock formations.

This obstacle resulted in the development of various adaptations of the slant face bit, each working to varying success, but none meeting the challenge of solid rock.

At the time industry opinion said that the only way to drill through solid rock was with a mud motor – a system where a downhole hydraulic motor driven by drilling fluid is located directly behind the drill bit. The mud motor also solved the problem of steering the bore head as operators were able to change the direction of the path by using a fixed or adjustable bend in the drilling motor, sometimes referred to as a kick.

While they were effective in large-scale applications, mud motors were not suitable for smaller utility projects. The small to medium HDD models used for utility work were not powerful enough to pump sufficient fluid to operate the motor.

The only solution was to invest in new drilling units with adequate pump systems or to set up auxiliary pumps and cleaning systems. For most operators this significant expense was difficult to justify.

These days mud motors are more common in utility installations and often used on large-diameter projects including pipelines and long water crossings.

An industry breakthrough
Once HDD was established as a viable method for utility installation the technology began to develop rapidly. This was driven by rig and tooling manufacturers, who developed drill bits suitable for hard rock. Some smaller contractors were also involved in designing and fabricating rock tools for specific applications.

In 1995 the industry took a big leap forward with the introduction of a 10,205 kg pullback drill unit with a mechanical dual pipe system. Since its introduction this system has been refined to become one of the most effective small to medium HDD solutions for drilling in hard rock.

The 1995 system, applied alongside continuing improvements in the design of slant face bits and the introduction of downhole air hammers for HDD projects, gave contractors a number of option for drilling in rock with small-medium rigs.

A sonde housing crisis
With the rapid development of HDD and drilling tools, operators encountered an unexpected hurdle – the powerful drill bits developed for tackling hard rock challenged the integrity of the corresponding sonde housing designs.

The increased torque loads and vibrations generated from drilling in difficult conditions resulted in the failure of housing lids, sonde covers, tracking sondes transmitters. To avoid the unnecessary cost of replacing sonde housing the industry needed to engineer side-load designs that could withstand the violent effects of rock drilling.

This story is not that uncommon in the drilling industry – when one technology or technique is developed to improve strength and performance it usually identifies weaknesses in other components further up the string.

As with all aspects of HDD technology, constant improvements are being made to match and improve the strength of drill tooling and sonde housing.

2015 and beyond
As the HDD industry continues to grow, associated technologies are seeing the benefits of increased investment in research and development, resulting in greater efficiency, accuracy and productivity across the board.

This positive growth is evidenced in everything from rig and tracking technology through to tooling and support products. Where once operators had a limited selection of drilling tools, these day they have multiple options for different ground conditions and types of installation.

One can only predict what the future of drill tooling will be.

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