Edge Drilling director, John Argiropoulos, recently took delivery of a Boart Longyear LS250 MiniSonic rig that is suited to a variety of soft ground, shallow drilling projects including environmental, tunneling, water management, grade control, leach pads, and tailings dams.

The rig delivers faster penetration for nearly undisturbed samples using little or no fluids, said John, and its casing system makes it ideal for a variety of applications including mining, environmental, and infrastructure projects.

The rig provides extremely accurate sampling for unconsolidated formations which makes it suited to mining, but it also eliminates the risk of cross contamination making it ideal for environmental and geotechnical work. It can also precisely drill straight holes at varying angles which ticks the box for infrastructure projects.

“We've already got five months of work lined up with the rig," John told Australasian Drilling.

The idea of acquiring a sonic rig first came to John during a visit to Christchurch in New Zealand where he saw the rigs undertaking post-earthquake recovery sampling work.

“I've been looking at getting into this type of drilling from the first time I saw it,” he said.

“After the earthquake in Christchurch, I saw massive advantages with sonic rigs in drilling overburden and getting near on 100 percent recovery sampling. The rigs were drilling every house in carports or garages and were looking for signs of liquefaction.”

Liquefaction is where the strength and stiffness of soil is reduced by earthquake shaking. If liquefaction was found following testing in Christchurch, the dwelling would be demolished.

“They had conventional rigs at the start including standard diamond drilling, but they weren't getting any core recovery, being glacial fill," John said. "However, the sonic rigs collected everything from pebbles and cobbles, to rock, clay, silt and sand. They were very impressive.”

With work increasing, John eventually took the plunge and invested in a sonic rig.

“We're getting much busier,” he said. “In the space of 12 months, we've gone from two rigs at the start of last year to seven rigs now. We've expanded quite a lot.”

John said work began to resurge since 2016. A big push by Main Roads WA (Western Australia) for testing bridges across the state is creating work from the rollout of the government's METRONET program and is expected to generate more construction activity and geotechnical work in the near future. The METRONET program is one of the largest single investments in public transport that Perth has seen and will involve about 72 km of new passenger rail and up to 18 new stations.

With enhanced capabilities thanks to the new rigs, John is upbeat in his outlook for the business. However, like most contractors, he is feeling the pain of skill shortages. John said he is managing the issue through in-house training.

"I'm a firm believer of training in-house as the best way forward because we can train personnel according to our standards, expectations, policies, and procedures.”

Originally published in Australasian Drilling Magazine, February/March 2020

Boart Longyear historically named their overburden and construction drilling products line for this type of drilling “Delta” tools. In addition to being the fourth letter of the Greek alphabet, and a code word representing the letter D, (used in radio communication), delta is also defined as the difference between two things or values, or the average change of any changeable quantity. In short, the overburden construction drilling product line was designed for drilling through changing ground conditions typically encountered above bedrock.

With more and more challenging and larger specialty geotechnical construction projects in difficult, complex, and varying ground conditions, rotary and percussive drill rigs in the construction industry were getting stronger and more powerful. Bigger, stronger, and more powerful rigs subsequently required larger, stronger, longer-lasting construction drilling tools – including better designed and manufactured casing bits.

Casing bits are used in deep, difficult overburden when a casing shoe is not sufficient to drill to depth. There have not been any significant advancements made in casing bit designs since the 1990’s. The so called “proven, bullet-proof” bits were made day after day without questioning the physical mechanics or what might be possible with a new or improved design.

In light of this, Boart Longyear decided to partner with its customers to look at redesigning casing bits in the geotechnical construction drilling field.

The first discovery in this initiative was that drilling site feedback often compared apples to oranges about bit designs and there was no real definition of drilling bit designs or any so-called standard. The sum of differing opinions needed more segmentation and analysis. After interviewing customers, experienced drillers, and engaging our internal engineers, all of the feedback was segmented and combined with proven manufacturing information and our new Z Design casing bits were created, tested, and are now available to the industry.

Combining the three main aspects in faster and longer lasting casing bits: cutting, flushing, and gauge protection, Z Design casing bits provide improved flushing, faster ROP (rate of penetration), and longer lasting bits. The difference is in the design and materials. Using premium tungsten carbides, high quality steel, improved gauge protection, and induction brazing to reduce blistering, Z Design casing bits are manufactured in our ISO-Certified, Eiterfeld, Germany manufacturing plant.

CONSTRUCTION

Casing bit bodies are constructed of high strength quenched and tempered steel. The high-quality tungsten carbide inserts are induction brazed into the steel bodies ensuring a secure fit without overheating issues associated with flame brazing. Strict machining control of the carbide seats prevents premature loss of carbide inserts.

GAUGE PROTECTION

Tungsten carbide gauge protection on casing bits prevents excessive wear on the outer diameter of the bit in abrasive ground conditions. Additionally, in unconsolidated conditions where the ground is caving in on the drill string, gauge protection assists in freeing the bit and casing by providing another cutting surface.

SHRINK FIT CARBIDES

When required, Boart Longyear offers shrink fit installation of all hemispherical, ballistic, and two-step tungsten carbide inserts instead of the standard induction brazing. This very precise construction method is often utilized when drilling in extremely hard ground conditions and provides both increased button retention and longer overall life.

ADVANTAGES

• Computer controlled induction brazing of tungsten carbide inserts for superior process control and overheating prevention, common with flame brazing
• High-grade body construction with quenched and tempered steels
• Optional tungsten carbide gauge protection available for unconsolidated grounds and increased bit life in abrasive conditions
• Specialized designs for unique drilling situations such as drilling through reinforced concrete and drilling without inner bits.

Better casing bits means better drilling outcomes and ultimately results in better ROI (return on investment). Casing bits are designed for rotary percussive or rotation only drilling based on the tungsten carbide inserts utilized as well as the geometry of the bit. Customized tools for unique drilling applications are also available upon request.

Contact your local Boart Longyear representative or distributor to order the best casing bits in the overburden drilling market. Still not convinced? Contact us for help designing and implementing a testing drilling program to prove using Boart Longyear casing bits have a higher ROI.

For part numbers, download the Boart Longyear Overburden and Construction Tooling catalog here.

Typically, manufacturing sonic drill rods is a three-piece construction process in which the rod ends are friction- or slip-fit and welded onto a mid-body. This allows manufacturers to use lower grades of steel in the mid-body to save on costs.

Boart Longyear utilizes an upset forging process in manufacturing its sonic drill rods. Upset forging refers to the process in which a drill rod begins its life as one single piece of high-grade steel tubing and is internally forged to ½” thickness on the thread ends which transitions to ¼” mid-body wall thickness. This eliminates welding the thread ends onto the mid-body, creating a significantly stronger one-piece-design sonic drill rod. 

At a high-level, the six manufacturing steps for sonic drill rods are:

1. Begin with high-grade steel tubing having 3 ½” outer diameter and ¼” wall thickness
2. Upset forge the rod ends to 9” in length and ½” wall thickness
3. Stress relieve the entire rod (heat and cool slowly)
4. Heat treat the rod pin and box ends (quench and temper) for strength and durability
5. Machine the pin and box tapered threads into the upset forged ends
6. Heat treat the pin thread a second time to a slightly higher hardness (increases life, prevents galling (rods seizing up into each other during drilling) and increases wear resistance)

This process, which draws on our vast experience manufacturing diamond coring rod, creates a 3 ½” outer diameter rod which has a 3” inner diameter mid-body and 2 ½” inner diameter thread ends. The rod ends are ½” wall thickness to 9” in length, while the mid-body is ¼” wall thickness, keeping the rod relatively light but extremely durable.

When you need the best and most efficient sonic tooling, look no further than Boart Longyear. High-quality precision steel plus special heat treatment processes provide unsurpassed stability, straightness, and durability of the sonic drill string assembly. Stringent manufacturing standards and ISO certification make sonic tooling from Boart Longyear the right choice for every sonic drilling project.

Contact your local Boart Longyear representative or distributor today.

Quality Policy:

Boart Longyear is committed to providing quality products, innovative solutions, exceptional service and value to our customers while meeting or exceeding all customers’ safety, environmental and regulatory requirements.

Mike Van Aacken is the US Water Services Commercial Manager for Boart Longyear Drilling Services. With more than 22 years of drilling experience, Mike started as a driller’s helper and has worked as a Driller, Field Supervisor, Contracts Manager, and an Operations Manager. Mike has extensive experience in large rotary and dual-tube flooded reverse circulation drilling methods.

Our host, Jon Peterson (Geo Jon for fun), works for the Products division as a Customer Service Representative. Jon graduated from the University of Utah in 2015 with his Bachelors of Science in Geology. He’s worked for Boart Longyear for the last two and a half years and interned as a geologist with an exploration company for about six months prior to coming to work for Boart Longyear. Jon has been married for a year and a half and in his free time enjoys trail running, hiking, working on his yard, spending time with family, and playing with his black lab Dexter. 

We would love to hear your questions and comments below. Thanks for listening and if you liked this episode, share it on LinkedIn, Facebook, or Twitter. 

The most common practice, in this case, is to drive T45 or T38 rods for percussive drilling and API rods for rotary drilling. But when the customer was drilling with top hammers, his drillers had to change the complete tooling setup from API rods to percussive rods and vice versa. This proved to be ineffective and was burning resources on job sites and in tooling stock. The customer came to Boart Longyear for a rod solution that would be able to drill both rotary and percussive without changing the tooling set up.

Our engineers designed the new CBXP rods capable of both rotary and roto-percussive. By using the new rods, the customer reduced his spend on drill rods by 60% annually, purchasing one dual-purpose CBXP rod, instead of having to buy twice the number of rods for the two types of drilling. Productivity on job sites increased as changing tooling between the two different drilling applications was unnecessary.

CBXP drill rods are designed to be used as inner drill strings in double-head drilling applications. CBXP rods offer a more robust design than the common API rod and outperform API rods in durability and performance, especially when occasional percussive drilling is involved. It combines the effectiveness of an API rod but comes with more advantages than T38 and API rods, like:

• Higher flushing for higher penetration compared to API
• Longer thread life with an asymmetric thread profile
• Can be used for roto-percussive drilling (e.g. drilling though overburden boulders)
• Higher outside diameter compared to T38 & T45 rods results in higher flushing speed
• Conical thread shape provides better alignment for quick and easy make and brake
• Dual drilling capabilities as it can be used in both rotary and percussive applications

CBXP drill rods are primarily intended for use in rotary and rotary DTH drilling applications but are also commonly used as the inner drill string on double head rotary-rotary applications or in a single head rotary duplex application. CBXP may also be used for smaller percussive drilling applications. The rod ends of our CBXP rods are constructed of high tensile strength quench and tempered steel and are gas nitrided to provide additional life. Rod ends are friction welded onto mid-grade mid-body material. CBXP rods are manufactured in a variety of lengths and wall thickness. Boart Longyear can manufacture alternative rod lengths and spanner flats upon request.

Boart Longyear began manufacturing overburden and construction drilling products in 1989 at its facility in Germany to serve the foundation construction market. Boart Longyear overburden and construction tools were quickly recognized by the industry as reliable and well-designed. From the start, customers appreciated the use of high-quality steels, precise heat treating and thread gauging as well as the development of new tungsten carbides for the drill bit line. The attention to detail with the overburden and construction drilling tooling product line has made Boart Longyear one of the most respected names in the industry.

Today, Boart Longyear manufactures a broad offering of overburden and construction tooling at our 5000 m2 (54,000 ft2) facility in Eiterfeld, Germany. The modern ISO9001-certified facility hosts an array of advanced manufacturing capabilities including CNC (computer numerical control) machining, friction-welding, and induction hardening equipment for rod and casing products, as well as computer controlled ovens for assembly of tungsten carbide-tipped bits and tools.

Check out the full-line of Boart Longyear overburden and construction tooling by downloading the catalog.

Dan Ernst is the Product Manager for Capital Equipment Spares and has worked at Boart Longyear since 2011. He has his Bachelor's degree in Business Management and has more than 40 years of experience in supply chain, procurement, and product management.

Zac Strauss has a bachelor’s degree in materials science and engineering and a master’s degree in business administration. He started at the company in 2006 as a new product development engineer in diamond drilling products. He’s held other roles such as product manager for capital equipment spares and operations manager for aftermarket and fleet maintenance. He has been in his current role as product manager, capital drilling equipment since 2015.

Our host, Jon Peterson (Geo Jon for fun), works for the Products division as a Customer Service Representative. Jon graduated from the University of Utah in 2015 with his Bachelors of Science in Geology. He’s worked for Boart Longyear for the last two and a half years and interned as a geologist with an exploration company for about six months prior to coming to work for Boart Longyear. Jon has been married for a year and a half and in his free time enjoys trail running, hiking, working on his yard, spending time with family, and playing with his black lab Dexter. 

We would love to hear your questions and comments below. Thanks for listening and if you liked this episode, share it on LinkedIn, Facebook, or Twitter. 

In July, Vice President of Global Engineering Shayne Drivdahl discussed how Boart Longyear’s engineering team might be one of the company’s best-kept secrets. Providing a variety of professional drilling services to exploration and mining companies, the Company also designs, manufactures, and sells reliable drilling rigs, quality tooling, and accurate instrumentation.

Thanks to its team of engineers located throughout the world, the company is able to develop products and put them through rigorous testing in the hands of its own Drilling Services personnel. Tools and equipment are not only tested in the lab but also in the field. The collaboration between members of the global engineering team and Boart Longyear’s drillers elevates the performance of both Boart Longyear Drilling Products and Boart Longyear Drilling Services. Read the full article to learn more about the beneficial synergy gained between the two divisions.

In July, Design Engineer Anthony Lachance wrote about the newest developments and early testing results from the Roller Latch Overshot. Since Boart Longyear introduced the Q Wireline system in 1966, retrieving the inner tube from the core barrel has been handled the same way: an overshot with lifting dogs (spring loaded hooked “fingers”) is lowered or pumped into the hole until it snaps over a pivoting spearhead mechanism affixed to the inner tube assembly. Once the head assembly has been removed from the hole, the driller uses the pivoting spearhead to position the head assembly on their workspace and squeezes the back of the lifting dogs to release.

Since being introduced, this system has had the same basic issues. Learn how Boart Longyear’s new Roller Latch^TM Overshot has been highly anticipated and how drillers are noting the various positive developments: it’s easier to use, saves on wireline, and makes working with Q/P Roller Latch head assemblies much easier in difficult conditions.

In March, Global EHS Manager Brian Maeck introduced us to the Boart Longyear Glove Matrix. More and more mining and drilling companies are developing automation technologies to improve employee safety and efficiency. However, there are still plenty of risks for the hard-working hands of drillers: pinch points, sharp edges, rotating equipment, chemicals, etc. Hand injuries are still one of the most common and preventable injuries.

Along with following safe practices like using a risk assessment prior to any task, using the appropriate work gloves can dramatically reduce hand injuries. One solution, designed and developed to help employees select the correct glove for the task, is the Boart Longyear Glove Matrix. The Glove Matrix clearly sets the guidelines for what glove to use and when to use them. Read the article and download Boart Longyear’s Glove Matrix.

In August, Senior Engineer Andrew Salisbury wrote about the MDR500 rig’s success. This mobile underground diamond drill rig was designed exclusively for Boart Longyear Drilling Services. It leverages the upcoming LMi power and control interface and comes equipped with 500m of on-board rod storage (NQ rods) making it a self-sufficient mobile drill rig.

The MDR500 was the long-term brainchild of Geoff Moroney (Drilling Services Asia Pacific Fleet & Asset Manager) and John Kirkwood (Drilling Services Asia Pacific Regional Director). The project was given the go-ahead in the third quarter of 2016 aftermarket research indicated that there was a desire from sections of the Australian market for a medium depth underground diamond drill rig which was in the most part self-sufficient and could move quickly from hole to hole.

In this article, Anthony Markham, Senior Product Designer of Capital Equipment, describes the challenge Boart Longyear’s Drilling Services faced with moving existing StopeMaster equipment safely and quickly through a mine. With the combined dedication of many remarkable Boart Longyear employees around the world, the team started engineering a new StopeMaster MDR rig that would solve the issues the mining company was experiencing.

The newly commissioned StopeMaster MDR rig solved the issues of moving the StopeMaster, making moves from stope to stope faster and requiring less time and resources from the mine. The StopeMaster MDR equipment is also safer with rod handling capabilities and semi-autonomous drilling with a new LMi control panel which controls both the rod handler and the StopeMaster MDR rig. Check out this article and download the Drilling Services Overview to learn more about Boart Longyear Drilling Services capabilities, fleet, safety programs, and drilling methods and applications.

Is a career in drilling right for you? In this article, the challenges of drilling are discussed, and key factors are considered when researching jobs in the drilling and mining industry. For example, at drill sites, a certain level of physical fitness is required for employees to adequately carry out their tasks. Working on a drill rig involves labor-intensive activities such as heavy lifting and manual handling.

A career in drilling is an important decision for both employees and their families. Individuals who work in drilling enjoy work that is often physically demanding in challenging conditions. But they’re also aware of the great benefits and rewards of this industry. If a career in drilling seems like a good fit for you, this article is a must-read.

In June, Global Product Manager Zac Strauss discussed the most important factors when considering a new drill rig purchase. Buying a new drill rig is a big decision and many variables and factors affect that decision. The biggest question one has to answer is, “Will this drill rig make money? Or cost more to own than some other option that can accomplish the same for less?”

It’s important to take time to consider options. Evaluate current drill rig fleet and consider what it will take to get everything maintained and updated to be competitive. Does your drilling rig take advantage of recent innovations and meet the latest safety standards? If repairs and available parts outweigh returns, look at updating your fleet. The number one reason to buy new equipment versus used equipment is to enhance productivity, improve safety, and enjoy long-term reliability.

Since 1890, Boart Longyear has been transforming the drilling industry with innovations like the wireline for faster core retrieval, dual-tube flooded reverse circulation drilling, and sonic drilling for mining applications. This article focuses on the LR500, a drill rig built specifically to meet the increasing needs for deeper dewatering wells for Nevada mining.

Check out this article to discover the distinct features of the LR500 such as the size and weight of the casing, how it’s electrically powered, and its automated drilling features. Also be sure to download the Drilling Services fleet depth chart to discover the wide range of services Boart Longyear provides.

In February, Chris Lambert, Senior Product Manager, discusses different factors that affect the way drilling could be affecting bits. The best way to save money on consumables like bits is to check drilling methods. In this article, these simple tips could decrease operating costs and add more cash to the bottom line.

Quick tips are also included, which give insight into rotational speed, weight on bits, torque, penetration rate, water flow, and sharpening. You can also download the Diamond Products Catalog to explore the full range of diamond bits Boart Longyear offers.

John Roberts, Professional Geologist and Commercial Manager for Boart Longyear, describes the complexities of designing and planning a drilling project. There are many risk factors which need to be considered in order to mitigate issues that could impact productivity and/or budget, ultimately impeding the success of the project.

This article addresses considerations and common pitfalls in drill pad planning, which is critical to the mobilization of the drills and crews that will complete your carefully designed drilling project. The first thoughts should be “what purpose is the hole, and what type of drilling will be performed.” Make sure to download the recommended drill pad layouts!

As we move into 2019, you can look forward to additional case studies, interesting and complex drilling projects, tips and tricks, and how-to articles. We are working hard to bring you the content that makes a difference and makes your life a little easier. Thank you for reading INSITE and engaging with Boart Longyear. We couldn’t do any of it without all of you! Wishing all of you a successful and prosperous 2019!

If you have any questions or feedback, we would love to hear from you! You can leave comments below by clicking to expand on the icon and word DISCUSSION.

The Hard Work Cycle is a continuous improvement program that uses a system of processes and key performance indicators (KPIs) as tools to ensure the highest productivity and efficiency while safely drilling more straight meters. A key component of the Hard Work Cycle is the comprehensive suite of reports used to manage individual driller performance, shift performance and project productivity. Sharing those metric-driven results with customers enhances communication, transparency, and accountability.

 “The program has helped us identify what’s important in our day-to-day operations, how we can focus attention on doing those things better, and how those improvements drive the bottom line,” said Terry Kirkey, regional director for Asia Pacific Drilling Services based in Adelaide.  “By implementing these improvements, we’ve been able to achieve gains in efficiency and productivity.”

The Hard Work Cycle consists of interlocking principles, including: 

• setting transparent KPIs
• reviewing KPIs as a team and agreeing on and recording actions
• continually generating, prioritizing and implementing ideas

During implementation, Boart Longyear emphasized participation from everyone, highlighting the benefits of not only improving productivity and efficiency, but also improving safety and communication (between crews and management and the customer) and reducing operating costs.

“Safety is the right thing to do and always our first priority; every driller deserves to go home safely to their family each day,” said Kirkey. “But safe operations also benefit productivity. If we are safer, we are more productive, because we aren’t spending time investigating incidents or dealing with reports or worst-case scenarios such as lost time and injured employees.”

The Hard Work Cycle also impacts safety by structuring safety conversations. By adding safety discussions to regular Hard Work Cycle meetings, crews are talking about incidents, near misses and concerns. They are also generating ideas about safer ways to do things, how to work better as teams, and how safe operations increase productivity.

One of the many improvement ideas implemented over the last 12 months involved using pre-start meetings more effectively. The improved format is now being standardized across all Boart Longyear drilling sites. Structured meetings between each level of operations also facilitate ongoing discussions and resolutions of any productivity or safety concerns. 

Another example was a special display board to improve communication between the drilling crews and mine operations. Supervisors use information posted from mining operations to prioritize and ensure the maximum number of drills are turning. Mine operations use the information to ensure sites are prioritized and ready for drilling. This process resulted in a significant increase in the number of rigs turning per shift and in the total meters drilled per shift and was tracked and measured to ensure effectiveness.

In the beginning, employees were asked to do a few things differently – help generate improvement ideas, have a weekly review, and adopt new practices – but the focus remained the same – being safe, getting productive meters and helping each other. 

According to Kirkey, the program is succeeding because supervisors and workers have taken ownership of it. When the program was introduced, supervisors and drillers were charged with implementing ideas to increase drill time and rate, improving processes and results rapidly, and discussing productivity metrics regularly.

A Boart Longyear driller in Canada recently won an award for suggesting a slight schedule change that resulted in a significant increase in productivity. This change decreased the drill start time and increased the average total meters drilled per shift. Measuring and tracking also give the company the opportunity to identify trends, implement corrective actions, and demonstrate transparency to customers. A win-win for everyone.

A local Boart Longyear supervisor, Dave Barrett, had an idea for improving a part on underground coring rigs. His design was engineered and tested and is now being used across the Asia Pacific region, delivering significant efficiency gains. Global implementation of the new design is in the works. 

Kirkey emphasizes the importance of measuring productivity for each driller, identifying actionable items and who is responsible for each action, and following up. “We graph drillers on each KPI metric, with drill logs, bit penetration logs, and productivity measures. We see which drillers drill faster and then find the how and why so we can replicate it where it makes sense. It promotes healthy competition and opens up conversations about what works and how we can strive to continually do things safer and better.”

“By involving everyone, the Hard Work Cycle has empowered our drillers and demonstrated that we can get big results from small changes. It’s rewarding for the guys to see the difference their ideas are making, and we think it’s imperative to recognize them for their efforts.”

The DTFR technique allowed the extraordinary bit to penetrate loss circulation zones that precluded the use of a more traditional raised bore rig.

The technique pumps air through the outer tube and forces mud and drill cuttings upward through the center tube, preventing them from plugging porous rock formations with cuttings, a common problem under the high pressure of conventional drilling.

Rotating three-member crews worked around the clock, utilizing a top head drive rig fitted with stabilizers and the massive bit. To minimize the risk of a mine entry collapse, the borehole was drilled off to the side of the mine tunnel and a 54-inch casing with 1/2-inch wall thickness was installed and cemented in place. Underground mine crews then mined over and punched through the concrete to open up the shaft.

Drilling such a large-diameter hole through loss circulation formations in a single pass – and in less than a month and a half – simply would not have been possible using any other method, and few companies have the necessary resources, expertise and experience, not to mention a large enough drill rig table.

Most often used for large-diameter water wells, DTFR is similarly suitable for pre-collar oil & gas and pre-collar geothermal applications as well as ventilation shafts like the one in Wyoming. It is also being used to drill two injection wells in central Utah at the site of the first underground salt cavern natural gas liquids (NGLs) storage facility in the Rocky Mountain region. Other uses include paste holes and utility holes.

Of course, not every application calls for the behemoth bit used at the Wyoming coal mine. Bits come in more than a dozen sizes, ranging from 7-7/8 inches on up, depending on the need.

DTFR can be used in both unconsolidated formations and hard rock formations. While specific tooling depends on the formation and the size of the hole that’s needed, it always entails dual-tube pipe, roller reamers, stabilizers and a skirted bit. This unique setup allows for a straight hole and consistent diameter in a single pass.

Even with flooded reverse, conventional drilling is needed to start the borehole. The surface borehole typically goes to a depth of 20 to 40 feet, where the surface casing is cemented in place.

The completion borehole is also drilled conventionally until submergence is reached, usually about 100 feet below the ground.

From there, the flooded reverse technique takes over, allowing adjustment of the inner tube, lower borehole pressure and the ability to drill through loss circulation zones. A key advantage is that the same rig and rods can be used for both methods, with the switch over simply involving a change of hoses and pumps, as well as the compressors and booster.

Moreover, DTFR drilling never pushes directly down on the bit but always holds back weight, resulting in a pendulum effect. This minimizes deviation of the well, resulting in a straight hole and decreasing wear and tear on the bit, thus increasing longevity.

The DTFR process itself is relatively straightforward. It begins with the use of clean, lower-viscosity mud-based drilling fluid, which is gravity-fed down the outer borehole, or annulus.

The mud collects cuttings from the bit face, mixing with air and flowing to the surface through the center tube much like a common drinking straw. This results in less pressure on the borehole and formation than conventional drilling, which pumps higher-viscosity fluid down the center tube and returns materials up the annulus.

At the surface, the cuttings and mud pass through the cyclone in the mud tank. A series of shaker screens then separates the cuttings from the mud, and de-sander cones separate sand from the drill fluid, which can then be recirculated down the hole.

Because the sample comes up the center pipe rather than the outer edge where it could pick up contaminants, the result is real-time, uncontaminated formation samples that accurately represent the formation at the bit face. This provides exact depth relations for reliable formation analysis.

You never know what you might find using DTFR. Several years ago, I was a driller on a crew brought in to drill a 31-inch exploratory hole at a Nevada gold mine dotted with exploration and core holes. But because of the size of the hole we drilled and quality of the samples we obtained, the result was a “Eureka!” moment – we discovered a gold vein the client didn’t know existed.

While the discovery didn’t trigger anything like the California Gold Rush of more than a century and a half ago, it did get the attention of a suddenly attentive and expanded team of geologists and resulted in re-drilling a number of previously disregarded areas.

Of course, not every company will discover gold. But for good reason, more and more are discovering dual-tube flooded reverse-circulation drilling and awaiting “Eureka!” moments of their own.

Following the advancement of the inner drill pipe and core barrel, the outer drill casing is advanced to within one foot of the leading edge of the core barrel.

The outer casing serves the same purpose as for conventional dual-line drilling systems by holding the borehole open for well installation, geophysical logging or other down-hole activities. Depending on drilling formations, drilling fluid may be introduced during the advancement of the outer drill casing.

Sonic drilling also greatly reduces the risk of project failure due to unknown or difficult subsurface conditions. It also offers the flexibility of advancing a temporary outer casing as the borehole is drilled, meaning more can be accomplished with a single borehole.

Although adoption of the technology has been slow, sonic drilling is now being seen as the solution for a variety of needs. In Canadian oil fields, for example, where soft rock formations predominate, companies are increasingly coming to recognize sonic’s advantages over both conventional rotary drills and auger drills for many applications.

After the 2014 failure of the Mount Polley tailings dam in British Columbia, the provincial government mandated the installation of monitoring wells and piezometers on tailing piles throughout the province. The difficult accessibility of many sites and the potential instability of the pilings made Boart Longyear’s new LS250 MiniSonic rig an obvious choice for the job.

The reliable, compact sonic rig is proving to be the ideal solution for a wide range of applications, including geotechnical, environmental, water and mining. Its compact size allows it to be easily transported to hard-to-reach sites like the tailing piles or to work in tight spaces.

Such was the case in downtown Calgary, Alberta, where a major sports and entertainment complex is proposed for an underdeveloped riverfront site that now includes auto dealerships and a bus station. Although a creosote plant there closed decades ago, creosote extends several meters below the surface across much of the proposed development area.

A recent environmental investigation required drilling sampling holes at multiple points across the property. Sonic technology and the rig’s maneuverability meant mission accomplished with practically perfect core samples.

Sonic drilling employs the use of high-frequency, resonant energy to advance a core barrel or casing into subsurface formations. During drilling, the resonant energy is transferred down the drill string to the bit face at various sonic frequencies. Simultaneously rotating the drill string evenly distributes the energy and impact at the bit face.

The resonant energy is generated inside the sonic head by four counter-rotating weights. A patented pneumatic isolation system prevents the resonant energy from transmitting to the drill rig and preferentially directs the energy down the drill string.

The driller controls the resonant energy generated by the sonic oscillator to match the formation being encountered to achieve maximum drilling productivity. When the resonant sonic energy coincides with the natural frequency of the drill string, resonance occurs.

This results in the maximum amount of energy being delivered to the face. At the same time, friction of the soil immediately adjacent to the entire drill string is substantially minimized, resulting in very fast penetration rates.

Sonic offers several distinct advantages over conventional technologies. Among them is the superior information provided by the continuous, relatively undisturbed core sample of unparalleled quality and accuracy through any type of soil — clay, till, loose or heaving sand, gravel, boulders or cobbles. When using the iso-flow groundwater profiling system, hydrogeological and geochemical data can be easily obtained.

Sonic drilling also reduces drill spoils and waste by up to 80 percent relative to conventional drilling methods. Unlike drilling with an auger, virtually no cleanup is necessary.

Superior well construction is another advantage. Sonic drilling causes minimal disturbance to the surrounding borehole wall, resulting in more efficient well development and performance. Then there’s the speed. Sonic drilling is up to two to three times faster than conventional overburden drilling methods.

Safety features of the LS250 MiniSonic rig include an interlocked rotation barrier, reduced noise levels, a dump mast and wiggle tail, and a rod presenter. The interlocked rotation barrier automatically slows head rotation when the barrier is open. The rig also provides lower noise levels when equipped with the Tier 4i engine package. 

The articulated mast and wiggle tail enable the mast to shift from left to right and front to back to position the mast precisely over the hole, eliminating time-consuming rig movements. The dump mast allows the crew to work from the ground, enhancing safety by avoiding stairs and safety rails often required when working from a platform.

The innovative rod presenter allows the rod and casing to be loaded horizontally, with an actuator that then presents the rod and casing vertically to the head. The head rotates 28 degrees to the side for sample extraction, while the head slide shift allows for unobstructed winch use down the hole.

The LS250 MiniSonic rig is capable of drilling to depths of up to 250 feet (78 meters) when used with a 4.75-inch (121 millimeter) casing. Its “big brother,” the LS 600 Sonic rig, can go even deeper — up to 600 feet (182 meters), as its name implies. The Boart Longyear lineup also includes high-quality sonic tooling, from bits and casing shoes to sonic rod, core barrel, casing and accessories.

As awareness of sonic drilling’s advantages continues to grow and as more and more geotechnical engineers specify sonic, the market will likely demand continued innovation and sonic drills capable of even deeper, larger-diameter samples. And Boart Longyear, already at the leading edge of sonic drilling, will continue to lead the way.