In all this time, this system (seen in photo on the right) has had the same basic issues:

Spearhead Handling: in up-hole applications underground, a driller is required to manually push the head assembly into the hole by the spearhead. Since it has a pointed end and pivots by design, it can be difficult to handle this operation comfortably.

Inner Tube Handling: When hoisting the inner tube assembly, elastic action of the wireline cable or accidental impact during handling can un-load cable tension and overcome spring loads which allows the hooked lifting dogs to accidentally release the spearhead. The surface ‘Ezy-Lock’ overshot includes a twist-sleeve that locks onto the spearhead even without cable tension, whereas competing overshots require cable tension to maintain a lock.

Lifting Dog and Spearhead Wear: To balance strength and wear resistance, lifting dogs and spear points are heat treated to a medium hardness. However, it’s difficult to visually evaluate or functionally test the degree of wear, especially in underground applications. 

Boart Longyear currently provides a secondary safety pin that clips through the overshot, passing just under the spearhead tip. This adds an extra layer of protection in case the lifting dogs are excessively worn or deformed. However, spearheads are loaded cyclically and often loaded ‘off-pivot’, which deforms the components over time, to the point of disassembly. While the more recent MKII version of the spearhead assembly is much more robust, in the case of spearhead failure, the head assembly will release from the overshot regardless of lifting dog or safety pin use or condition.

This patent-pending overshot leverages our previous experience with Roller Latch head assemblies to create a more reliable and longer lasting system that eliminates spearheads and lifting dogs entirely. The spearhead assembly is replaced by a one-piece socket receptacle (spearhead adapter) that accepts the overshot itself, which has rollers that latch into an internal groove in the spearhead adapter.

Swapping the pointed, jointed spearhead for a simple cylindrical socket makes for much easier handling of head assemblies in up-holes. Surface Quick Descent Roller Latch head assemblies don’t even require the spearhead adapter since the internal groove geometry was pre-built into their design.

The increased toughness and hardness of the bearing quality latch rollers have a proven history of outlasting traditional pivoting latches for wear life. The new overshot will also feature the same Nitreg-ONC surface treatment as Roller Latch head assemblies that drastically improves corrosion resistance (Nitreg is a trademark of Nitrex Inc.).

Safety pin integration in the new underground Quick Pump-In overshot now pulls double duty of both locking the overshot from accidentally releasing while hoisting, as well as holding the head assembly and overshot together in case of component failure due to excessive wear. Also, the socket and rollers are not affected by side loading and ‘off-pivot’ loading during tube handling outside the hole, eliminating gradual deformation or disassembly. The new surface overshot will also include a one-hand twist-lock sleeve to maintain a locked position while hoisting outside the hole, even with a loss of wireline cable tension.

It’s also easy to use.  Instead of pushing the backs of the lifting dogs together, the driller pushes the two halves of the assembly together, retracting the rollers and releasing the head assembly. This operation takes about the same amount of force as the current overshot, so drillers won’t miss a beat.

Additional benefits have been included[CA1]  apart from the elimination of the spearhead and lifting dogs. While the current design uses a solid pivot pin that is peened into place (making it difficult to re-build), the Roller Latch Overshot has no pins whatsoever. Everything is held in place by simple threaded connections for easy maintenance.

First, in the event of a stuck tube, the driller needs to disengage and retrieve wireline cable in order to pull rods. Today, that is done by overloading and breaking a shear pin placed just underneath the cable swivel. In theory this pin breaks at under half the wireline cable’s max load capacity, but in practice its strength is highly variable because shear pins are inherently weak and ductile. Many operators remove the shear pin, which removes release capability and may result in excessive wireline cable replacement.

The Roller Latch Overshot features a brand new pump-in cable release system, originally conceptualized and prototyped by one of our expert underground drillers in Canada. A slotted sleeve and pumping seal assembly is placed over the wireline and pumped up to the overshot. The sleeve engages a quick-release mechanism and releases the wireline. This system has proven to be much more reliable, and may be the feature drillers are most thrilled to have going forward.  Reports of fewer broken wirelines have been received from several sites testing the pump-in cable release system.

Second, while Q/P Roller Latch head assemblies with built-in brake features have had great success in stopping runaway tubes and creating a safer drilling environment underground, they are perhaps “too” successful. Currently, when retrieving the head assembly from an inclined hole, pressure has to be applied to disengage the brake. Getting this pressure and procedure exactly right can be difficult, especially with hydrostatic pressure at depth.

To combat this and make Q/P Roller Latch easier to use while maintaining its safety features, a ‘brake release spring’ was created. This spring assembles quickly inside of the spearhead adapter on the head assembly. While tripping on its own, the head assembly brake works normally, but when the overshot latches into it this spring is compressed, disengaging the brake. This feature has also been received very positively by drillers in the field.

A surface-style overshot is also in development in B/N/H sizes. In addition to many of the features outlined in this article, the aim is to add more innovations, including:

• An improved lock sleeve to disable accidental head assembly release and stop drillers from accidentally sending the overshot down the hole while locked.

• A built-in 360° pivot and shorter overall length for increased ease of handling.

Excitement is high as testing continues. 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. We’re looking forward to further field success as testing begins on the surface design.

For more information and downloads, visit: 
Roller Latch Quick Pump-In Overshot - Boart Longyear

This article was originally published in Coring Magazine, Issue 13, 2020.

In 2004, Chris started as a driller’s assistant with Drillcorp at Sunrise Dam, drilling initial diamond coring holes at Tropicana mine when it was still an exploration site, before moving onto deep directional drilling programs at Leonora and Forrestania. In 2006, Chris joined Boart Longyear (BLY) initially as a driller, before moving into a supervisory role at BHP Billiton’s Leinster and Mt Keith operations. This was when Chris developed a thorough appreciation of industry safety, and he’s grateful for the front row seat during a notable period of change in safety systems and workplace cultural maturity. In 2014, the Great Financial Crisis adversely impacted Australia’s mining and exploration with widespread reduction across all surface drilling. Chris was redirected to BLY’s Waterwell division across multiple Pilbara sites. Chris eventually returned to the Goldfields to assume a regional supervisor role before being rewarded with his current role as operations manager for BLY’s underground division, APAC.

Chris Hopkins: My father worked within Chevron’s lubrications business, collecting many small-scale models of heavy mining equipment. As a kid, I was fascinated by his ‘toys’ – sparking my interest and a subsequent stream of questions to my patient, receptive Dad who has since retired. I greatly admire my Dad for his genuine want to be of value to his community and local church. At age 24, I became a father for the first time while working in the liquor industry and wanted to veer to an industry where hard work, commitment and dedication were appreciated. I was also itching for adventure and a change in scenery, having been inside a lively wine store for too long. The prospect of working in the great outdoors at remote locations, being physical, and solving mechanical issues really appealed, so I made the switch.

CH: My professional role models and mentors include the esteemed and respected likes of Dale Barron, Des Forde, Gregor Stephenson, the late John Emerson, and Murray Hillier. Their collective drilling knowledge, willingness to engage and educate, while offering support has had the most profound effect on my career.

CH: I can’t recall a specific moment or project, as I’ve enjoyed many adventures during my career. Drilling challenges me on so many levels – from working and living away in remote locations and interesting environments, to geological undertakings through difficult formations, and the eventual satisfaction of completing a deep directional drilling program. In true A-type style, I beam with unwavering pride when my rig, fleet and team present well and drill effectively.

CH: 1. Good work habits and a positive mental attitude: the underground space is a very physical and challenging workplace, but it’s also a great place to work – I love it! Every task has an exacting set of measures which must be followed, as short cuts are not tolerated. Determination and attention to detail is necessary given the restricted work areas, equipment limitations and specific underground drilling requirements that can vary from +90 to -90 degrees. Excellent communication is paramount as daily interaction with mining teams is necessary to deliver quality samples within specific time frames. It is quite common for a mining team to immediately assume an area once drilling is complete.

2. Safety culture maturity: we must respect and understand our working environment, and maturity toward safety is a prerequisite to the underground mining sphere, given the inherent risk in what we do. I cannot and will not tolerate immaturity or lack of focus as either will result in someone being hurt and equipment being damaged.

3. People: are the most important and defining facet to success – in any industry. People who genuinely care and take pride in their work and accomplishments are who you want on your team. I’ve been fortunate to have worked with talented and capable people, and I’m most proud of my current team – they are enthusiastic, professional, highly motivated and experienced. We’ve developed an amazing and supportive working culture as a result.

CH: My somewhat cheeky response is whatever drilling type I’m currently focused on and involved in. Seriously, every discipline – underground or surface drilling has its own challenges including ground conditions, technical drilling requirements to achieve targets, underground grade control programs requiring multiple rig locations and set-ups per shift, to large diameter holes requiring large tooling to complete. The challenge of individual hole completion is what deems the drilling industry such an exciting business to work in. Up-hole drilling is a constant challenge, as underground geology departments strive to keep costs down. Sometimes the only way or location to achieve target is to drill ‘up’. Boart Longyear’s Roller Latch system allows crews to successfully and safely do so while following best drilling practices.

CH: Underground mining and drilling teams work closely, attending the same pre-start meetings and engaging more frequently than would occur at surface. When underground, everyone is under the supervision of the shift boss and underground mine manager, with increased engagement with the mining safety team. My drilling team has forged greater cohesion between the two groups, implementing exemplary practice and innovation that has been adopted by all, and I couldn’t be prouder.

CH: There are two reasons – risk and cost. Drilling is dangerous especially when poorly managed, so it makes sense to hire a professional contractor to complete the work. Contractors must be accountable and continually improve to secure future work. A lot of effort goes into delivering safe, seemingly hassle-free (for the client) drilling. Then there is cost. Most mining companies are incapable of cost-effective and productive in-house drilling. Contractors remain focused on achieving safe and productive outcomes for their ongoing financial survival and reputation.

CH: Delays associated with mine blasting and other mining activities significantly reduce the amount of time drilling crews must complete work, while eliciting an added expense to the client. BLY’s Drill Control Interface (DCi) system enables continuous drilling, even while the rig is unattended. Semi-autonomous capability within the underground drilling space is subject to an anticipated transformation, and it’s an exciting time. Many mines have, and continue to install underground Wi-Fi communication systems for enhanced communication between the drill crew and surface-based support crew.

CH: The underground space is in need of innovation, and Boart Longyear’s dynamic approach has meant that I’ve been involved in the development and release of some of the industry’s leading improvements including Roller Latch, diamond coring bits – designed and tested in the field by our drillers, and safety improvements to both drilling equipment and in the field training systems. Our fleet features machines that enhance the driller interface with improved safety and increased performance thanks to BLY’s ability to design and manufacture reliable rigs and drilling equipment, backed by adept and supportive maintenance teams, and an extensive global supply chain. I’m particularly excited about current innovations and advancements we expect to release within the next year. I can’t elaborate just yet, so watch this space.

CH: Most Australian underground drilling is N-size as it yields clients respectable sized core samples for the cost. For drilling contractors, N-size improves productivity with wireline systems, reduces manual handling when compared to conventional systems, and improves hole completion in poor formations. Boart Longyear’s Roller Latch system also provides much safer operations when drilling up holes, veering away from conventional processes.

CH: The potential to intercept an underground water source when drilling underground is both great, and undesirable. Thorough planning, detailed risk assessment and experience round out the high-pressure prevention trifecta, coupled with having the necessary tooling at the ready – should it be required.

CH: Drilling fluids are critical to hole completion in broken, unstable or pressurized formations – supporting all aspects of hole conditioning from reducing torque, assisting in the removal of cuttings, increasing hydrostatic pressure, stopping hydro sensitive formations from reacting, and some products hold together loose formations. Cost is critical and all staff – not just drilling crews must be educated as to correct usage to ensure zero to minimal wastage as this can greatly affect cost per meter. Reliable terminal equipment is key to ensure the most time down the hole. I’ve encountered many holes where formation stability is greatly reduced due to tripping of rods or introducing unnecessary pressures onto the formation, leading to extensive hole cleaning which then increases the likelihood of an unsuccessful hole completion.

CH: Boart Longyear makes use of wedging in both surface and underground operations. Wedging needn’t be a safety concern if effective planning and good communication are upheld. Importantly, we work closely with our clients to ensure this is the best option for them, as the cost to drill a new hole within the underground space can be cheaper than attempting directional drilling.

CH: Cementing works best when it is kept simple, checking everything twice. Like the carpentry adage, ‘measure twice; cut once.’ Training is key – as it is with all aspects of drilling. Be mindful of setting and correctly calculating grout volume. Other points to note: is the cement type correct or best suited to the formation? Is the product within its best before date, and has it been stored correctly? Are the slurry volume calculations correct? Is the potential for contamination being limited while mixing and displacing slurry? Be sure to extract a slurry sample to reference. Importantly, if you’re using an additive, be sure to follow the manufacturer guidelines as more is not always better. Lastly, don’t feel pressured when attempting as this is when most mistakes do occur. In Australia, we use VAN RUTH® cementing plugs as they’re a proven product that work well.

CH: Lack of preparation. A driller’s day starts with the all-important pre-start meeting, where supervisors outline and ensure that their teams understand what is expected to occur during that shift. Appropriate and reliable equipment is made available for the crew to safely complete every task and activity. Rushing to complete a job, particularly due to failure to plan, or lack of preparation is a recipe for disaster – namely injury.

CH: I’ve been fortunate to have been involved in many deep directional drilling programs throughout Western Australia, however, it’s important to note that this drilling method varies from production-based drilling within the underground space. The focus is on hole completion and hitting the desired target. It’s complex, extremely technical, and requires intensive supervision, as every decision affects how the hole is drilled from start to finish. I enjoy drilling at depth – the planning, preparation, and necessary attention to detail (correct choice and use of equipment, barrel configurations and monitoring the hole’s deviation) to achieve target. It’s a proud moment to be part of a team that successfully reaches end of hole, delivering a sample of an ore body to a client from over 2000-meters depth.

CH: Directional drilling using down hole motors is an effective method to hit multiple targets from a ‘parent’ hole. The method is best applied to deeper targets and areas where the cost to drill through waste rock exceeds the cost to complete the directional requirements to reach the targeted zone.

CH: The survey industry and its products are rapidly advancing in capability and reliability, with fantastic products available. Most importantly, the system must meet client requirements and be easy to operate, with flexibility for drilling teams to utilize tools to maintain effectiveness. I’m a firm advocate of the Azimuth Aligner® as it reduces rig set up time and relieves pressure on mine survey teams.

CH: Mining is critical to Australia’s economy, and every operation has been closely monitored to eliminate or minimize risk. Australia truly is the ‘lucky country’ for a few reasons – our geographic isolation and relatively small population combined with our swift acting government’s measures (international and state border lockdowns and mandatory 14-day self-isolation), has so far protected us as a nation. Over 25 million people live in Australia, yet our death rate from the pandemic is deemed low – just over 100 people. We must never be complacent and we’re mindful of the much talked about second and third phases, hence Australia’s strict border controls.

CH: Exciting technologies are being harnessed and adapted within diamond drilling. Many contractors are relentless in their pursuit to remove manual handling for a twofold result – eliminate and minimize injuries, while encouraging the broader community to consider the profession. Drilling cannot occur without people and the industry benefits when dedicated, focused and diligent people continually strive to improve perception and conditions. People are the future of drilling, so we must ensure that our industry evolves with safety, education, innovative systems and solutions at its forefront, as evidenced by key groups such as Australian Drilling Industry Association (ADIA) – endeavoring to improve standards and protocol for collective success – now and in the future. I’m currently involved at a research and development level, applying expert advice and feedback to hone various soon-to-be-released Boart Longyear equipment and tools that will greatly improve safety and productivity, while questioning how we approach drilling. It’s an incredibly exciting time to be in the industry and I personally cannot wait to see it come to fruition. Watch this space!

The drill string’s resistance to deviation—otherwise known as ‘stiffness’—can be determined by its material and mechanical properties. Since all wireline tubular components are made from cold-drawn steel tubing, they all have the same fundamental properties. Specifically, regardless of chemistry, heat treatment, or hardness, all steel grades respond with the same amount of bend to a given load (the ratio of stress (load) to strain (bend) is known as the “modulus of elasticity”). Furthermore, any two steel tubular components with equal dimensions will have equal stiffness, even if produced by different suppliers, regardless of the steel grade, heat treatment, or hardness.

The directional response or sensitivity of the drill string to changes in drilling loads or speeds, or in formation changes, depends heavily on the drill string stiffness. The stiffness of wireline drill rods more than doubles in moving to the next larger system (e.g. BQ to NQ, NQ to HQ, etc.). As a result, larger systems drill straighter but have much more resistance and greater lateral loading when drilling through borehole deviations. Given a typical impregnated coring bit, and constant drilling parameters (assuming no formation changes), the borehole will tend to form a slow helix that is determined primarily by the stiffness of the drill string. With borehole friction, the drill string itself can become unstable, buckling into a helical shape which tightens or loosens with changes in drilling loads and speeds, but then elastically returns straight when unloaded.

The Q wireline core barrel was originally designed to utilize an outer tube with a substantially larger diameter and wall thickness than the unstable string of drill rods behind it. Standard outer tubes provide approximately 40% greater stiffness, and full-hole style outer tubes provide approximately 70% greater stiffness! The outer tube can then act as a stabilizing bearing or collar. The greater the increase in stiffness, the more effective a directional control to resist changes in the formation, drilling parameters, or drill string stability. This control can be enhanced with stabilized reaming shells, stabilized adapter couplings, and stabilized locking couplings.

Consider the directional impact if the outer tube is replaced with another drill rod, completely removing any difference in drill string stiffness, and the related directional control. Originally developed in the 1980’s in an attempt to direct borehole deviations, core barrel configurations, known as “flexi-barrels,” replace the outer tube with an equivalent length assembly of a drill rod and adapters. However, the lack of directional control combined with the lack of directional predictability, typically results in erratic deviations requiring either corrective deviation attempts or reaming to reduce excessive deviations. Therefore, the use of flexi-barrels is not recommended.

When planning holes, consider the potential impact of rod deviation. The stiffness of steel tubes is relatively high, and as mentioned before, increases with system size and section thickness. As a result, the drill string will respond with high side loads against the borehole wall, especially just before and after a deviation. For example, an NQ size drill rod deflected to the recommended maximum deviation of 1.0 degrees over its length produces approximately 9kN (2,000lb) of side load, and an HQ produces 18kN (4,000lb) at only 0.8deg per rod length. Depending on the formation, these high side loads can produce high torque, heavy rod wear or even ‘heat check cracking.’ Additionally, these contact points generate drag and ‘stick-slip’ conditions, which can produce a dynamic response sufficient to permanently deform the drill string into a helical shape. In extreme cases, where the drill string completes enough rotations approaching or exceeding maximum deviation, fatigue failures will occur. Using the minimum deviation possible to hit target and sticking to NQ size rod will reduce the side loads, torque and chances of twisting or cracking rod.

Originally published in Australasian Drilling Magazine, February/March 2020

On one particular project, Boart Longyear mobilized underground coring rigs to a client’s mine in the US where the mine was faced with a big water problem that was making the underground exploration coring impossible to complete. The mine had two shafts located at different levels, one above the other. The deeper shaft had pumps installed and was ready to pump water to the surface. However, the upper shaft had flooded with water – where there were no pumps.

Typical underground coring setup.

Rather than attempt to install additional pumps in the flooded upper shaft to remove the water, Boart Longyear moved their underground coring rigs down to the lower shaft and drilled a fan-shaped series of up-holes to the flooded shaft above. The idea worked, effectively using gravity to drain the water from the upper shaft to the lower shaft where the pumps were then able to move the excess water to the surface. The mine was able to continue operations in the upper shaft and Boart Longyear was able to start the diamond coring exploration drilling.

On another project, the mine was thought to be dry. After the underground coring began, the Boart Longyear crew ended up finding water – a lot of it, quite unexpectedly. The crew was able to come up with a plan to manage the water so the exploration drilling could be completed. After pressure grouting in a cement collar casing, a blow-out- preventer (BOP – used to seal, control, and monitor water to prevent blow outs and the uncontrolled release of high-pressure water) and rock pack were installed successfully, shutting the water in. Most instances where that amount of water is encountered play out quite differently. Everyone has experienced, or knows someone who has, a situation where a high volume of water blows all your tooling out of the hole, resulting in a complicated mess.

Other examples of unexpected challenges include creative solutions using Boart Longyear’s own engineered underground rigs on the surface. The Drilling Services Underground Coring division mobilized rigs to a mine site where a delay in underground diamond coring exploration had the underground rigs idle on the surface. Someone saw the rigs waiting and asked if the idle underground rigs could drill flat-angled holes on the surface. Accepting the challenge, the underground coring rigs have been drilling these low, flat-angled boreholes ever since.

The mine site has a limited surface disturbance permit – which means that to reach the geological formations outside the area of their disturbance permit, Boart Longyear’s Underground Coring division is operating underground rigs on the surface to drill low-angled and flat holes that surface rigs often can’t reach because of their truck-mounted tall masts.

The underground rigs can drill at low angles from -40 degrees down to flat. They drill underneath the area where the mining client isn’t allowed to disturb the surface. This means exploration coring can follow ore veins without disturbing the surface and drill beneath the area outside of the issued disturbance permit.

The boreholes are 2600 ft to 2700 ft (792.48 m to 822.96 m) at a -40 to -12 degree angle. Boart Longyear has the tooling and the expertise for that type of drilling but was unable to accomplish the job with surface rigs because when set up flat, you’re going to be 12 ft (3.66 m) off the ground because the mast is way up on a truck carrier. With the underground rigs, a work platform or deck was constructed, which enabled the team to work right up close to them.

The Boart Longyear Drilling Services Underground Coring division in the US runs all Boart Longyear-engineered and manufactured LM and MDR rigs. The LM series of rigs feature easily interchangeable components, allowing for space constraints without sacrificing depth requirements. These modular coring rigs offer easier access in tight underground spaces and mobility for easier moves from hole to hole or shaft to shaft. Boart Longyear’s patented tooling offers safer and more efficient up-holes at any angle.

The underground coring rigs in the Drilling Services’ fleet are modified and customized, as compared to the commercially available Boart Longyear underground coring rigs. For example, the LM90 is souped up with a 150-horsepower engine instead of the typical 90-horsepower engine and includes additional modifications for increased depth capacity and core size.

The Drilling Services Underground Coring division has the experience and technical expertise to drill dewatering galleries, geotechnical borings, tunnel investigations, grouting services, and utility borings. The division also has experience with overcore drilling to measure in-situ stress. Overcore drilling involves drilling a hole to depth with a small diameter EX- or AX-sized bit, placing a probe to measure strain response data, and then using a special resin to glue the probe in place. After drilling out a larger diameter core to retrieve the probe, the overcore sample and probe are used for stress testing the rock formation to plan for ground support. This method is often used in both horizontal tunnels and vertical shafts to measure the amount of stress the rock can take.

Another unique application for underground rigs and crews is drilling on the surface into high walls for dewatering purposes. Flat to close-to-horizontal boreholes – from 10 degrees up to 10 degrees down – can be used to create self-draining dewatering boreholes in high walls. Pressure grouting in a cement collar casing keeps the hole from collapsing and can be used with a BOP valve in case the mining client wants to shut the water in the rock formation.

To maintain the integrity of the hole, installing slotted polyvinyl chloride (PVC) keeps the hole from collapsing. If you go through a broken zone, when water starts flowing, the hole can bridge off after a couple of months. The PVC keeps the hole open and the water running.

The benefit of using underground rigs for this type of drilling is the difference between large rotary rigs that produce chip samples and use lower rotation per minute (rpm) and higher torque whereas a coring rig operates at higher rpms and less torque. Chuck-drive underground coring rigs drill slower, straighter, and deeper and collect core for further analysis.

Geologists can use core samples from horizontal drilling into a high wall to look for fractures, faults, and oxidation (to identify water-bearing zones). They can also be identified in chip samples using rotary drilling rigs, but it’s more difficult to see them that way. A core sample provides a better physical view of the rock formation. Drilling high walls with underground coring rigs accomplishes two goals with one borehole – dewatering and obtaining core samples for assaying for fractures, faults, and oxidation.

LM90 with customized feed frame. Expert drillers from left to right: John Sanchez, Jimmie Maggard, Marcus Woody, and Sal Renteria.

Whether it’s an underground coring project or a surface application for underground coring rigs, the drilling crews are the real heroes at Boart Longyear. They have wide-reaching (global) resources to find unique and inventive solutions for complex, technical, and sometimes immense drilling challenges and they’re not afraid to ask questions.

More than just a can-do attitude, great work ethic, diverse skills, vast experience, technical knowledge, and a commitment to safety and each customer’s success, they get the job done. Drillers, driller assistants, welders, mechanics, supervisors, and other support personnel travel to work in remote locations, in all kinds of challenging weather, climates, and altitudes, all while spending extended time away from their families. The work is strenuous, involves extensive training, and requires their full attention for safety’s sake.

These real heroes all contributed to Boart Longyear’s latest safety achievement of 10 million man-hours and one year of being lost-time injury-free. A big congratulations to all the drilling crews and support personnel on this company-wide accomplishment! Denis Despres, Chief Operating Officer stated, "On a site level, we value the everyday procedures from standardized pre-start information meetings that focus on daily job tasks and associated hazards and risks, our online data management system, including the system’s mobile app, and the daily team and individual-based field level risk assessments. At Boart Longyear, it is everyone’s responsibility to work safely."

Originally published in Issue 11 of Coring Magazine, November 2019

Division Manager West Africa, Jonathan Madigan commented “Our drilling crew in Ghana on this project worked safely and diligently in directionally drilling the hole to the target depth. I couldn’t be more proud of the team that completed the project. Boart Longyear’s consistent hazard and risk-focused safety culture is embraced by the crews here in Ghana and they appreciate that the field level risk assessments, pre-shift meetings and other safety programs are designed to get them home safe to their families.” 

Crew pictured from left to right:
Jon Enu : Driller Assistant, Ebenezer Adu-Atta : Driller Assistant, Lewis Donkoh : Driller, Solomon Essien : Driller Assistant, Patrick Benfor : Driller
Kwame Yeboah : Driller Assistant, Benoni Kwabiah : Driller Assistant

Not pictured:
John Owusu : Driller, Glover Quaw : Driller Assistant, Daniel Emmanual : Driller Assistant, Frank Ennin : Supervisor, Fanie Van der Walt : Supervisor, Chris Milligan : Supervisor

The Company has received client recognition for their safe, on-target, and ahead of schedule completion of the deep coring exploration drilling project. Boart Longyear acknowledges the participation, collaboration, and contributions from every employee within Ghana and especially the drilling crew that worked directly on this record-depth hole. 

To learn more about Boart Longyear's contract Drilling Services, find your local Boart Longyear representative.

Greenstone and sedimentary formations like mudstone and conglomerate, while variable, are typically low in Moh’s hardness. Moving into the actual ore zone, the formation consists of various types of rock such as feldspar, muscovite schist, and fragmental biotite, introducing abrasiveness related to the rock’s quartz content.

The challenge in softer abrasive formations is to pick a diamond drilling bit tough enough to get good life without sacrificing penetration rate.

Adding in the drive for productivity creates an additional challenge. The driller cannot simply pick the toughest bit available; life needs to be increased while still maximizing penetration rate or tripping out rods to change bits impacts overall productivity.

Using patented technology, the new Longyear Bits have diamonds that are chemically bonded to the matrix creating a more versatile, faster penetrating, and a longer-lived bit. All drillers from the newly promoted to the seasoned veteran find the color-coded Longyear Diamond Bits considerably more effective in obtaining higher productivity. For each hardness rating on Mohs hardness scale, Boart Longyear has created a recommended color. The complete line of Longyear Diamond Bits includes a Red, Orange, Yellow, Green, Blue, and Purple Bit.

Originally, Alpha series 08 and 09 were chosen in Stage3 to get a good combination of life and penetration rate. These bits, while achieving acceptable penetration rates, fell significantly short on life at 43m, the average over three months. In looking at the Longyear Bit series cross reference chart, Alpha series 08 and 09 would be replaced by the Longyear Green bit. Given the low hardness of the formation, the Longyear Blue bit was also selected to determine the best solution. In stark contrast, to the Alpha series bits, the penetration rate and bit life both increased. Using a combination of the Longyear Blue and Green bits, driller’s averaged 109 meters per bit and increased penetration rate. When drilling softer formations at site, the drillers used the Blue bit and found this bit to be incomparable when looking at the production rates and bit life. The two formulas combined yielded a 60% improvement in life and an 8% increase in productivity.

Boart Longyear Canada East Coring Supervisor, Jeremy Dykstra said, “In the beginning, we struggled to meet our production targets due to slower penetration rates and poor bit life. Once we started to trial the new Longyear Diamond Bits, the performance improvement was noticed immediately with all crews at site. Smoother cutting of the formations and longer bit life helped push us towards the successful and safe production shifts we aimed to have both for our client and our business.”

Established in 1890, Boart Longyear is the world’s leading provider of drilling services, drilling equipment and performance tooling for mining and drilling companies.

The Global Drilling Services division operates for a diverse mining customer base spanning a wide range of commodities, including copper, gold, nickel, zinc, uranium, and other metals and minerals. The Global Products division designs, manufactures and sells drilling equipment, performance tooling, down-hole instrumentation and parts and services.

Ready to take the Longyear Bit challenge? Contact your Boart Longyear representative today to order trial bits and download this blank bit log sheet to keep track of bit performance so you can compare the productivity and speed of both your current diamond bits and Longyear Bits.

The Drilling Services Surface Coring drill crew used the powerful LF350e along with the new, patented XQ wireline coring rods featuring W-Wall, and the new Longyear diamond bits to successfully directionally drill at an angle of 65 degrees to the client’s required depth – which was almost 10,500 feet (3200 meters). An impressive feat in and of itself, the project had measurable productivity gains and proved the newest Boart Longyear rigs and tooling make a real difference in the field. 

With innovative features of the drill rig, combined with the deepest rated coring rods in the market and the fastest, smoothest cutting bits, the project’s success was also attributed to the talent, experience, and technical expertise of the crew.

Boart Longyear has combined proven technology from its most popular surface coring drill rigs to create the powerful LF350e.The forward tilting head design simplifies the rod handling process and reduces the need for operator intervention and maintenance. The rod breaking clamp is a hydraulic breaking device which means no wrench under power. The foot clamp rotates to break rod joints located between the foot clamp and rod breaking clamp. The rig also features a heated and air conditioned drillers cab to protect the operator from the elements and overhead hazards. Utilizing CAN bus communication and PLC programming, all LF350e functions are controlled electronically. The “e” in LF350e refers to the fully electronic control system. The rig is designed ergonomically to lessen fatigue and stress to the driller and helper. The LF350e has adjustable wireline speed to be able to set to lower the over shot and then pull the tube, which allows a hands-off safer approach. This is just one-way ergonomic design plays a part in reducing fatigue with this drill rig. The beauty of Boart Longyear’s business model of both contract drilling services and a drilling products business is access to immediate, direct, unfiltered feedback from drillers in the field. Drill rigs built for drillers.

A unique combination of -20 degree self-locking reverse flank angle on the threads and symmetrical load distribution when combined with W-Wall double-annealed mid-body, make XQ wireline coring rods some of the deepest rated coring rods in the market. XQ has an increased negative flank angle from of -20 degrees compared to -10 degrees in RQ rods. The increased negative flank angle combined with the double-start threads, nearly eliminate box bulging and provides greater strength in high torque applications.

Patented XQ joints have opposite double-start threads that are self-aligning so mating engages smoothly. This provides a balanced load response and double the contact area, which means half the contact pressure. This symmetrical load distribution increases load capacity significantly for stronger rods with deeper capacity. The lighter drill string increased drill rig depth capacity and reduced fatigue in driller's when manually tripping. The enlarged inner diameter also significantly reduced inner tube tripping time for improved productivity.

The new NXQ and HXQ W-Wall coring rods feature patent-pending, double-upset tubing, with the same overall weight reduction and faster wireline tripping speed as V-Wall. However, the standard wall thickness in the middle of XQ rod eliminates premature mid-body wear and resists bending, performing like straight wall tubing.

As all Boart Longyear coring rod, XQ W-Wall tubing is cold-drawn from high quality, North American alloy steel, uniquely processed to Boart Longyear specifications.

Boart Longyear has successfully created a chemical bond between diamond and matrix, which is stronger than the diamond itself. The increased diamond projection and improved face flushing create a bit with more versatility, higher penetration rates, and longer life. The Longyear Bits are similar to large diamond bits, but with the easy, smooth drilling characteristics drillers prefer. This means increased productivity throughout the entire operation, and ultimately more core.

To support higher penetration rates, the new Longyear formulas are combined with a new, more open, express geometry. Tapered intermediate waterways improve flushing and prevent accumulation of debris. Designed for fast cutting in competent ground, the new express geometry is available in our 16mm crown heights to maintain bit life at higher cutting speeds.

The unique Razorcut protrusions on the face of the bit contain diamonds that enable the bit to begin cutting right out of the box – even in the softest ground. The arrangement of these protrusions also improves the tracking and balance in the hole when drilling begins.

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. 

Even experienced drillers can make mistakes when retrieving core. Before core recovery, there are a few factors when drilling that can negatively impact the core, such as the type of bit used and the location of the drill site. For example, if one is drilling in a soft formation, like sand, it’s a good idea to use a TT bit with a closed center so the water is not directly contacting the core before it gets into the inner tube. By doing so, more core will be recovered than with a bit that allows water contact with core samples.

Another factor is core loss at the beginning of a run, due to drilled material left from a previous run. This material rolls around in front of the bit and breaks up the core as drillers attempt to drill their new run.

One of the most critical steps to remember is the core placement within the box. This includes how it’s labeled, the order, and the specific direction of the sample. One common pitfall is failing to adapt to the client’s needs. It might be standard practice for a team to put the core in a particular direction, and may be confusing if the client requires a different placement. If the core is positioned backward inside the box, it’s difficult to decipher the correct direction, affecting the information. It’s essential to quickly learn the client’s expectations and train teams accordingly to produce accurate representative samples.

Many different methods contribute to better intact core recovery. One easy practice is to shorten the length of the runs. For example, if one is drilling five-foot runs as a standard for his/her shift and core is lost, the run can be shortened. This will cause less stress for the core to enter the tube and core recovery will increase. It adds up to significantly more runs for the day, and less footage per shift, but the goal of retaining quality core samples is more likely to be achieved.

Another practice is coating the inner tube or splits with EZ-Mud®* or polymer, which helps keep some of the core in the tube. One can also pump Enviroplug®* or bentonite pellets down the hole after each run, which creates a clay that sticks the broken rock together.

One approach to retrieving quality core is the use of splits in the inner tubes. When pumping the splits out, the core remains intact and appears just as it was in the ground. Then, as the core is placed in boxes, it’s less likely to break which results in a cleaner presentation. Overall, splits provide a more consistent and representative core sample.

When drilling with a standard HQ core, splits aren’t an option. Drillers must meticulously retrieve the core from the inner tube without breaking the core. Using hammers and other tools are not recommended as they tend to break up the core, making it difficult to neatly store the sample in the box. Instead, it’s more effective to pump or push the core out with alternative methods like a hydraulic press system.

Quality core does not solely depend on the percentage of core recovery rate, but also considers the core being washed, placed inside the box, and transported. Once the core is retrieved, many times clients may come to the site to pick up the core sample. However, often it’s the responsibility of the company to transport the core. Teams must be aware of the potential of core breaking en route. It’s crucial to drive carefully and slowly, and always avoid bumps or divots in the road.

There’s no book that can teach all of life’s experiences. Every hole drilled becomes a new life experience that can’t be captured in a textbook. With the experience of surface coring, there’s a lot to be learned about the importance of quality core, difficulties encountered when retrieving core, and best practices for obtaining quality core samples. If everyone knew as much as a geologist to piece core back together, everyone would have consistent results in the field. Since this isn’t possible, however, it’s important to learn best practices and troubleshoot when necessary to recover quality core on a consistent basis.

*EZ-Mud is a registered trademark of Baroid Industrial Drilling Products. Enviroplug is a registered trademark of Wyo-Ben, Inc.

Q is a trademark of Boart Longyear