A global and dedicated engineering department works tirelessly to improve safety, increase productivity, and solve drilling challenges in collaboration with drillers and operations. Both Boart Longyear Drilling Services and Boart Longyear Products divisions benefit from the opportunity to collaborate on equipment design and prototype development with a global team of engineers.

For the Large Rotary Drilling Services division, the engineering team makes incredibly powerful and advanced rigs like the LR500 possible. Recognizing Boart Longyear’s LR300 had depth and pullback limitations, the engineering team built the significant and incredibly powerful LR500. Completely designed and developed internally, the LR500 was built specifically to meet the increasing needs for deeper dewatering wells for Nevada mining.

While there are deep hole drill rigs in the market, not all can achieve a 60 inch (152 centimeter) diameter hole for dewatering wells for mines. The LR500 can drill hole sizes large enough to accommodate 20 inch (50 centimeter) casing down to 5,000 feet (1,524 meters). While there are rigs in the oil and gas market that are capable of more pullback, these slim hole rigs are not capable of drilling the diameters achievable by the LR500 while also being able to install the casing.

The size and weight of the casing is what sets the LR500 apart from other large rotary drill rigs in the industry. The LR500 can drill deeper with 500,000 lbs (35714 stones) of pull-back. This capability allows the rig to set the casing without having to move the rig off the hole and use a crane to set the casing. This is an all-around savings in time, labor, and equipment mobilization and demobilization costs.

Another significant benefit of the LR500 is that it is electrically powered. It seamlessly connects into the power grid source. This technology provides a considerable benefit for emissions reduction and fuel savings. Decreasing emissions was extremely important to the Nevada mining client that commissioned the LR500.

The LR500 is equipped with sensors and provides the driller with constant real-time feedback about ground conditions being encountered down the hole. The driller sets up drilling parameters and the rig will set off alarms or shut down depending on those set parameters. When drilling conditions change as the hole progresses, for example, if the tri-cone drill bit hits a void, the rig will throw an alarm or shut down and allow the driller to make the proper adjustments.

In addition to the automated drilling features, the LR500 is equipped with a fully hands-free rod handler. A mechanical rod arm picks up a rod from the rod rack and feeds it into the mast, allowing the head to begin threading the rod. This hands-free technology allows making or breaking rods when tripping in or out. This is a substantial safety feature that removes drillers and driller assistants away from the hazards of rod handling, making and breaking rods, and being under a suspended load of a rod.

Drillers are in a climate controlled cab, protected from the elements. Several screens and a camera system allow the driller to monitor important areas of the rig from the cab – like the draw works, the head, rod handling, work deck, mud tank system, etc. The cab is also equipped with an intercom which allows the driller to communicate with the crew deck.

This unique drilling process uses dual wall drill pipe and drilling fluid along with the injection of air in order to drill large diameter holes. In the drill string, perforations allow the air to return up the center, following the path of least resistance. The air traveling back up the inner tube evacuates the fluid inside the drill pipe, which in turn allows the mud fluid on the backside of the drill rod to move down the hole, across the bit face and back up the center to surface bringing the cuttings with it. Using Dual Tube Flooded Reverse (DTFR), fluid returns inside the dual tube pipe and cannot escape into the formation. Instead of maintaining fluids at the surface and circulating throughout the wellbore, DTFR allows drilling to take place with the borehole fluids at their naturally occurring level.

Most other contractors drill a pilot hole at a smaller diameter and then go back in and ream the hole again in the larger diameter. Sometimes this can take several passes. The beauty of DTFR is the capability to drill to the large diameter and depths with a single pass. This shortens the total time the hole is open and decreases risks of collapse and flooding the formation. Not only is DTFR more efficient, but it minimizes development time and maximizes well efficiency.

Boart Longyear uses a self-contained drilling fluids system where, as the drilling fluids return to the surface, they are collected in a tank where the cuttings are stripped from the fluid through shale shaker screens and de-sanding units and the drilling fluid is then reused in the drilling process. Self-contained drilling fluids tanks ensure proper mixture and maintenance of drilling fluids and save money by eliminating the need for a pit. Eliminating a pit for drilling fluids reduces the drill pad size, may require fewer disturbance permits, and eliminates the need to backfill a pit.

The LR500 has outperformed the expectations of the drillers and the engineers. The first hole drilled was a true straight hole and was accomplished in a single pass. It was critical that the first hole the LR500 drilled be exceptionally straight because it was drilling in extremely close proximity to an underground stope. There was a real possibility of intersecting and flooding that stope. But the results from the LR500 impressed both the client and the drillers. The ability to accomplish such straight holes is attributed three major features: the automated drilling features, an electric hoist, and the larger tooling.

The constant real-time feedback during drilling allows the driller to make adjustments while drilling to accommodate changing conditions as they happen down the hole. The electric hoist allows very finite control for immediate adjustments in weight and rotation tuning. The larger the tooling the more rigid it is, so it offers a straighter hole. The stout tooling and bottom hole assembly maximizes potential for plumbness and alignment.

After completion of the first hole, the LR500 was moved infield with the mast and base assembled. This is a time-saver because once you’re onsite, there’s a lot less disassembly of the rig to move hole to hole. The LR500 was moved 1.5 miles in about 3 hours. The rig sits on a modified track hoe and was designed with the support equipment needed for the move.

On the first well, traditional gravel was used. On the second well, the client ordered glass SiLibeads® to set the screen casing, another unique component of the project. The filter pack glass beads were substituted for gravel to minimize biological build-up, maximize well capacity, and conserve energy and backwash water.

Whether you need a mineral exploration drilling contractor, water services, or production drilling, you need a contractor with a rock-solid reputation and a track record for safety and innovative solutions. Boart Longyear operates safely with integrity and drills for results, consistently delivering innovative solutions to the most technical drilling challenges, in some of the most complex operating environments around the world. The LR500 is just another example of how we accomplish it all through our investment in safety, our people, and equipment.

Northern Star Resources Limited awarded Boart Longyear Drilling Services the directional drilling job to develop a paste fill hole at Paulsens gold mine, located in northern Western Australia.

The paste fill hole acts as a delivery system and allows for a paste-like mixture of cement and mine tailings to backfill the underground zones where mining and excavations occurred. This provides additional ground support and pillar recovery, which optimizes further mining of adjacent stopes.

The paste fill hole needed to be drilled to a 310-millimeter (12.25 in) diameter to allow it to be internally lined down its entire length with a 203.2-millimeter (8 in) diameter casing. Because of the unusual requirement for a larger hole, a regular mineral exploration drill rig could not be used.

The traditional method of drilling this type of hole would be to first drill a pilot hole with diamond drills, then enlarge the hole using rotary drilling methods on a second — and potentially even a third — pass. This method could take as many as 45 to 50 shifts to complete the drill.

An additional challenge for the driller was making sure the hole would intersect within the 5-meter (16.4 ft) diameter target in the underground development zone. This created the need for concise and accurate surveying over the duration of the directional drilling. Meaning Boart Longyear would have to work with a third-party specialist, Surtron Technologies, to deliver the paste fill hole on target.

Because of the large hole requirements, Boart Longyear elected to use a water-well-style drill rig with the ability to accommodate large-diameter casing and a deeper drilling capability via a powerful 130,000-pound pullback.

An additional booster compressor was also provided as the entire hole was drilled using conventional DTH hammers. The booster compressor was essential to keep the DTH hammer efficient and to lift and clear the cuttings from the hole.

The Boart Longyear crew set up the rig and was operational within one week after arriving on the jobsite. As drilling commenced, the hole was collared and cased with a 470-millimeter (18½ in) diameter drill bit for the top 6 meters (19.6 ft) before reducing to a 381-millimeter (15 in) diameter. This was progressed to a depth of 56 meters (183.7 ft) before the hole was once again cased. The bottom hole assembly was then reduced to the final diameter of 310 millimeters (12.25 in), and drilling recommenced.

As the hole progressed, multi-shot surveys were regularly undertaken by Surtron Technologies and Boart Longyear adjusted drilling parameters as needed to ensure the hole trajectory remained on target.

“It is great that Northern Star Resources Limited and Boart Longyear can come together on a well-planned and executed program to an outcome using a technique that is unique, but also safe and accurate,” says Bernie Sostak, general manager of business development and technical services at Northern Star Resources Limited. “Both teams are to be commended on a high quality technical success story.”

Actual drilling operations required a total of 39 12-hour shifts to reach the target depth of 656 meters (2,152 ft). Most importantly, the hole successfully intersected its required target at only 2 meters (6.56 ft) from center. The average drilling was 22.6 meters (74.14 ft) per shift, and the single best shift produced 90 meters (295.28 ft) between the depths of 428 and 518 meters (1,404.2 to 1,699.5 ft).

Regular rod pulls were conducted for drill bit inspection/replacement, as well as surveying of the hole. As ground formations became harder, Boart Longyear pulled the rods to switch out drill bits and DTH hammers to provide an optimized combination for the drilling conditions.

“This was one of the most successful surface paste fill delivery holes I have been associated with, and considering it was drilled in one pass, this saved not only time, but, as we all know, money,” added Sostak. “The hole was drilled 656 meters (2,152 ft) from surface and intersected within 2.1 meters (6.9 ft) of target, which was very impressive.”

With the use of a water-well-style rig, Boart Longyear was able to achieve a one-pass shot in 39 shifts, helping the owner to realize approximately $5 million in future gold value per mining level for this particular pillar extraction.

Mountain Regional Water Special Service District is a large government water supplier which serves nearly 5,000 customers in the western region of Summit County, near Park City, Utah. The District covers roughly a 25 square mile territory and has an elevation gain of over 3,000 feet. “Serving customers in this area can be a real trial, not only because of the energy challenges with servicing such a diverse geography, but also the difficulties finding groundwater at high elevations, and in a steep mountainous environment. All groundwater sources in this territory are based on deep bedrock aquifers, with many obstacles. And most of the District’s 15 or so wells produce 200 gallons per minute or less.” says Mountain Regional Water District’s Doug Evans.

In 2015, the District decided to expand its well production and targeted an aquifer that would be highly productive. The Bison Bluff well was proposed to be a 1,000 foot deep well, with a completed depth of 700 feet and fitted with a 16 inch diameter steel louvered casing.

The District outlined several criteria that needed to be met to make this a succcessful project. First, the drilling to be performed near Park City was situated within a residential neighborhood. This would require critical noise control, as well as lighting and difficult access considerations. Secondly, the project needed to be completed in the winter, before the Christmas holiday season, when water demands were at a minimum.  The timing was important because an existing production well near the project would be precluded from operation during the drilling. This all meant that the project would need to be drilled around the clock and would also be under the microscope of the local home owner’s association and Summit County officials.

Local County ordinances identified noise prohibitions as well as criterion for measuring noise levels when it is anticipated the requirements in the ordinance might be exceeded. The stated noise threshold required that the noise levels not exceed 65 dBA.

Before the project began, noise monitoring was conducted to measure and document the existing ambient conditions adjacent to the project site. The results of the ambient noise levels indicated existing dBA levels between 60.3dBA and 69.3dBA which meant that essentially no recordable increase to the ambient dBA levels could be added by drilling activities. Boart Longyear proactively prepared and delivered a detailed report of the study to both the District and the County.

As a result, a Boart Longyear LR175 electric/hydraulic rotary drill with a quiet genset operating the electric motor and a self-contained electric mud system was utilized in place of the typical diesel/hydraulic rotary drill. This greatly reduced the typical operating noise level.

Sound attenuation curtains were also constructed on three sides of the project site and air dump mufflers were installed on the drilling rig, to further reduce noise output. In addition, since the drill site could create intermittent noise that could have exceeded the 65dBA threshold, Boart Longyear instituted additional mitigation measures.

• Shift changes were scheduled for 7:00 am and 7:00 pm.
• Truck deliveries were restricted to daytime hours.
• Back-up alarms were disconnected and spotters were used.
• Noise from banging, hitting of down hole tools, hand tools, and other equipment was monitored and reduced to “as absolutely necessary” situations and was restricted to daytime only.

Using the same methodology used for identifying the existing ambient noise levels, the maximum noise level generated by the Boart Longyear drilling operations was recorded at the same three locations. One additional site (SML 4) was added in order to evaluate how much of the noise energy traveled above the sound attenuation walls and potentially impacted the residences on the bluff overlooking the project site. The average measured and calculated noise levels were well below the threshold.

The project was completed successfully with no disruption to the local community and there was no recordable down-time or violations to the strict noise ordinance.

According to Doug Evans, Chief Technical Officer at Mountain Regional Water, “District management and staff could not say enough about the professionalism and technical expertise exhibited by the Boart Logyear team. The District was included in all phases of the drilling project, from initial safety planning to completion and cleanup. The Boart Longyear team met the challenges head on, and worked with the District on a community education plan, and even went door to door with District personnel as we handed out literature and educated the community, not only on the needs of the project, but how all of their concerns would be mitigated. Boart Longyear also utilized state of the art equipment in this project to minimize drill time and to lessen any impacts. Utilizing their LR175 electric drilling rig, which had an extremely large impact on noise, the entire site was also protected by sound walls, and lighting at night was minimized by using many small shop lights on the site instead of large construction flood lights. The site also abutted up against a very popular community walking trail and the area was kept very safe, clean, and neat.”