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. 

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.”

Dual-tube flooded reverse circulation method develops water wells
Boart Longyear has multi-year contracts with the largest iron ore mining operations in the Pilbara region of northern Western Australia (WA) to undertake water well drilling at active and future mine sites.

The fleet of Boart Longyear dual-tube flooded reverse circulation (DTFR) water-well drill rigs have the ability to accommodate casing diameters of up to 28-inches, attain deep drill targets via a powerful 130,000-pound pullback and are mounted on a highly mobile platform. The rigs use a closed circulation mud system with a proprietary mud tank. By installing dewatering wells via DTFR, it is possible to control high producing aquifers during drilling that are problematic for conventional mud or conventional air drilling.

The DTFR method is distinguished from other drilling methods by the way the drill cuttings are returned to the surface through the drill string, whereas with conventional mud or air operations the cuttings are returned up the annulus. 

1. Cutting return is quicker than a conventional mud method. Cuttings don’t co-mingle with the annulus, as with conventional drilling systems, eliminating contamination and reducing annular washouts or hole enlargement. Cutting return via the drill string means that mud loss will not stop drilling operations as long as the drill bit remains submerged. Circulation is almost never lost and drilling mud can be replaced during drilling without the need to stop.
   
   
2. The mud system is a closed loop. Utilizing a special mud tank and drill cutting exchange, DTFR greatly reduces the drilling footprint compared to conventional mud drilling operations. Formation water is not an issue during drilling with almost zero discharge during drilling operations — making water management a non-issue.
   
   
3. DTFR mud circulates in the annulus under ambient pressure conditions reducing development time. The residual mud is easily removed from the annulus wall during development. In addition to faster and more complete mud removal, the amount of discharge water managed at the surface is lessened due to the reduction in development time.

The Boart Longyear DTFR drilling method was used to work in active mine sites in the Pilbara region — where there is a high volume of water discharged during drilling — without hindering active mining operations.

Historically, conventional air drilling or dual rotary drilling was used to set large diameter water supply, dewatering and injection wells. While these methods have the potential to drill quickly, maintaining circulation and hole integrity can be a challenge in fractured and friable ground conditions.  As a result of circulation loss or collapsing, boreholes are often completed at shallower depths.

Drilling a large diameter hole with either conventional air or dual rotary air, can also produce a tremendous amount of discharge water. This is an issue because many drill locations cannot release water to the environment due to water quality issues. So, the water is contained in giant sumps dug parallel to the drill rig. Often these pits fill quickly during drilling and operations must be stopped to allow for draining. With DTFR the need for large sumps is eliminated because water is not discharged during drilling. This is a tremendous advantage working in-pit where water management issues can interrupt mining operations.

Over the period of a year, Boart Longyear drilled 2300 meters for a large mine operator in the Pilbara region with hole diameters of 17.5 and 20 inches. The completed wells reached depths of 250 meters and were cased with 10- to 12-inch production strings.

For the development of one ex-pit dewatering well in particular, the DTFR reached a depth of 144 meters with less than 1 percent of deviation during drilling.

Geology encountered included, banded iron, thick sequences of friable mineralized ore, and shale inter-bedded with hard chert bands. These changing ground conditions were easily handled by the DTFR and drilling did not stop at any point due to loss of circulation. Prior to the use of the DTFR in the Pilbara region, there was speculation that a tri-cone drill bit, which is typically used on all types of mud drilling, would not be able to handle the hard rocks associated with iron ore deposits. These concerns were quickly alleviated with DTFR, which helped persuade other large iron ore producers to sign multi-year contracts with Boart Longyear.