Our consultants have extensive experience in drilling rig noise control. In this article, we discuss the noise issues we’ve encountered in this field and the best mitigation practices to control the noise.
The control of sound produced drilling rigs is a major environmental concern in specific areas of the US. Much of our work has been focused on oil and gas well drilling operations in the Barnett Shale in Texas, Haynesville Shale in Louisiana, Marcellus Shale in Pennsylvania, DJ Basin in Colorado and the Santa Maria and Los Angeles Basins in California. As drilling operations in these areas expand over time, oil supplies in older wells in remote areas are depleted. Drilling inevitably moves closer to built-up areas and has become an increasing issue for residents in recent years.
What are the sources of noise on a drilling rig?
Typically, a drilling rig comprises of the equipment shown in the image to the right. Drill rigs have several main noise sources, each with their own characteristics. The main sources of noise are:
the generator sets (13);
the shale shakers (21);
the mud pumps (16); and
the top drive (6).
Additional noise may also be produced by:
metal-on-metal impacts from pipe handling;
blowers and HVAC systems;
ancillary equipment (eg. loaders and trucking operations)
The overall noise levels depend on the actual equipment used on the rig. However, our extensive experience in this field has shown that drilling rigs tend to produce noise levels of 60 to 65 dBA at a distance of 500 ft from the rig. Effective noise control measures can significantly reduce sound levels. Reductions of 10 dBA or more are usually achievable.
Below, we look at the main sources in more detail and explain how noise levels can be reduced.
1. Crown Block and Water Table
2. Catline Boom and Hoist Line
3. Drilling Line
5. Traveling Block
6. Top Drive
8. Drill Pipe
10. Blowout Preventer
11. Water Tank
12. Electric Cable Tray
13. Engine Generator Sets
14. Fuel Tanks
15. Electric Control House
16. Mud Pump
17. Bulk Mud Components Storage
18. Mud Pits
19. Reserve Pits
20. Mud Gas Separator
21. Shale Shaker
22. Choke Manifold
23. Pipe Ramp
24. Pipe Racks
Engine Generator Sets
A drilling rig typically has two to four large diesel engine generator sets. These are usually located side-by-side on the ground next to the rig. The generators supply power to most onsite equipment. Each engine generator set requires a large cooling fan, which is located at one end of the equipment. The primary noise sources are:
The engine exhaust
The generator cooling fans.
Noise produced by the engine can be mitigated by enclosing it (ie. by installing acoustical barriers and a roof around it). This mitigation is usually highly effective for this source and easy to implement, so long as any ventilation and cooling issues inside the enclosure are dealt with.
The engine exhaust noise can be reduced by replacing existing silencers with upgraded 'hospital grade' silencers. If this grade of silencers is not sufficient, additional reactive silencers can be installed that greatly reduce noise while adding almost no back pressure at the engine.
The cooling fans are often the cause of low-frequency sound issues. Low frequency noise from these sources can be problematic as it travels easily over acoustic barriers and carries over long distances. An effective solution to the problem is to install a set of duct silencers to each fan. This type of silencer allows air to pass through it while dramatically reducing fan noise.
The mud pumps are reciprocating pumps that circulate drilling fluid (or “mud”) around the drilling column. The flow of mud lubricates the drilling bit and removes drilled cuttings away from the bore hole. The pumps are located on the ground next to the rig. They may be fully enclosed, semi-enclosed or they may not have any kind of enclosure at all.
The most effective noise control solution for mud pumps is to contain them within a sound-attenuating enclosure. The pumps generate significant heat and, when fully enclosed, require a cooling system. The enclosure will therefore usually need air intakes and vents that leak noise to the outside. These leaks can be mitigated with the use of duct silencers.
The rig’s shale shakers remove cuttings from the drilling fluid before it is recirculated in the drilling column. Each shaker contains a table that is vibrated at a low frequency to separate the solid cutting materials from the liquid mud. A rig will often have a set of three to five shakers, which are usually located on a raised platform about eight to ten feet above the ground.
The shakers are usually the main source of low-frequency noise on the rig and can be very difficult to mitigate. It is usually not possible to enclose shakers due to the potential dangers resulting from toxic gases building up within the enclosed space. Since low-frequency noise is often the biggest issue on a drilling rig, the noise produced by the shakers is often the most critical factor in achieving noise limits. When oil companies run into compliance issues at low frequencies, they are often left with no option other than to replace this equipment with lower-noise versions.
Our noise modeling and calculations have demonstrated that an enclosure around the shakers can be an effective mitigation option so long as safety concerns are resolved to make this option viable (ie. adequate ventilation must be provided inside the enclosure).
The top drive is a hydraulic-driven device that rotates the drill string to drill the borehole. It generally produces lower noise levels than the equipment described above. However, its elevation above ground level means it usually has a clear-line-of-sight to sensitive receptors nearby. It travels up and down the mast and can reach elevations well above any acoustical barriers that may in place around the site, meaning it may need mitigation measures of its own.
Top drive noise may be mitigated with the installation of acoustical barriers applied to the mast. It is often possible to wrap acoustical blankets around at least three sides of the mast, to direct the top drive noise in one direction only.
How do oil companies approach environmental noise control?
Before a well is drilled, the oil company needs to obtain a drilling permit. This is typically awarded from a State or local authority. The permit requirements vary by location but usually require the oil company to demonstrate it will comply with State or local environmental noise control regulations, including noise ordinances. In many areas, the noise ordinances contain specific provisions applying to drilling and fracking operations. For example, in Colorado, permits are approved by the Colorado Oil and Gas Conservation Commission (COGCC), which prohibits noise levels from exceeding specific decibel levels for various receptor property uses. The most stringent regulations apply to residences, while commercial and industrial properties are subject to less stringent limits. (For a full explanation of these noise limits, see our Guide to the COGCC Noise Standards ).
If it is determined that drilling noise may impact a community, the oil company must submit a Noise Management Plan prior to permit approval. Additionally, they must perform noise monitoring at compliance points during the drilling process and provide periodic (often daily) noise reports to the authority.
The Noise Management Plan is typically prepared by a third-party acoustical consultant. The consultant will typically:
Perform calculations, or utilize noise modeling software to predict the noise impact at locations where compliance must be achieved. The predicted noise levels should be based on noise measurements conducted on the actual rig that will drill the wells. Noise modeling software enables the consultant to provide a ‘noise contour map’ showing the spread of noise into the surrounding area.
Provide a report containing the results of the noise impact analysis and the mitigation measures required to achieve compliance with the noise limits.
Noise monitoring during drilling is also usually provided by an independent consultant. Noise monitors are generally installed at compliance points around the drilling site and remain in place throughout the drilling process.
Current monitoring technology allows real-time online noise monitoring at remote locations. The noise monitors are usually installed and managed by the acoustical consultancy, who provide data access to the oil company. This allows the oil company to view noise levels in real-time. Monitoring systems such as these can provide email or SMS alerts to oil company or onsite drilling personnel to immediately alert them if the noise level exceeds the permissible noise limits.
1How seriously do oil companies take noise issues?
Oil companies employ teams of people to deal with environmental compliance issues during the permitting process through to the drilling, fracking and production phases of their wells. These personnel are responsible for managing third party acoustical consultants and may also work on R&D projects designed to reduce equipment noise levels.
Oil companies are often subject to fines when non-compliant with environmental regulations. In our experience, local authorities do enforce noise regulations and issue fines when drilling activities exceed permissible noise levels. It is therefore in the interest of oil companies to comply with noise regulations. They are motivated to comply not only to minimize any fines but also to demonstrate goodwill to the local community and avoid future permitting objections. Oil companies consider noise control to be an important issue, but have to balance noise problems with safety issues or practicality issues. This may mean noise problems don’t get solved immediately, and may not be solved during the current drilling operation.
2What are good ways to assess low frequency drilling noise?
Low frequency noise can be of concern during drilling. The low frequency noise produced by shaker tables and generators can be very difficult to mitigate. General environmental noise levels are measured in terms of “A-weighted” decibels. The A-weighted decibel scale is