Noise

What is noise? It is defined as sounds, usually of excessive intensity (too loud), that in particular place and time are felt as: "purposeless, then unpleasant, irritating, annoying and, finally, harmful” (PWN Encyclopedia).

Noise from seismic surveying

Seismic surveying is the first stage of field exploration. They are intended to give an insight into geological structures and choose the best drilling locations.

Two methods are applied in sesimic surveying, namely:

Vibroseis method – wherein special vehicles – vibrator trucks – are used
explosive-based method – applied exclusively in locations that are inaccessible to vehicles

Vibroseis method

Noise from Vibroseis-based surveys is caused by:

a fleet of several vibrator trucks moving along the seismic line at a close distance to each other, as well as during the travel to and back from the survey location
operation of the seismic wave generating devices (vibrator plate)

Noise nuisance from seismic surveying is of a short duration. It takes a few minutes to perform measurements at a single shot point and then the vehicles move to the next point. Seismic operations are usually carried out in non-built up areas – farm or timberland. The vehicles moves along clearly defined routes. Seismic surveys are delivered in daytime hours only (6.00 AM – 10.00 PM).

Noise from seismic wave generation by vibrators may achieve up to 90 dB at a distance of 10 metres from the vehicles at work.

Explosive-based seismic surveying

Seismic survey may also be performed using the explosives.

The sources of noise are:

shot hole drilling operations,
firing small (up to 0.5 kg) charges of explosives in shot holes.

Normally, three to five shot are located in one measurement point. They are drilled manually or using truck-mounted rig. The explosion always takes place under the ground, on average at a depth f 2 to 6 metres. Therefore, the sound of explosion is muffled.

Drilling stage

Drill site development is the next stage. Normally, it takes 2 to 4 weeks to build the drill site. Earthworks – site leveling, top soil removal for storage in embankments around the site, access road hardening, etc. – are done first.

At the drill site construction stage noise is generated by:

operation of heavy equipment during construction and installation works
traffic of vehicles that deliver the equipment, components and materials,
operation of generator sets

Drill site construction stage has a short-time effect on the acoustic climate of the surroundings and ceases on completion of construction works.

Noise emissions tend to decrease when works are performed inside the drill site, as they are limited to installation of plant and machinery.

Once drill site completed and equipment installed drilling operations may begin. Rotary drilling is used. Rocks are penetrated by a bit which is attached to the drill pipe. Drilling mud injected to the drill pipe carries cuttings to the surface.

At the drilling stage noise is generated by:

drilling rig – hoist, rotary table operation and drill pipe running and retrieving from the borehole
operation of generator sets
operation of mud pumps
blender operation
operation of mud treatment devices (shale shakers, hydrocyclones, centrifuges, desanders, etc.),
operation of air compressors
fans
other process procedures performed at the drill site (e.g. silo filling),
other plant and facilities (e.g. preventer control stations)
traffic of vehicles that deliver the equipment, components and materials,

Drilling operations are delivered on a continuous basis, i.e. round-the-clock and seven days a week.

Typical intensities of noise emitted during drilling operations are :

rotary table - 90 dB,
mud pumps - 90 dB,
generator sets - 105 dB

Except for duration of operations, there is no significant difference between vertical and horizontal well drilling in terms of noise intensity.

Reservoir stimulation stage

Noise from hydraulic fracturing operations occurs during delivery of a single procedure which usually lasts for a few hours. The procedures are repeated in several well sections day by day or every few days.

At the stage of stimulation procedures noise is generated by:

operation of pumps sets that inject pressurized fracturing fluid into the well
blender operation
measurement and control system operation
traffic of vehicles that deliver the equipment, components and materials,
other process procedures performed at the drill site (e.g. silo filling),
other plant and facilities

Noise intensity of a single pump set is in the order of 90 - 120 dB. A few or several simultaneously operated pump sets are required to perform the procedure. Blender's noise intensity is equal to approx. 90 dB.

Well testing stage

At well testing stage noise is generated by:

generator sets,
traffic of vehicles that haul flowback water out of the drill site,
well kicking operations (e.g. nitrogen pumping),
gas flaring (if any produced from the well).

Noise intensity of the flare may reach 102 dB.

Well abandonment and site reclamation stage

Chief noise sources at well abandonment and site reclamation stage are:

heavy equipment at dismantling, demolition and reclamation operations
traffic of vehicles hauling out the equipment, materials and wastes,
Diesel-powered generator sets.

Noise abatement

Measures intended to minimize or eliminate the impact of noise on the environment are:

drill site location at a safe distance from residential buildings or protected sites (e.g. animal habitats)
construction of earthen embankments or placement of sound screens around the drill site to absorb the noise
use of low-noise equipment with sound screens installed (e.g. wrapping the drilling rig, generator sets, etc. with special sound screens)
use of muffled machines
use of equipment with a low acoustic power
good maintenance and operation of plant and equipment
delivery of noise-intensive operations in hours when they are least burdensome to the local residents (i.e. in daytime hours, from 6.00 AM to 10.00 PM)
keeping intensity of traffic from and to the drill site as low as possible.

author: Anita Starzycka