Tiakina Te Moana

Impacts of Seismic Surveys on Marine Mammals and Fish

What are seismic surveys?

Seismic surveys are used by the offshore oil and gas industry to help determine the location of oil and gas

deposits beneath the seafloor. These surveys utilize large, specialized ships which tow an array of powerful

air guns that generate sound waves by firing off explosive blasts of air. The sound waves are reflected off

the seafloor and create a picture of underwater geological formations.

A typical seismic survey lasts 2-3 weeks and covers a range of about 300-600 miles. The intensity of sound

waves produced by the firing of seismic air guns can reach up to 250 decibels (dB) near the source and can

be as high as 117 dB over 20 miles away. The sound intensity produced by a jackhammer is around 120

dB, which can damage human ears in as little as 15 seconds.

What impacts can seismic surveys have on marine mammals?

Unlike humans and other terrestrial animals, marine mammals rely on sound instead of sight as their

primary sense. Dolphins, whales and seals utilize their sense of hearing to locate prey, avoid predators,

choose migration routes, and to communicate across long distances. The noise associated with seismic

surveys can affect the ability of these animals to detect natural underwater sounds, thereby disrupting these

critical activities.

Numerous scientific studies have solidified what Eskimo subsistence hunters have known for years: that

whales avoid expansive areas where seismic surveys are being conducted. One recent study showed that

fall-migrating bowhead whales in the Beaufort Sea were displaced from an area within 12 miles of the

seismic source and began to show avoidance behavior up to 21 miles away. Researchers have also observed

signs of physical stress such as startle responses in humpback whales while seismic surveys were being

conducted many miles away (see Figure 1 below).

Scientists believe that pods of whales that include calves are at serious risk from seismic activities due to

their need to utilize critical habitats for feeding and resting. If seismic surveys continually displace whales

from these important areas, population-level consequences may result. Dr. Barret-Lennard, Senior Marine

Mammal Researcher at the Vancouver Marine Science Center, has asserted that seismic exploration is one

of the two greatest threats to whales and dolphins.

1

What impacts can seismic surveys have on fish?

The powerful sound waves generated by seismic surveys can have a variety of harmful effects on fish.

Within close range, seismic surveys have been found to kill adult fish as well as larvae and fish eggs.

Scientific studies have also shown that air gun blasts can cause a variety of sublethal impacts on fish such

as damaging orientation systems and reducing their ability to find food. Researchers have noted

disturbances in the migration routes of salmon and other anadromous species as a result of seismic

operations.

Seismic surveys can cause physical damage to fish ears and other tissues and organs such as swim bladders.

Although such effects may not kill fish immediately, they may lead to reduced fitness, which increases

their susceptibility to predation and decreases their ability to carry out important life processes.

Furthermore, if important prey species in the food web such as squid and zooplankton are harmed by

seismic testing, the fish dependent on these creatures may also be negatively affected.

Proponents of offshore oil and gas production often argue that overall impacts of seismic surveys on fish

are negligible. However, Stanislav Patin, an international expert on the environmental impacts of offshore

oil and gas development, has warned that “…there seems to be no reason for the optimism that is

sometimes expressed regarding the ecological safety of seismic surveys and their harmlessness to fish

resources.”

2

(over please)How do seismic surveys impact fishing efforts?

Seismic surveys not only threaten commercial and subsistence fishing by harming fish resources, but also

by interfering with fishing operations and dramatically affecting catch rates. Seismic ships tow streamers

that can be miles long. These can get tangled up with crab pots, set nets and trawl nets causing damage and

decreasing crucial fishing time. The best time to conduct seismic surveys in Arctic environments is during

the summer, which is also prime season for many Alaskan fisheries. As a result, seismic survey operations

can end up competing with fishing for time and space on the water.

Even if these kinds of conflicts can be avoided, several studies have shown that seismic operations have

greatly reduced catches of fish around areas where air guns were being fired. These studies have

demonstrated reduced catches over 20 miles away from the source with catch reductions continuing five

days after the testing was complete (See Table 1 below). Researchers believe these catch reductions are a

result of altered fish behavior due to seismic operations which cause them to be less likely to take hooks

and/or to move down and away from the seismic firing.

Table 1: Reductions in fish catch rates as a result of seismic survey activity

Species Gear type Noise level of

seismic testing

Catch reduction Source

Atlantic cod

(Gadus morhua)

Trawl 250 decibels (dB) 46-69% lasting at least

5 days

Engas et al. 1993

Atlantic cod

(Gadus morhua)

Longline 250 dB 17-45% lasting at least

5 days

Engas et al. 1993

Atlantic cod

(Gadus morhua)

Longline Undetermined, 9.32

miles from source

55-79 % lasting at least

24 hours

Lokkeborg and Soldal, 1993

Haddock

(Melanogrammus aeglefinus)

Trawl 250 dB 70-72% lasting at least

5 days

Engas et al. 1993

Haddock

(Melanogrammus aeglefinus)

Longline 250 dB 49-73% lasting at least

5 days

Engas et al. 1993

Rockfish

(Sebastes spp.)

Longline 223 dB 52%- effect period not

determined

Skalski et al., 1992

Prospecting for oil and gas using exploration seismology, a geophysical method of determining geologic structure by means of prospector-induced elastic waves. By studying body waves such as compressional and shear waves propagating through the Earth's interior, the constituent and elastic properties of its solid and liquid core, its solid mantle, and its thin crust are defined. The major differences between earthquake seismology and petroleum exploration seismology are scales and knowledge of the location of seismic disturbances. Earthquake seismology studies naturally generated seismic waves, which have periods in minutes and resolution in kilometers. In exploration seismology, artificial sources are used that have periods of tenths of a second and tens of meters of resolution. Production seismology requires higher-frequency seismic waves and better resolution, often resolution in the order of a few meters. See also Earth; Earth interior.

Computer technology allows resolution of some of the theoretical complexities of elastic wave propagation so that deeper insight into the wave field phenomena can be obtained. The availability of a large number of channels in the recording instrument facilitates three-dimensional and three-component acquisitions. Powerful supercomputers allow manipulation of larger and larger data sets, and they have facilitated display and interpretation of them as a single data unit through the use of advanced computer visualization techniques. See also Computer; Supercomputer.

The availability of powerful workstations led to the wide use of interactive processing and interpretation. When such is coupled with technically advanced algorithms, the amount of information that the interpreter can obtain from the data increases significantly. Better quality control is provided, fine-tuning analysis is achieved more easily, and the data can be enhanced to meet specific objectives. If there are discrepancies between the model and the real data, a hypothesis can be proposed based on information derived from the data. This process can be iterated until the Earth model derived is consistent with all available surface and subsurface geophysical, petrophysical, geological, and engineering data sets. See also Algorithm; Model theory; Simulation.

The seismic method as applied to exploration of oil and gas involves field acquisition, data processing, and geologic interpretation. Seismic field acquisition requires placement of acoustic receivers (geophones) on the surface in the case of land exploration, or strings of hydrophones in the water in the case of marine exploration. Seismic data processing is usually done in large computing centers with digital mainframe computers or a large number of processors in parallel configurations. The end result of seismic data processing is the production of a subsurface profile similar to a geologic cross section. It is commonly plotted in a time scale, but it is also possible to plot it in depth. These time or depth profiles are used for geologic interpretation. Geologic interpretation of seismic data has two key components, structural and stratigraphic. Structural interpretation of seismic data involves mapping of the geologic relief of different subsurface strata by using seismic data as well as information from boreholes and outcrops. Stratigraphic interpretation looks at attributes within a common stratum and interprets changes to infer varying reservoir conditions such as lithology, porosity, and fluid content.

Historically, surface seismic acquisition is done by placing sources and receivers along a straight line so that it can be assumed that all the reflection points fall in a two-dimensional plane formed between the line of traverse and the vertical. This is known as two-dimensional seismic. Three-dimensional seismic is a method of acquiring surface seismic data by placing sources and receivers in an areal pattern. One example of a simple three-dimensional layout is to place the receivers along a line and shoot into these receivers along a path perpendicular to this line. See also Computer graphics.

A three-dimensional seismic survey provides a more accurate and detailed image of the subsurface. It offers significantly higher signal quality than the two-dimensional data commonly acquired. It also improves both spatial and temporal resolutions. The three-dimensional seismic technique is being applied to exploration and production of oil and gas, accounting for more than half of the seismic activity in the Gulf of Mexico and North Sea.

Production seismology is the application of seismic techniques to problems related to the production and exploitation of petroleum reservoirs. Since production geophysics is the only effective method available that can image the reservoirs under in-place conditions, it has become an active field of applied research aimed at improving descriptions and understanding of reservoirs and their fluid flow behaviors. See also Geophysical exploration; Petroleum enhanced recovery; Petroleum geology; Petroleum reservoir engineering; Seismology.

Read more: http://www.answers.com/topic/seismic-exploration-for-oil-and-gas#ixzz1JOpHgqp3

History

Underwater sound has probably been used by marine animals for millions of years. The science of underwater acoustics began in 1490, when Leonardo Da Vinci wrote,[1]

"If you cause your ship to stop and place the head of a long tube in the water and place the outer extremity to your ear, you will hear ships at a great distance from you."

In 1687 Isaac Newton wrote his Mathematical Principles of Natural Philosophy which included the first mathematical treatment of sound. The next major step in the development of underwater acoustics was made by Daniel Colladon, a Swiss physicist, and Charles Sturm, a French mathematician. In 1826, on Lake Geneva, they measured the elapsed time between a flash of light and the sound of a submerged ship's bell heard using an underwater listening horn.[2] They measured a sound speed of 1435 meters per second over a 17 kilometer distance, providing the first quantitative measurement of sound speed in water.[3] The result they obtained was within about 2 % of currently accepted values. In 1877 Lord Rayleigh wrote the Theory of Sound and established modern acoustic theory.

The sinking of Titanic in 1912 and the start of World War I provided the impetus for the next wave of progress in underwater acoustics. Anti-submarine listening systems were developed. Between 1912 and 1914, a number of echolocation patents were granted in Europe and the U.S., culminating in Reginald A. Fessenden's echo-ranger in 1914. Pioneering work was carried out during this time in France by Paul Langevin and in Britain by A B Wood and associates.[4] The development of both active ASDIC and passive sonar (SOund Navigation And Ranging) proceeded apace during the war, driven by the first large scale deployments of submarines. Other advances in underwater acoustics included the development of acoustic mines.

In 1919, the first scientific paper on underwater acoustics was published,[5] theoretically describing the refraction of sound waves produced by temperature and salinity gradients in the ocean. The range predictions of the paper were experimentally validated by transmission loss measurements.

The next two decades saw the development of several applications of underwater acoustics. The fathometer, or depth sounder, was developed commercially during the 1920s. Originally natural materials were used for the transducers, but by the 1930s sonar systems incorporating piezoelectric transducers made from synthetic materials were being used for passive listening systems and for active echo-ranging systems. These systems were used to good effect during World War II by both submarines and anti-submarine vessels. Many advances in underwater acoustics were made which were summarised later in the series Physics of Sound in the Sea, published in 1946.

After World War II, the development of sonar systems was driven largely by the Cold War, resulting in advances in the theoretical and practical understanding of underwater acoustics, aided by computer-based techniques.

[edit]Theory

[edit]Sound waves in water

A sound wave propagating underwater consists of alternating compressions and rarefactions of the water. These compressions and rarefactions are detected by a receiver, such as the human ear or a hydrophone, as changes in pressure. These waves may be man-made or naturally generated.

[edit]Speed of sound, density and impedance

The speed of sound (i.e., the longitudinal motion of wavefronts) is related to frequency and wavelength of a wave by .

This is different from the particle velocity , which refers to the motion of molecules in the medium due to the sound, and relates the plane wave the pressure to the fluid density and sound speed by .

The product of c and from the above formula is known as the characteristic acoustic impedance. The acoustic power (energy per second) crossing unit area is known as the intensity of the wave and for a plane wave the average intensity is given by , where is the root mean square acoustic pressure.

At 1 kHz, the wavelength is about 1.5 m. Sometimes the term "sound velocity" is used but this is incorrect as the quantity is a scalar.

The large impedance contrast between air and water (the ratio is about 3600) and the scale of surface roughness means that the sea surface behaves as an almost perfect reflector of sound at frequencies below 1 kHz. Sound speed in water exceeds that in air by a factor of 4.4 and the density ratio is about 820.

[edit]Absorption of sound

Absorption of low frequency sound is weak.[6] (see Technical Guides - Calculation of absorption of sound in seawater for an on-line calculator). The main cause of sound attenuation in fresh water, and at high frequency in sea water (above 100 kHz) is viscosity. Important additional contributions at lower frequency in seawater are associated with the ionic relaxation of boric acid (up to c. 10 kHz)[6] and magnesium sulfate (c. 10 kHz-500 kHz).[7]

Sound may be absorbed by losses at the fluid boundaries. Near the surface of the sea losses can occur in a bubble layer or in ice, while at the bottom sound can penetrate into the sediment and be absorbed.

[edit]Sound Reflection and Scattering

[edit]Boundary interactions

Both the water surface and bottom are reflecting and scattering boundaries.

[edit]Surface

For many purposes the sea-air surface can be thought of as a perfect reflector. The impedance contrast is so great that little energy is able to cross this boundary. Acoustic pressure waves reflected from the sea surface experience a reversal in phase, often stated as either a “pi phase change” or a “180 deg phase change”. This is represented mathematically by assigning a reflection coefficient of minus 1 instead of plus one to the sea surface.

At high frequency (above about 1 kHz) or when the sea is rough, some of the incident sound is scattered, and this is taken into account by assigning a reflection coefficient whose magnitude is less than one. For example, close to normal incidence, the reflection coefficient becomes , where h is the rms wave height.[8]

A further complication is the presence of wind generated bubbles or fish close to the sea surface.[9] The bubbles can also form plumes that absorb some of the incident and scattered sound, and scatter some of the sound themselves.[10]

[edit]Seabed

The acoustic impedance mismatch between water and the bottom is generally much less than at the surface and is more complex. It depends on the bottom material types and depth of the layers. Theories have been developed for predicting the sound propagation in the bottom in this case, for example by Biot [11] and by Buckingham.[12]

[edit]At Target

The reflection of sound at a target whose dimensions are large compared with the acoustic wavelength depends on its size and shape as well as the impedance of the target relative to that of water. Formulae have been developed for the target strength of various simple shapes as a function of angle of sound incidence. More complex shapes may be approximated by combining these simple ones.[1]

[edit]Propagation of sound

Underwater acoustic propagation depends on many factors. The direction of sound propagation is determined by the sound speed gradients in the water. In the sea the vertical gradients are generally much larger than the horizontal ones. These facts, combined with a tendency for increasing sound speed with increasing depth due to the increasing pressure in the deep sea reverses the sound speed gradient in the thermocline creating an efficient waveguide at the depth corresponding to the minimum sound speed. The sound speed profile may cause regions of low sound intensity called "Shadow Zones" and regions of high intensity called "Caustics". These may be found by ray tracing methods.

At equatorial and temperate latitudes in the ocean the surface temperature is high enough to reverse the pressure effect, such that a sound speed minimum occurs at depth of a few hundred metres. The presence of this minimum creates a special channel known as Deep Sound Channel, previously known as the SOFAR (sound fixing and ranging) channel, permitting guided propagation of underwater sound for thousands of kilometres without interaction with the sea surface or the seabed. Another phenomenon in the deep sea is the formation of sound focussing areas known as Convergence Zones. In this case sound is refracted downward from a near-surface source and then back up again. The horizontal distance from the source at which this occurs depends on the positive and negative sound speed gradients. A surface duct can also occur in both deep and moderately shallow water when there is upward refraction, for example due to cold surface temperatures. Propagation is by repeated sound bounces off the surface.

In general, as sound propagates underwater there is a reduction in the sound intensity over increasing ranges, though in some circumstances a gain can be obtained due to focussing. Propagation loss (sometimes referred to as transmission loss) is a quantitative measure of the reduction in sound intensity between two points, normally the sound source and a distant receiver. If Is is the far field intensity of the source referred to a point 1 m from its acoustic centre and Ir is the intensity at the receiver, then the propagation loss is given by[1] PL = 10log(Is / Ir). In this equation Ir is not the true acoustic intensity at the receiver, which is a vector quantity, but a scalar equal to the equivalent plane wave intensity (EPWI) of the sound field. The EPWI is defined as the magnitude of the intensity of a plane wave of the same RMS pressure as the true acoustic field. At short range the propagation loss is dominated by spreading while at long range it is dominated by absorption and/or scattering losses.

An alternative definition is possible in terms of pressure instead of intensity,[13] giving PL = 20log(ps / pr), where ps is the RMS acoustic pressure in the far-field of the projector, scaled to a standard distance of 1 m, and pr is the RMS pressure at the receiver position.

These two definitions are not exactly equivalent because the characteristic impedance at the receiver may be different from that at the source. Because of this, the use of the intensity definition leads to a different sonar equation to the definition based on a pressure ratio.[14] If the source and receiver are both in water, the difference is small.

[edit]Propagation modeling

The propagation of sound through water is described by the wave equation, with appropriate boundary conditions. A number of models have been developed to simplify propagation calculations. These models include ray theory, normal mode solutions, and parabolic equation simplifications of the wave equation.[15] Each set of solutions is generally valid and computationally efficient in a limited frequency and range regime, and may involve other limits as well. Ray theory is more appropriate at short range and high frequency, while the other solutions function better at long range and low frequency.[16] Various empirical and analytical formulae have also been derived from measurements that are useful approximations.[17]

[edit]Reverberation

Transient sounds result in a decaying background that can be of much larger duration than the original transient signal. The cause of this background, known as reverberation, is partly due to scattering from rough boundaries and partly due to scattering from fish and other biota. For an acoustic signal to be detected easily, it must exceed the reverberation level as well as the background noise level.

[edit]Doppler Shift

If an underwater object is moving relative to an underwater receiver, the frequency of the received sound is different from that of the sound radiated (or reflected) by the object. This change in frequency is known as a Doppler shift. The shift can be observed in active sonar systems, particularly narrowband ones, because the transmitter frequency is known, and the relative motion between sonar and object can be calculated. Sometimes the frequency of the radiated noise (a tonal) may also be known, in which case the same calculation can be done for passive sonar. For active systems the change in frequency is 0.69 Hz per knot per kHz and half this for passive systems as propagation is only one way. The shift corresponds to an increase in frequency for an approaching target.

[edit]Sound Fluctuations

Though acoustic propagation modelling generally predicts a constant received sound level, in practice there are both temporal and spatial fluctuations. These may be due to both small and large scale environmental phenomena. These can include sound speed profile fine structure and frontal zones as well as internal waves. Because in general there are multiple propagation paths between a source and receiver, small phase changes in the interference pattern between these paths can lead to large fluctuations in sound intensity.

[edit]Non-linearity

In water, especially with air bubbles, the change in density due to a change in pressure is not exactly linearly proportional. As a consequence for a sinusoidal wave input additional harmonic and subharmonic frequencies are generated. When two sinusoids are input sum and difference frequencies are generated. The conversion process is greater at high source levels than small ones. Because of the non-linearity there is a dependence of sound speed on the pressure amplitude so that large changes travel faster than small ones. Thus a sinusoidal waveform gradually becomes a sawtooth one with a steep rise and a gradual tail. Use is made of this phenomenon in parametric sonar and theories have been developed to account for this, e.g. by Westerfield.

[edit]Measurements

Sound in water is measured using a hydrophone, which is the underwater equivalent of a microphone. A hydrophone measures pressure fluctuations, and these are usually converted to sound pressure level (SPL), which is a logarithmic measure of the mean square acoustic pressure.

Measurements are usually reported in one of three forms :-

RMS acoustic pressure in micropascals (or dB re 1 μPa)

RMS acoustic pressure in a specified bandwidth, usually octaves or thirds of octave (dB re 1 μPa)

spectral density (mean square pressure per unit bandwidth) in micropascals per hertz (dB re 1 μPa²/Hz)

[edit]Sound speed

Approximate values for fresh water and seawater, respectively, at atmospheric pressure are 1450 and 1500 m/s for the sound speed, and 1000 and 1030 kg/m³ for the density.[18] The speed of sound in water increases with increasing pressure, temperature and salinity.[19][20] On-line calculators can be found at Technical Guides - Speed of Sound in Sea-Water and Technical Guides - Speed of Sound in Pure Water.

[edit]Absorption

Many measurements have been made of sound absorption in lakes and the ocean [6] [7] (see Technical Guides - Calculation of absorption of sound in seawater for an on-line calculator).

[edit]Ambient noise

Measurement of acoustic signals are possible if their amplitude exceeds a minimum threshold, determined partly by the signal processing used and partly by the level of background noise. Ambient noise is that part of the received noise that is independent of the source, receiver and platform characteristics. This it excludes reverberation and towing noise for example.

The background noise present in the ocean, or ambient noise, has many different sources and varies with location and frequency.[21] At the lowest frequencies, from about 0.1 Hz to 10 Hz, ocean turbulence and microseisms are the primary contributors to the noise background.[22] Typical noise spectrum levels decrease with increasing frequency from about 140 dB re 1 μPa²/Hz at 1 Hz to about 30 dB re 1 μPa²/Hz at 100 kHz. Distant ship traffic is one of the dominant noise sources in most areas for frequencies of around 100 Hz, while wind-induced surface noise is the main source between 1 kHz and 30 kHz. At very high frequencies, above 100 kHz, thermal noise of water molecules begins to dominate. The thermal noise spectral level at 100 kHz is 25 dB re 1 μPa²/Hz. The spectral density of thermal noise increases by 20 dB per decade (approximately 6 dB per octave).

Transient sound sources also contribute to ambient noise. These can include intermittent geological activity, such as earthquakes and underwater volcanoes,[23] rainfall on the surface, and biological activity. Biological sources include cetaceans (especially blue, fin and sperm whales),[24][25] certain types of fish, and snapping shrimp.

Rain can produce high levels of ambient noise. However the numerical relationship between rain rate and ambient noise level is difficult to determine because measurement of rain rate is problematical at sea.

[edit]Reverberation

Many measurements have been made of sea surface, bottom and volume reverberation. Empirical models have sometimes been derived from these. A commonly used expression for the band 0.4 to 6.4 kHz is that by Chapman and Harris.[26] It is found that a sinusoidal waveform is spread in frequency due to the surface motion. For bottom reverberation a Lambert's Law is found often to apply approximately, for example see Mackenzie.[27] Volume reverberation is usually found to occur mainly in layers, which change depth with the time of day, e.g., see Marshall and Chapman.[28] The under-surface of ice can produce strong reverberation when it is rough, see for example Milne.[29]

[edit]Bottom Loss

Bottom loss has been measured as a function of grazing angle for many frequencies in various locations, for example those by the US Marine Geophysical Survey.[30] The loss depends on the sound speed in the bottom (which is affected by gradients and layering) and by roughness. Graphs have been produced for the loss to be expected in particular circumstances. In shallow water bottom loss often has the dominant impact on long range propagation. At low frequencies sound can propagate through the sediment then back into the water.

[edit]Underwater hearing

[edit]Comparison with airborne sound levels

As with airborne sound, sound pressure level underwater is usually reported in units of decibels, but there are some important differences that make it difficult (and often inappropriate) to compare SPL in water with SPL in air. These differences include:[31]

difference in reference pressure: 1 μPa (one micropascal, or one millionth of a pascal) instead of 20 μPa.[13]

difference in interpretation: there are two schools of thought, one maintaining that pressures should be compared directly, and that the other that one should first convert to the intensity of an equivalent plane wave.

difference in hearing sensitivity: any comparison with (A-weighted) sound in air needs to take into account the differences in hearing sensitivity, either of a human diver or other animal.[32]

[edit]Hearing sensitivity

The lowest audible SPL for a human diver with normal hearing is about 67 dB re 1 μPa, with greatest sensitivity occurring at frequencies around 1 kHz.[33] Dolphins and other toothed whales are renowned for their acute hearing sensitivity, especially in the frequency range 5 to 50 kHz.[32][34] Several species have hearing thresholds between 30 and 50 dB re 1 μPa in this frequency range. For example the hearing threshold of the killer whale occurs at an RMS acoustic pressure of 0.02 mPa (and frequency 15 kHz), corresponding to an SPL threshold of 26 dB re 1 μPa.[35] By comparison the most sensitive fish is the soldier fish, whose threshold is 0.32 mPa (50 dB re 1 μPa) at 1.3 kHz, whereas the lobster has a hearing threshold of 1.3 Pa at 70 Hz (122 dB re 1 μPa).[35]

[edit]Safety thresholds

High levels of underwater sound create a potential hazard to marine and amphibious animals as well as to human divers.[32][36] Guidelines for exposure of human divers and marine mammals to underwater sound are reported by the SOLMAR project of the NATO Undersea Research Centre.[37] Human divers exposed to SPL above 154 dB re 1 μPa in the frequency range 0.6 to 2.5 kHz are reported to experience changes in their heart rate or breathing frequency. Diver aversion to low frequency sound is dependent upon sound pressure level and center frequency.[38]

[edit]Applications of underwater acoustics

[edit]Sonar

Main article: Sonar

Sonar is the name given to the acoustic equivalent of radar. Pulses of sound are used to probe the sea, and the echoes are then processed to extract information about the sea, its boundaries and submerged objects. An alternative use, known as passive sonar, attempts to do the same by listening to the sounds radiated by underwater objects.

[edit]Underwater communication

Main article: Underwater acoustic communication

The need for underwater acoustic telemetry exists in applications such as data harvesting for environmental monitoring, communication with and between manned and unmanned underwater vehicles, transmission of diver speech, etc. A related application is underwater remote control, in which acoustic telemetry is used to remotely actuate a switch or trigger an event. A prominent example of underwater remote control are acoustic releases, devices that are used to return sea floor deployed instrument packages or other payloads to the surface per remote command at the end of a deployment. Acoustic communications form an active field of research [39][40] with significant challenges to overcome, especially in horizontal, shallow-water channels. Compared with radio telecommunications, the available bandwidth is reduced by several orders of magnitude. Moreover, the low speed of sound causes multipath propagation to stretch over time delay intervals of tens or hundreds of milliseconds, as well as significant Doppler shifts and spreading. Often acoustic communication systems are not limited by noise, but by reverberation and time variability beyond the capability of receiver algorithms. The fidelity of underwater communication links can be greatly improved by the use of hydrophone arrays, which allow processing techniques such as adaptive beamforming and diversity combining.

[edit]Underwater Navigation and Tracking

Main article: Underwater Acoustic Positioning System

Underwater navigation and tracking is a common requirement for exploration and work by divers, ROV, autonomous underwater vehicles (AUV), manned submersibles and submarines alike. Unlike most radio signals which are quickly absorbed, sound propagates far underwater and at a rate that can be precisely measured or estimated.[41] It can thus be used to measure distances between a tracked target and one or multiple reference of baseline stations precisely, and triangulate the position of the target, sometimes with centimeter accuracy. Starting in the 1960s, this has given rise to underwater acoustic positioning systems which are now widely used.

[edit]Seismic exploration

Main article: Reflection seismology

Seismic exploration involves the use of low frequency sound (< 100 Hz) to probe deep into the seabed. Despite the relatively poor resolution due to their long wavelength, low frequency sounds are preferred because high frequencies are heavily attenuated when they travel through the seabed. Sound sources used include airguns, vibroseis and explosives.

[edit]Weather and climate observation

Acoustic sensors can be used to monitor the sound made by wind and precipitation. For example, an acoustic rain gauge is described by Nystuen.[42] Lightning strikes can also be detected.[43]Acoustic thermometry of ocean climate (ATOC) uses low frequency sound to measure the global ocean temperature.

[edit]Oceanography

This section requires expansion.

Main article: Acoustical oceanography

Large scale ocean features can be detected by acoustic tomography. Bottom characteristics can be measured by side-scan sonar and sub-bottom profiling.

[edit]Marine biology

Main article: Bioacoustics

Due to its excellent propagation properties, underwater sound is used as a tool to aid the study of marine life, from microplankton to the blue whale. Echo sounders are often used to provide data on marine life abundance, distribution, and behavior information. Echo sounders, also referred to as hydroacoustics is also used for fish location, quantity, size, and biomass.

[edit]Particle physics

A neutrino is a fundamental particle that interacts very weakly with other matter. For this reason, it requires detection apparatus on a very large scale, and the ocean is sometimes used for this purpose. In particular, it is thought that ultra-high energy neutrinos in seawater can be detected acoustically.[44]

[edit]See also

Acoustical oceanography

Bioacoustics

Hydroacoustics

Ocean Tracking Network

Sonar

Underwater Acoustic Positioning System

SOFAR channel

SEP 22, 2010 11:19 EDT

BRAZIL | PETROBRAS

Brazil’s massive sale of about $79 billion of Petrobras stock looks set for a string of financial superlatives. One of them, however, won’t be loudly crowed about by investment bankers. The underwriting fee on the deal, which is expected to close this week, looks to be among the lowest yet in a global stock offering of this kind.

According to the Brazilian prospectus for the offering, Petrobras is paying just 0.21 percent of the total size of the offering to its coalition of bankers. To put that in context, even the increasingly indebted U.S. government is paying the underwriters in the planned sale of the state’s shares in General Motors a fee three-and-a-half times larger.

Of course, a relatively low gross underwriting spread was to be expected for an offering like the Petrobras deal. For starters, it’s just humungous by any standard. Inclusion on the deal will make or break this year’s league tables of the world’s biggest underwriters, which securities firms use to market their services.

Second, Petrobras is controlled by the government on the eve of elections. No minister wants to explain why millions of reals are flowing to Banco Bradesco, Bank of America, Morgan Stanley, Santander, Itau and Citigroup instead of the country’s favelas, or slums. And finally, fees in general are lower in Brazil, reflecting both the high competition among São Paulo’s banking community and the fact it’s still a poor country.

But poor is a relative concept when it comes to banking. Moreover, look closely at the Petrobras deal and it’s hard to feel much sympathy for Brazil’s bankers. While the deal does technically involve the sale of around $79 billion of Petrobras equity, $43 billion of that represents the transfer of stock to the government for 5 billion barrels of reserves.

So the underwriters are really only selling around $36 billion of new stock. That’s still a lot of phone calls to portfolio managers, rubber-chicken lunches with hedge funds and one-on-ones with Asian sovereign wealth funds. But strike out the government’s bit, and the more than $140 million they divvy up is closer to half a percent. Not bad for half a job.

MONDAY, JUNE 28, 2010

Petrobras less than spotless on the enviornment and indigenous rights

Petrobras, the Brazilian petrochemical giant which the New Zealand Government has done a deal with to explore deep off the country’s North Island East Coast, has a less than spotless environmental record.

At about the same time as the Brazilian state-controlled company was sewing up New Zealand’s first petroleum exploration permit over the Raukumara Basin, Petrobras was announcing that it had successfully controlled an oil leak at an offshore platform in the Campos Basin.

The P-47 platform leaked an estimated 1500 litres (396 gallons) of oil at Marlin field during preparations to transfer oil to a ship, Petrobras said in an emailed statement reported by upstreammeidaonline.com.

A helicopter and four boats assisted with clean up efforts, it reported the company as saying, and the spill was immediately controlled. Campos Basin comprises 7015 sq km and is located offshore the states of Rio de Janeiro, Espírito Sant, according to Brazilian Government information.

While this spill was relatively small, Petrobras has been on the radar of environmental watchdogs for a number years following a series of incidents dating as far back as 1984, according to Crocodyl, a collaboration between non-profit organizations such as Center for Corporate Policy, CorpWatch, Corporate Research Project, other contributing organisations and individual contributors from around the world.” See http://www.crocodyl.org/

New Zealand Energy and Resources Minister Gerry Brownlee may not have known about the Campos basin incident when he announced on 2 June 2010 that the government had awarded New Zealand's first petroleum exploration permit over the Raukumara Basin off the North Island's East Coast to Petrobras International Braspetro B.V.

"Petrobras is an international giant in this industry and a world leader in development of offshore drilling technology and production. Given Petrobras's expertise, and financial and technical pedigree, this is an exciting step into areas of New Zealand until now unexplored," Mr Brownlee said at the time.

He also noted that the announcement represented a major step forward in the relationship between New Zealand and Brazil.

"Petrobras's investment will add a substantial new dimension to the economic relationship between New Zealand and Brazil. This is a very welcome development," Mr Brownlee said in his statement.

However, it would appear that his officials must have overlooked a number of other incidents which have raised concerns.

For example, Crocodyl in a chronology of Petrobras problems notes that the company owned the largest floating oil platform in the world, called the "P36", until it sunk in 2001, after several explosions killed eleven workers. The estimated loss was $350 Million in USD to the company.

However, incidents involving loss of life go back even further, the Crocodyl chronology noted as follows (see quoted items below):

* In August 1984, 36 workers drowned and 17 were injured in an explosion and fire on a Petrobras oil-drilling platform in the Campos Basin off Brazil.

* In November, 1995 one person died and five were wounded in a Petrobras pipeline fire in Sao Paulo.

* In December, 1998 a fire at Petrobras's Gabriel Passos Refinery in Minas Gerais killed three workers.

* In January, 2001 two workers died from a fire on a Petrobras offshore natural gas platform in Campos Basin.

* In March, 2001 11 people were killed after explosions rocked the world's biggest offshore oil platform. Days later, the platform sank.

Environment and product safety:

* In 2000, a broken Petrobras pipeline resulted in the biggest oil spill in 25 years -- four million liters (1 million gallons), spilled in the Iguacu River. The government fined the company $100 million -- less than two days revenues.

* Just months before, a ruptured pipeline at a Petrobras refinery in Rio de Janeiro's scenic Guanabara Bay resulted in a 350,000 gallon (1.3 million litre) oil spill into the bay, killing hundreds of fish, birds and plants.

* Six months after the Iguacu River spill, a Petrobras refinery near Curitiba in the southern state of Parana resulted in another oil leak, the company's sixth environmental accident in 2000.

* On March 15, 2001, Petrobras' biggest offshore platform, P-36, suffered two major explosions and sank ten days later. The incident resulted in 11 deaths.”

More recently, Crocodyl noted, in 2004,Petrobras reported finding an oil leak on the sea floor in Marlin Sul.

“In 2006, after losing a court dispute it had initiated, Petrobras announced it would abandon plans to build a road into an environmentally sensitive region of the Amazon - Yasuni National Park. “The company had already built a road through a buffer zone right up to the edge of the park and the company asserted that it has not given up on oil development within the park, saying it will employ helicopters to access the site.”

Brian Keane of Land is Life, a Cambridge, Massachusetts-based indigenous rights group is quoted as saying: “Allowing Petrobras to drill in Yasuni would be a gross violation of the rights of the Huaorani and Taromenane peoples.” See http://www.landislife.org/

Petrobras has invested heavily in the development of biofuels. Biodiesel is available at more than 500 Petrobras stations in Brazil.

It should be noted that biofuels in Brazil have been become extremely politically sensitive over the replacement of tropical forests with feedstock crops, depriving indigenous peoples of land rights.

The issues surround Petrobras and indigenous rights are of increasing interest in New Zealand, where the Ngati Porou tribe on the North Island’s East Coast has questioned the licence.

So the bottom line here is: What was the New Zealand Government thinking, what will be the ultimate cost to the New Zealand taxpayer, and how does this fit in with the country’s increasingly besmirched “clean, green” image?

Petrobras Abandons Plans for Oil Road in Ecuadorian Amazon Park

WASHINGTON, DC, April 24, 2006 (ENS) - The Brazilian national oil company Petrobras has relinquished plans to build a new access road into Yasuni National Park, located in the megadiverse Ecuadorian Amazon. The company has not given up on oil development within the park, but now says it will employ helicopters to access the site.

For nearly two years, Ecuadorian and international conservation, indigenous, and scientific groups have been fighting to stop the road into the park, which is a designated UNESCO Biosphere and is currently roadless. They fear a road would allow land development of all kinds to penetrate the pristine rainforest that shelters a rich diversity of species as well as indigenous peoples who prefer to avoid contact and retain traditional ways.

In a written statement last week from Petrobras to Save America�s Forests, a conservation group based in Washington, DC, the company explained that it will follow the advice of the Ecuadorian government not to build the road.

A completed portion of the Petrobras road to the boundary of Yasuni National Park, June 2005. (Photo courtesy Save America's Forests)

�The new operation will be based on helicopter transportation inside Yasun� National Park, therefore, it eliminates the access road inside the park,� explained the Petrobras statement. �It includes recommendations of both the Environment and Energy Ministries and the suggestions of other organizations of civil society, which had contributed to its improvement.�

�This is a huge step in the right direction,� said ecologist Dr. Matt Finer of Save America�s Forests. �The two most potentially damaging components of the project - the road and the processing facility - have been taken out of the park and Huaorani territory.� The Huaorani are an independent indigenous tribe of the Ecuadorian Amazon.

�Given the proliferation of oil concessions throughout the Amazon, hopefully this will set a critical precedent," said Finer. "No new oil access roads through primary rainforest.�

�We applaud the Ecuadorian government�s decision to insist on roadless oil development in Yasuni,� said Leda Huta of Finding Species, based in Takoma Park, Maryland. �Yasuni is one of the most important national parks in the world and this road would have opened up one of the most intact sections of the park."

This outcome seemed unlikely in May 2005, when Petrobras began constructing the road through primary forest in the northern buffer zone of the park. By June, the road had reached the northern boundary of Yasuni, and Petrobras requested permission from the Environment Ministry to continue road construction into the park.

But the turning point had come just a month earlier, in April, when the Ecuadorian Congress, responding to widespread street protests, ousted Lucio Gutierrez from the presidency. The Gutierrez administration had granted Petrobras the environmental license for the project in August 2004.

President of Ecuador Dr. Alredo Palacio took office on April 20, 2005 after the Ecuadorian Congress removed Lucio Gutierrez from the presidency. (Photo courtesy Office of the President)

The incoming administration of Alfredo Palacio, and in particular the new Environment Minister Anita Alban, were more sympathetic to the concerns of conservationists and scientists that a new road into the intact northeast section of Yasuni would be devastating.

A report prepared by a group of 50 park scientists in November 2004 concluded that Yasuni was one of the most biodiverse rainforests on Earth, and that new oil access roads would pose the greatest threat to that biodiversity.

The report advocated roadless oil development, a position also supported by the Smithsonian Institution based in the United States as well as and Ecuadorian nongovernmental organizations.

On July 7, 2005, Alban wrote a letter to the Petrobras President and CEO Jos� Sergio Gabrielli de Azevedo denying the company authorization to enter the park and continue road construction.

Ecuadorian Environment Minister Anita Alba (Photo courtesy Office of the Minister)

Among the principal reasons cited for this refusal of authorization was the lack of environmental study for building the processing plant within the park, and the lack of consideration of access alternatives that would minimize impact.

The letter concluded that if the processing plant were built outside the park, as called for in the original environmental impact study, it would not be necessary to build an access road into the park.

South America�s most profitable company in 2004 with net profits of $6.6 billion, Petrobras responded to Alban's letter with a lawsuit on July 28, 2005. On August 25, Petrobras� lawsuit was rejected in court, and now Petrobras has agreed to give up road construction within the park.

Still, Finer warns that several major problems still exist in connection with the oil development at Yasuni National Park.

Oil extraction is being allowed to continue within ancestral Huaorani territory despite the indigenous people's call for a 10 year moratorium on new oil activities on their lands.

At the symbolic globe in Quit, Huaorani women protest oil development in their traditional territory in Yasuni National Park. July, 2005. (Photo courtesy Finding Species)

The Huaorani demanded the moratorium last summer when 150 Huaorani marched through the streets of the capital, Quito, to protest widespread oil extraction in their territory. Huaorani leaders presented their plan for a moratorium to Congress and high-ranking officials in the Palacio administration.

�The Huaorani have made it clear they oppose new oil activities,� said Brian Keane of the indigenous rights group Land is Life, based in Cambridge, Massachusetts. �They complain of widespread illnesses due to contamination and fear for the survival of their brother clans living in voluntary isolation," Keane said.

"Allowing Petrobras to drill in Yasuni would be a gross violation of the rights of the Huaorani and Taromenane peoples. In fact, it would most likely be the end for the Taromenane," he said. The small group of Taromenane still live by choice as one of the world's most isolated tribes.

Conservationists are concerned that Ecuador is still permitting oil extraction to take place within a national park. Other Amazonian countries such as Brazil and Peru prohibit such activities within parks. Finer says Yasuni is the only national park in this incredibly biodiverse region, thus there is added urgency to fully protect it.

In addition, conservationists worry that the petroleum processing facility is planned for construction just two kilometers (1.24 miles) from the park boundary in a primary rainforest environment.

Nonetheless, says Finer, given the "extremely difficult task" of persuading an oil giant such as Petrobras to make costly adjustments to minimize environmental damage in an oil dependent country such as Ecuador, many people in the environmental community consider Petrobras' decision to stop the road a major victory, especially in view of the fact that the road is constructed right up to the boundary line of Yasuni National Park.

Huta of Finding Species says, �That�s snatching victory from the jaws of defeat."

Yasuni National Park encompasses a large stretch of the world�s most diverse tree community, has the highest documented insect diversity in the world, and has many diverse species of mammals, birds, amphibians, and plants.

Eight species of monkeys live in Yasuni along with the golden-mantle tamarin, the giant otter and two other otter species, endangered tapirs, deer and anteaters, peccaries and sloths, racoons, armadillos, and in the rivers, pink dolphins and dwarf dolphins.

Harpy eagles and king vultures soar above the canopy, while scarlet macaws as well as blue and yellow macaws feast on clay licks. Well known cats such as jaguars and ocelots inhabit the Yasuni rainforest, which they share with lesser known species such as the jaguarundi and the oncilla.

Petrobras

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Last edited by lenazun on November 25, 2009 - 1:18pm Oil & gas Globalization

Company Snapshot:

Petróleo Brasileiro S.A., is a semi-public Brazilian oil company headquartered in Rio de Janeiro. The company was founded in 1953 and is a former Brazilian oil monopoly. Its output is more than 2 million Barrels of oil equivalent per day. The company owned the largest floating oil platform in the world, called the "P36", until it sunk in 2001, after several explosions killed eleven workers. The estimated loss was $350 Million in USD to the company.

Number of employees worldwide: 62,266

Chief executive officer: José Sergio Gabrielli de Azevedo

Website: http://www.petrobras.com.br/

Global Fortune 500 rank: 34

Total revenue: $72,347.0 Million

Corporate accountability

Labor:

Accidents

In August, 1984 36 workers drowned and 17 were injured in an explosion and fire on a Petrobras oil-drilling platform in the Campos Basin off Brazil.

In November, 1995 one person died and five were wounded in a Petrobras pipeline fire in Sao Paulo.

In December, 1998 a fire at Petrobras's Gabriel Passos Refinery in Minas Gerais killed three workers.

In January, 2001 two workers died from a fire on a Petrobras offshore natural gas platform in Campos Basin.

In March, 2001 11 people were killed after explosions rocked the world's biggest offshore oil platform. Days later, the platform sank.

Environment and product safety:

In 2000, a broken Petrobras pipeline resulted in the biggest oil spill in 25 years -- four million liters (1 million gallons), spilled in the Iguacu River. The government fined the company $100 million -- less than two days revenues.

Just months before, a ruptured pipeline at a Petrobras refinery in Rio de Janeiro's scenic Guanabara Bay resulted in a 350,000 gallon (1.3 million litre) oil spill into the bay, killing hundreds of fish, birds and plants.

Six months after the Iguacu River spill, a Petrobras refinery near Curitiba in the southern state of Parana resulted in another oil leak, the company's sixth environmental accident in 2000.

On March 15, 2001, Petrobras' biggest offshore platform, P-36, suffered two major explosions and sank ten days later. The incident resulted in 11 deaths.

(For a chronology of Petrobras accidents from 1984 to 2001 go here)

In 2004, Petrobras reported finding an oil leak on the sea floor in Marlin Sul.

Petrobras has invested heavily in the development of biofuels. Biodiesel is available at more than 500 Petrobras stations in Brazil.

In 2006, after losing a court dispute it had initiated, Petrobras announced it would abandon plans to build a road into an environmentally sensitive region of the Amazon -- Yasuni National Park. The company had already built a road through a buffer zone right up to the edge of the park and the company asserted that it has not given up on oil development within the park, saying it will employ helicopters to access the site.

"Allowing Petrobras to drill in Yasuni would be a gross violation of the rights of the Huaorani and Taromenane peoples," asserts Brian Keane of Land is Life, a Cambridge, Massachusetts-based indigenous rights group.

Political influence (national and international):

55.7% of Petrobras' common shares (with vote right) is owned by the Brazilian government.

Friday, 16 March, 2001, 20:33 GMT

Brazil oil spill company in spotlight

Barriers used to fight the slicks have been ineffective

By Jan Rocha in Brazil

Two massive oil spills in Brazil in six months last year focused international attention on the state oil company, Petrobras.

A disastrous oil leak at the Brazilian refinery near Curitiba in the southern state of Parana was state producer Petrobras's sixth environmental accident in 2000.

It came only six months after an oil spill of more than one million litres polluted Rio de Janeiro's picture-postcard Guanabara Bay.

The leak revealed an embarrassing level of incompetence. It was only detected two hours after it began because the 23-year-old oil pipe did not have modern oil pressure detectors.

Petrobras workers are being blamed for negligence

And the barriers Petrobras used to try to stop the oil travelling upriver were designed for use at sea, and therefore failed to do their work properly.

Strangely, the company has just won an award for environmental excellence, which is now being questioned.

Click here to see a map of the area

On Friday, Petrobras pinned the blame on a combination of a forgetful worker and a faulty pipe joint which broke before an emergency valve could release the rising oil pressure.

But there have been no shortage of alternative theories for the disaster.

Sabotage

Some Petrobras engineers even raised the possibility that the latest leak could have been caused by sabotage, to make the company, once a source of pride to Brazilians, unpopular and facilitate its sell off.

The famous Iguacu falls have been protected ...

The government is engaged in a policy of privatisation of Brazil's hundreds of state companies but because of the patriotic sentiment that has always surrounded Petrobras, it has denied plans to sell it off completely.

But accused by the Brazilian Environment Minister, Jose Sarney Filho, of negligence, and threatened with a multi million dollar fine, Petrobras is now being seen as a villain.

Petrobras was set up in 1950 as the result of a campaign to nationalise Brazil's oil.

Up until then exploration and production had been in the hands of American companies.

In the last 30 years Petrobras has discovered important offshore oilfields along the Brazilian coast and now supplies 65% of the domestic market.

With a population of 165 million, Brazil consumes 1.8 million barrels a day.

... but the slick has polluted rivers throughout the area

Petrobras also has an overseas arm called Braspetro, which runs successful operations in the Middle East and Latin America.

But up until 1975, Brazil relied on imported oil to supply the needs of its fast growing economy.

Then came the oil shock, with a disastrous effect on Brazil's balance of payments caused by the huge hike in international oil prices.

New fuels

This led to the decision to invest heavily in offshore exploration and turn to a new fuel, gasohol, produced from sugarcane alcohol to substitute petrol.

Under the Pro-Alcool programme, farmers received generous subsidies to turn their fields over to sugarcane.

The price at the pump was also subsidised to make the new fuel cheaper than petrol. As a result, by the 1980s, more than 90% of the cars produced by Brazil's car factories were designed for alcohol consumption.

Although performance was slightly lower, the alcohol fuel had the advantage of being much less polluting than petrol. However when oil prices fell again, the incentive for the alcohol programme disappeared.

In the 1990s Petrobras discovered a huge natural gas field in the Brazilian Amazon. The company has also developed state of the art technology for deep sea exploration and production.

But the one area where it has consistently failed is in environmental protection.

Kea awarded onshore Northland permit around Kaipara Harbour

16 October 2009 - Private New Zealand company Kea Petroleum Ltd has been awarded an exploration permit over an area surrounding Kaipara Harbour just north of Auckland.

Kea chief executive Dr Dave Bennett said PEP 51339, covering an area of 2,157 km2, was a longer term exploration project over the little explored onshore Northland Basin.

He said attention has focussed on offshore Northland with the Karewa gas discovery and now two further wells planned by Origin Energy next year.

Dr Bennett said an oil or gas discovery in the Kaipara permit could be readily developed, with gas being particularly well placed for power generation to the expanding Auckland electricity market.

Kea is operator of the permit on behalf of itself and two Australian alliance partners Rawson Resources Ltd, and Hardie Oceanic Pty Ltd.

The initial work programme will involve gravity and soil gas geochemical surveys. This would lead to seismic surveys over areas of greater interest with potential drilling within four years.