www.seismicsurvey.co.nz Open in urlscan Pro
218.185.224.230  Public Scan

Form analysis
0 forms found in the DOM

Text Content

 * 
 * 
 * 
 * 
 * 
 * 
 * 
 * 
 * 


SEISMIC SURVEYING IS A VITAL PART OF EXPLORING FOR OIL AND GAS. THAT MAKES IT
CRITICAL TO PRODUCING THE ENERGY WE NEED TO POWER OUR HOMES AND BUSINESSES




SEISMIC SURVEY OVERVIEW


SEISMIC SURVEYS PRODUCE DETAILED IMAGES OF THE VARIOUS ROCK TYPES AND THEIR
LOCATION BENEATH THE EARTH’S SURFACE. THIS INFORMATION CAN TELL US THE LOCATION
AND SIZE OF OIL AND GAS RESERVOIRS, WITHOUT HAVING TO DISTURB THE LAND OR
SEABED.

Reflection seismology (or seismic reflection) is a method of exploration
geophysics that uses the principles of seismology to estimate the properties of
the Earth’s subsurface from reflected seismic waves.

Seismic surveys involve an acoustic source that release bubbles of compressed
air, these bubbles collapse and send a directionally focused low frequency sound
wave towards the sea floor.

Sound waves are bounced off rock formations below the seafloor and the waves
that reflect back to the surface are captured by recording sensors within the
streamers of the seismic vessel.
The time it takes for each sound wave to return to the hydrophones provides
valuable information about the depth of different structures and possible gases
or fluids trapped in rock formations.

HYDROPHONE STREAMERS

The streamers towed behind the seismic vessel can be up to 10km long, and
contain pressure sensitive devices called hydrophones. The hydrophones convert
the reflected pressure signals and transmit back to the recording system on
board the seismic vessel. Each streamer is solid and filled with neutrally
buoyant foam.


DATA COLLECTION


SEISMIC DATA ACQUISITION INVOLVES APPLYING A SEISMIC ENERGY SOURCE AT A SURFACE
LOCATION. THE RESULTING ENERGY IS REFLECTED BACK FROM INTERFACES WHERE ROCK
PROPERTIES CHANGE.

Seismic data must then be interpreted by geophysicists. The results produce
detailed understanding of the underlying geology.

ONSHORE

The acoustic energy source for onshore seismic survey operations is either small
explosive charges placed in shot-holes (commonly 10-50 m deep) or by specialised
trucks that carry a heavy plate which is vibrated. Both of these methods send
sound waves beneath the earth’s surface and listening devices called geophones
are placed on the surface nearby to capture the returning sound waves.

MARINE

A specialised seismic vessel tows from one up to ten streamers depending on
whether it is a 2D or 3D seismic survey. Acoustic sources use compressed air to
produce acoustic energy sending sound waves towards the seabed. The hydrophones
within the streamers capture the returning sound waves.


DATA PROCESSING


ONCE DATA HAS BEEN COLLECTED IT MUST BE INTERPRETED BY GEOPHYSICISTS. THE
RESULTS ARE COMPARED WITH OTHER DATA TO ENHANCE THE ACCURACY OF THE READING.
THIS OFTEN PRODUCES DETAILED UNDERSTANDING OF UNDERLYING GEOLOGY TO DEPTHS OF
MORE THAN 10KM.



Geophysicists use geological mapping software to create 2D and 3D geological
maps of an exploration site. This process is called ‘Geomodelling’. Software
developers have built several packages for geologic modeling purposes. Such
software can display, edit, digitise and automatically calculate the parameters
required by engineers, geologists and surveyors.


ENVIRONMENTAL IMPACT OF SEISMIC SURVEYING


SEISMIC SURVEYING IS AN ESTABLISHED SCIENCE WITH STRICT REQUIREMENTS AND
OPERATIONAL PROCEDURES SET IN PLACE TO ENSURE MARINE HABITATS REMAIN UNDAMAGED
BY EXPLORATION ACTIVITIES. THE OIL AND GAS INDUSTRY USES EXTENSIVE ENVIRONMENTAL
MANAGEMENT PLANS TO ENSURE ALL OPERATIONS ARE CONDUCTED SAFELY AND RESPONSIBLY.

BACKGROUND

After more than four decades of seismic surveying and countless research
projects (both in New Zealand and world-wide) there is no clear evidence that
sound from exploration activities in normal operating circumstances has
permanently harmed marine mammal species.

TECHNOLOGY

Technological developments have provided much better detection of marine mammals
that are not visible on the surface during seismic surveys, allowing explorers
to conduct environmentally responsible marine seismic operations.

TECHNOLOGY: PASSIVE ACOUSTIC MONITORING SYSTEMS

Passive acoustic monitoring systems (PAM) are designed to detect the presence of
marine mammals (whale, dolphin and porpoise) during seismic operations. This
allows explorers to implement mitigation measures that minimise the potential
impact of man-made sound.
Unlike visual observations, which are constrained by animals being at the
surface, available daylight hours and sea/weather conditions, PAM can operate 24
hours-per-day and in more extreme conditions. It provides industry confidence
that vocalising cetaceans in the vicinity of night time operations can be
accurately and reliably located and tracked.
PAM observation is undertaken 24/7 during seismic surveys.


GOVERNMENT SAFETY GUIDELINES FOR SEISMIC SURVEYING


OFFSHORE SEISMIC SURVEYS MUST ADHERE TO THE DEPARTMENT OF CONSERVATION’S (DOC)
CODE OF CONDUCT FOR MINIMISING ACOUSTIC DISTURBANCE TO MARINE MAMMALS.

OPERATORS UNDERTAKING A SEISMIC SURVEY ARE REQUIRED TO:

Have present two independent trained marine mammal observers and two passive
acoustic monitoring operators. Record all observations/sightings of marine
mammals before and during operations. Have regard to the mitigation zones. 1.5km
radius for species of concern with young, 1km for species of concern without
young, and 200m for all other species. The acoustic source must be stopped if
any marine mammals enter the relevant mitigation zones. Use the lowest practical
acoustic source volume for the survey that will still achieve survey objectives.
Conduct 30 minutes of pre-observation prior to commencing the soft-start
procedures, which slowly builds up the source volume over a period of 20
minutes.


LEVEL 1 MITIGATION ZONES

UNDER THE CODE THERE ARE THREE MITIGATION ZONES FOR SURVEYS, DETERMINED
ACCORDING TO THE SENSITIVITY OF THE MARINE MAMMALS TO WHICH THEY APPLY AND THE
POTENTIAL EFFECT OF THE SOUND LEVELS LIKELY TO BE ENCOUNTERED AT THAT DISTANCE
FROM THE SOURCE. THE DIAGRAM OPPOSITE OUTLINES THE KEY DISTANCES.

 * Level 1: the highest power surveys, generally used by the oil and gas
   industry for exploration.
 * Level 2: less powerful surveys, often used for scientific research by NIWA
   and GNS
 * Level 3: includes all other small-scale seismic surveys – with noise levels
   less than commercial shipping – and is not covered by the provisions of the
   Code

LEVEL 1 MITIGATION ZONES



MĀUI’S DOLPHIN: SPECIES OF CONCERN


AS NEW ZEALANDERS WE NEED TO PROTECT THE MĀUI’S DOLPHIN FROM REAL THREATS THAT
MAY CAUSE A FURTHER DECLINE IN POPULATION.

THE MĀUI’S DOLPHIN IS THE WORLD’S RAREST MARINE DOLPHIN, WITH FEWER THAN 100
LEFT IN THE WILD. THE SUBSPECIES IS FOUND IN INSHORE WATERS ON THE WEST COAST OF
THE NORTH ISLAND, COMMONLY WITHIN ABOUT FIVE NAUTICAL MILES OF THE SHORE.

Scientific information indicates that petroleum exploration or mining activities
have not been cited to have any adverse effects on the Maui Dolphin. Oil and gas
exploration operations can be managed to minimise and effectively avoid adverse
environmental effects, which includes marine mammals, and it is for this reason
that the current Marine Mammal Sanctuary still allows petroleum exploration.


THREATS TO MAUI’S DOLPHINS INCLUDE:

 * Disease
 * Pollution from discharges into the coastal marine area
 * Plastic debris generated from dumping of both urban and marine based waste
 * Impacts associated with interactions between the dolphins and vessel
   operations
 * Permitted and non-permitted tourist vessels


HOW LOUD IS A MARINE SEISMIC SURVEY


THE SOUND FROM SEISMIC SURVEYING IS COMPARABLE TO MANY NATURALLY OCCURRING
MARINE SOUNDS – INCLUDING THOSE MADE BY ANIMALS THEMSELVES.

FREQUENCY

Frequency is the number of times per second, that a sound wave cycles from
positive to negative to positive again. Frequency is measured in cycles per
second, or hertz (Hz). Humans have a range of hearing from 20 Hz (low) to 20,000
Hz (high). Frequencies beyond this range exist, but they are inaudible to
humans.

AMPLITUDE

Amplitude (or intensity) refers to the strength of a sound wave, which the human
ear interprets as volume or loudness.

SOURCE SOUND INTENSITY (Decibels) FREQUENCY (Hertz) Ambient sea noise 80-120
Varied Blue whale vocalisation 190 12 – 400 Breaching whale 200 20 Ship sound
200 10 – 100 Bottlenose dolphin click 229 120,000 Seismic acoustic source 230 –
255 200 Sperm whale click 235 100 – 30,000 Lightning on sea surface 250 Varied
Seafloor volcanic eruption 255 Varied Undersea earthquake 272 50




WHY DO WE NEED TO USE SEISMIC SURVEYS?


HERE IN NEW ZEALAND WE HAVE 18 SEDIMENTARY BASINS – WITH ONLY ONE OF THOSE
BASINS (TARANAKI) CURRENTLY PRODUCING OIL AND GAS.

BY CONDUCTING SEISMIC SURVEYS (BOTH ONSHORE AND OFFSHORE) WE ARE ABLE TO GET A
BETTER UNDERSTANDING OF WHAT KIND OF PETROLEUM POTENTIAL LIES BENEATH OUR LAND
AND SEAS – WITHOUT A HUGE ENVIRONMENTAL EFFECT.

NEW ZEALAND'S SEDIMENTARY BASINS

New Zealand's main oil, gas and coal resources are contained in onshore and
offshore sedimentary basins. These Cretaceous-Cenozoic basins cover about 1.7
million square kilometers.
A sedimentary basin is an area where the Earth’s crust has subsided (sunk) and a
thick layer of sediment has accumulated over millions of years.
Examples of active sedimentary basins include inland river valleys, lakes,
gravel out wash plains and the undersea continental margins.


THE OIL AND GAS INDUSTRY HERE IN NEW ZEALAND CURRENTLY EMPLOYS 7,500 KIWIS
NATIONWIDE, CONTRIBUTING BILLIONS TO OUR NATIONAL ECONOMY AND PROVIDING ENERGY
SECURITY FOR KIWI HOUSEHOLDS.

AND THAT IS JUST FROM ONE OF OUR BASINS.


By exploring what lies beneath the 17 other petroleum basins, the oil and gas
industry may be able to grow the number of kiwis it employs, the financial
contribution it makes to the country and provide more energy security to
households and businesses.