Non Seismic Exploration
Some non-seismic data is already available for ANWR,
but it is impossible to know whether scientists will find that they need
more data when the time comes to actually undertake the exploration process.
If more is necessary, then it will be collected as the petroleum geologists
and environmental experts deem appropriate. Non-seismic data is essential
to the exploration process because it provides a unique viewpoint that supplements
seismic data. The type of non-seismic exploration techniques that would be
most valuable in ANWR would be those involving potential field methods, i.e.
Magnetic and Gravitational. Magnetic field methods can be done with an aerial
pass of a magnetometer or on the ground using a type of magnetometer called
a vertical field balance. These readings tell experts whether there is likely
to be oil because there is a correlation between low magnetic readings and
rocks that contain oil. Gravitational methods can also be done aerially with
a gravimeter or on the ground using a more precise instrument called a gravity
gradiometer. The data from gravitational methods is valuable because differences
in the gravitational field indicate a difference in the density of the ground
which correlates to rocks that contain oil. Both of these methods are relatively
low impact because they only involve either not touching the ground at all,
or by setting up stations approximately 100 yards apart using low-impact transportation. Thus the impact of non-seismic techniques is significantly lower than
the impact that would be caused by drilling unnecessary wells.
Based on the USGS report, the ANWR region was seismically
explored in 1984-1985. Data, acquired using seismic surveying, totaling 1,451
miles is available. Furthermore, this data has already been processed and
is a substantial part of the USGS report on the ANWR region. Based on those
evaluations alone, it is possible that no further seismic or non-seismic surveying
will be necessary in order to proceed with exploratory wells drillings. However,
it is also possible that in order to suggest a more specific location of
drilling further seismic exploration will be required. There are several advantages
in doing at least some part of seismic exploration because of the progressed
technology in the field of both data inquisition and data processing. Thus
several of the seismic exploration methods should be considered.
First, the Explosives method: This method possesses much
potential. Very little equipment is needed in order to drill the holes and
to pack them with explosives. Although many safety measures have to be taken,
it is quite possible to achieve low impact on the surface using this method.
The intrusion factor of the personnel to the area of exploration is minimal.
However, due to the close packed grid using this equipment it is needed to
further asses the possible damage that can be caused underground.
The second possibility is the use of Vibroseis trucks,
which will be adapted to the Alaskan area. One of the methods is to replace
the wheels of such trucks with tracks or thick tires, thus maximizing the
spread of the weight and minimizing the pressure per point on the permafrost.
Another factor is the precision of this method. Vibroseis trucks are much
more precise than explosives because they deliver controlled vibration to
the ground. It is even possible to send different type of waves, such as P
waves (vertical) or S waves (horizontal). This way the data that will be further
analyzed may yield a more precise evaluation. The trucks will be stopping
for a short period of time to send the vibration and then evacuate the area,
such that there is no long term damage. However, further assessment of the
damage done by such tracks to the permafrost needed, as well as the assessment
of the way the trucks will get into the reservoir
Depending on the quantity and quality of existing seismic
data, one or both of these methods may be used in such a way that they complement
eachother in order to have the least environmental impact. If a small area
needs to be assessed, the explosions provide the least amount of impact. However,
if the existing data is insufficient it might be necessary to use the trucks.
The impact of these trucks will be significantly lowered by using large inflatable
rolligon tires to lessen the applied pressure and adequate snow cover will
be assured before their deployment.
Production and Drilling
Estimating Number of Wells
Once all of the exploration data has been gathered, the
drilling locations will be selected. The goal is to minimize the number of
drilling sites required and the environmental impact of each while hitting
as much of the oil in the undeformed region as possible. The maximum reach
of a single oil well is between three and four miles, depending on the depth
of the wellbore, the depth of the kickoff point and the amount of deviation
from vertical. This opens somewhere between thirty and fifty square miles.
Given that the proposed drilling region is approximately 470 square miles,
this require ten to fifteen production sites if the oil were evenly distributed.
Since it is unlikely that the oil is evenly distributed, there will most likely
be no more than around 15 drilling sites and probably no less than five.
Choosing the Drill Site
Foremost in choosing these sites is the avoidance of
especially sensitive environmental areas. Drilling sites will be kept a distance
to be determined by field study away from major water ways and away from
the more sensitive coast in order to prevent possible significant platform
spills from devastating the aquatic ecosystem. Smaller creeks and streams
will not be built upon but will have activity much closer to them if it is
necessary to reduce the total number of drilling sites. The site will also
need to be tested for tundra integrity to ensure that the soil in the area
can support the drilling platform and equipment.
Transportation of Materials
Once the winter begins, construction will start at the
first sites. For the drilling companies, the winter season should be as long
as possible in order to conduct the most efficient drilling and production
strategy. However, primary interest concerns the well being of the 1002 ecosystem,
and towards that end the drilling season will be evaluated each year to assess
the drilling time which would have the least environmental impact. The three
main priorities include a) a significant drop in the wildlife population as
the migratory species leave, b) to have the active layer of the permafrost
refreeze, and c) to have adequate snow cover to protect the tundra from moderate
Sites closest to the western border of ANWR will be built
first and then radiate east over the years. Since the pipeline network will
use the production sites as both pumping stations and nodes, it is important
to expand in this manner. The first site, assuming that oil is found, will
connect to the single output line.
In order to minimize long term impact on the tundra ecosystem
and to minimize the transportation burden of traditional gravel pads and the
water requirements of their modern ice equivalents, the drilling and production
equipment will be located on elevated platforms. Such fast assembly platforms
have already been prototyped in the North Slope area and in 1002 will operate
like offshore platforms in the midst of a fragile tundra sea. Such platforms
would be prefabricated in modular sections and taken to the airbase outside
of ANWR. In order to assemble the platforms on site, several pieces of construction
equipment will be required including an auger, a crane and a forklift, as
well as temporary housing until the modular sections for housing can be assembled.
These platform modules will be transported to the sites
in one of two ways. The most straightforward would be by heavy-lift helicopter.
Capable of loads between 7000 kg and 9000 kg, heavy-lift helicopters can carry
in the modular sections or least significant pieces of them. Ground crews
would arrive on site via smaller helicopter and see to the lowering of the
platform modules into nearly the perfect position. The obstacle to this method
of cargo transport is the arctic weather with frequently low visibility and
the potential for high winds. This decision revolves around weather and flight
data which is not yet fully collected or analyzed.
The alternate option, still by air, would be to use C-130
Hercules or equivalently rugged cargo planes to haul in the platform modules.
This would require partial disassembly of the module sections or a more linear
design capable of fitting in the fuselage. Such aircraft are capable of punching
through weather more severe than likely to be found in the arctic and have
a greater fuel range and weight capacity. The disadvantage is that while they
can land directly on the snow covered tundra, in order to protect the underlying
vegetation they might require an airstrip. It is possible that the frozen
ground and the average snow cover will be sufficient to withstand the impact
of landing. This could be aided by the use of larger rolligon tires. In this
case no airstrip will be built and aircraft will be used instead of helicopters.
If an airstrip does need to be constructed, the standard
material - gravel - is not really feasible as it a) has a high environmental
impact but more importantly b) needs to be brought in by truck, requiring
roads, etc. The next most common option - ice - is possible, but at an estimated
one million liters per airstrip, acquiring the necessary water locally will
be very difficult and transporting it seems even more preposterous. It might
be possible to use some sort of synthetic material which could be applied
to the ground in layers to help cushion the impact of landing aircraft. The
decision of which plan to implement is contingent on future studies.
The platforms, which are are supported on posts which
are screwed into the ground, will need to have pilot holes drilled by a small
auger; cranes and forklifts are also required to put the platform in place.
This equipment may rest on a small ice pad in order to minimize damage to
the tundra. All construction activities will take place in the winter.
Once the platform modules arrived at the sites, the construction
crews would start assembling them. Portable hydraulic jacks will lift the
pieces onto sleds which snowcats can haul into the desired place. This equipment
will all be brought in with the platform modules, each built to obtain the
largest surface area which could reasonably be airlifted in. A drilling platform
should be approximately half an acre, with an appropriate number
of pylons for support. Assembly of the entire platform should take about one
month. The support pylons are designed to be screwed into the ground to provide
maximum support and easy assembly. Holes to get the pylons started will be
bored with the backpack drills similar to those used by the seismic teams
earlier. Snowcats will move equipment around the site while mobile cat mounted
cranes will help with the initial construction. Once the pylons are in place,
winch towers will be bolted on to hoist the platform pieces themselves into
place to be bolted on. The whole assembly should erect itself accordingly
with bolting and bracing so the final platform can be dissembled just as
In order to prevent the permafrost from thawing due to
the thermal conductivity of the platform legs, the pylons themselves will
contain some type of circulating coolant, perhaps anhydrous ammonia
and the radiator system employed on the Trans-Alaskan Pipeline. The first
platform to be built will hold the dwelling modules for the platform workers.
Supply storage will also be on this platform. The habitation platform will
connect to the rising production platform by a suspended metal link bridge.
Once the production platform is in place, the drilling
equipment can be bolted on. The rig must be pieced together on the platform
in a space-efficient way in order to make the smallest drill pad possible.
The derrick will be bolted directly to supporting pylons to give it maximum
stability. Other equipment will be attached to pylons directly or to the crossbars,
however the engineering specifics dictate. The diesel engines should be placed
in an out of way place along with the generators, possibly insulated to cut
down on noise pollution. The mud tanks should also be placed out of the way,
but in such a way that the feeder pipes can be run to and from the drill
string. The full list of equipment can be found here. Ideally assembly will
finish only partly through the winterseason. If it takes the whole season,
operations will shut down and only a small watch staff will remain at the
platform. If there is significant time left in the winter, drilling will
The well must be spudded by driving a conductor pipe
of approximately 12" diameter into the ground with a pile driver. The pipe
will then be cleaned of rubble using a small drill head which breaks up the
rubble and forces it to the surface. Once the pilot hole has been started,
the drill bit of approximately 24" diameter will be lowered. Before any drilling
commences, a blowout preventer must be installed in the event that the drill
bit runs into a natural gas reservoir in the shallow strata.
The initial drill bit is lowered into the hole and depends
on a top drive motor to drill the initial strata. Once some depth has been
achieved, the drill string is raised and the down hole motor is attached directly
behind the drill bit. At this point, the mud pump is connected to the drill
string via a rotary hose, and the mud pump will pressurize the drilling fluid.
The drilling fluid flows into the mud motor and then strikes a spiral shaft
which then goes into tubular housing in such a way as to cause it to turn.
As the drill goes further into the ground, drill collars are added to the
drill string in order to give the drill bit the right amount of pressure
drilling into the formation. The pressure needs to be just right in order
to ensure the bit is contacting and drilling the formation efficiently. Each
drill collar weighs approximately 6,000 pounds; it is not uncommon to have
6 drill collars to apply pressure to the drill bit. The drill bit can then
be raised or lowered in order to modify the pressure put on the drill bit
in order to achieve maximum drilling efficiency at all times. The drilling
fluid will constantly be moving down the drill string and then up the sides
of the hole, cooling and cleaning the bit and lifting the cuttings to the
surface where they can be collected.
A smaller, second well will need to be drilled well away
from the reservoir to be used for reinjection of well wastes. It could be
drilled from a small, portable drill rig on an ice pad and take a matter of
days. This is the most cost efficient and safest way to dispose of well wastes
which cannot be cleaned effectively.
Once a stable formation has been reached, drilling momentarily
ceases as the first casing may be cemented. Casing pipe of slightly smaller
diameter than the hole is lowered into the drill site in 30 foot sections.
Once the first casing section is in, cement is poured in-between the casing
and the outside diameter of the drill hole, cementing the casing to the hole.
It is important that the formation that the first casing is cemented into
is strong enough to hold the casing, especially in the case of a blowout;
if the formation is not strong enough to hold the cemented casing and a high
pressure pocket is hit, the casing may shoot straight out of the hole.
Once the first casing has been cemented, drilling resumes
and continues with the drill mud rotating the bit. Special mud logging equipment,
attached behind the mud motor, can analyze the mud as it moves past on its
way out of the hole and send that information back to the drill bit operator;
it can give important notice about formation composition and pressures. Soon
the cementing and casing process is repeated. After several lengths of casing
has been installed, the next casing lowered will be of a slightly smaller
diameter. This decreases the amount of friction exerted on the drill string.
Eventually, the well bore will only be 5" in diameter, cutting down on expense
and waste products.
Drilling fluids will rise out of the wellbore, carrying
with it the cuttings from the formation. These will need to be cleaned out
of the mud before it can be reused; this is done by a collection of mud purification
and storage devices. The mud is sent through the shale shaker, which removes
the larger cuttings; it is then strained through the desilter, degasser anddesander
which remove the finer particles which would dramatically contribute to the
deterioration of the well bit if they were recirculated in the mud. The cleaned
mud is then drawn back to the mud pump, pressurized, and sent down the drill
string, repeating the process.
A large diameter hole may be drilled vertically in order
to penetrate all oil reservoirs vertically below the rig. That hole will then
be closed by pour some cement down the hole and closing off the bottom of
the hole, after the drill bit has been raised. Once the initial hole as been
completed, the drill bit can be lowered again with a whipstock. This special
tool fits around the drill head and forces it to deviate; how it is positioned
determines the amount of deviation. In this way, the well may be explored
directionally to exploit reservoirs not directly below the drill pad; the
drill path may also flow horizontally through a reservoir, increasing the
surface area of the pipe to the formation and allowing for faster oil production.
Once that well has been fully drilled, it too will be sealed off with cement
and the process will be repeated until all possible reservoirs have been
tapped and exploited in an efficient manner.
Once all well bores have been drilled, coiled tubing
is run into each well bore. This tubing, fairly thin, protects the casing
from corrosion and is much easier to repair in the case of an accident. After
each bore has been lined with coiled tubing, small explosive guns are lowered
into each wellbore. These guns shoot metal slugs in all directions, perforating
the tubing and shooting into the formation, perhaps even fracturing the formation.
Once each charge has been set off, all wells are then opened into the main
pipe and formation pressures will force the oil up the pipe. In this final
stage of production, a Christmas tree (a series of valves and gauges) is installed
over the producing hole which regulates the pressure of the formations and
triggers safety measures if the pressure should rise outside controllable
areas. The flow of the oil out of the reservoir may be controlled by the Christmas
tree. A subsurface safety valve will also be installed, which remains open
as long as fluid flow is normal; if the valve senses a discrepancy in the
flow, it will immediately shut down. Ideally, the entire bore will be online
before the end of winter. Likely it will not as there are so many sub-wells
to drill in which case drilling will resume in the next winter and the platform
will go into summertime hibernation. But as soon as a significant oil reserve
is discovered, pipeline construction will begin. The pipeline will be constructed
in sections, proceeding to each drill site after oil has been found but ideally
before production has begun. Oil flow cannot begin until the pipeline is
Enhanced Oil Recovery
The initial drilling process will only allow as much
oil out of the well as the pressure forces out. The easiest way to stimulate
a flagging pressure is by means of pumps to keep the tubing pressure less
than the formation pressure. However, soon this no longer becomes feasible
and at this point only 5-10% of the oil may have been recovered. Therefore
secondary methods have been developed to increase the oil production from
reservoirs; these usually involve flooding the reservoir with water and using
the water to create pressure, driving the oil before it and up the pipe. This
water flooding method may increase oil production by approximately 45% of
the original oil concentration. In order to make the well extract the greatest
amount of oil, tertiary (enhanced recovery methods) may be used. If the viscosity
of the crude oil could be reduced, it would not need high pressures to push
it up the drill pipe; therefore by adding solvents or by forcing steam into
the well, the now "thinned" oil will flow up the pipe. This method may remove
approximately 60% of the reservoir's initial concentration.
The pipeline will be routed so that one line comes into
1002 and then it branches progressively into the region to hit all of the
platforms using each successive platform as a potential split. The platforms
themselves will house the pumping equipment to keep the oil flowing as well
as storage tanks to regulate flow. All of this will be housed on a third platform
connected to the production one by another bridge. A facility to launch and
retrieve "pigs" (bullet-shaped sensing devices which travels the length of
the line) into the pipeline will also be erected on the platform.
The pipeline itself will be designed in a manner
similar to the Trans-Alaskan Pipeline <http://www.alyeska-pipe.com/Pipelinefacts/PipelineEngineering.html>
with a few small changes and one major one - the erection of a small cog rail
line directly parallel to the pipeline. The pipeline and rails will be suspended
from triplets of vertical pylons spaced at 20 meter intervals with two meters
between them each. Between one pairing will run the crossbar supports for
the pipeline while the other will have the supports for the tracks. The pipeline
will be built much like TAPS with the ability to rock on the crossbars and
with bumpers to soften its motion. This will also give it the ability to
deal with thermal expansion. The rail lines will be cog tracks as are used
in many parts of the world with high snowfall and will make it very difficult
for vehicles to derail. The whole gap for the rail line is only about two
meters but the structure will be designed for moving inspection and maintenance
crews along the pipeline, allowing for emergency access to valves and leaks,
and for regular activities like platform crew changes and supply delivery.
Replacement parts for the production platforms will also be brought in this
way. The trams themselves will be powered by replaceable batteries which
can be changed and recharged at every platform.
Additionally, the actual construction of the pipeline
will take advantage of the rail line to minimize surface impact. The rail
line will be built first in pieces so that each new piece can be moved along
the line to the growing end. The support pylons will be installed much like
those of the platforms and the rails will be hoisted into position from those
pylons. The final structure will be bolted and welded as it is much harder
to inspect and maintain every bolt on the pipeline than it is for the platform.
As the rail line goes in, the third pylons will be screwed into the ground
and the pipeline itself will be raised into place in 10 meter sections from
rail mounted cranes and pylon mounted hoists. As many of the parts as possible
for the construction will be prefabricated to ensure the highest level of
factory based quality control and to ease and speed assembly. When the winter
ends, construction will be halted as is the norm.
In addition to transporting oil and moderate freight,
the line will also carry fiber-optic cable for communicating between platforms
and outside of ANWR as an alternate to satellite. Also, the pipeline will
be built with a catch basin running the length under it to catch any small
spills. This basin will also hold all of the sensing equipment so that should
a leak occur, workers all over the region will know and be able to respond
via cog rail or helicopter if weather permits.
Once the pipeline is connected to a platform, it is able
to go online - assuming the drilling is complete. The production equipment
(oil/water/gas/sand separators, further dehydration, water treatment, etc)
will have also been set up in this time. A secondary derrick will have also
drilled a single bore for reinjection of waste water, unburned gas, and rock
fragments. Gas generators will also be set up to transfer electrical production
from import diesel to produced natural gas. If it is not dangerous to do so,
electrical lines will also be run with the pipeline (on the far side of the
track) to allow drilling platforms to run off of the gas electricity of producing
platforms and to provide greater electrical reliability.
Facilities Outside of ANWR:
In addition to pipeline pumping stations, the water requirments
of the drilling project will require the construction of a sizeable desalinaztion
plant on the coast outside of ANWR, preferably in the already disturbed region
of Prudhoe bay. Powered by local natural gas sources, the plant will generate
the pure water necessary for manufacturing drilling muds and for making ice
airstrips should they be necessary for landing cargo planes. The water will
be distributed to the platforms via a smaller pipe coupled to the oil pipeline
and cog rail system.
In addition to the many sensors that will be monitoring
the pipeline for any discrepencies in its integrity, there will be routin
visual checks of the pipeline by platform crews sent out on the rail system.
They will check individual sensor calibration at valve points and assess pipeline
integrity. On the platforms, on-duty mechanics will be monitoring valve
and formation pressures at all times in case of a sudden change in formation
pressure. This is an added measure in conjunction with the Christmas tree
and subsurface valves.
Accident Clean Up:
Current methods for how to clean-up oil spills in arctic environments vary
depending on the season. During the winter months when there is snow
cover on the tundra, any crude oil spilled can be absorbed by the snow, allowing
for fairly easy removal using hand tools or heavy equipment on rolligon tires.
The saturated snow could then be recovered in plastic bags or disposal drums
and transported to offsite facilities for treatment for disposal. If
the crude oil has reached the soil, contamination will penetrate into the
ground 1 to 3 inches. As much of the contaminated material as possible
should be removed, but the roots and stem bases of plants should be preserved
to allow for re-sprouting.
For a crude oil spill in the warmer months large-diameter water-filler hoses
could be used to contain and stabilize the contaminated area. Sand bags would
be needed to surround the spill so that fresh warm water could be used to
flood the spill site and thereby reduce the infiltration of oil into the root
zone and the amount of oil in contact with vegetation. The floating oil would
then be recovered by using skimmers such as a portable rope-mop or vacuums.
Coupling these two seasonal methods with bioremediation efforts (microorganisms
and fertilizers) could potentially decrease original hydrocarbon content of
contaminated waters and sediments by up to 70% – 90% of the original spill.
It is difficult to completely remove the pollutant even with bioremediation
efforts because there is often a buildup of inhibiting metabolites as well
as recalcitrant "leftover" compounds. Nevertheless, the damage remaining
after clean-up would be minimal if all these clean-up efforts are taken.
Once the period of production has ended the production
equipment, drilling platforms, and pipelines will be deconstructed and transported
out of ANWR for reuse or disposal. The tundra underneath will be restored
with whatever is believed to be the most effective treatment at the time.
Since this will likely occur 90 years down the road, it is difficult if not
impossible to determine the exact technologies which will be employed. Replanting
or tundra vegetation and application of fertilizers are likely to be the