Unconventional Natural Gas
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Transcript Unconventional Natural Gas
Unconventional Natural Gas
Kenneth M. Klemow, Ph.D.
BIO / EES 105 at Wilkes University
What is unconventional natural gas?
Natural gas extracted from sources difficult
to obtain through conventional drilling
techniques.
Deep sources (>15,000’)
Unconventional natural gas derived from
dense (tight) rock formations:
◦ Shale
◦ Tight sandstone
◦ Coal bed methane
Geopressurized zones
Methane hydrates
Geologists have long known of gas in
tight rock
Technology didn’t exist to extract that gas
in marketable quantities.
http://www.wintershall.com/en/different-types-of-reserves-tight-gas-and-shale-gas.html
Extracting gas from tight formations
Problems
◦ Occurs in rock that has low permeability
Gas locked in small fractures / bubbles
◦ Much gas associated with horizontally bedded
rock
Extracting gas from tight rock possible
due to two technologies
http://magazine.mst.edu
Horizontal drilling
http://energy.umich.edu/
Hydraulic fracturing
Horizontal drilling
Well drilled vertically to gas rich zone,
then turned horizontally
Possible due to advanced drill bits
History of horizontal drilling
First used in WWII in oil wells of
northern PA
During 1970s, expanded to much of the
Appalachian basin
Later employed in large scale in Barnett
shales of Texas.
Hydraulic fracturing (HF, “fracking”)
Fluid forced down wellbore under high
pressure
Open crevices in rocks to liberate methane
http://savethewater.org/
Fracking fluid composed of various
components
Component
Purpose
Water
Primary solvent
Sand
Prop open pores
Biocides
Kill bacteria
Scale inhibitors
Prevent scale on wellbore
Lubricant
Promote flow through pumps & pipes
Corrosion inhibitors
Prevent rust from forming
Gelling agents
Thicken solution to promote proppant movement
Acid
Dissolve debris in wellbore, opening it up
HF not a new technology
HF first used in 1947 in
an oil well in Grant
County, Kansas.
• By 2002, used
approximately a million
times in US.
• Up to 95% of wells drilled
today are hydraulically
fractured, accounting for
more than 67% of natural
gas production.
•
https://student.societyforscience.org/article/frackin
g-fuels-energy-debate
Development of Marcellus
First attempted by Range Resources in
Washington County PA in 2004
By 2006 other companies started buying
and leasing land
Benefits of horizontal drilling
Need fewer wells and well pads to obtain gas
from rock
◦ Thus less surface damage
Worldwide distribution of UNG
US Distribution of UNG
http://need-media.smugmug.com
How much gas is there?
•
Different estimates:
– Total in place
– Technically recoverable
• Proven
• Unproven
•
Estimates difficult
– Undiscovered shale
– Several variables:
• % gas content in given volume of shale
• % recoverable of total
• Depletion rates of wells
Technically recoverable gas (Tcf)
(EIA 2013)
• World: 7,299
– China: 1,115
– Argentina: 802
– Algeria: 707
– US: 665
– Canada: 573
•
Annual consumption:
– Worldwide: 113 Tcf
– US: 24
• 1 Tcf can heat 15 million homes for a year
•
Much uncertainty
– Behr (2013)
http://www.eenews.net/stories/1059976102
One view of shale gas supplies
http://www.globalresearch.ca/
Issues associated with unconventional
gas development
Water consumption
Wastewater disposal
Potential groundwater pollution
Habitat fragmentation
Potential surface water pollution
Air pollution
Health issues
Water consumption
Each well requires 4-6 million gallons of water
Generally taken from regional waterbodies
In eastern PA, regulated by SRBC
◦ Give permits for all withdrawals
◦ Deny during drought conditions
No similar agency for western PA
Proposal to use abandoned mine drainage
http://alleghenydefenseproject.files.wordpress.com
http://ecowatch.com
Water use in relation to other activities
http://fracfocus.org/water-protection/hydraulic-fracturing-usage
Wastewater disposal
Approx. 20-80% of water injected returns as flowback
and produced water
High levels of salinity, radioactivity
Stored in onsite holding tanks
Once treated in municipal treatment facilities
Now specialized treatment
◦ Clean water returned to drillers
◦ Brine trucked to disposal site
http://www.ogpe.com/articles
Groundwater pollution
•
•
•
Drilling fluid
contains toxic
substances
Flowback and
produced water
contains salts,
radioactivity and
methane.
Studies indicate
methane leakage
Osborne et al (2011)
Habitat fragmentation
Potential surface water pollution
Spills from flowback
Holding pond
accidents
Release of
wastewater
Waste water
shipping accidents
Poor E&S control
measures
http://cen.acs.org/
http://www.gcbl.org
Air pollution
Fugitive methane
Ozone
Particulate matter
Diesel exhaust
◦ Carbon monoxide
◦ Nitrous oxide
◦ Sulfur dioxide
BTEX
http://www.telegraph.co.uk/
Health issues
Some HF chemicals
carcinogenic
Suggested links to
autism, respiratory,
cardiovascular,
neurologic
problems, loss of
taste and smell
Mostly anecdotal
Studies being
conducted – mostly
epidemiological
http://news.nationalgeographic.com
Quality of life
Industrialization of rural landscape
Displacement of families
http://money.cnn.com/
http://www.lowersusquehannariverkeeper.org/
Earthquakes
Injection of wastewater into boreholes
may trigger earthquakes
Some concern that HD and HF may
cumulatively cause seismic activity
http://www.huffingtonpost.com/2011/04/21/
Longevity of wells a question
http://www.leebsmarketforecast.com
Shale gas moratoria - US
In place
◦
◦
◦
◦
New York State
New Jersey
Delaware basin
Mora County, NM
Proposed
◦ Pennsylvania
◦ Colorado
European moratoria
Coalbed methane
Associated
with coal
seams
Once a
nuisance and
vented
Now efforts to
collect
May represent
8% of NG
supplies
http://www.naturalgas.org/overview/unconvent_ng_resource.asp
Geopressurized methane
Methane in porous rock overtopped by
clay layer
At depth of 10,000-25,000’
Thus under tremendous pressure
May hold 5,000 – 49,000 TCF of methane
◦ Compare with 1,100 TCF of known reserves
Not possible to extract with current
technology
http://www.naturalgas.org/overview/unconvent_ng_resource.asp
Methane hydrates
Molecules of methane
surrounded by “cage” of
frozen water
Found in seafloor and
Arctic soils
May contain 7000 – 73,000
Tcf of methane
◦ More than all coal, oil and
natural gas combined
Research in its infancy
Utilization may impact
global carbon cycle
http://www.naturalgas.org/overview/unconvent_ng_resource.asp
Global distribution of methane hydrates
http://www.wou.edu/las/physci/Energy/Gas_Hydrates.html
Conclusions
Unconventional gas has changed the
energy picture in the US and worldwide
◦ Due to improvements in extraction
technology
Supporters believe that UNG can supply
energy needs for decades, if not longer
◦ In US, can relieve need to import energy
Detractors point to many risks
◦ Science critically needed
◦ What to do in the mean