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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’)
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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 http://energy.umich.edu/ Horizontal drilling 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/
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/fracking-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 http://www.ogj.com/articles/uogr/print/
Benefits of horizontal drilling • Need fewer wells and well pads to obtain gas from rock • Thus less surface damage Vertical Drilling (WY) Horizontal Drilling (PA)
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)
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://www.lowersusquehannariverkeeper.org/ http://money.cnn.com/
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
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