Came across another great report while surfing on air pollution and shale.  I came across these paragraphs in The Tyee, a British Columbia newsletter:      http://thetyee.ca/Opinion/2011/07/07/ShaleEmissions/

"Al Armendariz at Southern Methodist University in Dallas, Texas and now a regional manager for the U.S. Environmental Protection Agency, got things off to a roaring start in 2009. That's when he calculated that the compressors and equipment required to drill the Barnett Shale (a 5000 square mile region in north Texas) released more smog-forming pollutants than all the cars, trucks and airplanes in the Dallas-Fort Worth area. The engineer also recorded that 7,700 wells in the Barnett Shale sent more CO2 and methane into the air than two 750 MW coal-fired power plants."

I clicked on the link to the Armendiraz report.  Full of good info. 
Look at the pie chart on page 25 of report......emission sources.    http://www.edf.org/documents/9235_Barnett_Shale_Report.pdf


Within that report, it says on page 1,
Cost effective control strategies are readily available that can substantially reduce emissions, and in some cases, reduce costs for oil and gas operators. These options include:
• use of "green completions" to capture methane and VOC compounds during well completions, • phasing in electric motors as an alternative to internal-combustion engines to drive compressors, • the control of VOC emissions from condensate tanks with vapor recovery units, and • replacement of high-bleed pneumatic valves and fittings on the pipeline networks with no-bleed
alternatives.

Back to The Tyee.  A nice tidy summary of the Cornell study.   This focuses on GHG impacts of shale drilling.  

"Then came a real myth buster from Cornell University. The ecologist Robert Howarth crunched some numbers and concluded that methane leaks and venting from shale gas wells (3.6 per cent to 7.9 per cent of production or twice as much as conventional gas) made the resource's carbon footprint 20 per cent to 100 per cent greater than coal over a 20-year period. (Methane has a 72 to 105 times greater impact than CO2 over a 20-year timeframe, but only a 25 to 33 times greater impact over a 100 year timeframe.)
Howarth concluded that a lot the methane burped into the atmosphere during flow-back from fracking fluids and well completion. Substituting shale gas for coal or oil, he concluded, "may not have the desired effect of mitigating climate warming."