Experts speak to public about hydraulic fracturing
HUGHESVILLE – A gain in technology, knowledge learned from previous gas drilling efforts in other parts of the country, and a cooperative effort to understand the research and development behind the controversial water issues surrounding the natural gas extraction process were the main highlights of three key presenters on hydraulic fracturing at Hughesville High School’s auditorium last Monday evening.
“There are great risks as well as great rewards,” referred Dr. Terry Engelder, professor of Geosciences at Penn State University, to the role of geology and physics in relation to water usage and its involvement in the natural gas extraction.
He assured that the drill sites are aligned with the Appalachian Plateau called a syncline and that “horizontal drilling follows the ups and downs of the synclines,” said Engelder. Much of the drilling depends on the distance between ground water and the depth of the shale. “Shale is fractured by the pressure inside the well,” he explained. Hydraulic fractures are natural systematic joints that occur naturally. They have no curves as he showed diagrams and examples of fractures occurring in northern Lycoming County. The Marcellus Shale is a continuous network of fractures trapping natural gas that can only be released with the flow and pressure of water and sand. He added that small fractures leak a great deal when embedded in a larger rock and the low permeability in the larger rock controls the flow. “Frack fluid needs to get through a low permeability first, and with the flow of groundwater through the earth, this frack fluid will take millions of years to reach the earth’s surface,” Engelder said.
Horizontal drilling drills across those fractures, not down. 7,000 ft. can bring one billion cubic feet of gas in just a few days. The joints are what make the Marcellus rich in gas production according to Engelder. “Tiny earthquakes set off during joint fracturing, go towards the stress in the rocks, and can be mapped out with confidence.” This micro-seismic technique measures the fracturing stages. As fluid is driven into the rock, it goes upward and outward. Fluids are stacked by density which increases further down. “Fracking fluid is dense,” said Engelder.
So far tests show that fracking fluid is not compromising our groundwater in Pennsylvania he added. “The flowback immediately relieves any differential pressure that the frack fluid may have had during stimulation,” Engelder added.
Next, Scott Perry director of bureau of Oil and Gas Management for DEP spoke on the new environmental protection regulations with the industry. “Our main concern is to protect the streams and rivers,” he said noting that 5 to 10 million gallons of water a day are needed to remove the fluids. “Operators must review and identify all substances and must be part of a plan,” said Perry. “Records must be kept daily, and a chemical analysis is also required at each treatment facility.” There has been an increase now in recycling disposal water. “The water that comes out of these wells is extraordinarily salty, more so than the ocean, and can have an environmental impact,” he said.
There is an underground injection control program in place according to Harris. There are new regulations for casing and cementing with regular inspections by DEP. They must provide cementing procedural information such as pumping rates, pressures, total volume of water and sources used, procedure time, and a list of chemicals used. “A cement job log must be available at each site. We now have some of the best standards in place in the country,” Perry added. He said that these regulations were set up in October 2010.
Engineer, Joe Lima from Schlumberger, an oilfield services company, gave a brief history on hydrofracturing stating that the first one dates back to July 1947 in Grant County, Kansas when the process was primitive.
Lima has a degree in petroleum engineering and has spent 23 years working with hydraulic fracturing technology. He said that the fabric of the rock changes. “Gas shales are organic rich source of rocks, extremely low in permeability. Rock is tight so many wells need to be produced for extraction,” said Lima. “Good shales have low permeability and need horizontal drilling and multiple stages for hydraulic fracturing.” Advances have been made in materials, chemicals and techniques used, adding that multi-stage technologies are now coming into play.
Horizontal well applications are now being used for fracturing and the process is more streamlined according to Lima. Some lateral lines are being drilled down to 2,000 feet so more gas can be removed from a larger area.
Less time is now spent in one location because multiple wells can be placed at the same pad thus reducing surface disturbances. Some environmental initiatives have also taken place starting with the use of safer substances and additives that do not pollute. “The industry really wants to help educate the public,” Lima said. He added that the American Petroleum Institute and Society of Petroleum Engineers plus several other organizations are passing a list of best practices in the industry.
“The value of the Marcellus is the increment of its depth,” concluded Engelder. “The size of this resource is unbelievable – it is that large.”