This session addressed the fact that Northeastern Pennsylvania has naturally occurring thermogenic gas that is part of the geology and has nothing to do with methane from fracking. It is located in relatively shallow areas. Shale gas is thousand of feet further down below the surface. This thermogenic gas can also be found in groundwater aquifers. This can sometime create confusion with the public.
These thermogenic areas of gas are generated by thin seams of coal that were too small to develop economically in the late 1800's and early 1900's and thus essentially were forgotten. The coal was caused by decay of old plant and organic material. This thermogenic gas has been rediscovered as a result of more drilling related to the Marcellus shale gas play. Companies may be able to drill for this thermogenic gas, in addition to the shale gas further down.
Drinking water wells are 50-200 feet down, and some of these shallow thermogenic gas seams can be as close as 50 feet from the surface. Thus, some of the water wells go through these thermogenic areas and can become contaminated with methane. And since this type of rock near the surface can have many fractures, it is not unusual for methane to migrate over to groundwater.
In order to determine the impact thermogenic gas may have on groundwater, most companies are now doing baseline sampling before drilling for shale gas. Independent researchers have also confirmed the presence of "stray" thermogenic gas. Using certain types of testing that analyze carbon isotopes, it is apparent that the thermogenic methane gas is different from the methane gas in the Marcellus Shale play.
Geologically, right around 4,000 feet below the surface, there is a rock barrier which does not allow for methane to flow up toward the surface. The Marcellus shale gas is below that barrier at approximately 5,000 feet or deeper. Thermogenic gas can also exist between 500 to 3,000 feet below the surface. Although the character of this gas is different from the thermogenic gas closer to the surface, it is still clear that this mid-level thermogenic gas is different from what is being extracted from the Marcellus area.
Given the presence of shallow thermogenic gas, companies need to follow casing and cementing practices to minimize potential contamination of groundwater when drilling. In essence, must seal off any thermogenic gas areas from the drill hole. Generally, most regulations require that surface casings are set 50-200 feet below the deepest fresh groundwater. Once the surface casing is set, you must have a blow out preventer. This is required under Pennsylvania law.
The Marcellus Shale Coalition has rig tours every week for the public so that they can see what is occurring. There are many well site construction regulations. Pennsylvania has many rivers and creeks. Plenty of water compared to other states where fracking is occurring. The amount of water drained by other industries is far greater. In fact, the golf industry uses about the same as the shale gas industry. The most water is used by the power generation industry and by industry in general.
A rig site will usually use some fresh water and produced water combined. The produced water impoundments come from the water that is generated as part of the drilling process. There is a great deal of oversight regarding the produced water that goes back into the drill hole for fracking. It is common to have produced water and fresh water storage areas. 87.5% of the produced water is re-used, thereby reducing the demand for fresh water.
The fresh water table is usually around 300-600 feet deep. It is highly unlikely that hydraulic fracturing at 5000 feet can have any impact on groundwater. In fact, there has never been a confirmed example of a fracked well having contaminated groundwater despite thousands of fracked wells having been drilled.
As for fracking fluids, there is a constant effort to reduce the amount and toxicity of the chemicals used for this process. 99.5% of the frack fluid is water and sand. Many of the fracking additives are bio-degradable. This is becoming much less of an issue that it was when the press first picked up on it a year or two ago.
The industry is now focusing on complete containment. Any spill that may occur at a drill site can be collected and cleaned up. Efforts have also been made to eliminate vapors at the drill site. Generally, with dry gas, this is not a problem. With wet gas, you can get some heavier vapors that the industry is now capturing. The "precipitates" or oil that comes out of wet gas is the source of these heavier vapors that must be controlled. Right now, some operators will use flaring to control these vapors, while others use closed systems to capture these vapors and sell them. All companies will be required to capture the vapors by the beginning of 2015.