Microsoft Word Marcellus Radon doc

Radon at the wellhead

In exploring for gas and oil in shale, the industry identifies natural gas formations by the high radioactivity and high carbon content at the Marcellus Shale horizon. Within the Marcellus Shale formation, the radioactive concentrations are 20 to 25 times background. However, the New York Department of Environmental Conservation (DEC) claims that “black shale typically contains trace levels of uranium and gamma ray logs indicate that this is true of the Marcellus shale.”⁵ Based on gamma ray logs, a study by the United States Geological Survey and statements in the Draft Supplemental Environmental

Impact Statement, we differ strongly with the DEC assessment that the concentrations are “trace levels.”

At RWMA, we analyzed the gamma-ray well logs from wells in three towns in New

York State, Reading, Dix and Pulteney. The Pulteney well (also referred to as the Bergstresser well) would be used as a disposal well for radioactive waste water from other exploratory wells in New York State.⁶ Gamma radioactivity within each well was sampled with a sensitive Geiger counter and the measurements were plotted on a graph as what are known as GAPI (Gamma-ray, American Petroleum Industry) units against depth.

The GAPI unit is defined by a calibration facility at the University of Houston, Texas. Located at this facility are three pits, each with a different mixture of thorium, uranium, and potassium. The actual GAPI unit is arbitrary. It is defined as 1/200th of the deflection measured between the high and low activity zones in the pits.⁷ In order to convert the GAPI units to curies we used a method cited by several sources, in which 16.5 GAPI units equal 1 microgram of Radium-equivalent per metric ton (or 1 picocurie per gram).⁸

In general, the radioactivity throughout the depth of the bedrock appears to be equal to or less than 10 picocuries per gram (pCi/g). However, at certain depths in each well the radioactive activity is significantly higher.

All logs have a provision for the shifting of scale from the standard 0-200 GAPI range to greater than 200 GAPI or even greater than 400 GAPI. It is unclear from the logs how the shifting of scale is recorded, but at a certain depth the gamma ray line indicates measurements beyond the 0-200 GAPI range (Figure1).

In the three well logs in Figure 1, the y-axis represents the depth of the well in feet and the x-axis represents the gamma ray measurement in units of GAPI. The gamma ray radioactivity can be traced through the depth of the well by following the solid black line. At a certain point this line, which has been recording the gamma ray radioactivity within the 0-200 GAPI range, stops and traces curves that indicate measurements beyond this range for duration of a little less than 100 feet.

The measurements beyond the 0-200 GAPI range are found at the following depths: In the well log for the Reading, NY well (Shiavone 2), this occurs approximately between 1550 and 1650 feet, in the well log for Dixon, NY (WGI11) this occurs between 2400 and 2500 feet, and in the log for the Bergstresser well in Pulteney, NY we see it between 1700 and 1800 feet. These sections of increased radioactivity represent the Marcellus shale.

In each case the thickness (less than 100 feet) and the depth of the shale is consistent with the general geological predictions of the Marcellus formation in the region. It is not possible to give the specific radioactivity measurement due to the log quality, but if we consider that these sections indicate the gamma ray range of 200-400 GAPI, it would represent radioactive radium concentrations of about 12-24 pCi/g or higher. These radium concentrations are far higher than background radium concentrations in New York State⁹, which are 0.85 pCi/g.

In 1981 the United States Geological Survey (USGS) performed a geochemical study of trace elements and uranium in the Devonian shale of the Appalachian Basin.¹⁰ A brief review of this analysis is necessary to evaluate and verify the data provided by the GAPI logs for the three locations in New York State.

The Devonian layer refers to sediment formed 350 million years ago from mud in shallow seas. Since the layers do not form in a line parallel to the ground surface, the depth at which Marcellus is found can vary from surface outcroppings to as deep as 7,000 feet or more below the ground surface along the Pennsylvania border in the Delaware River valley,¹¹ and as deep as 9000 feet in Pennsylvania.¹²

The USGS study analyzed seventeen cores from wells in Pennsylvania, New York, Ohio, West Virginia, Kentucky, Tennessee, and Illinois. The researchers collected a variety of geochemical data to be used for resource assessment and identification of possible environmental problems. It is important to note the method of analyzing cores.

Rather than the direct gamma spectroscopy employed by CoPhysics¹³, in the USGS study uranium was measured in each core with a more appropriate and precise method. This is called delayed-neutron analysis. In contrast, the oil and gas industry hired, CoPhysics, a non-ELAP-certified lab, it cannot do this more precise analysis. Nevertheless, DEC or its contractor, Alpha Environmental, quotes these measurements in Appendix 1. The Alpha Environmental report does not even cite the USGS study. Since USGS is a reputable and objective government agency, DEC should request an explanation why this reference was omitted.

Although the cores varied in thickness and in depth, geologists identified the Marcellus Shale stratum in several cores using data on the organic matter (carbon), sulfur, and uranium content of the samples. Table 1 below summarizes the results from four cores that tapped into the radioactive Marcellus formation. The depths at which the layer was found as well as the uranium measurements are presented.