Microsoft Word Marcellus Radon doc

Table 2. Input Parameters For Model Simulation

Parameter	Value	Unit
Depth of Horizontal Bore	5000	feet
Gas Temperature	105	° F
Well Bore r(min)	0.5	feet
Max gas-yielding radius r(max)	200	feet
Length of horizontal well bore	4000	feet
Gas Production Rate	10000	MCFD
Standard temperature for gas	59	° F
Standard pressure for gas	1	atm
Flowing pressures at r(min)	1500	psi
Flowing pressures at r(max)	2000	psi
Porosities at r(min)	10 - 50	%
Porosities at r(max)	4	%
Radium Activity	6.6 - 30	pCi/g
Rock Density	2.55	g/cm^3
Radon Emanation Factor	10 - 30	%

Numerical simulation thus shows – for typical flow rates, well dimensions, and other reasonable assumptions – that the concentration of radon in natural gas at the wellhead (expressed in pCi/liter) ranges between 36.9 to 2576 pCi/L. The two high values in Table 3, 1,858.6 pCi/L and 2576 pCi/L, are based on a radium concentration of 30 pCi/g. For the radon concentration 858.6 pCi/L, we assume a porosity of 30% and an emanation rate of 30%. The highest value assumes a porosity of 10% and an emanation rate of 30%.

All these are reasonable values and indicate the need for independent testing of production wells in the Marcellus shale formation. These radon concentrations in gas at the wellhead are far higher than the 40 pCi/liter wellhead concentration estimated by ATSDR or the 37 pCi/liter concentration that Raymond Johnson et al. considered average in pre-fracking days, though Johnson did find a maximum of 1450 pCi/L.

Transport from Wellhead to Household

Marcellus Shale gas and the accompanying radioactive gas, radon, is transported from the natural gas wellheads in Pennsylvania and New York to apartments and homes via pipelines. It is known that natural gas moves through pipelines at a speed of 10 to 12 miles per hour.

Because of the longer transit time from the Gulf Coast to New York City there is a lower concentration of radon than is the case with Marcellus Shale gas. The natural gas piped in from the Gulf Coast allows a radon decay up to two half-lives. This is equal to a

reduction by 75% of the wellhead radon concentration.

The distance from Marcellus shale to New York City is much shorter; we are estimating this distance at the conservative figure of 400 miles. As shown in Table 3, the fraction of radon (Rn-222) remaining after transit is 76%.

Thus, over and above the effects of increased well concentrations of radon, the shorter transit time for Marcellus Shale gas will at least triple the risk compared to the risk that Raymond Johnson et al calculated for New York residents.