ANALYSIS OF METHANE IN SHALLOW AQUIFERS OVERLYING OIL AND GAS PRODUCTION IN PENNSYLVANIA AND COLORADO

High concentrations of shallow aquifer methane overlying deep oil and gas reservoirs has garnered a great deal of public concern in recent years as hydraulic fracturing and horizontal drilling technologies have been used extensively. Yet, there is still uncertainty in the existing literature as to the sources of methane. Studies (Osborn et al., 2011 and Jackson et al., 2013) of groundwater wells in northeastern Pennsylvania and upstate New York concluded that there was a correlation between the proximity to oil/gas-wells and methane content in some shallow aquifer wells. Other subsequent studies assert that methane content was not affected by the proximity of oil/gas-wells but rather by a combination of shallow flow paths and local topography. This study seeks to use publicly available shallow aquifer methane data from the Colorado Oil and Gas Conservation Commission and data collected by Osborn from areas of oil/gas production in Pennsylvania and Colorado to asses methane concentrations against proximity and topography. The ArcGIS program was used to find the highest and lowest elevation points for various radii around the data points to compare the differences of local topography with methane content. To facilitate this comparison, a script was written with Python code that would take the coordinates of each point and create a circle of a given radius around the point. The circle and a digital elevation module from the United States Geological Survey were then used in the code to form a raster file using zonal statistics that determined the highest and lowest points within the radius. The elevations of these points were gathered and compared to the original data point’s elevation to determine its relative topography as a ratio between the high and low locations. Preliminary examinations of the Pennsylvania data displayed no obvious correlation between local topography and methane levels for a radius of one kilometer when milligrams per liter of methane were compared to the relative height percent of each data point.