USING EXISTING DATASETS TO STUDY RELATIONSHIPS BETWEEN ORPHANED/ABANDONED WELLS AND WATER QUALITY IN THE UNITED STATES

There is little information available about the scope and magnitude of risks that orphaned and abandoned wells pose to water resources on a national scale. Generally, orphaned wells (OW) can release similar substances to the environment as from active petroleum production, including greenhouse gases, hydrocarbons, and formation water. OW could have unique emissions profiles from producing wells as they are not artificially stimulated or pumped like active producing wells, so they may release materials over long timescales and at lower rates. Over time, there are chemical, seismic, and anthropogenic forces acting on the well integrity that can allow transport between formations along the wellbore. Developing field studies to test these concepts is time consuming and expensive due to the limited data available for orphaned well locations, and limited access to the wells themselves.

To assess water quality near OW, we compared the known locations of OW in the USGS Orphaned Well Dataset to water quality measurements in the Water Quality Data Portal. We retrieved water quality measurements within a 1-mile radius of OW from several classes:

1. Methane, light hydrocarbons, and their isotopes
2. Total dissolved solids and major ions linked to produced water
3. Anions, nutrients, and oxidation/reduction potential to identify biogenic methane production potential
4. pH and water chemistry to identify corrosive water that could accelerate decay of OW integrity
5. Stable isotope and tritium data of groundwater.

Overall, a total of 2,182,756 water quality measurements in these categories were within the search radius of 29,156 orphaned wells in the USGS orphaned well dataset, including 389,874 measurements at 8,409 groundwater sites and 1,789,473 measurements at 3,481 surface water sites. The most abundant groundwater measurements are those useful for estimating corrosivity near orphaned wells (13,863 OW), while hydrocarbon and produced water indicators are relatively scarce, for example there are 924 OW with associated groundwater methane data. While existing data provides some indication of the scope of OW impacts on water quality, the lack of existing measurements of constituents of interest near known orphaned wells means additional work is needed to fully develop a national scale understanding of the topic.