PLUGGING KENTUCKY’S ORPHANED OIL AND GAS WELLS: HAZARD SCORES TO OPTIMIZE ENVIRONMENTAL PROTECTION

The Kentucky Geological Survey and the Kentucky Division of Oil and Gas are heading up a program to measure methane emissions from orphaned oil and gas wells (OOGWs), supported by funding allocated by the Bipartisan Infrastructure Law (BIL) for OOGW remediation. To ensure the long-term success of this program, funding must be used as efficiently as possible. We have developed a relative hazard scoring tool to assist with the prioritization of OOGWs for plugging. Each well received a relative hazard score based on several spatial and environmental factors. These factors include proximity of orphaned wells to residential and commercial areas, important cultural and natural resource features, groundwater wells, disadvantaged communities, and flood zones. In addition to these factors, we considered attributes that are unique to each OOGW. These attributes include the vertical separation between the potable water zone and the producing formation, well age, and well subtype. The OOGWs fall into 15 subtypes we have established which are defined by the age of the producing geologic formation and type of hydrocarbons produced.

Of the roughly 14,000 known OOGWs in Kentucky approximately 50% have no records or limited records. These wells have been grouped into the unknown (UN) subtype. The lack of records presents a significant problem in assigning the UN wells with an appropriate hazard score. The UN wells follow the same spatial distribution as the broader OOGW population in Kentucky, spanning the Appalachian Basin, Illinois Basin, and Cincinnati Arch. Using a 1-mile buffer analysis and knowledge of historical oil and gas production trends in Kentucky, we drastically decreased the number of UN wells to less than 10% of the total population by grouping qualifying wells into one of the other subtypes. Additionally, we conducted methane measurements on a subset of OOGWs (~100) throughout Kentucky to characterize methane emissions for the larger population of OOGWs. The reclassifying of the UN wells and continuing field measurements allow us to more accurately seek out wells which pose significant environmental risk. This method of addressing UN wells may prove fruitful nationwide, allowing states to make more informed plugging decisions for OOGWs.