Public data from three US states provide new insights into well integrity

Abstract

Oil and gas wells with compromised integrity are a concern because they can potentially leak hydrocarbons or other fluids into groundwater and/or the atmosphere. Most states in the United States require some form of integrity testing, but few jurisdictions mandate widespread testing and open reporting on a scale informative for leakage risk assessment. In this study, we searched 33 US state oil and gas regulatory agency databases and identified records useful for evaluating well integrity in Colorado, New Mexico, and Pennsylvania. In total, we compiled 474,621 testing records from 105,031 wells across these states into a uniform dataset. We found that 14.1% of wells tested prior to 2018 in Pennsylvania exhibited sustained casing pressure (SCP) or casing vent flow (CVF)—two indicators of compromised well integrity. Data from different hydrocarbon-producing regions within Colorado and New Mexico revealed a wider range (0.3 to 26.5%) of SCP and/or CVF occurrence than previously reported, highlighting the need to better understand regional trends in well integrity. Directional wells were more likely to exhibit SCP and/or CVF than vertical wells in Colorado and Pennsylvania, and their installation corresponded with statewide increases in SCP and/or CVF occurrence in Colorado (2005 to 2009) and Pennsylvania (2007 to 2011). Testing the ground around wells for indicators of gas leakage is not a widespread practice in the states considered. However, 3.0% of Colorado wells tested and 0.1% of New Mexico wells tested exhibited a degree of SCP sufficient to potentially induce leakage outside the well.

Fate of Fugitive Natural Gas in Heterogeneous Near‐Surface Sediments in a Region of Extensive Petroleum Resource Development

“…This shallow geologic trapping of fugitive gas is beneficial from a climate standpoint, mitigating greenhouse gas emissions to atmosphere but poses greater risk to groundwater resources, if present. Furthermore, most fugitive gas leakage monitoring and detection regulations rely on surface‐focused methods with little emphasis on the identification or quantification of subsurface gas migration (Karion et al., 2013; Lackey et al., 2021). These surface‐based methods will likely not be able to delineate subsurface leakage in regions with surficial geology similar to the WCSB.…”

Geochemical Evidence of Potential Groundwater Contamination with Human Health Risks Where Hydraulic Fracturing Overlaps with Extensive Legacy Hydrocarbon Extraction

“…The migration of methane (CH 4 ), the primary component of natural gas, into shallow groundwater is the most cited water quality issue associated with UOGD in the Marcellus Shale of Pennsylvania (PA), the largest U.S. shale gas play, and has been noted in other shale gas basins nationwide. , CH 4 leakage typically results from improper well construction (i.e., lacking casings to prevent gas migration from overpressured formations) or well integrity issues (i.e., defective casings or gas migration along the well annulus). − Additionally, CH 4 can reach groundwater wells several kilometers away from a leaking UOG well via migration along faults or fractures. , CH 4 is nontoxic and common in shallow groundwater throughout hydrocarbon-bearing basins prior to UOGD due to the ubiquity of microbial methanogenesis − and upward migration of thermogenic CH 4 (produced via the thermal maturation of organic matter at depth) over geologic timescales. − However, recently migrated CH 4 from leaking UOG wells poses an explosion hazard above 10 mg/L and can induce redox effects that mobilize toxic species (e.g., arsenic) or lead to the formation of toxic compounds (e.g., sulfide). , …”

Composition and Origin of Surface Casing Fluids in a Major US Oil- and Gas-Producing Region

“…36,37 Wells in the GWA have a history with integrity issues�26.5% of wells in the region have exhibited SCP at some point during their lifetime. 28 Review of construction records has shown that excess levels of SCP in older wells that have surface casings too shallow to protect the deepest groundwater aquifer may be a potential source of groundwater contamination in the GWA. 13,31 The release of surface casing gases during SCP testing or venting may also contribute to the elevated emissions of methane and nonmethane hydrocarbons detected from oil and gas operations in the region.…”

“…In some jurisdictions, migrated surface casing fluids remain trapped beneath a sealed valve at the wellhead, where they build pressure and can escape into groundwater if left unchecked . Other jurisdictions require operators to leave annular valves open, which releases surface casing gases into the atmosphere, where they contribute to emissions of methane and volatile organic compounds . The relative ease with which sustained casing pressure (SCP) and casing-vent flow (CVF) can be detected and measured makes these observations valuable indicators of well integrity.…”

“…Currently, three state oil and gas regulatory agencies in the U.S. (Colorado, New Mexico, and Pennsylvania) make data from regional well integrity testing programs publicly available . Of these states, only Colorado has compiled a publicly available dataset of surface casing fluid geochemical analyses .…”