Direct measurements from shut-in and other abandoned wells in the Permian Basin of Texas indicate some wells are a major source of methane emissions and produced water

Abstract

Oil and gas production wells are a major anthropogenic source of the greenhouse gas methane (CH4) in the United States. Oil and gas production rates from these wells fluctuate due to changes in demand, and is expected to decline over the coming decades to centuries due to the transition to renewable energy. The CH4 emissions profile from wells that are ‘shut-in’ to accommodate changes in demand has not been previously measured, and thus it is unclear whether reduced demand will actually result in reduced CH4 emissions from oil and gas production. Here we present the results of a measurement campaign of CH4 emissions from shut-in and other non-producing oil wells in the Permian Basin, Texas, the largest oil production basin on Earth. All the wells we measured were conventionally drilled oil wells, and we did not measure CH4 emissions from any shut-in unconventional wells. We found that, of 37 wells measured, two-thirds had an emission rate of less than 1 g CH4 hr−1, with the remaining seven wells ranging from 1.3 to 132.0 g CH4 hr−1. The average CH4 emission rate from all wells was 6.2 g CH4 hr−1, lower than previous measurements of CH4 emissions from active conventional wells in the Permian Basin (∼400 g CH4 hr−1) (Robertson et al (2020 Environ. Sci. Technol. 54 13926–34)). Some shut-in wells could be a substantial source of CH4 emissions if this category is not subject to leak detection and repair regulations. We also found five orphaned wells that were a source of produced water to the surface, sometimes in very large quantities (1000s of liters per minute), with evidence for emissions of CH4, hydrogen sulfide, brine, and possibly other hazardous chemicals such as oil residue. Future work should further characterize the impacts of shut-in and orphaned wells on greenhouse gas emissions, water quality and human health.