A study of methane emissions from orphan wells in Louisiana

Document Type

Article

Publication Date

11-20-2025

Abstract

The Louisiana Department of Energy and Natural Resources (LA DENR) has been conducting a comprehensive program to permanently plug and abandon (P&A) these wells measuring methane emissions from orphan wells prior to and after plugging. In this study, we analyzed 600 well measurements to assess the impact of well and reservoir attributes or contributing factors on methane emissions. All measurements are from well-heads at surface, and the factors analyzed are vis-à-vis these measurements and represent well or reservoir characteristics for each measured well. The list of attributes that could impact methane emissions from oil and gas wells in Louisiana namely field, fluid type, well age, depth, density, uncemented-interval casing to borehole annulus, current reservoir pressure, cumulative oil or gas production, time after production shut-off, borehole size, and perforation interval length were compiled for analyses. The correlation between emission occurrence and the potential contributing attribute are first investigated using trend analysis. Chi-Square tests on emission occurrence and Kruskal-Wallis on emission magnitude distribution are then conducted to understand methane emissions from these wells. While trend analyses did not establish any clear correlation, our study identified uncemented interval length, well age, time since production shut-down, borehole size, and perforation interval length as bearing association with emission occurrence and the distribution of leak rate intensity. Additionally, an analysis of covariance indicated an interaction between location and well density and supported the significance of well age found in the Kruskal-Wallis test. Newer wells were associated with higher emission occurrence and greater emission magnitudes. Expanding the analysis to a larger emissions dataset across different fields and reservoirs would improve the robustness and reliability of the findings and bear more definitive conclusions from all sets of statistical analyses.

Publication Source (Journal or Book title)

Science of the Total Environment

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