FEAST-based evaluation of methane emissions regulations – the case of state-level leak detection and repair programs

Abstract:

Addressing methane emissions from the oil and gas industry through leak detection and repair (LDAR) programs is a critical component of greenhouse gas mitigation measures in several U.S. states. The Colorado Department of Public Health and Environment (CDPHE), California Air Resources Board, and other regulatory agencies have adopted optical gas imaging (OGI) based LDAR policies to reduce methane leaks from upstream operations. In Colorado, CDPHE has required OGI-based LDAR surveys since 2014, with the frequency of surveys based on facility type and expected emissions. Under this policy, operators have reported LDAR data such as the number of sites surveyed, emissions found, and repairs completed in the first six years of the program.

In this work, we use these state-level LDAR program data to model the effectiveness of methane mitigation policies using the FEAST simulation platform. FEAST (Fugitive Emissions Abatement Simulation Tool) is an open source model that simulates upstream methane emissions through time, including intermittent vents, short duration high intensity events such as liquids unloading, and fugitive emissions. LDAR surveys using OGI technologies are simulated by modeling leak detection through probability of detection surfaces that depend on meteorological conditions and emission rate. These parameters are based on prior experimental studies of technology performance conducted at the METEC test site in Colorado. In addition, parameters that affect real-world performance such as infrastructure density, survey speed, survey frequency, and survey disruptions due to extreme conditions can be tuned to represent Colorado-specific LDAR programs.

The LDAR program data collected by the CDPHE provides an unprecedented opportunity to evaluate current understanding of the temporal evolution of methane emissions under mitigation policies. We present our analysis of the last six years of LDAR program implementation in Colorado and the lessons for future oil and gas methane mitigation regulations.