Detection, localization, and quantification of single-source methane emissions on oil and gas production sites using point-in-space continuous monitoring systems

Abstract

We propose a generic, modular framework for emission event detection, localization, and quantification on oil and gas production sites that uses concentration data collected by point-in-space continuous monitoring systems (CMS). The framework uses a gradient-based spike detection algorithm to estimate emission start and end times (event detection) and pattern matches simulated and observed concentrations to estimate emission source location (localization) and rate (quantification). We test the framework on a month of non-blinded, single-source controlled releases ranging from 0.50 to 8.25 hours in duration and 0.18 to 6.39 kg/hr in size. All controlled releases are identified and 82% are localized correctly. 5.5% of predicted events are false positives. For emissions <= 1 kg/hr, the framework underestimates by 37.2% on average, with 90% of rate estimates within a factor of [-4.6, 2.8] or a percent difference of [-78.1%, 178.6%] from the true rate. For emissions > 1 kg/hr, the framework overestimates by 1.5% on average, with 90% of rate estimates within a factor of [-2.0, 1.8] or a percent difference of [-49.6%, 77.4%]. Potential uses for the proposed framework include near real-time alerting for rapid emissions mitigation and emission quantification for data-driven inventory estimation on production sites.

Toward Multiscale Measurement-Informed Methane Inventories: Reconciling Bottom-Up Site-Level Inventories with Top-Down Measurements Using Continuous Monitoring Systems

“…The framework further assumes that all emissions come from a single source within each interval, which may introduce further errors if multiple sources are emitting simultaneously. Note that these errors are discussed fully by Daniels et al…”

“…If full site coverage is not possible, then assumptions about the persistence of emissions during periods when the wind is not blowing toward the sensors may be required. Finally, the quantification framework used in this study has only been evaluated on single-source controlled releases . Additional development and testing are required to obtain rate estimates from this framework under more complex emission scenarios, which will be addressed in future work.…”

“…To provide context to the end-of-project measurements, we use the raw concentration and wind data from the CMS to estimate emission source location (localization) and rate (quantification) on fixed 30 min intervals. This is done using the modeling framework proposed by Daniels et al, 30 which was tested on nonblinded, single-source controlled releases at the Methane Emissions Technology Evaluation Center (METEC). For emissions >1 kg/h, the framework has an average quantification error of 4.3%, and 90% of rate estimates fall within a factor of [−2.0, 1.8] or a percent difference of [−49%, 79%] from the true emission rate.…”

“…Point-in-space CMS measure ambient methane concentrations at fixed sensor locations rather than emission rates and typically require a method for translating concentration data into emission rate estimates. Methods for doing so are available in the published literature − and are also developing rapidly in the private sector. Bell et al evaluate 11 of these proprietary solutions and find that event detection and quantification performance vary widely across solutions, with average quantification errors ranging from −40 to 93% for both single- and multisource emissions > 1 kg/h.…”

“…Bell et al 31 evaluate 11 of these proprietary solutions and find that event detection and quantification performance vary widely across solutions, with average quantification errors ranging from −40 to 93% for both single- and multisource emissions > 1 kg/h. Despite the generally poor quantification performance of these 11 proprietary solutions, improvements to quantification algorithms are occurring rapidly both in the private sector and publicly, with Daniels et al 30 having an average quantification error of 4.3% for single-source emissions > 1 kg/h.…”