California Air Resources Board

“Development of Methane Leak Correlations for Natural Gas Transmission and Storage Facilities: Final Report,” TRICORD Consulting LLC, May 2023

Tricord Consulting LLC completed a methane emissions study for CARB. The study involved testing of process equipment at three (3) natural gas transmission and three (3) natural gas underground storage facilities for the purpose of determining correlations between component leak concentrations (ppmv) and their emission rates (kg/hr). Test procedures followed guidelines detailed in the U.S. Environmental Protection Agency’s Protocol for Equipment Leak Emission Estimates.

For questions regarding this study, or if you are interested in obtaining copies of the Excel workbooks described in the Final Report, please contact the Oil and Gas Section.

“Open-Source High Flow Sampler for Natural Gas Leak Quantification,” Colorado State University, April 2022

Colorado State University developed and tested a new design for a high flow sampler (HFS) instrument to quantify leaks from natural gas systems. CARB initiated this project to inform and incentivize production of HFS instruments after the only commercially available HFS was no longer in production. CARB’s Greenhouse Gas Emission Standards for Crude Oil and Natural Gas Facilities (Oil and Gas Regulation) includes methane emission rate standards for compressor vent stacks, low bleed natural gas-powered pneumatic devices, and well casing vents, and operators are required to measure emission rates to ensure equipment complies with the flow rate standards. CARB funded this study to identify key required technologies and to develop a working prototype HFS.

This report includes an open-source design of the prototype HFS, results from testing of the prototype, and results from testing three additional pre-production HFS instruments. For questions regarding this project, or if you are interested in obtaining a copy of any of the data files or additional materials described in Appendix A, please contact the Oil and Gas Section.

"Enhanced Inspection and Maintenance for GHG and VOCs at Upstream Facilities (Revised)," SAGE Environmental Consulting, November 2019

The report was revised in 2019 to correct errors identified in some of the calculations. Appendix D in the revised report includes notes outlining the changes that were made to the calculations; results and figures were updated throughout the report to reflect the corrected calculations.

The purpose of the field study was to measure mass emissions of total hydrocarbons reported as methane from leaking components in natural gas service and correlate them with EPA Method 21 screening values. The study was conducted in three (3) phases: (1) Phase I: January 20 to January 30 at sites within the South Coast Air Quality Management District and the Ventura County Air Pollution Control District; (2) Phase II: February 23 to March 3, 2015 at sites within the Glenn County and San Joaquin Valley Air Pollution Control District; and (3) Phase III: August 6 to August 14, 2015 at sites within the Feather River Air Quality Management District.

Emission testing was conducted at natural gas production facilities on valves, flanges, connectors, open-ended lines (OELs), and a diverse “catch-all” group of “Other” component types. The “Other” group, included gas regulators, pressure gauges, pressure relief devices (PRD), flow and pressure meter fittings, pneumatic devices, compressor vents, temperature controllers, and inactive flare pilots. Pumps were not tested since the study focused only on equipment in gas service.

"Source Testing of Fugitive and Vented Emissions from Hydraulic Fracturing Operations and Wastewater Ponds Used in Crude Oil and Natural Gas Operations in California," SAGE Environmental Consulting, June 2016

Because of a limited sample size, this report did not estimate greenhouse gas, criteria pollutant, or toxic air contaminant emissions from well stimulation treatments. However, an uncontrolled step in the well stimulation process was discovered: uncovered circulation tanks. This source is being addressed in the Oil and Gas Methane Regulation.

This study also examined a set of oil field produced water ponds. These ponds may or may not have held produced water from a well that had been stimulated. Regardless, no well stimulation chemicals were detected, but methane, carbon dioxide, non-methane hydrocarbon, and toxic air contaminant emissions were measured. Again, due to a small sample size, CARB is proposing a new research study to get additional data from ponds, before deciding whether or not to proceed with possible control measures.

Recirculation Tank Emissions Testing, WSPA, October 2015

ERM-West, Inc. (ERM) prepared this source test report on behalf of the Western States Petroleum Association (WSPA) for internal research purposes – to understand the quantity of methane emissions resulting from recirculation tanks used during and after well stimulation events. Two types of tests were conducted: 1) Source test (capture and measurement) per WSPA/ERM protocol and 2) Proposed flash liberation test method by CARB. The report presents the test results from testing performed on recirculation tanks used during and after well stimulation treatments.

Methane and Carbon Dioxide Emissions from California Oil and Gas Operations, CSU Fullerton, June 2011

A research team, led by Dr. Jeff Kuo of the Department of Civil and Environmental Engineering, California State University, Fullerton (CSUF) was awarded an 18-month contract by CARB to conduct sample gathering and emission testing at oil and gas facilities in California. The objective of this project was to gather fugitive emission information from oil and gas systems in order to improve the California GHG emissions inventory estimates. The results are to be used to support regulatory programs that achieve effective emission reductions from oil and gas operations and, consequently, minimize adverse environmental impacts from these potential emission sources.