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The Shell Center for Sustainability's mission is to foster an interdisciplinary program of research, outreach, and education to address actions that can be taken to ensure the sustainable development of communities' living standards, interpreted broadly, to encompass all factors affecting the overall quality of life.

An Observational and Modeling Study of Natural Gas Leakage in Urban Houston

Exploring coupled engineering and societal implications of hazard risks in coastal communities 


Robert Griffin, Rice University, Department of Civil and Environmental Engineering, Chemical and Biomolecular Engineering
Daniel Cohan, Rice University, Department of Civil and Environmental Engineering
Beata Czader, Rice University, Department of Civil and Environmental Engineering
Christian Davies, Shell Oil Company
Nancy Sanchez, Rice University, Department of Civil and Environmental Engineering, Postdoctoral Research Associate
Frank Tittel, Rice University, Baker Institute, Electrical and Computer Engineering 

  Griffin pic 2015  Cohan pic 2015 Czader Beata pic 2015     Davies Christian pic 2015
Robert Griffin Daniel Cohan Beata Czader Christian Davies
  Sanchez lic 2015  Tittel pic 2015
Nancy Sanchez Frank Tittel

Project Background

Technologies such as hydraulic fracturing and horizontal drilling have increased greatly

the production and accessible reserves of natural gas in the United States. Natural gas

has the potential to reduce greenhouse gas and air pollutant emissions by substituting for

higher-emitting fossil fuels such as coal and oil. However, potential reductions could be

offset by leaks of methane, the primary constituent of natural gas and a potent greenhouse

gas that also contributes to background levels of ozone pollution. Such leaks also

constitute a significant loss of fuel. Global modeling studies estimate that overall fugitive

emission rates from natural gas are on the order of 2-5%, but these studies are unable to

determine the stage at which the emissions occur. Studies that have quantified emissions

from the natural gas life cycle have found conflicting results – some showing more than

expected relative to emissions inventories, others showing less – based on approach used,

segment of the life cycle studied, and geographic location.

Methane leakage rates have not been characterized in Houston, a region whose diverse

neighborhoods and abundance of natural gas and petrochemical facilities create a

heterogeneous mix of potential sources. The rapid growth of the region means that new

natural gas infrastructure continues to be built, even as aging infrastructure may offer

opportunities for control. Characterizing the rates of ethane and methane leaks from

natural gas facilities and infrastructure in the Houston region is the focus of this project.

The sampling for this project will utilize instrumentation deployed on a mobile platform.

We will focus on determination of the ethane to methane ratio in Houston natural gas,

identification of the isotopic nature of the methane and ethane, quantify methane

concentrations that can be attributable to sources other than the natural gas distribution

system, and investigate the influence of natural gas leakage to methane and ethane levels

on the neighborhood scale. Here, we will focus on aging infrastructure. We plan a total

of six months of sampling efforts combined between characterization of the natural gas

near production sites, other sources of methane, and neighborhood scale measurements.

In parallel with the measurement campaign, modeling efforts will develop a spatial

distribution of expected methane and ethane emissions for the Houston region. While we

pursue characteristics of local natural gas distribution infrastructure, we also will use data

on neighborhood age, housing density, and other features to map the expected spatial

distribution of local leaks. The Community Multiscale Air Quality (CMAQ) model will

then be used to simulate the expected distribution of ethane and methane in the Houston

atmosphere by simulating the physical transport and chemical reactivity of the emitted

gases. Our primary focus in comparing modeling results with measurements will be to

identify discrepancies between the CMAQ-predicted distributions of methane and ethane

and observed hotspots of the gases. These discrepancies may indicate potentially

underestimated sources of methane and ethane leaks, which could help better characterize

emissions and highlight opportunities for addressing them. These results will be 

evaluated in the context of policy and economics.


Final Report 2017

 Shell Center for Sustainability 

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