Study reveals how to improve natural gas production in shale

November 12, 2020

LOS ALAMOS, N.M., November 12, 2020--A new hydrocarbon study contradicts conventional wisdom about how methane is trapped in rock, revealing a new strategy to more easily access the valuable energy resource.

"The most challenging issue facing the shale energy industry is the very low hydrocarbon recovery rates: less than 10 percent for oil and 20 percent for gas. Our study yielded new insights into the fundamental mechanisms governing hydrocarbon transport within shale nanopores," said Hongwu Xu, an author from Los Alamos National Laboratory's Earth and Environmental Sciences Division. "The results will ultimately help develop better pressure management strategies for enhancing unconventional hydrocarbon recovery."

Most of U.S. natural gas is hidden deep within shale reservoirs. Low shale porosity and permeability make recovering natural gas in tight reservoirs challenging, especially in the late stage of well life. The pores are miniscule--typically less than five nanometers--and poorly understood. Understanding the hydrocarbon retention mechanisms deep underground is critical to increase methane recovering efficiency. Pressure management is a cheap and effective tool available to control production efficiency that can be readily adjusted during well operation--but the study's multi-institution research team discovered a trade-off.

This team, including the lead author, Chelsea Neil, also of Los Alamos, integrated molecular dynamics simulations with novel in situ high-pressure small-angle neutron scattering (SANS) to examine methane behavior in Marcellus shale in the Appalachian basin, the nation's largest natural gas field, to better understand gas transport and recovery as pressure is modified to extract the gas. The investigation focused on interactions between methane and the organic content (kerogen) in rock that stores a majority of hydrocarbons.

The study's findings indicate that while high pressures are beneficial for methane recovery from larger pores, dense gas is trapped in smaller, common shale nanopores due to kerogen deformation. For the first time, they present experimental evidence that this deformation exists and proposed a methane-releasing pressure range that significantly impacts methane recovery. These insights help optimize strategies to boost natural gas production as well as better understand fluid mechanics.

Methane behavior was compared during two pressure cycles with peak pressures of 3000 psi and 6000 psi, as it was previously believed that increasing pressure from injected fluids into fractures would increase gas recovery. The team discovered that unexpected methane behavior occurrs in very small but prevalent nanopores in the kerogen: the pore uptake of methane was elastic up to the lower peak pressure, but became plastic and irreversible at 6,000 psi, trapping dense methane clusters that developed in the sub-2 nanometer pore, which encompass 90 percent of the measured shale porosity.

Led by Los Alamos, the multi-institution study was published in Nature's new Communications Earth & Environment journal this week. Partners include the New Mexico Consortium, University of Maryland, and the National Institute of Standards and Technology Center for Neutron Research.
-end-
Funding:
This work was supported by the Department of Energy's Office of Fossil Energy, the National Energy Technology Laboratory and the Los Alamos National Laboratory Laboratory Directed Research and Development (LDRD) program.

The paper:
"Reduced methane recovery at high pressure due to methane trapping in shale nanopores"; Chelsea W. Neil, Mohamed Mehana, Rex P. Hjelm, Marilyn E. Hawley, Erik B. Watkins, Yimin Mao, Hari Viswanathan, Qinjun Kang, and Hongwu Xu;
Communications Earth & Environment; DOI: https://doi.org/10.1038/s43247-020-00047-w

About Los Alamos National Laboratory (http://www.lanl.gov)

Los Alamos National Laboratory, a multidisciplinary research institution engaged in strategic science on behalf of national security, is managed by Triad, a public service oriented, national security science organization equally owned by its three founding members: Battelle Memorial Institute (Battelle), the Texas A&M University System (TAMUS), and the Regents of the University of California (UC) for the Department of Energy's National Nuclear Security Administration.

Los Alamos enhances national security by ensuring the safety and reliability of the U.S. nuclear stockpile, developing technologies to reduce threats from weapons of mass destruction, and solving problems related to energy, environment, infrastructure, health, and global security concerns.
LA-UR-20-29245

DOE/Los Alamos National Laboratory

Related Methane Articles from Brightsurf:

When methane-eating microbes eat ammonia instead
As a side effect of their metabolism, microorganisms living on methane can also convert ammonia.

Making more of methane
Looking closely at the chemical process that transforms methane into useful products could help unveil more efficient ways to use natural gas.

Methane: emissions increase and it's not a good news
It is the second greenhouse gas with even a global warming potential larger than CO2.

Measuring methane from space
A group of researchers from Alaska and Germany is reporting for the first time on remote sensing methods that can observe thousands of lakes and thus allow more precise estimates of methane emissions.

New 3D view of methane tracks sources
NASA's new 3-dimensional portrait of methane concentrations shows the world's second largest contributor to greenhouse warming.

Show me the methane
Though not as prevalent in the atmosphere as carbon dioxide, methane is a far more potent greenhouse gas.

Containing methane and its contribution to global warming
Methane is a gas that deserves more attention in the climate debate as it contributes to almost half of human-made global warming in the short-term.

Microorganisms reduce methane release from the ocean
Bacteria in the Pacific Ocean remove large amounts of the greenhouse gas methane.

Origin of massive methane reservoir identified
New research provides evidence of the formation and abundance of abiotic methane -- methane formed by chemical reactions that don't involve organic matter -- on Earth and shows how the gases could have a similar origin on other planets and moons, even those no longer home to liquid water.

Unexpected culprit -- wetlands as source of methane
Knowing how emissions are created can help reduce them.

Read More: Methane News and Methane Current Events
Brightsurf.com is a participant in the Amazon Services LLC Associates Program, an affiliate advertising program designed to provide a means for sites to earn advertising fees by advertising and linking to Amazon.com.