👋 Welcome back to Core Elements, where we are celebrating a total solar eclipse in some parts of North America! 

In this week’s newsletter, we will embark on the first part of a two-part look at ways to give new life to depleted gas reservoirs. We’ll also examine a new tool to help with reservoir modeling. Finally, I hope you’ll join me in May at a conference and field trip in Canada—a fabulous place to visit. For now, let’s dive in...

Rasoul Sorkhabi

Editor, Core Elements

New Life for Depleted Gas Reservoirs, Pt 1.

Hydrogen storage, Shutterstock

Hydrogen storage is a new undertaking for the energy sector and full of geological challenges, because the gas reacts or escapes easily. A recent report by Alex Procky, upstream editor for Oil and Gas Journal, combines several conference presentations to analyze the growing niche.

Why it matters:

• Salt caverns are currently considered the best hydrogen storage sites; however, depleted gas reservoirs are also viable options.

• This method is particularly attractive to the petroleum industry, which has access to numerous abandoned wells and legacy information.

Advantages: Unlike salt caverns, which require years to construct, depleted gas reservoirs are readily available and are also connected to pipelines that can be used for hydrogen transportation.

Disadvantage: Depleted gas reservoirs must have perfect cap rock and closure; otherwise, hydrogen will leak.

Scientific puzzles: Beyond the much-easier piece of locating viable reservoirs for hydrogen storage, there are several scientific considerations to keep in mind.

• Buffer zone needed: Hydrogen storage in underground gas reservoirs requires a cushion gas between hydrogen and the underlying water. Residual natural gas (methane) is often considered this buffer. A study by a group of Chinese scientists found that nitrogen and CO2 could also serve as cushion gases.

• Quality or quantity: The same scientists also conducted a numerical simulation of a conventional, partially depleted gas reservoir in the Ordos Basin in China. Their results show that cyclic injection of hydrogen into the reservoir several years before the reservoir is used for storage results in higher hydrogen recovery but lower hydrogen purity.

Transportation: If hydrogen storage in depleted reservoirs is successful, challenges remain around hydrogen transport, including:

• Metal matters: A study by Rosen Group shows pipeline metallurgy and monitoring hydrogen pressures are critical for safe transportation. Hydrogen accumulated at crack-tips can expand and widen pre-existing cracks in the pipeline, particularly in carbon and low-alloy pipelines.

• Unknown territory: There are no established technical standards for conversion of existing natural gas pipelines to hydrogen transportation.

Go deeper: Read the full article here. And stay tuned for part two next week, which will explore using depleted gas reservoirs for geothermal.

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New Study Could Increase Detail and Validity in Reservoir Modeling

Lithology and grain size process overview, AAPG Bulletin, Abdelaziz et al. 

A group of geologists from the University of Toronto and Petronas-Canada have developed a digital tool for transferring sedimentologic data and images to reservoir simulation software.

How it works: The researchers have designed what they call a Log Digitizer.

• This uses Python script to read, extract, and analyze words, data, and images saved in PDFs. Examples include information on rock type, grain size, sedimentary structures, depositional environments, etc.

• The tool then puts out digitized data in standardized formats that can be transferred to reservoir software packages such as Petrel.

Why it matters: Such sedimentologic information is often collected and stored in files that do not interface with reservoir modeling software. This study offers a practical, cost-effective interface tool and could help create more robust reservoir models.

Limitations:

• Log Digitizer uses only computer-generated images and data rendered in PDFs. It cannot process hand-written and hand-drawn documents or scanned well logs.

• Lithology must be color-coded.

Go deeper: Read the article by Abdelaziz and colleagues in the March edition of AAPG Bulletin. Log Digitizer is cited as a free tool; contact the senior author for more information.

Come with Me to Canada

Canada sign, Shutterstock

Speaking of Canada, this year’s Petroleum History Symposium will be held in Canmore, Alberta from May 20–22. I, for one, am planning to attend and present a paper.

In the field: I’m looking forward in particular to the one-day field trip to the Alberta Basin, following a day of technical talks. It aims to view the geology and the historic landmarks of the area.

Region highlights: Canmore is located just east of Banf National Park, and the area showcases:

• The Turner Valley oil field with its Mississippian to Cretaceous reservoirs, which was the main focus of Canada’s petroleum industry in the first half of the 20th century.

• Amazing geologic cross-sections of the Canadian Rocky Mountain foothills.

In case you miss it: The proceedings of the symposium will be published in Oil-Industry History Journal, which is also included in AAPG Datapages.

Go deeper: Visit the Petroleum History Institute’s website to learn more, and I hope to see you there!

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