A special issue of AAPG Bulletin dives into deep petroleum systems; the Eagle Ford Shale celebrates its sixteenth year of production; and a new book on psychics in oil and gas.
It’s impressive to think about how far the oil and gas industry has come. Fun fact: the industry used to employ psychics, diviners, and the like to plan its drilling locales.
Now, with advances in drilling technology, the E&P spaces are moving into deeper and deeper reservoirs on land and offshore. We will explore some of these deep and ultradeep fields, then look back at the industry-changing shale revolution in the Eagle Ford, which is celebrating its sweet sixteen this year. Let’s begin …
Rasoul Sorkhabi
Editor, Core Elements
Deep Petroleum Systems
Courtesy of AAPG Bulletin
In this month’s special edition on Deep Petroleum Systems, guest editors of AAPG Bulletin Fang Hao and Keyu Liu from China University of Petroleum define deep reservoirs as: “Oil and gas accumulations buried at depths from 4,500 to 6,000 m.” They consider reservoirs deeper than 6,000 m ultradeep.
By the numbers:
As of 2020, there were 1,975 oil and gas reservoirs deeper than 4,500 m and 285 oil and gas wells deeper than 6,000 m.
From 2008–2018, the proven reserves of deep and ultradeep fields accounted for 66 percent and 61 percent, respectively, of newly added reserves.
The top six deep and ultradeep basins in the world are: The Gulf of Mexico (28.4 percent); the Tarim Basin in China (7.6 percent); the South Caspian Basin (7.4 percent); the Santos Basin in offshore Brazil (5.1 percent); and the Sichuan Basin in China (4.9 percent).
What’s covered: The special issue of the AAPG Bulletin includes eight articles that touch on the following basins and petroleum systems:
The Tarim Basin with Ordovician faulted karst reservoirs and Cambrian carbonate reservoirs. It holds more than 21 billion barrels of oil.
The Bohai Basin, a deep rift basin with Paleogene-Miocene clastic reservoirs
The Junggar Basin, which formed as a Permian lacustrine basin
The Ordos Basin, which hosts lacustrine Triassic sediments
The Northwest Shelf, consisting of the Exmouth and Dampier rift sub-basins. It contains Triassic- Jurassic age petroleum systems of clastic rocks deposited in fluvial, deltaic, and shallow marine environments.
A recent feature report in The American Oil & Gas Reporter covers growth in the Eagle Ford shale in Texas, where the U.S. shale revolution began 16 years ago.
Defining features:
Deposition: The Eagle Ford Shale was deposited during the Late Cretaceous Cenomanian and Turonian epochs. It consists of organic-rich marine shales and marls deposited in an anoxic environment.
Naming: It was named after the community Eagle Ford on the banks of the West Fork of the Trinity River, about six miles west of Dallas. The formation’s outcrop was first studied and reported by Robert Hill in The American Journal of Science in 1887.
Unique play: The Eagle Ford offers diverse opportunities to oil and gas companies: oil, dry gas, condensate.
Stratigraphic position: The Eagle Ford Shale sits just below the Austin Chalk, another prolific play. The Eagle Ford is also the source rock for the Austin Chalk reservoirs and the giant East Texas field.
First production: In 2008, Petrohawk drilled a horizonal and hydraulically fractured well in the Hawkville field (in La Salle County). This producing well ushered in the Eagle Ford shale oil revolution.
Players: Pioneering and major companies have helped develop the Eagle Ford, but several small and determined companies are shaping its future. All except one are based in Texas. Among these key players are:
Canadian company Baytex Energy, which acquired Ranger Oil’s 269,00 acres last year. Ranger’s acreage came with 300 wells selected for refracking. Baytex now produces 92,000 boe/d.
Tidal Petroleum started in the Eagle Ford in 1994 and is growing its position via sharing agreements, which save the company money by splitting well costs with adjoining operators.
Castlerock Exploration, which operates 48 producing wells and is assessing candidate wells for refracking
Ageron Energy, which is utilizing wider well spacing to get better results from Austin Chalk gas wells as it experiments with lower-cost completion designs for fracking the Eagle Ford
Private company BBL Operating Co, which continues to develop a 10,000-acre position in Robertson County, mainly targeting the Austin Chalk and testing the Eagle Ford Shale
The bottom line: Refracking is the current game in the U.S. Eagle Ford. To date, more than 300 wells have been refracked across the play.
What to watch: The Eagle Ford also extends into northern Mexico’s Burgos Basin, where it is known as the Boquillas Formation and is much thicker—660 ft on average. This huge potential is awaiting development.
Doodlebugs and Dowsers: Unusual Ways to Search for Oil
Krungchingpix/ Shutterstock.com
Dan Plazak is a retired geologist and engineer in Denver. I met him at the Petroleum History Institute’s annual symposium in Canada in May.
New book: During our conversation, he mentioned that he had just published a book about how the oil industry used psychics, dreamers, diviners, and dowsers to locate drill locations, well before it employed geologists.
Fact, not a joke: I thought he was joking. I had read a few pages about this in history books before, but I wondered if there could be enough information out there on this unusual topic to fill a book.
Pleasantly surprised: He handed me a flyer for his book, Doodlebugs and Dowsers: A History of Unusual Ways to Search for Oil, which waspublished by Texas Tech University Press in 2023.I later bought a copy and began to read. It is an impressive piece of research and writing across more than 300 pages!
Go deeper: You can purchase copies of the book from the publisher, on Amazon, or inside major book retailers.
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