With microfossils on petroleum hunting

How Bonn micropaleontologists are helping to track down new deposits

Star Sands: entire beaches and regions between the northern Great Barrier Reef off Australia and southern Japan are covered by the calcareous shells of microscopic foraminifera. © Martin Langer
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Motorists all over the world are experiencing their "blue miracle" almost every day right now. The fuel prices at petrol stations are constantly rising - an end to this development is not in sight. In addition to the almost insatiable thirst for energy of the rapidly growing world population, speculation of hedge funds or OPEC production restrictions, the dwindling oil reserves are responsible for the fact that fossil hydrocarbons regularly become more expensive. In order to find out about previously unknown deposits, Bonn micropaleontologists use very efficient methods of investigation. In the process, even the smallest microfossils are used, which prove to be real nose for oil and natural gas.

The little ones are getting big

For about two billion years, tiny organisms such as acritics, foraminifera, dinoflagellates and conodonts have been populating the waters of the oceans in large numbers. At certain times in the Earth's history, their skeletons and shells formed extensive layers in the sediment, which, as so-called porous reservoirs, are ideal reservoirs for oil and natural gas. Comparable mass deposits are still found today on numerous tropical beaches. They present themselves under the microscope as truly "living sands" of shells and skeletons of unicellular organisms.

In the course of evolution, these primordial animals have developed an enormous variety of forms and species. They are now used by micropaleontologists as markers to date the sequence of rock layers with the utmost precision. "This technique is called biostratigraphy and can accurately determine the age of sediments up to one million years, " explains Professor Martin Langer of the Steinmann Institute of Geology, Mineralogy and Paleontology at the University of Bonn. The method has been used successfully for more than 100 years, and micropaleontologists have long been part of the standard occupation of any petroleum company.

Research diving: an integral part of the training in the field of micropalaeontology at the University of Bonn Martin Langer

Seismic revolutionizes natural gas and natural gas exploration

But in the 1980s, the picture changed. At that time, seismic, a kind of underground tomography of the earth layers, was established as a standard method in the petroleum industry. The corporations were so excited by the seismic images that they believed they could solve all exploration problems. However, industrial micropalumontology was almost condemned to extinction by this development.

The seismic actually served the geologists and mining engineers in the aftermath. In the meantime, almost all particularly large earth fields of the earth are known or even exploited. display

The renaissance of micropal ontology

The search for new deposits is therefore concentrated on smaller and fragmented fields, which are often only a few tens of meters in size. And also the "mother rocks", the source rocks of the earth, these deposits are often not thickener than a few meters.

Storage areas of this size are not detected and overlooked by seismic surveys. Their vertical resolution to distinguish different rock strata reaches only about 50 or 100 meters. The method is simply too inaccurate, explains Langer. A completely different approach to micropal ontology: it provides a vertical resolution of about one meter by means of precise biostratigraphy. This allows precise control of vertical and horizontal wells and economic exploration of the entire natural gas or petroleum source.

Microfossils as a bubbling source of information

Bonn micropalumontologists Martin Langer

But how do the researchers get the necessary knowledge? With each drilling, microfossils are washed up with the crushed rock. They provide the micropaleontologists with information about the exact age of the rock strata and about the location and size of the possible deposits. In addition, the colors of the microfossils provide information about the thermal maturity of the rock. With their help, experts such as Langer can also detect whether there is any soil or natural gas in the subsurface - and if so, what quality it has.

The high precision of micropal ontology is based on the exact interpretation of the finds, based on the smallest structures of the microfossils. For this reason, oil companies have long since recognized that micropaleontologists can significantly improve the success rate and exploitation of deposits. Microfossil researchers with their knowledge of foraminifera, nanoplankton, conodonts or dinoflagellates are therefore in great demand again today. The subject is experiencing a unique renaissance, says Langer.

Link:

Further information: www.paleontology.uni-bonn.de/frame02.htm

(Prof. Dr. Martin Langer, Steinmann Institute of Geology, Mineralogy and Paleontology, University of Bonn, 20.06.2008 - DLO)