Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

New Model of Geological Strata May Aid Oil Extraction, Water Recovery and Earth History Studies

25.05.2012
‘Largest known chemical wave’ caused previously unrecognized effects, said Sandia researcher

A Sandia modeling study contradicts a long-held belief of geologists that pore sizes and chemical compositions are uniform throughout a given strata, which are horizontal slices of sedimentary rock.

By understanding the variety of pore sizes and spatial patterns in strata, geologists can help achieve more production from underground oil reservoirs and water aquifers. Better understanding also means more efficient use of potential underground carbon storage sites, and better evaluations of the possible movement of radionuclides in nuclear waste depositories to determine how well the waste will be isolated.

Yifeng Wang examines a sedimentary outcrop in New Mexico's Tijeras Canyon. Wang is the lead author of a paper published recently in Nature Communications that offers new insights into pore size and distribution in horizontal slices of sedimentary rock. (Photo by Randy Montoya) Click on thumbnail for high-resolution image.

“I think our paper for the first time provides a reasonable explanation for the origin of patterns,” said lead researcher Yifeng Wang. “We found we could predict the variations in pores as well as the heterogeneity of a reservoir.”

The analysis, published Feb. 21 in Nature Communications, was able to match the field observations published in 2006 by second author David Budd, professor of geological sciences at the University of Colorado at Boulder.

Budd said Wang put together a session at the 2010 annual meeting of the Geochemical Society at which Budd presented field studies of porosity and chemical composition. “He recognized that the data I showed could be explained by stress-induced chemical waves. He subsequently developed the numerical model to test his idea. Then we used the 2006 data set to demonstrate the correspondence between his model’s outcomes and the field data.”

A chemical wave in this context relies upon mineral dissolution and precipitation, powered by geologic stress, to penetrate surrounding material, just as an ocean wave powered by the moon’s gravitational pull rides up on a beach. Ocean waves shift sand; Wang found that chemical waves modify the spatial distribution of rock porosity.

As Wang puts it, a chemical wave is “like water rippling. The concentration of a chemical species varies periodically in space (a standing wave) or sometime such variations propagate through space (a travelling wave).

“The one we revealed in dolomite (a type of sedimentary rock) may be the largest chemical wave ever known, because no one has thought to look for chemical waves in strata. It occurred on the scale of meters to tens of meters and propagated between a hundred to a thousand years.” Chemical waves are usually observed on much smaller scales in laboratories.

Using the chemical wave concept and well-known equations for material stresses, Wang formulated a mathematical model.

The upper diagram portrays the mechanism driving a chemical wave, with stress from surrounding formations acting to percolate water through a horizontal layer of dolomite. The bottom graph shows the results of high-resolution sampling performed every 0.3 meters showing complex patterns of lateral porosity and permeability in dolomite strata. The solid red line is a three-day moving average. The images are modified from the technical paper. (Image by Yifeng Wang) Click on thumbnail for high-resolution image.

“The remarkable thing is that the model predictions match very well with many seemingly uncorrelated observations. The model predictions not only match the observed porosity patterns, but also match very well with chemical and isotopic signatures. This is the power of mathematical analysis,” Wang said.

Wang’s model isn’t large enough yet to derive equations meaningful to an entire reservoir — a process called upscaling. Still, he said, “Another way to capture this variability is to use mathematical analysis to derive upscaled flow-transport equations. This work is on the way.”

The work may help trounce geologists’ belief that each layer of sedimentary rock, deposited over eons, is more or less homogenous in porosity and composition. Thus a single core sample obtained from a given depth was thought to chemically represent the entire layer.

But Budd’s findings showed that horizontal variations within a layer of sedimentary rock could be quite significant — in some cases, as large as vertical variations. This would affect not only the amount of fluid stored or percolating through a rock but the amount of pressure needed to shoot liquids to Earth’s surface. No one knew why these variations occurred, nor had anyone measured their magnitude.

The problem has always been how to extend horizontally the knowledge gained from vertical bore holes that may be 1,300 feet apart, Budd said.

Wang’s model also reveals important information about Earth’s geological changes.

“Even the shape of a variation may reveal important facts about past times,” he said. “Our work may have geologists rethinking their method of field sampling and their interpretation of data about Earth’s evolution.”

The work was supported by Sandia’s Laboratory Directed Research and Development program and by industrial supporters of the AVID (analysis of variability in dolomites) consortium.

Sandia National Laboratories is a multi-program laboratory operated by Sandia Corporation, a wholly owned subsidiary of Lockheed Martin company, for the U.S. Department of Energy’s National Nuclear Security Administration. With main facilities in Albuquerque, N.M., and Livermore, Calif., Sandia has major R&D responsibilities in national security, energy and environmental technologies and economic competitiveness.

Sandia news media contact: Neal Singer, nsinger@sandia.gov, (505) 845-7078

Neal Singer | Newswise Science News
Further information:
http://www.sandia.gov

All articles from Earth Sciences >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: Fizzy soda water could be key to clean manufacture of flat wonder material: Graphene

Whether you call it effervescent, fizzy, or sparkling, carbonated water is making a comeback as a beverage. Aside from quenching thirst, researchers at the University of Illinois at Urbana-Champaign have discovered a new use for these "bubbly" concoctions that will have major impact on the manufacturer of the world's thinnest, flattest, and one most useful materials -- graphene.

As graphene's popularity grows as an advanced "wonder" material, the speed and quality at which it can be manufactured will be paramount. With that in mind,...

Im Focus: Exotic quantum states made from light: Physicists create optical “wells” for a super-photon

Physicists at the University of Bonn have managed to create optical hollows and more complex patterns into which the light of a Bose-Einstein condensate flows. The creation of such highly low-loss structures for light is a prerequisite for complex light circuits, such as for quantum information processing for a new generation of computers. The researchers are now presenting their results in the journal Nature Photonics.

Light particles (photons) occur as tiny, indivisible portions. Many thousands of these light portions can be merged to form a single super-photon if they are...

Im Focus: Circular RNA linked to brain function

For the first time, scientists have shown that circular RNA is linked to brain function. When a RNA molecule called Cdr1as was deleted from the genome of mice, the animals had problems filtering out unnecessary information – like patients suffering from neuropsychiatric disorders.

While hundreds of circular RNAs (circRNAs) are abundant in mammalian brains, one big question has remained unanswered: What are they actually good for? In the...

Im Focus: RAVAN CubeSat measures Earth's outgoing energy

An experimental small satellite has successfully collected and delivered data on a key measurement for predicting changes in Earth's climate.

The Radiometer Assessment using Vertically Aligned Nanotubes (RAVAN) CubeSat was launched into low-Earth orbit on Nov. 11, 2016, in order to test new...

Im Focus: Scientists shine new light on the “other high temperature superconductor”

A study led by scientists of the Max Planck Institute for the Structure and Dynamics of Matter (MPSD) at the Center for Free-Electron Laser Science in Hamburg presents evidence of the coexistence of superconductivity and “charge-density-waves” in compounds of the poorly-studied family of bismuthates. This observation opens up new perspectives for a deeper understanding of the phenomenon of high-temperature superconductivity, a topic which is at the core of condensed matter research since more than 30 years. The paper by Nicoletti et al has been published in the PNAS.

Since the beginning of the 20th century, superconductivity had been observed in some metals at temperatures only a few degrees above the absolute zero (minus...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

Call for Papers – ICNFT 2018, 5th International Conference on New Forming Technology

16.08.2017 | Event News

Sustainability is the business model of tomorrow

04.08.2017 | Event News

Clash of Realities 2017: Registration now open. International Conference at TH Köln

26.07.2017 | Event News

 
Latest News

A Map of the Cell’s Power Station

18.08.2017 | Life Sciences

Engineering team images tiny quasicrystals as they form

18.08.2017 | Physics and Astronomy

Researchers printed graphene-like materials with inkjet

18.08.2017 | Materials Sciences

VideoLinks
B2B-VideoLinks
More VideoLinks >>>