Researchers turn to 3-D technology to examine the formation of cliffband landscapes

This is a scene from the Colorado Plateau region of Utah. -  Dylan Ward
This is a scene from the Colorado Plateau region of Utah. – Dylan Ward

A blend of photos and technology takes a new twist on studying cliff landscapes and how they were formed. Dylan Ward, a University of Cincinnati assistant professor of geology, will present a case study on this unique technology application at The Geological Society of America’s Annual Meeting & Exposition. The meeting takes place Oct. 19-22, in Vancouver.

Ward is using a method called Structure-From-Motion Photogrammetry – computational photo image processing techniques – to study the formation of cliff landscapes in Colorado and Utah and to understand how the layered rock formations in the cliffs are affected by erosion.

To get an idea of these cliff formations, think of one of the nation’s most spectacular tourist attractions, the Grand Canyon.

“The Colorado plateau, for example, has areas with a very simple, sandstone-over-shale layered stratigraphy. We’re examining how the debris and sediment off that sandstone ends up down in the stream channels on the shale, and affects the erosion by those streams,” explains Ward. “The river cuts down through the rock, creating the cliffs. The cliffs walk back by erosion, so there’s this spectacular staircase of stratigraphy that owes its existence and form to that general process.”

Ward’s research takes a new approach to documenting the topography in very high resolution, using a new method of photogrammetry – measurement in 3-D, based on stereo photographs.

“First, we use a digital camera to take photos of the landscape from different angles. Then, we use a sophisticated imaging processing program than can take that set of photos and find the common points between the photographs. From there, we can build a 3-D computer model of that landscape. Months of fieldwork, in comparison, would only produce a fraction of the data that we produce in the computer model,” says Ward.

Ward says that ultimately, examining this piece of the puzzle will give researchers an idea as to how the broader U.S. landscape was formed.

Oil- and metal-munching microbes dominate deep sandstone formations

<IMG SRC="/Images/325645565.jpg" WIDTH="350" HEIGHT="245" BORDER="0" ALT="Halomonas bacteria are well-known for consuming the metal parts of the Titanic. Researchers now have found Halomonas in sandstone formations deep underground. – NOAA”>
Halomonas bacteria are well-known for consuming the metal parts of the Titanic. Researchers now have found Halomonas in sandstone formations deep underground. – NOAA

Halomonas are a hardy breed of bacteria. They can withstand heat, high salinity, low oxygen, utter darkness and pressures that would kill most other organisms. These traits enable these microbes to eke out a living in deep sandstone formations that also happen to be useful for hydrocarbon extraction and carbon sequestration, researchers report in a new study.

The analysis, the first unobstructed view of the microbial life of sandstone formations more than a mile below the surface, appears in the journal Environmental Microbiology.

“We are using new DNA technologies to understand the distribution of life in extreme natural environments,” said study leader Bruce Fouke, a professor of geology and of microbiology at the University of Illinois at Urbana-Champaign. Fouke also is an investigator with the Energy Biosciences Institute, which funded the research, and an affiliate of the Institute for Genomic Biology at Illinois.

Underground microbes are at least as diverse as their surface-dwelling counterparts, Fouke said, and that diversity has gone largely unstudied.

“Astonishingly little is known of this vast subsurface reservoir of biodiversity, despite our civilization’s regular access to and exploitation of subterranean environments,” he said.

To address this gap in knowledge, Fouke and his colleagues collected microbial samples from a sandstone reservoir 1.8 kilometers (1.1 miles) below the surface.

The team used a probe developed by the oilfield services company Schlumberger that reduces or eliminates contamination from mud and microbes at intermediate depths. The researchers sampled sandstone deposits of the Illinois Basin, a vast, subterranean bowl underlying much of Illinois and parts of Indiana, Kentucky and Tennessee, and a rich source of coal and oil.

A genomic study and analysis of the microbes the team recovered revealed “a low-diversity microbial community dominated by Halomonas sulfidaeris-like bacteria that have evolved several strategies to cope with and survive the high-pressure, high-temperature and nutrient deprived deep subsurface environment,” Fouke said.

An analysis of the microbes’ metabolism found that these bacteria are able to utilize iron and nitrogen from their surroundings and recycle scarce nutrients to meet their metabolic needs. (Another member of the same group, Halomonas titanicae, is so named because it is consuming the iron superstructure of the Titanic.)

Perhaps most importantly, the team found that the microbes living in the deep sandstone deposits of the Illinois Basin were capable of metabolizing aromatic compounds, a common component of petroleum.

“This means that these indigenous microbes would have the adaptive edge if hydrocarbon migration eventually does occur,” Fouke said.

A better understanding of the microbial life of the subterranean world will “enhance our ability to explore for and recover oil and gas, and to make more environmentally sound choices for subsurface gas storage,” he said.

Building a full-scale model of a trapped oil reservoir in a laboratory

Getting trapped oil out of porous layers of sandstone and limestone is a tricky and costly operation for energy exploration companies the world over. But now, University of Alberta researchers have developed a way to replicate oil-trapping rock layers in a laboratory and show energy producers the best way to recover every last bit of oil from these reservoirs.

Mechanical engineering professor Sushanta Mitra led a research team that uses core samples from oil drilling sites to make 3-D mathematical models of the porous rock formations that can trap huge quantities of valuable oil.

The process starts with a tiny chip of rock from a core sample where oil has become trapped, That slice of rock is scanned by a Focused Ion Beam-Scanning Electron Microscopy machine, which produces a 3-D copy of the porous rock. The replica is made of a thin layer of silicon and quartz at Nanofab, the U of A’s micro/nanofabrication facility.

The researchers call the finished product a “reservoir on a chip”, or ROC.

The hugely expensive process of recovering oil in the field is recreated right in our laboratory.. The researchers soak the ROC in oil and then water, which is under pressure, is forced into the chip to see how much oil can be pushed through the microscopic channels and recovered.

ROC replicas can be made from core samples from oil-trapping rock anywhere in the world. “Oil exploration companies will be able to use ROC technology to determine what concentration of water and chemicals they’ll need to pump into layers of sandstone or limestone to maximize oil recovery,” said Mitra.

Going with the flow: Researchers find compaction bands in sandstone are permeable

Compaction bands at multiple scales ranging from the field scale to the specimen scale to the meso and grain scale. At the field scale, picture shows the presence of narrow tabular structures within the host rock in the Valley of Fire. At the grain scale, images show clear differences in porosity (dark spots) density. This research aims at quantifying the impact of grain scale features in macroscopic physical properties that control behavior all the way to the field scale. -  José Andrade/Caltech
Compaction bands at multiple scales ranging from the field scale to the specimen scale to the meso and grain scale. At the field scale, picture shows the presence of narrow tabular structures within the host rock in the Valley of Fire. At the grain scale, images show clear differences in porosity (dark spots) density. This research aims at quantifying the impact of grain scale features in macroscopic physical properties that control behavior all the way to the field scale. – José Andrade/Caltech

When geologists survey an area of land for the potential that gas or petroleum deposits could exist there, they must take into account the composition of rocks that lie below the surface. Take, for instance, sandstone-a sedimentary rock composed mostly of weakly cemented quartz grains. Previous research had suggested that compaction bands-highly compressed, narrow, flat layers within the sandstone-are much less permeable than the host rock and might act as barriers to the flow of oil or gas.

Now, researchers led by José Andrade, associate professor of civil and mechanical engineering at the California Institute of Technology (Caltech), have analyzed X-ray images of Aztec sandstone and revealed that compaction bands are actually more permeable than earlier models indicated. While they do appear to be less permeable than the surrounding host rock, they do not appear to block the flow of fluids. Their findings were reported in the May 17 issue of Geophysical Research Letters.

The study includes the first observations and calculations that show fluids have the ability to flow in sandstone that has compaction bands. Prior to this study, there had been inferences of how permeable these formations were, but those inferences were made from 2D images. This paper provides the first permeability calculations based on actual rock samples taken directly from the field in the Valley of Fire, Nevada. From the data they collected, the researchers concluded that these formations are not as impermeable as previously believed, and that therefore their ability to trap fluids-like oil, gas, and CO2-should be measured based on 3D images taken from the field.

“These results are very important for the development of new technologies such as CO2 sequestration-removing CO2 from the atmosphere and depositing it in an underground reservoir-and hydraulic fracturing of rocks for natural gas extraction,” says Andrade. “The quantitative connection between the microstructure of the rock and the rock’s macroscopic properties, such as hydraulic conductivity, is crucial, as physical processes are controlled by pore-scale features in porous materials. This work is at the forefront of making this quantitative connection.”

The research team connected the rocks’ 3D micromechanical features-such as grain size distribution, which was obtained using microcomputed tomography images of the rocks to build a 3D model-with quantitative macroscopic flow properties in rocks from the field, which they measured on many different scales. Those measurements were the first ever to look at the three-dimensional ability of compaction bands to transmit fluid. The researchers say the combination of these advanced imaging technologies and multiscale computational models will lead to unprecedentedly accurate measurements of crucial physical properties, such as permeability, in rocks and similar materials.

Andrade says the team wants to expand these findings and techniques. “An immediate idea involves the coupling of solid deformation and chemistry,” he says. “Accounting for the effect of pressures and their potential to exacerbate chemical reactions between fluids and the solid matrix in porous materials, such as compaction bands, remains a fundamental problem with multiple applications ranging from hydraulic fracturing for geothermal energy and natural gas extraction, to applications in biological tissue for modeling important processes such as osteoporosis. For instance, chemical reactions take place as part of the process utilized in fracturing rocks to enhance the extraction of natural gas.”