NASA In Deep Water
To the uninitiated, it’s not immediately obvious why NASA would be sponsoring an expedition into the deepest known sinkhole on Earth. On the other hand, the involvement of Environmental Science and Engineering Professor John Spear is a little more apparent—he’s a microbiologist and in this more than 1,000-feet deep, warm, water-filled and mineral-rich cave known as El Zacatón, in Mexico's Yucatan Peninsula, the microbial life is fairly unusual.
Below 30 meters there is no light or oxygen, yet life abounds. “The walls are lined with spongy red and purple microbe mats,” says Spear. Jim Bowden, a deep water diver, dove to 82 meters and brought back samples in which 27 divisions of bacteria were identified, including six new divisions. “The diversity is astounding. I think that if we get down further, there will be even more,” Spear says. There may even be whole ecosystems in the depths of El Zacatón that are entirely independent of photosynthetic energy, instead metabolizing sulphides from volcanic plumes.
However, Bowden won’t be diving any deeper to find out—82 meters is way past the limit of most recreational divers. Instead, starting in mid-May, the expedition will be using a highly sophisticated autonomous robot called the Deep Phreatic Thermal Explorer (DEPTHX). Loaded with a total of 30 computers and able to use sonar, temperature, pressure and light to self-navigate as it searches for environments likely to support life, DEPTHX might be the most sophisticated robot ever designed
for autonomous exploration. Of course this is where NASA’s interest lies—DEPTHX was designed
as a prototype for a vehicle that might someday go looking for life in the ice-covered oceans of Jupiter’s moon, Europa.
Imaging the Earth’s Core
Luis Tenorio, associate professor in the Department of Mathematical and Computer Sciences, is participating in an NSF-funded project to image the earth’s core mantle boundary (CMB). The collaboration includes geophysicists, mathematicians and statisticians from MIT, Purdue and the University of Illinois. Their results, published in the Journal of Geophysical Research and in Science, clearly show structures at two depths close to the CMB, and the existence of new phase transitions in the mantle.
The team’s methodology involves a rich mix of physics, mathematics and statistics to extract information from seismic wave data through “inverse scattering.” Whereas in the past, existing knowledge of geophysical structures was used to interpret scattering patterns, this method allows researchers to take scattered wave data and reconstruct an image of the subsurface without relying on existing knowledge. Combined with considerably better data coverage, this advance in imaging is leading to a rapid expansion in our knowledge of the subsurface and the inner workings of the planet.
Materials and Metallurgical Engineering professor, Ivar Reimanis recently discovered a unique material behavior in which particles are ejected from the surface of an indented ceramic over periods lasting up to a few minutes. Because many of the ejected particles are submicron in size, it looks to the unaided eye like the ceramic is smoking.
The key ingredient in the ceramic is a lithium aluminum silicate called β-eucryptite, a strange material that has a negative coefficient of thermal expansion. It is thought that a high compressive stress, such as that experienced under an indenter, stimulates a transformation to a denser ceramic phase. Upon release, a reverse transformation leads to a popcorn-like effect where particles ranging from submicron to 50 microns are ejected violently from the material. There is no known report of this phenomenon in any other material. With assistance from undergraduate students Chris Seick and Kyle Fitzpatrick, Reimanis is exploring whether this discovery can inform development of a toughened ceramic composite—the phase transformation may be able to shut cracks before they can propagate through a composite.
In fact, this latter idea has already been submitted for a United States patent. To better understand the phenomenon, the Mines researchers have involved collaborators at the National Institute for Standards and Technology in Gaithersburg, the Los Alamos National Laboratory and the Indian Institute of Science. The work is being supported by the U.S. Department of Energy, Office of Basic Energy Sciences.
Enhanced Imaging of the Subsurface
Paul Sava, who joined the Department of Geophysics faculty in the fall of 2006, is working on increasing the accuracy of seismic imaging. When computers generate a visual representation of the subsurface from a seismic dataset, finer details are often obscured by background “noise.” While imaging may provide a coherent overall picture, it emerges from a fuzzy background, much as a badly oriented TV antenna produces a poor image. The noise is created by random sound waves that are inevitably recorded during seismic surveying. This random data makes finer details of the subsurface indistinguishable—only “louder” signals emerge from buzz. Sava’s work aims to cancel out background noise and bring more subtle features into focus. Instead of imaging data received at individual locations, he takes information recorded at multiple nearby sites and mathematically compares them. Data that bears no relation across sites is filtered out, leaving only spatially coherent information. Essentially, he is mathematically cross-checking the data received at multiple nearby sites and building an image from only the information that is corroborated. The result is greatly enhanced imaging, as the accompanying illustrations demonstrate.
Project Enters Phase XII
Geophysics Professor Tom Davis presented results of Phase XI of the Reservoir Characterization Project (RCP) to a packed house of sponsors April 12-13.
The Phase XI project focused on nine-component, full wavefield seismic data collected at Rulison Field, in Western Colorado’s Piceance Basin. Three multi-component seismic surveys were acquired in 2003, 2004 and 2006 across the same area, enabling interpretation of the efficacy of time-lapse data. Additionally, a downhole test that measured in-situ pore pressure was carried out on a field well within the study area, and multi-component microseismic data were recorded during a four-stage hydraulic fracture treatment on a nearby well.
To date, RCP’s Phase XI graduate students have concluded that shear waves are the most valuable wave mode for characterizing and monitoring Rulison’s Williams Fork and Iles tight-gas sands. The RCP project also validated the use of nine-component seismic data for detecting faults and fractures, detecting and predicting lithology and pressures, monitoring reservoir connectivity and depletion, and locating prime well locations.
Pressure-test results were able to show a correlation with depletion zones that were predicted from time-lapse shear-wave data. Furthermore, the data showed coincidence with depleted areas in the Cameo Coal interval.
High-resolution dynamic reservoir characterization appears to be a key technology for tight gas, said Davis, as it gives operators the potential to improve recovery efficiencies.
Going forward, RCP is circulating research proposals for its Phase XII project. Under consideration is dynamic reservoir characterization on Postle Field, in Texas
County, OK. Postle’s Morrow reservoir is undergoing enhanced oil recovery using CO2, a very germane subject in today’s oilfield.
Courtesy of Oil and Gas Investor