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BY BETSY MASON South America may seem like an odd place to go to learn about Africa, but that's exactly what some Stanford geologists are doing. A crew of 13 students, professors and alumni recently traveled to Chile to find clues about rocks buried deep beneath the sea floor off the coast of West Africa -- rocks that hold vast reserves of petroleum. Their quest took them on a three-day, 9,000-mile journey to Patagonia in March to explore the spectacular Torres del Paine National Park near the southernmost tip of South America. Here, in the shadow of a stunning mountain range -- armed with compasses, hammers, hand lenses and measuring staffs -- they tackled a daunting pile of rocks.
A group of Stanford researchers traveled to Patagonia in search of rock formations that yielded clues to extracting oil off the coast of West Africa. Photo: Betsy Mason "It may not seem immediately obvious since there's a world of difference, at least in geography and distance, between West Africa and the far-south tip of South America," says Steve Graham, professor of geological and environmental sciences. "But in terms of the processes by which sediment is laid down, there are pretty great similarities." The mud, sand and gravel that make up the Patagonian rocks were deposited on the sea floor 100 million years ago after tumbling down as dense mixtures of sediment and water through a submarine canyon. The sediments then hardened into rock and were thrust upward onto the continent by the movement of the Earth's massive tectonic plates. In the process, the rocks were folded on land much like a tablecloth rumples as it is pushed across a table. The resulting troughs and ridges slowly eroded to reveal the layers of rock within them. This fortuitous set of events conspired to expose one of the troughs as a broad, gently curving half-pipe 10 miles long and 2 miles wide. It is here along this ancient rock face that Stanford geologists are hoping to learn more about the geology of West Africa and its vast petroleum potential. The enormous amount of sand that was deposited and then buried off the coast millions of years ago provides an ideal setting for oil. Today, the African oil reservoirs lie several thousand feet below the sea floor. "The problem is that you can't walk around on subsurface deposits," says Graham. "You only have remote sensing tools and the occasional drill hole to understand and define them, and you'd like to somehow be able to be more predictive in exploration for petroleum."
In search of rock systems One solution to this problem is to study similar rock systems that have been brought to the surface, such as those in southern Patagonia. "These sediments are very similar to, and are good analogs for, some of the deep-water sediments that they're exploring for oil today," says Professor Don Lowe of the Geological and Environmental Sciences Department. He and Graham head up the Stanford Project on Deep-Sea Depositional Systems (SPODDS) -- a consortium funded by 15 different oil companies that has been researching subsurface reservoirs and above-surface outcrops around the world for 10 years. Graduate students in SPODDS have traveled to Arkansas, Austria, Peru and Chile and throughout California in search of the rare outcrops that make good analogs for deep-water systems. The rocks in the Patagonian national park represent one of the best outcrops the Stanford group has ever studied and is perhaps one of the best examples in the world, according to Lowe. He says that, when oil industry representatives visited the field site last year and saw the work being done there, several of them were so impressed that their companies decided to give Stanford extra funds toward an intensive group research project. Support from the family-endowed Lawton and James funds also contributed to the effort. "It's an unusual set of outcrop circumstances that really makes this a special place to do this type of study," says Graham. "The processes that brought these rocks up to the surface have folded them, so that you can actually walk all around these things much like a mesa and get a three-dimensional view instead of what you normally get, which is just basically a one-dimensional slice up through some rocks. And glaciation during the Ice Age has essentially removed all soil cover, so in addition to being the right kind of rocks, they are almost perfectly exposed in many places. You couldn't ask for much better." But getting to the Patagonian field site isn't the easiest task, and consequently no one has done any serious geological work there for almost 30 years. To reach the field site, the Stanford group had to haul themselves and their equipment on three or four different flights -- plus a six-hour drive largely on dirt and gravel roads. "It's just off the beaten path," Lowe says. "If this outcrop were in the United States, it would have been beaten on a hundred years ago and every year since by geologists." Getting to the outcrop isn't the only challenge to studying in Patagonia. Despite the beautiful setting, fieldwork can be grueling. Strenuous hiking and wild, unpredictable weather confront the geologists every day. Southernmost Chile lies smack in the middle of the westerly wind belt where gusts race unimpeded across thousands of miles of ocean before hitting the continent full force. Consequently, working in Torres del Paine National Park often feels like being buffeted by the wake of an 18-wheeler on the highway. Add some rain, sleet, hail and even snow, and hiking becomes a challenge, let alone taking precise measurements and detailed notes. Glaciers, parrots and penguins Despite the trials of field research, the students who journeyed to Patagonia all counted themselves lucky to have visited Chile's most beautiful national park. The striking views of jagged, glacier-clad mountains alone would make the trip worthwhile for any geologist. But the students also were enchanted by the exotic wildlife they encountered. Bright green parrots filled the trees in the park, herons and flamingos occasionally visited the lakes, Andean condors peered down from surrounding cliffs and a short side trip led to a penguin hangout. Flightless birds called nandus, and wild llamas known as guanacos, dotted the landscape. And though only their tracks were spotted on this trip, pumas are known to lurk in the hills.
Stanford geology professors Steve Graham, Don Lowe and Jim Ingle have been researching the geology of southern Patagonia for more than three years. Photo courtesy of Steve Graham For graduate student Will Crane, the scenery and wildlife is just an added bonus. He has been working on the same outcrop for three years. He designed and orchestrated the group project and hopes that the results will provide an enormous boost to his dissertation work. "It's an opportunity I don't think I would have had if I had gone to another university," he says. Crane, six other graduate students, one undergraduate and two former grad students spent three weeks documenting the Chilean outcrop. They took careful measurements of the thickness of each rock layer to map the architecture of the system, and described the characteristics of the sediments. By examining the size and composition of the grains of sand, mud and gravel and the textures of each layer, they were able to deduce details such as where the sediments came from and the strength and direction of the currents that deposited them. "We did easily eight times as much work as I could have done with just one field assistant during the same amount of time," Crane says. The SPODDS group made a similar collaborative effort in 1997. Students mapped, studied and modeled a well-exposed outcrop of deep-sea sediments in three dimensions at Wagon Caves Rock in Los Padres National Forest near King City, Calif. The project was enormously successful and acted as a blueprint for the Patagonia venture. A group research opportunity Though Crane stands to gain the most from the current project, the experience was rewarding for everyone involved, says Graham. "It gives people experience with doing group research, gives them a chance to work outside of their own dissertation areas and sometimes outside of their own specializations -- and it gives them a chance to publish together." Tzvetina Erohina, the sole undergraduate in the group, agrees. "This was an amazing experience, because it gave me a chance to learn and practice skills that I'm going to need for my graduate work," she says. In fact, Erohina will join SPODDS as a graduate student next year and has plans to tackle her own dissertation project in southern Patagonia. The oil companies that funded the project also hope to benefit from Stanford's work in Chile. Lowe and Crane will use what the group learned in the field to develop a three-dimensional model of the rock system that can help oil exploration geologists better understand subsurface reservoirs in places like offshore West Africa, as well as the Gulf of Mexico, Indonesia and the North Sea. In these locations, hefty amounts of sand piled up long ago, later solidifying into sandstone where petroleum could hide in the tiny spaces between sand grains. Impermeable layers of mudstone act as seals that trap the oil in the sandstone. Understanding how thick the different layers of sandstone are, how they are connected with each other and how they interact with the mudstone is critical to successful and efficient oil extraction. "This kind of petroleum reservoir, the deep-water reservoir, certainly has been of interest for some time. But as technology allows people to go in deeper and deeper water, but at greater and greater cost, you really want to reduce risk," says Graham. By studying outcrops in Patagonia's rugged mountains, Stanford geologists are going a long way toward reducing that risk through a hands-on understanding of deep-water reservoirs. Science writer Betsy Mason, who earned a master's degree in
geological and environmental sciences from Stanford in 1998,
accompanied the research team to Patagonia. |
Betsy Mason, M.S. Geology '98, measured the orientation of ripple crests on an ancient seabed to determine which way the current was flowing when the sand was deposited.
"If this outcrop were in the United States, it would have been
beaten on a hundred years ago and every year since by
geologists."
Ammonite fossils reveal information about the environment 100 million years ago. Photo: Cari Johnson
With a view of glacially carved mountians, Stanford geologists examined rocks that were deposited on the ocean floor and later pushed up onto the South American continent by the motion of the Earth's tectonic plates. Photo: Cari Johnson |
Stanford Report, May 15, 2002
