Weyburn. Vacuum. Silo. To those in the exploration business, these fields are practically celebrities. They've all been the focus of Colorado School of Mines' Reservoir Project (RCP) over the past 20 years, and the strides made at these and other fields have been the topics of countless presentations.
What has RCP accomplished in these 2 decades? It's managed to conduct US $15 million of sponsored research. It conducted the first 3-D/nine-component (9-C), or total wavefield, seismic survey in the Silo field. It conducted the first 3-D/9-C survey in Canada in the Joffre field. It conducted the first 4-D/9-C survey in the Vacuum field. And it conducted the first Canadian 4-D/9-C survey at the Weyburn field.
A key to the program's success is the willingness of the fields' operators to offer up their fields for 2 years of study so they get in return a better characterization of their difficult reservoirs. In fact, Dr. Tom Davis, head of the RCP program, said that he doesn't have to do much begging to get oil companies involved.
"They largely come to us," he said. "We put out a call for proposals every 2 years and see what companies respond. We encourage them to make a proposal in our spring meeting. Those are voted on by our sponsors."

Each 2-year phase has two projects on board since sometimes the first-choice projects have to be pulled. That was actually the case with Phase X, which is studying the Rulison field in northwest Colorado.
"Valhall was the one that everybody got excited about, and Rulison was in the second category," Davis said. "Valhall was pulled off the table because they just weren't ready to turn all of their data over to us."
Projects are chosen on the basis of their potential to aid in the development of leading-edge technologies - fracture technologies, directional wells, multilateral wells, etc. "We don't want to go out and do something and never have it tested," Davis said. "We want it to have an immediate effect, to see a well drilled that will either confirm or negate our ideas."

It's hard to imagine a full-scale reservoir characterization project in 1985, when seismic and computer technology was still evolving. "For the amount of geophones that we needed, we had to use parallel groupings of vertical geophones and combine them with horizontal geophones," Davis recalled. "And then we were working in weather conditions like wintertime in Wyoming, where the equipment would freeze in for a couple of weeks and we'd have to wait until springtime."

The researchers worked with Landmark Graphics and some of its early workstation and advanced geophysics software products to do the early interpretation. "Some of it was almost done by hand and rolling paper sections," he said. "It was interesting to see that evolution unfold."

Fractured reservoirs have been one of the main themes throughout the years. "Those darn fractured reservoirs are so complicated and challenging, but also so exciting in the sense that we've really got to understand the fracture systems to better produce the reservoir."

Early work in the Silo field led to better mapping of fracture patterns and density, and the work was tested by the drilling of horizontal wells, the first horizontal drilling to take place in the Rockies. Results of the characterization also led to the extension of the field from its original 3 sq-mile (7.8 sq-km) size to a 30-mile (48-km) long, 2-mile (3.2-km) wide fairway.

Other areas of study included attempts to image reef systems in Alberta and channel sandstones in the Pennsylvanian Morrow play in southeastern Colorado. Coalbed methane plays were the focus of a project in the San Juan Basin, the program's first foray into unconventional gas.
"Now we're immersed in it in the Rulison field," Davis said.

By the mid '90s the project was studying CO2 flood monitoring and enhanced oil recovery in carbonate reservoirs. The Vacuum field in southeastern New Mexico was the site of this study, where it was determined that the shear and converted waves resulting from multicomponent surveys were superior to traditional compressional (P)-wave data in imaging the areas of the flood fronts. Work continued at the Weyburn Field in Canada to detect fractures and to determine that they change over time as the field is produced.

"A lot of people think that geology is stagnant and doesn't change," Davis said. "But it's remarkable how pressures in the subsurface and stress changes can change fracture systems over time as reservoirs are developed. That got us excited."

The goal of Rulison is not to determine injection pathways but to find the faults and fractures and locate wells near those to intersect the fracture systems that control the production from the tight gas sands.
"Multicomponent has very much been the common thread in all of these projects," he said. "We do the full 9-C, not just the converted wave, and the full wavefield recording. I think in the future we're going to be able to understand fractured reservoirs more completely using these new integrated technologies, and multicomponent technology is going to lead the way."

Then what? There's always turbidite systems, deepwater sandstones, anything that's causing operators headaches. "There's a geometry to them; there's fabric," Davis said. "Fractures cause fabric, but there are other mechanisms that occur as well - stratification, diagenetic traps. Some of the most elusive exploration targets are diagentic traps."

So far about 100 students have gone through the program, about an equal number of masters and doctoral candidates. Many of these will, in turn, help develop technologies that independent software vendors and others can license and commercialize. "One of our masters students is developing almost a game-type environment," he said. "The push is to do the interpretation faster, better and easier. That's the kind of thing we're doing. A lot of the companies at our fall sponsors' meeting were quite interested in this."

The list of sponsors reads like a who's who of the oil and gas industry. There have been some changes over time, due both to more interest in some projects than others and to mergers and acquisitions, but Davis said there's still a good cross-section of companies willing to invest money in the program.
"We keep trying different things, different angles," he said. "Is it going to end? I guess it will end when the funding runs out and somebody turns off the lights. But there are a lot of exciting things that still need to be done in reservoir characterization."

For more information, visit www.mines.edu/academic/geophysics/rcp/

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