As with the old saw, “It took my whole life to become an overnight success,” it’s taken nearly 60 years to find a company in the position to coax the notoriously stingy West Tavaputs Plateau in Utah into releasing its riches.

But in five short years, the geologists, engineers and field personnel at Denver-based Bill Barrett Corp. have spent more than a third of a billion dollars to drive a nearly 100-fold increase in production from the inhospitable reaches of this high plateau north of the Book Cliffs.

“The success we’ve seen is a testament to the technological advances available in the field today,” says Greg Hinds, Bill Barrett asset manager and geologist. “CO2 has been the key that has taken us from the 1.4 million cubic feet per day of production we inherited in 2002 to more than 100 million today.”

The field sits along the northwest termination of the Garmesa fault trend of the southern Uinta Basin, a prominent structural feature bounding the southern margin of the basin and the Uncompahgre Uplift. Named the West Tavaputs Plateau project, after the mesas that lie above a canyon carved by Nine Mile Creek, it is characterized by two prominent structural closures—the Peter’s Point and Prickly Pear anticlines.

While prospective, its remoteness (two hours from the nearest services) and rugged terrain make exploration daunting for operators.
Several prospectors have taken on the challenge, the first being Carter Oil Co. when, in 1951, it spud the Canyon Government JC #1. Ten months later, the 10,000-foot Mancos test was plugged and abandoned.

In 1953, El Paso produced first gas from Wasatch and Green River alluvial sands. With several productive offsets, they established a shallow gas field, eventually leading to creation of the Peter’s Point Federal Unit. Constrained by takeaway capacity, oil production downdip was the only economic play in the area where, from relatively shallow depths, the Jack Canyon oil field generated 24,000 barrels on average per well during the next 25 years.

Concurrent with the Green River and Wasatch gas developments, a number of deeper wells were drilled from the late 1950s through the 1980s that targeted the Cretaceous Blackhawk, Castlegate, Price River and North Horn formations.

Going deeper still, Chevron Corp. drilled Stone Cabin #1 to 17,261 feet in 1967 to test the Weber formation, hoping to discover the next Rangely Field. Unsuccessful, the well was plugged and abandoned.

In 1979, Getty Oil re-entered a shallow well on the western plunge of the Peter’s Point structure, known as the 101-A, and deepened it to 17,956 feet. A number of formations were tested. The Dakota eventually produced some 143 million cubic feet of gas from 1982 to 1986.

During this early exploratory phase at West Tavaputs, the sporadic development history made for a complicated lease situation. It wasn’t until McCuliss Oil and Gas stitched together the majority of the predominantly federal leasehold before selling the project to Wasatch Oil & Gas that a focused effort could be made to truly test the area’s potential.

New gas efforts
Enter Bill Barrett Corp. In 2002, the newly formed company paid $8 million for some 46,222 acres held in three federal units. The purchase included approximately 40 miles of an antiquated polypipe gathering system, two small compressors and 1.4 million cubic feet per day of production from 13 wells.

“In reviewing the area, two things stood out,” says Kurt Reinecke, Bill Barrett senior vice president of exploration, southern division. “Those were the North Horn production from the 2-B-27 and the lack of energizing fluids used in completions.” The Chorney 2-B-27 was the best well in the field, having produced 1.5 billion cubic feet, almost all coming from a single North Horn sand, he says.

The company got right after it in 2002 with its Prickly Pear Unit State #16-15 well, but because of winter stipulations, only two zones were allowed to be conventionally perforated and fracture-stimulated before operations had to be suspended. The results were less than satisfactory.

“We recognized that subsurface pressures at almost all depths were, at best, normally pressured along the Garmesa trend, giving us a much lower gradient than in the fields in the more central and deeper parts of the Uinta Basin,” says Hinds. “Therefore, slickwater and gel fracs weren’t getting us there. We might have been a bit too eager to see what we had during that fall of 2002.”

As drilling resumed in the spring of 2003, the company began applying CO2 assist to all completions, ranging from Blackhawk marine reservoirs to Wasatch alluvial sands. Typical completions ranged from 20,000 to 30,000 gallons of gel and water, 25,000 to 100,000 pounds of 20/40 sand and 60 to 160 tons of 70-quality CO2.

“This combination of sand and fluids has changed very little to this day, except we’ve tweaked our gel type, started overflushing each stage and added a micro-emulsion to our fluids in 2005,” Hinds says. “Results were dramatic. We saw up to a 10-fold increase in well initial potentials and estimated ultimate recoveries.”

He says that average estimated ultimate recovery (EUR) in the established sweet spots of the Peter’s Point and Prickly Pear units is 2.5 billion cubic feet per well, a marked improvement from the 6 million per well seen in earlier drilling.

The dramatic production and reserve increases did not come without a few setbacks and operational hurdles. Pre-3-D structural interpretations resulted in drilling a few downdip wells that were dry.

“A 3-D survey we shot in 2004 helped clear up the structural picture and, along with drilling results, led us to identify sweet spots on the northern and northeastern flanks of both structures,” says Hinds.

This off-structure production is likely the result of the fluvial reservoirs that are tilted basin-ward following late rotation on the southern bounding Garmesa fault, combined with overall late stage sediment filling of the Uinta Basin, according to Hinds.

The company also recognized that the blanket-type marine reservoirs of the deeper Blackhawk formation, as well as braided-type fluvial reservoirs of the Castlegate, were either wet or too tight to produce commercially, despite applying CO2-assisted stimulations.

“We’ve narrowed our focus these last few years to the lenticular, fluvial reservoirs of the Price River, North Horn and lower Wasatch formations,” he says.

Operationally, applying a frac-and-stack completion technique, where up to six stages are done in one day using flow-through frac plugs, has posed logistical challenges. The company uses at least two CO2 suppliers, with their associated trucking and storage, during completion operations.

Locations are typically on mesas with more than 1,500 feet of relief and are only accessible by less-than-ideal dirt roads made more challenging in winter.

Modernizing and expanding the gathering and compression systems with two new compressor sites and more than 100 miles of new pipeline was challenging as well, due to the remoteness and topography, “to say nothing of the regulatory challenges that are part and parcel of working on federal lands (in the West today).”

Jim Kinser, Bill Barrett development geologist, says the company has drilled 95 wells to the main reservoirs of the Price River and North Horn formations and performed more than 1,000 fracs. It has performed an additional 15 treatments in six wells completed in deep Triassic and Jurassic reservoirs.

Production has seen an almost 100-fold increase from the 1.4 million cubic feet per day in late 2002 to an estimated capability of 110 million at year-end 2007, he says.

“The introduction of CO2-assisted fracs has made drastic improvements,” says Kinser. “We are using rigless completions and getting them online sooner, which obviously helps our economics.”

As production increases, Bill Barrett is investing in more infrastructure at West Tavaputs. “We have a large infrastructure now,” says Hinds, “but we need to build more. We built our first compressor station at our Dry Canyon site adjacent to Nine Mile Canyon. It now has 10 units running and can compress approximately 100 million cubic feet per day.”

The company has completed a second site on the Prickly Pear Mesa, which has four units and can compress 40 million cubic feet per day.

Recently, Questar Corp., based in Salt Lake City, built a new pipeline over Prickly Pear Mesa, so Bill Barrett delivers its compressed gas directly to the Questar line, and then pipes the remaining gas to the Dry Canyon station, where it is compressed and delivered into the Questar line at Nine Mile Canyon along with Peter’s Point Unit’s production.

“Pending environmental approval, we plan to build up to three more compression stations, along with expanding our Prickly Pear station, for which we have approval,” Hinds says. “We currently have two units on order and expect delivery mid-year 2008. We also hope to expand on our gathering system to accommodate increasing volumes, and also add water and condensate lines to help decrease truck traffic in the canyon.”

BBC’s operations are also directly benefitting Price, Utah, and elsewhere throughout Carbon County. “Our county name says it all,” says Dave Levanger, Carbon County director of planning. “We’re rich in natural resources, and coal has been the anchor of our economy for more than 100 years.

“Of course, economic diversity is our goal, and the emergence of the West Tavaputs project is perfectly timed. We face increasing regulatory hurdles on coal, and the Drunkard’s Wash gas field is in decline. If full field development is allowed on the plateau, the prospect of 250 million cubic feet a day of gas from atop the plateau literally reinvigorates our community,” he says.