Denver-based Whiting Petroleum Corp. is the winner of Oil and Gas Investor’s Best Field Rejuvenation 2008 award for its work in Postle Field in Texas County, Oklahoma.

Since it acquired Postle in mid-2005, the company has nearly doubled production, from 4,200 net barrels of 42-degree oil per day to more than 8,000 at present. Whiting has expanded and optimized the field’s enhanced-oil-recovery project, which features a CO2 flood.

Postle’s eastern side was under active CO2 flood when it was acquired. The field produces from high-quality, anastomosing Pennsylvanian Morrow sandstones with excellent reservoir properties. Porosities average 18%, permeabilities are robust, and depths to the reservoir are moderate, around 6,300 feet. Original in-place oil is estimated at some 300 million barrels.

The company owns nearly all of the five units that comprise Postle, and 60% of the CO2 pipeline that delivers to the field.

“Our first effort was to evaluate the surface facilities, and reengineer them to make them more stable and efficient,” says Pete Hagist, Midland-based vice president of operations, Permian Basin business unit. “Having a stable operation is a cornerstone of making these floods run properly.”

Postle’s mid-1990s gas plant was not old, but was notoriously unreliable. Constant equipment failures resulted from basic design flaws. One of Whiting’s first actions was to replace equipment and upgrade control systems, and institute a program of predictive diagnostics.

“We use vibrometers to monitor vibrations of the rotating equipment, to try and predict failures,” says Hagist. The goal is to prevent problems before they happen. The effort has been a strong success: Whiting has built the on-time reliability of the plant to 99%. Hand-in-hand, its maintenance and operating costs have dropped sharply.

The operator also strategically realigned well patterns and aggressively expanded the existing CO2 flood to the west, drilling 130 new wells. Currently, 185 producers and 144 injectors are active. Four units are under flood; Whiting plans to add the fifth unit.

Additionally, it built a new, extremely reliable, state-of-the-art gas plant to handle volumes from the expanded flood. As the CO2 process acts on the lighter-end hydrocarbon chain, Whiting recovers some 850 barrels of NGLs a day from the gas stream in addition to its crude production.

The operator actively manages its flood, pushing and pulling CO2 to places where it is needed. Each month, it holds a pattern review to look at its reservoir surveillance data.

“We focus on reservoir management and cost of operations on each individual pattern,” says Scott Wehner, operations and engineering manager.

The company aims for a recovery factor of 18%, bringing total expected recovery from Postle’s primary through tertiary processes to 55%. “It’s very good recovery, and a very good field,” says Hagist.

In keeping with its continuing interest in proactive management, Whiting hosts a research project at Postle that focuses on reservoir dynamics. The Reservoir Characterization Project (RCP), led by Colorado School of Mines, uses 4-D multicomponent seismic and reservoir-imaging techniques to enhance subsurface understanding. The project is in Hovey Morrow Unit in the midst of Whiting’s latest expansion efforts.

The RCP effort kicked off with a geophysical survey prior to CO2 injection, and was followed by additional surveys after injection was under way.

“Results to date have been encouraging,” says Wehner. “We think it’s going to give us a dynamic picture of where CO2 is moving within the reservoir. The prize will be more hydrocarbon recovery.”

Between now and 2019, Whiting plans to invest $143 million at Postle. A good piece of that goes to CO2 purchases; the bulk of heavy expenses in plants and wells are already behind the company. At present, some 140- to 150 million cubic feet of CO2 is pumped into Postle each day, and at the end of injection the mid-sized flood will retain some 370 billion cubic feet of CO2.

“We are now at a 31-year high on production,” says Wehner. “And it’s continuing to incline.” Whiting forecasts that oil volumes will exceed 9,000 barrels a day, exclusive of NGLs, before beginning a gradual decline.

“It’s a great project,” says Hagist. “And it keeps us on our toes.”

—Peggy Williams