Jonah reserves may need 5-acre spacing

by Cat Urbigkit

To adequately tap into the reserves underlying the Jonah natural gas field may require 10- and five-acre spacing of wells, industry representatives said last week.

The need for increased well density is one aspect that will be examined in the upcoming Environmental Impact Statement by the Bureau of Land Management. It is the fourth environmental planning document the federal agency has prepared since gas development began in the area about 20 years ago.

EnCana Oil and Gas (USA) Inc. recently hosted tours of the Jonah Field. Sublette County businessmen, town government representatives, museum officials, ranchers, media and industry representatives attended, as did other segments of the public and government.

The Jonah Field is currently producing 600 million cubic feet of natural gas per day, with an estimated 10 trillion cubic feet of recoverable reserves in the ground, EnCana reported.

EnCana entered the scene in June 2000.

"It's definitely a world-class asset," said EnCana's Jonah Field Team Leader Jeff Johnson of Denver, Colo., said of reserves in the Jonah Field. He explained that Jonah is unique in having such a large accumulation of gas within such a small area.

EnCana's Jeff Delaney explained that, using 40-acre spacing, industry officials estimate that 33 percent of the reserves can be recovered. If 10- or 5-acre spacing is utilized, Delaney said up to 80 percent of the reserves can be recovered. He said the proven productive area of the field totals about 20,000 acres, although the EIS area is about 30,000 acres. Most of the field is currently being drilled on a 40-acre spacing and industry officials are advocating the increased density. To put this into perspective, wells drilled on 20-acre spacing have 1,000 feet between the wells.

"Even with 10s, there are sands that are missed," said Johnson. "There may even be a need for five-acre spacing."

EnCana has a little more than 300 producing wells in Jonah Field. The total number of wells that have been drilled in the field, regardless of company, is about 420. The current EIS allows for 533 wells before further analysis is required, so the upcoming EIS is a critical component for further development.

Johnson said that there could be as many as 2,000 additional wells drilled in the field in the future.

The BLM plans to host an open house on the Jonah analysis on Nov. 13 from 3-8 p.m. at the Pinedale Fire Hall.

Did you know?

• The Jonah Field is not crucial winter range for big game animals, so drilling and completion activities are allowed to occur throughout the winter months.

• Archaeological resources are a common occurrence in the Sand Draw area of the field. EnCana's Cally McKee reported that a find last year revealed five housepits, one with human remains that have been carbon dated back 7,200 years ago. These are the oldest human remains ever discovered in Wyoming.

• A typical Jonah well costs an estimated $600,000 to drill.