Tight gas flow growing in Wyoming's Jonah field

Operators in Jonah natural gas field in the Green River basin of Wyoming have had on average two rigs running since May 1996, and production from the field's 24 producing wells has reached 45 MMcfd. The field, which first produced gas in 1993, is still undefined in three directions. Reserve estimates "have been the subject of enormous speculation" and could total upwards of 500 bcf, said John Martin, president of tiny McMurry Oil Co. in Casper, Wyo. McMurry is one of four working interest

Jan. 6, 1997

2 min read

Operators in Jonah natural gas field in the Green River basin of Wyoming have had on average two rigs running since May 1996, and production from the field's 24 producing wells has reached 45 MMcfd.

The field, which first produced gas in 1993, is still undefined in three directions. Reserve estimates "have been the subject of enormous speculation" and could total upwards of 500 bcf, said John Martin, president of tiny McMurry Oil Co. in Casper, Wyo.

McMurry is one of four working interest operators in Jonah field, along with Amoco, Snyder Oil, and Western Gas Resources.

As of late November four rigs were working in Jonah. Current drilling is centered in 28n- and 29n-108w, Sublette County. The first well in the area was completed in 1977, but depth, low gas prices, and lack of market outlets delayed development.

Exploitation plans

Operators plan to ultimately drill at least 150 wells into the field's tight gas sands.

Although the wells have high initial decline rates, they also have multiple pay intervals, and well lives are estimated at a minimum 30 years.

The vertical wells, which go as deep as 11,000 ft, so far have averaged 300-500 ft of net pay in Upper Cretaceous Lance, and it's taking three to five frac jobs per well bore to free the gas.

Jonah field is mostly on federal land. The operators have obtained approval to drill 40 wells so far, along with additional field delineation wells. The remaining development will be contingent on federal environmental reviews.

Realization of the field's potential could be hampered by a nitrous oxide emissions cap that currently applies to development on federal lands in southwestern Wyoming (OGJ, Nov. 4, p. 30).

In any case, Jonah field has already been a big breakthrough for McMurry Oil. "This is a company-maker for us," said Martin. "We've just been a little two-bit, seven-person company, and this field has put us on the map."