John W. Robinson¹
(1) McMurry Oil Company, Denver, CO

Abstract: Jonah Field - A new TCF gas field in the Green River Basin, Wyoming

Jonah field is currently producing over 300 MMCFG/D from over-pressured fluvial sandstones of the Upper Cretaceous Lance Formation. The field was “discovered” in 1986, but due to market conditions and primitive stimulation methods, the field was not economic. In 1992, McMurry Oil bought the three-well field, and invoked new drilling and completion technology that unlocked the full potential of the play. Jonah field now has over 150 wells and is poised to become the next TCF gas field in the Rocky Mountain region.

The depositional setting of the Lance was a large alluvial plain composed of heterolithic floodplain deposits and multiple channel complexes. Most channel sandstones are 5-20 feet thick, although some amalgamated intervals are up to 100 feet thick.

The field is bounded by two wrench faults that form a pressure compartment with over 3000 feet of relief. Pressure gradients in the field range from 0.55 to 0.59 psi/ft.

Producing wells average 600 feet of gross sandstone and 335 feet of net pay. Log analysis indicates pay intervals average 7.5% porosity (range 6-13%) and 43% Sw (range 37-71%). Volumetric reserve analysis indicates over 100 BCF gas-in-place per section. Reserves range from 0.7 to 14.0 BCFG/well. Full field development will include 350-450 wells. Peak production will reach 400 MMCF/D between 2000-2002. Estimated ultimate production will exceed 1.5 TCFG and could be greater if market conditions are favorable.

AAPG Search and Discovery Article #90914©2000 AAPG Annual Convention, New Orleans, Louisiana