Abstract

Gas, oil, and water production data were collected from the Fuller Reservoir, Cooper Reservoir, Frenchie Draw, Cave Gulch, and Madden fields in the Wind River Basin, Wyoming. These fields produce from the Mississippian Madison Limestone, the Upper Cretaceous Cody Shale and Mesaverde Formation, and the Paleocene lower unnamed member and Shotgun Member of the Fort Union Formation.

Diagrams of water and gas production from tight gas accumulations in three formations in the Madden field show that (1) water production either increased or decreased with time in all three formations, (2) increases and decreases in water production were greater in the Cody Shale than in either the Mesaverde Formation or the lower unnamed member of the Fort Union Formation, (3) the gas production rate declined more slowly in the lower part of the Fort Union Formation than in the Cody Shale or the Mesaverde Formation, (4) changes in gas and water production were not related to their initial production rates, and (5) there appears to be no relation between well location and the magnitudes or trends of gas and water production.

To explain the apparent independence of gas and water production in the Cody Shale and Mesaverde Formation, a two-step scenario is proposed: gas was generated and emplaced under the compressive stress regime resulting from Laramide tectonism; then, fractures formed during a subsequent period of stress relaxation and extension. Gas is produced from the pore and fracture system near the wellbore, whereas water is produced from a larger scale system of extension fractures. The distribution of gas and water in the lower Fort Union resulted from a similar scenario, but continued generation of gas during post-Laramide extension may have allowed its more widespread distribution.

First posted June 30, 2009