ABSTRACT

Production of shallow natural gas on Bowdoin dome in northeastern Montana, is controlled in part by natural fractures in the Bowdoin and Phillips Sandstones (Upper Cretaceous). Linear features mapped on Landsat images correspond with geomorphic elements of Milk River, Whitewater Creek, and Beaver Creek. Regional lineament zones interpreted from linear features outline basement blocks which influenced deposition and deformation.

Historical gas pressure data from 1944 to 1956 show patterns of pressure decline on the main, southern part of the dome. A series of pressure maps illustrate isobars elongate along a northwest lineament zone and shifting to the northwest as production continues. Maps showing differences in pressure between 1944 and 1950 and between 1950 and 1956 have close correspondence of isobar patterns and Landsat linear features.

Two ancillary data sets also suggest that naturally fractured reservoirs are present to the north of Bowdoin dome. Pressure gradients for wells drilled after 1970 along a northwest-plunging nose show patterns clearly related to Landsat linear features. Groundwater geochemical data published for an area of southwestern Saskatchewan also show patterns similar to linear features.

Recognition of fractured reservoirs around Bowdoin dome could assist in exploration and development of shallow gas.