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Abstract: 3-D Distribution of Gas Production across the Wattenberg Field, Denver Basin, Colorado


3-D distribution of gas production for perforated zones in the Lower Cretaceous Muddy ("J") Sandstone is shown by a computer-generated model of the Wattenberg field. Upper surface of the 3-D model is the elevation of the top of the Muddy ("J") Sandstone; the lower surface is -3,200 ft elevation. The western margin of the field borders the north-south trending axis of the Denver Basin. A northeast-trending trough across the center of the field is coincident with a northeastern extension of the Colorado Mineral Belt towards the Transcontinental Arch. The field area is within a thermal "hot spot". Bounding hydrocarbon source rocks are thermally mature for gas generation (vitrinite reflectance contours range from 0.9% to 1.5% R[o]).

More than 7.3 million cubic feet of gas have been produced from greater than 1,300 wells in the field. Both the model and 2-D maps show highly irregular distribution of gas production across the field area. Initial and best-year-cumulative gas production are closely associated to locations of fault and fracture networks. Heterogeneity also results from variation in depositional energy of producing intervals. Primary producing intervals are low-porosity and low-permeability delta-front and nearshore-marine, thin-bedded, fine-grained, sandstone-shale units of the Fort Collins Member. Gas is also produced from overlying fine- to medium-grained valley-fill sandstones of the Horsetooth Member.

AAPG Search and Discovery Article #90946©1997 AAPG Rocky Mountain Section Meeting, Denver, Colorado