--> History and Development of the Giant Wattenberg Field, Denver Basin, Colorado

AAPG Rocky Mountain Section Meeting

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History and Development of the Giant Wattenberg Field, Denver Basin, Colorado

Abstract

The giant Wattenberg Field area of Colorado was discovered in 1970 by Amoco Production Company and Vessels Oil and Gas with completions in the Lower Cretaceous Muddy (J) Sandstone. Wattenberg straddles the Denver Basin synclinal axis and is regarded as a basin-center stratigraphic petroleum accumulation. Additional production was encountered in five other formations during the development of the field (Plainview, Codell Sandstone, Niobrara Formation, Terry and Hygiene sandstone members of the Pierre Shale). The Terry and Hygiene were first produced in 1972; the Codell in 1981; the Niobrara in 1985; and the Plainview in 1998. Reservoir quality in the various horizons is generally poor which mandates hydraulic fracture stimulation for production. The greater Wattenberg area (GWA) covers approximately 2600 square miles. Production occurs from approximately 4,000 to 8500 ft across the field. Cumulative production from the field is 812 MMBO and 7.5 TCFG from over 35,000 wells. The field is currently at peak production due to recent horizontal drilling activity in the Codell and Niobrara. Original reserves were estimated to be 1.1 TCFG for the J Sandstone. The addition of multiple productive horizons in the field area has significantly added to the total reserve number. The field is ranked by the EIA based on reserves as the fourth largest oil field and the ninth largest gas field in the US. Source beds for oil and gas in Wattenberg are the Skull Creek Shale, Graneros Shale, Greenhorn Limestone, Carlile Formation, Niobrara Formation, and Sharon Springs member of the Pierre Shale. The Wattenberg area is a “hot spot” or positive temperature anomaly. This is an important reason the area is so prolific. Temperature gradients range from 16 – 18oF/1000 ft on the edges of the field to about 28 to 29oF/1000ft in high GOR areas. The temperature anomaly is related to where the Colorado Mineral Belt intersects the Denver Basin. The mineral belt is a northeast trending zone across Colorado of Late Cretaceous to early Tertiary mineralization. The mineralization is associated with high geothermal gradients and hot fluids.