Update: Tertiary and Cretaceous Development, East Blanco Field, San Juan Basin

White, Richard J. ¹, Glen A. Luebking¹ (1) Black Hills Exploration and Production, Golden, CO

Since 2003, Black Hills Exploration and Production has drilled 87 wells at East Blanco Field on the Jicarilla Apache Indian Reservation, northeast flank San Juan Basin. Drilling objectives include 12 potential reservoirs from the Tertiary San Jose Formation through the Lower Cretaceous Dakota.

The only commercial accumulations of Tertiary gas are found in this portion of the San Juan Basin. Reservoirs in the Eocene San Jose and Paleocene Nacimiento are conventional nonmarine fluvial, overbank and lacustrine deposits. The sands are lenticular, discontinuous and generally uncorrelatable at current drilling density. The Regina member provides a local stratigraphic seal in the San Jose. Stratigraphic discontinuities within the Ojo Alamo trap hydrocarbons in this basin-wide, sheet-like sandstone.

Although coal completions are made, the field area is outside of the Fruitland Coal fairway and coal accumulations are generally 25’ or less in thickness. The Upper Cretaceous Pictured Cliffs Formation is completed in nearly every well in the field. The Pictured Cliffs is a basin-centered accumulation characterized by the absence of discrete stratigraphic or structural seals, under-pressured reservoirs and mostly water-free gas production downdip from water saturated sandstones. These coastal barrier sandstones, deposited during the final regression of the Late Cretaceous Sea, average 12% porosity and 0.04 md permeability. Black Hills has completed 20 horizontal wells in the Pictured Cliffs, improving the production and ultimate recovery from this fractured reservoir.

AAPG Search and Discovery Article #90055©2006 AAPG Rocky Mountain Section Meeting, Billings, Montana