Petroleum Geology of the West Puerto Chiquito Field Area, Rio Arriba County, New Mexico, San Juan Basin, U.S.A.

Thomas Arthur and Steve Sonnenberg

West Puerto Chiquito Field, discovered in 1962 in Rio Arriba County, New Mexico, produces from Late Cretaceous Turonian Mancos Group Niobrara Formation. The ultimate recoverable resource is 15-25 MMBO at a recovery factor of 25-30%. The Mancos Formation is comprised of 1,000 ft of laminated sequences of marine shales, siltstones, mudstones and carbonates. Hydrocarbons are produced from fractured dolomite-rich units that are 10-30 ft thick. The field does not have a structural closure and hydrocarbons are trapped in a west-dipping monocline with tight Mancos shale top seal. Oil is light 38-40° API and is produced by solution-gas drive, gravity drainage, and a small amount of gas-cap expansion and the water cut is 4%. Reservoir porosity is 0.8-1.5% and permeability is 1,000-20,000 mD-ft with the dominant production coming from fractures. Total organic content is 1-3% and the reservoir is self-sourced Mancos shale. The field is under-pressured at a gradient of 0.313 psi/ft. A total petroleum system approach from source rock to reservoir was used to define potential field extensions for the West Puerto Chiquito Mancos Niobrara Formation reservoir. Well log analysis for source rock and reservoir properties, core analysis and identification of fracture swarms were used to identify potentially productive areas. The stratigraphy in the eastern San Juan Basin represents the major sea level changes throughout the Late Cretaceous through stratigraphic pinch-outs of sandstones and shale units that were deposited on the western edge of the Cretaceous Interior Seaway. Tracking the stratigraphic pinch-outs and the regional basal Niobrara-Tocito unconformity are important for development of this tight oil and gas play.

AAPG Search and Discovery Article #90156©2012 AAPG Rocky Mountain Section Meeting, Grand Junction, Colorado, 9-12 September 2012