Evaporite geometries and diagenetic traps, lower San Andres, Northwest shelf, New Mexico

Conference · Wed Apr 01 00:00:00 EST 1992 · AAPG Bulletin (American Association of Petroleum Geologists); (United States)

OSTI ID:7195620

Keller, D R ^[1]

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1. Chevron USA, Midland, TX (United States)

An east-west-trending belt of lower San Andres oil fields extends 80 mi across southeastern New Mexico from the Pecos River near Roswell to the Texas-New Mexico border. These fields are along a porosity pinch-out zone where porous carbonates grade laterally into bedded anhydrite and halite. The lower San Andres traps are associated with pre-Tertiary structural or stratigraphic traps. Oil and water production relationships from these fields are not consistent with present-day structure. These fields have been commonly interpreted to be hydrodynamic traps created by the eastern flow of fresh surface water that enters the lower San Andres outcrops west of Pecos River. There is no evidence, however, that surface water has moved through the lower San Andres in this area. This conclusion is supported by the fact that formation-water resistivities are uniform throughout the producing trend, no significant dissolution of carbonates or evaporites has occurred, and there has been no increase in biogradation of oils adjacent to the lower San Andres outcrops. These fields actually are diagenetic traps created by porosity occlusion in the water column beneath the oil accumulations. Hydrocarbons originally were trapped in pre-Tertiary structural and structural-stratigraphic traps. Bedded evaporites were effective barriers to vertical and lateral hydrocarbon migration. Eastward tilting of the Northwest shelf during the Tertiary opened these traps, but the oil remained in these structurally unfavorable positions because of the diagenetic sealing. The gas-solution drive in these reservoirs is a result of this sealing. The sequence of events leading to diagenetic entrapment include (1) Triassic and Jurassic migration of hydrocarbons into broad, low-relief post-San Andres structural and structural-stratigraphic traps; (2) rapid occlusion of porosity in the water column beneath oil reservoirs, and (3) Tertiary tilt-out traps.

• OSTI ID: 7195620
• Report Number(s): CONF-9204139-; CODEN: AABUD
• Journal Information: AAPG Bulletin (American Association of Petroleum Geologists); (United States), Vol. 76:4; Conference: American Association of Petroleum Geologists (AAPG) Southwest section meeting, Midland, TX (United States), 21-24 Apr 1992; ISSN 0149-1423
• Country of Publication: United States
• Language: English

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