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The AAPG/Datapages Combined Publications Database

AAPG Bulletin


Volume: 65 (1981)

Issue: 3. (March)

First Page: 559

Last Page: 559

Title: Upper Cretaceous Tocito Sandstone Lentil of Mancos Shale, San Juan Basin, New Mexico--Is There Any Oil Left?: ABSTRACT

Author(s): James E. Fassett

Article Type: Meeting abstract


The Upper Cretaceous Tocito Sandstone Lentil of the Mancos Shale consists of a series of northwest-trending linear sandstone bodies in the San Juan basin of New Mexico. This sandstone unit, which has produced most of the basin's crude oil (more than 125 million bbl to date), was referred to as the "Gallup" Sandstone for many years. Recent stratigraphic studies of the Tocito by several authors clearly demonstrated that the Tocito Sandstone Lentil is a totally different stratigraphic unit from the Gallup; thus, the Tocito name was reinstated as a lentil of the Mancos Shale. (Actually, the "Tocito" was thought to be part of the Gallup years ago and the Tocito name was dropped in favor of the "Gallup" name.) Even though hundreds of holes drilled to produce natural gas from th deeper Dakota Sandstone have penetrated the Tocito, these holes cannot be thought of as Tocito dry holes because, for many of them, no attempt was made to test the Tocito for its possible oil potential. There is still a good chance that significant amounts of oil remain to be found in the Tocito.

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Copyright 1997 American Association of Petroleum Geologists