AREAS OF STUDY


     The oil and gas resources of the United States were evaluated on the
basis of interpretation of the geology of its petroleum provinces. For
this study, the United States was divided into eight regions, which, in
turn, encompassed 71 separate provinces. Regional and provincial
boundaries are illustrated in figure 3. The regions are basically
geographic but are intended to provide broad geologic groupings of
provinces. The provinces themselves are based on natural geologic
entities and may include a single dominant structural element or a
number of contiguous elements. The provinces are named for structural
or geographic features within their boundaries.

     The regions and provinces used in this study are generally similar 
to those used in recent USGS assessments, with a few changes. Notable
among these changes are the consolidation of the provinces of Alaska
into a simpler three-province scheme, the merging of the Atlantic Coast
and Eastern Interior into a single region, the inclusion and assessment
of Florida with the rest of the Gulf Coast, and the movement of the
boundary between the Pacific Coast Region and the Colorado Plateau and
Basin and Range Region along more geologically defined boundaries, such
as the San Andreas fault in southern California. A few other smaller
changes have also been made and are described in the supporting play-
level documentation included in the CD-ROM (Gautier and others, 1995).