A fuller discussion of the geologic provinces and their relative ranking in terms of total known petroleum volume is given in USGS Open File Report 97-463 entitled Ranking of the world s oil and gas provinces by known petroleum volumes . The relative ranking of petroleum provinces on this map is discussed in Open File 97-463 to which the reader is referred. For the World Energy assessment, the world was divided into eight energy regions which correspond approximately with the economic regions of the world as defined by the U.S. Department of State. Precambrian rocks are undivided and consist of sedimentary, metamorphic, and igneous types. Each region was divided into geologic provinces.
Some provinces contain multiple basins that are genetically related.
An attempt was made to number the provinces in geographical order. In Northern Africa, the numbering starts in the northeast corner of Africa, a continuation of the numbering of the Middle East part of Region 2. Numbering in Region 7 begins in the northwest part of the region, with the second and third digits sequentially numbering provinces north to south, west to east.