Survey of Energy Resources 2007
Natural Bitumen and Extra-Heavy Oil Country Notes
United States of America
The United States was endowed with very large petroleum resources, which are to be found in nearly all the various types of geologic basins. The resources of extra-heavy oil and natural bitumen likewise are distributed in numerous geological settings. Geologically, about 80% of the discovered US natural bitumen is deposited in basins similar to the Western Canada Sedimentary Basin. Such basins possess ideal conditions for occurrences of degraded oil. However, the bitumen deposits of the United States are much smaller, much less numerous, but more scattered. About 98% of the reported extra-heavy oil is found in basins which evolved along the rift-faulted, convergent continental margin of California where the island arcs which originally trapped the sediments against the land mass to the east have been destroyed. Distillation of oil from Casmalia tar sands in California was attempted in 1923. Many tar sands deposits in the United States have served as sources of road asphalt, but this industry disappeared with the advent of manufactured asphalt tailor-made from refinery stills. The largest deposits in the lower conterminous 48 states are in Utah. During the 1980s US energy analysts studied criteria, both technical and economic, for supply of synthetic crude oil from tar sands and several tar sands pilot projects were started. With the decline in and stagnation of crude oil prices from the later 1980s to about 2000, there was little interest in pursuing these projects. The recent sustained increases in oil prices have revived this interest.
The extra-heavy oil accumulations in California account for about 97% of the extra-heavy oil produced to date. These are typically reservoirs found in large fields, multiple reservoir fields, and fields that may have already installed a thermal recovery operation for production of heavy oil in underlying reservoirs or overlying reservoirs.