Section VI. Recovery
Published:January 01, 1987
For many, the idea of an energy crisis has passed, but it behooves those who accept the vagaries of government and international dissent to prepare for the future, when spot shortages of energy are likely to occur again. Since petroleum has selected uses and properties for which few or no substitutes are available, we need to reevaluate continually the potential of unconventional recovery of petroleum from heavy crude oils and tar sands.
Several methods are worthy of consideration. Among these are (1) recovery using selected fluids (EOR), to find the best mobilization fluids, e.g., CO2; (2) recovery by conventional mining methods, e.g., room and pillar, long-wall mining, modified block caving, pressurized block caving coupled with hydrofracing, etc.; (3) remote mining, using robots; (4) possible mobilization using gases other than CO2 and steam; (5) consideration of solidification techniques coupled with conventional mining; (6) geothermal energy; (7) biological methods; and (8) electrical methods.
While these approaches are, at present, completely uneconomic and impractical, we cannot predict when the next technological breakthrough will occur that could make these concepts possible. I urge a searching look down the long corridors of the future. The only hold-back is our own timidity to consider “far-out” ideas.
Figures & Tables
Exploration for Heavy Crude Oil and Natural Bitumen
Gross volumes of oil, which must be kept in mind to address the volume/size framework, may be thought of in order from largest to probably smallest volumes as follows: (1) generated; (2) dissipated; (3) degraded/ partially preserved; and (4) trapped and conventionally producible. Basic knowledge of these volumes may be from greatest to least in essentially reverse order.
The 332 largest known accumulations (less than 1% of the total number) account for more than three-quarters of the known 7.6 trillion bbl of oil and heavy oil or tar in more than 40,000 accumulations in the world. About 2.4 trillion bbl of estimated undiscovered conventional oil added to the known volume of 7.6 trillion bbl yields a total of 10 trillion bbl known or reasonably estimated. World-wide cumulative production of about 500 billion bbl of oil accounts for only 5% of the gross.
Oil in place must be estimated for conventional oil fields before comparison with heavy oil and tar accumulations. The size range of accumulations considered in the size distribution of the 332 largest known accumulations is from 0.8 to 1850 billion bbl of oil. The smallest conventional fields in the distribution are about 1 billion bbl because the size cut-off is 0.5 billion bbl of oil recoverable. The size distribution of the 332 largest known accumulations approaches log normal and is overwhelmed by the largest three supergiant tar deposits that hold nearly half of the total 5495 billion bbl.
Globally, the largest three accumulations, all heavy oil or tar, are in South and North America; the two largest conventional oil fields are in the Middle East. Prudhoe Bay and East Texas fields rank 18 and 34, respectively, in descending size order.