Future Technology and Resources

Even direct flash and binary cycles do not comprise the full spectrum of generation possibilities. Another is the combination of combustion and steam or binary cycles in geothermal energy technology, perhaps to exploit the methane and thermal content of some geopresured resources.

In General, Geopresured resources are not yet a large prospect for electric power generation. A study of 20 specific prospects in Texas and Louisiana by southwest research concludes that the potential exists for extracting 7 x 10^12 ft^3 (200 x 10^15) of methane containing 7 quadrillion (7 x10 ^15) BTU, for total equivalent to about 5300 MW over 30 years. Economic feasibility would depend, for one thing , on a methane pric of a least $5/1000 ft^3 ($17.75/m^3)

The biggest shadow hanging over this resources, however, are the methane content of the geopressured fluid, the cost of production and reservoir life. For example, early indications are that methane content runs about 20-25 ft^3/bbl. of fluid of that reservoirs are small because of their geologic structure. Data for full evaluation of the resource potential are being developed in a $39 million DOE program.

Cost of Synthetic Fuel

In table above various cost estimates for liquid and gaseous fuels produced from coal and shale are presented. The consensus of the industrial companies most involved in these processes is that shale oil is the least costly of any the alternative fossil fuels. It is believed to be roughly cost-competitive with the international price of crude. Taking refinery-grade crude from shale oil as reference and recognizing that fuel derived from multi product processes is independent upon the value assigned each product produces the costs (given in table bellow) of synthetic fuels relative to those shale oil.

Cost of Synthetic Fuel relative to shale

Low-Btu Gas 0.8 to shale

Medium-Btu Gas 0.9 to 1.1

High-Btu Gas (SNC) 1.2 to 1.3

Methanol 1.3 to 1.5

Direct Coal Liquids 1.2 to 1.6

Indirect Coal Liquids 1.4 to 1.6

Gasoline, Middle Distillate 1.5 to 2.0

In term of these capital investment for synthetics fuel plants, the decade of the 70’s has seen an order-or-magnitude escalation in the estimated capital costs. Currently a 250.000 MMBtu/Day (40,000 bbl/day) Plant is estimated to cost 2 to 3 billion dollars, i.e.,$50,000 – 75,000 per daily barrel equivalent. This compares to the $10,000 - $20,000 per daily barrel of conventional petroleum in the most difficult environment in the north sea or Alaska and to cost of under $1,000/daily barrel in area which are easily accessible is shallow wells or large high-production fields. These large cost differentials of synthetic fuel plus the immature state of the technology are strong indications that a cost competitive synfuel technology is not yet truly here. Also the cost of developing the very heavy oil or large tar deposits such as those in Canada or the Orinoco belt in Venezuela are very real competitors to synfuels price in the worlds market.

Technical Challenges

The chart of H/C ratios for various fossil fuels indicates one of the technical challenges facing the advanced fossil fuel technology-namely adding hydrogen to produce the light liquid or gaseous fuels desired. The production of hydrogen, usually by the water-gas reaction, is expensive in both primary energy and dollars. The addition of hydrogen to a solid, low-hydrocarbon-ratio fuel usually requires elevated temperatures and pressures in the presence of catalyst to form a higher-order hydrocarbon. A catalyst second problem with both coal and oil from shale is the organically bound nitrogen and sulfur in coal and oil shale, product that are undesirable in the liquid crude produced. They poison catalyst in refining and are undesirable in finished product because of NOx and SOx emission levels. Hydrogen can also be used to remove these elements but the combination of hydrogen for liquefying plus nitrogen or sulfur removal places enormous demand on the amounts of hydrogen required, affecting both primary resource efficiency and resultant product cost.

The problems associated with producing a liquid hydrocarbon from the kerogen contained in oil shale are different than those in upgrading coal to a liquid product. The kerogen has a much higher H/C ratio (see figure), and for rich oil shales it is the binding agent for the rock which must by pyrolysed thermally or removed by some other process to be available for recovery.