| Description |
Since the mid 1970s, IIT Research Institute (IITRI) has been developing an energy efficient, in situ radio-frequency (RF) heating process. Large blocks of oil shale or tar sand typically found in the Western United States have been emplanted with closely spaced electrodes and excited electromagnetically with high-frequency RF energy. This process has efficiently heated the blocks in situ to temperatures high enough to generate autogeneous vapor drives and to develop some in situ upgrading. A version of the IITRI RF process can be applied to thick, shallow, moist oil sands or heavy-oil deposits by changing the configuration to allow placement of the electrodes from the surface, thus permitting efficient use of energy at very low frequencies, such as 60 Hz. An efficient low-cost power delivery system and a "coolelectrode" array design were developed, which prevent vaporization of the water in the deposit near the electrodes. The bulk of the deposit could thus be heated above the vaporization point of water to develop an autogeneous vapor drive or the deposit could be further heated to cause in situ upgrading. Computer-aided analysis, which was used to consider the heating patterns and thermal diffusion of the two approaches, demonstrated the advantage of applying the "cool-electrode" design to a five-spot, electrode-well pattern compared to a possible 60 Hz heating approach. The five-spot heating approach creates excessive temperatures near the electrodes. This excess not only wastes energy, but can also stop the heating process if the water near the electrode is vaporized. With the "cool-electrode" approach, however, temperatures near the electrodes can be kept below the vaporization point while temperatures within the bulk of the deposit reach very high values. These analytical results were validated by using 60 Hz to heat a 3-1/2 ton block of tar sand, simulating on a l/20th size scale model, a section of a full-size field operation. Various product recovery options are available such as gravity-drive, autogeneous vapor drive, or waterf lood. Depending on the deposit, the product can be recovered through conventional vertical wells or horizontal drain holes. When the comprehensive cost analyses are applied to a thick, rich, shallow deposit producing 1500 barrels per day, operating costs are about $6 to $8 per barrel and pre-production capital requirements about $3,000 to $6,000 per barrel per day. |
