| 摘要 |
In the preparation of an underground strata of solid bitumen (such as coal) for underground gasification a heated mixture is injected into the strata through a borehole at a pressure sufficient to fracture the formation, the mixture comprising a gas or gases which are not condensible under the conditions prevailing in the strata and hydrocarbons which are condensible under such conditions. Suitable hydrocarbons are benzene, pentane, hexane, heptane, and suitable gases are methane, oxygen, steam and air. The gases form small bubbles in the hydrocarbons which condense in the colder parts of the fracture. After fracturing explosions may be set off in gas removal boreholes spaced from the injection boreholes, and prior to fracturing the strata may be treated by explosions. After fracturing explosives or oxygen releasing compositions may be deposited in the fracture, the contents of the injection borehole are ignited, and finally air and then oxygen enriched air is supplied through the injection borehole and the required gas issues from the removal borehole. The gas issuing from the removal borehole may be recycled and reheated until the strata is sufficiently permeable for the production of gas. Where the lower part of the strata is not permeable, the process of gasefication is carried out in the upper part to heat the lower part which is supplied with oxygen and hydrocarbons, or water and hydrocarbons, to render it porous. The mixture may be heated by an atomic reactor or an electrical heater. |
