| 摘要 |
<p>A secondary (or tertiary) oil recovery process is disclosed involving the injection of a polysaccharide polymer naturally produced by certain bacteria in a solubilized form into the oil sand or horizon. When such polymer is injected, it is solubilized in alkali solution such as sodium hydroxide. Solubilized (unprecipitated) polymer may be used as a secondary recovery sweep fluid, per se. Within the formation, the polysaccharide polymer may be precipitated by the later injection of an acid solution or carbon dioxide. The order of injection of the acidic materials and the solubilized polymer is not critical, except with respect to carbon dioxide injection, which must follow the solubilized polymer injection. By such precipitation, high permeability zones are selectively blocked off, giving sweep access primarily to the lower permeability zones containing mostly oil.</p> |
