Research on relationship of oil-gas and sandstone-type uranium mineralization of northern China

Interaction between oil-gas and sandstone type uranium has aroused much interest among geologists, especially uranium geologists. In spite of rapid development of mineralization theory for single energy mines, the study of interaction is very insufficient. Therefore, this problem should be regarded as the key frontier scientific issue which deserves investigation. Based on an analysis of distribution characteristics of uranium and oil-gas, microscope testing, geochemical calculation, it can be inferred that uranium enrichment can be improved by adsorption, reduction, uranium-supply and preservation of oil-gas, in which asphalt and organic acid, cracked by oil-gas, can adsorb uranium strongly. For reduction of oil-gas, high valence and activated uranium ion can be reduced to +4 valence and form stable uranium minerals by more reducing gas, such as H₂, CH₄, CO, and H₂S. By means of acid dissolving, extraction and metallic-organic complexation, organic acid, produced by the interaction of oil-gas and SO₄^2-, can accumulate partial uranium nearby surrounding rocks. And then this uranium can be released in mineralization location, which can reform mineralization and increase the source of uranium. Besides, more reducing H₂, CO, escaping from oil-gas, can cause acidification and kaolinization of the formation, which leads to the feature that the oxidation zone is slightly alkaline and the metallogenic belt is slightly acidic. Therefore, the interaction between oil-gas and uranium can be very important for the determination of uranium-bearing beds, locating of uranium deposits, developing of mineralization theory, and oil-gas exploration guided by 'chimney effect'.