This paper deals with the metallogenic model of the sandstone type uranium deposit in the northeastern Ordos Basin from aspects of uranium source, migration and deposition. A superposition metallogenic model has been ...This paper deals with the metallogenic model of the sandstone type uranium deposit in the northeastern Ordos Basin from aspects of uranium source, migration and deposition. A superposition metallogenic model has been established due to complex uranium mineralization processes with superposition of oil-gas reduction and thermal reformation.展开更多
The Markit Slope is an important area for the petroleum exploration in the Tarim Basin. Elucidation of the oil filling history of discovered oilfields has great significance for recognizing the accumulation processes ...The Markit Slope is an important area for the petroleum exploration in the Tarim Basin. Elucidation of the oil filling history of discovered oilfields has great significance for recognizing the accumulation processes of the whole region. Using molecular geochemistry, fluid inclusion techniques and basin modeling, we studied the oil filling process of the Bashituo Oilfield that is located in the west of the Markit Slope. The molecular migration indexes, such as the methyldibenzothiophene ratio （4-/1-MDBT）, trimethylnaphthalene ratio （TMNr） and pyrrolic nitrogen compounds content, decrease from west to east, indicating that the charging direction and migration pathways are from west to east. Lithological analysis and homogenization temperatures of saline fluid inclusions accompanied with oil fluid inclusions suggest that two charging periods occurred in the Devonian oil reservoir. Combining the burial history and heating history of well BT4, Basinmod 1D software modeling shows the two oil filling periods are from 290 Ma to 285 Ma and from l0 Ma to 4 Ma, respectively, and later oil filling dominates. This study may be helpful to understand the accumulation process and provide useful references for oil and gas exploration in the Markit Slope.展开更多
Dongsheng sandstone-type uranium deposit is located in the northern part of Ordos Basin,occurring in the transitional zones between gray-green and gray sandstones of Jurassic Zhiluo Formation.Sandstones in oxidized zo...Dongsheng sandstone-type uranium deposit is located in the northern part of Ordos Basin,occurring in the transitional zones between gray-green and gray sandstones of Jurassic Zhiluo Formation.Sandstones in oxidized zone of the ore bed look gray-green,being of unique signature and different from one of ordinary inter-layered oxidation zone of sandstone-type uranium deposits.The character and origin of gray-green sandstones are systematically studied through their petrology,mineralogy and geochemistry.It is pointed out that this color of sandstones is originated from secondary oil-gas reduction processes after paleo-oxidation,being due to acicular-leaf chlorite covering surfaces of the sandstone grains.To find out the origin of gray-green sandstone and recognize paleo-oxidation zones in the ore bed are of not only theoretical significance for understanding metallogenesis of this kind of sandstone-type uranium deposit,but also very importantly practical significance for prospecting for similar kind of sandstone-type uranium deposit.展开更多
文摘This paper deals with the metallogenic model of the sandstone type uranium deposit in the northeastern Ordos Basin from aspects of uranium source, migration and deposition. A superposition metallogenic model has been established due to complex uranium mineralization processes with superposition of oil-gas reduction and thermal reformation.
基金supported by the Natural Science Foundation of China (Grant No.40972089)the Foundation of the State Key Laboratory of Petroleum Resources and Prospecting (Grant No.PRPDX2008-01)
文摘The Markit Slope is an important area for the petroleum exploration in the Tarim Basin. Elucidation of the oil filling history of discovered oilfields has great significance for recognizing the accumulation processes of the whole region. Using molecular geochemistry, fluid inclusion techniques and basin modeling, we studied the oil filling process of the Bashituo Oilfield that is located in the west of the Markit Slope. The molecular migration indexes, such as the methyldibenzothiophene ratio （4-/1-MDBT）, trimethylnaphthalene ratio （TMNr） and pyrrolic nitrogen compounds content, decrease from west to east, indicating that the charging direction and migration pathways are from west to east. Lithological analysis and homogenization temperatures of saline fluid inclusions accompanied with oil fluid inclusions suggest that two charging periods occurred in the Devonian oil reservoir. Combining the burial history and heating history of well BT4, Basinmod 1D software modeling shows the two oil filling periods are from 290 Ma to 285 Ma and from l0 Ma to 4 Ma, respectively, and later oil filling dominates. This study may be helpful to understand the accumulation process and provide useful references for oil and gas exploration in the Markit Slope.
基金Suppored by the National Basic Research Program of China(Grant No.2003CB214608)and BOG Uranium Geology Research Project(Code:HDKY20020501)
文摘Dongsheng sandstone-type uranium deposit is located in the northern part of Ordos Basin,occurring in the transitional zones between gray-green and gray sandstones of Jurassic Zhiluo Formation.Sandstones in oxidized zone of the ore bed look gray-green,being of unique signature and different from one of ordinary inter-layered oxidation zone of sandstone-type uranium deposits.The character and origin of gray-green sandstones are systematically studied through their petrology,mineralogy and geochemistry.It is pointed out that this color of sandstones is originated from secondary oil-gas reduction processes after paleo-oxidation,being due to acicular-leaf chlorite covering surfaces of the sandstone grains.To find out the origin of gray-green sandstone and recognize paleo-oxidation zones in the ore bed are of not only theoretical significance for understanding metallogenesis of this kind of sandstone-type uranium deposit,but also very importantly practical significance for prospecting for similar kind of sandstone-type uranium deposit.
