| As the raw material of nuclear power and nuclear weapons in China,uranium resources play an important role in clean energy and national defense.China also attaches great importance to uranium exploration.In recent 20 years,great breakthroughs have been made in sandstone uranium exploration in north China,especially in Ordos Basin.Ordos Basin covers an area of about 300,000 square kilometers and is rich in internal resources,such as oil and gas,coal and uranium resources.Several large uranium deposits have been discovered in the northeastern and northern parts of the basin,while exploration in the southwestern margin remains scarce and unproductive.Recently,the uranium exploration in the southwest margin of Ordos has been strengthened,and a new type of uranium deposit has been discovered initially,and the exploration is continuing.The exploration of sandstone-type uranium deposits in Pengyang area,southwest margin of Ordos Basin is studied in this paper.Supported by the project of Deep Exploration Technology Demonstration of Northern Sandstone Type Uranium Energy Mineral Base and Demonstration of Deep Resource Accumulation demonstration of Jingchuan Uranium Mine in Ordos Basin,seismic,oil and gas,geology and gravity data were collected in Pengyang area and a series of geophysical comprehensive studies were carried out for luohe Formation,the uranium target layer.Through processing interpretation and comprehensive inversion of seismic data in the study area,combined with three-dimensional inversion of gravity data in the area,interpretation of geological data and drilling data,finally three-dimensional modeling of uranium target layer and pointing out favorable uranium-bearing horizon,the research has achieved the following achievements and understandings:(1)By extracting the attributes of instantaneous amplitude and instantaneous frequency of seismic data,the information of ore-bearing and non-ore-bearing layers is analyzed,and the location and frequency response characteristics of ore-bearing layers in seismic profile are determined.By analyzing gravity data,especially residual gravity anomaly and gravity field notch,the fault distribution in the study area was obtained.(2)On the basis of geophysical data processing and analysis,combined with geological and drilling data in the study area,the structural analysis process is designed,the structural characteristics and sand body distribution of Luohe Formation are obtained,and the top and bottom structure maps and thickness maps of Luohe Formation are compiled.(3)From the joint inversion results of well and seismic,the overall characteristics of ore bearing sand bodies in Luohe Formation are obvious.The inversion profile of aeolian sand bodies shows earthworm shape,and the wave impedance is 7200-9500,medium and weak.The low-lying parts of faults are favorable uranium bearing sandstone bodies,which is basically consistent with the drilling results.(4)Fast 3d modeling of gravity constrained inversion can obtain the strata,basic structure and physical property distribution characteristics of the study area.(5)Through the establishment of a THREE-DIMENSIONAL model of the target horizon,the Spatial distribution of The Luohe Formation is a low-uplift shape,the favorable horizon is controlled by the structure,mainly distributed in the relatively low-lying area near the fault,and the reductive oil and gas from deep reaches the target horizon through the fault.(6)The sand body of Luohe Formation deposited in eolian environment lacks the carbonized plant debris needed for sandstone type uranium mineralization.The comprehensive study of seismic,gravity information and geological data in this paper shows that the faults developed in Luohe Formation can communicate with the sand body of the target layer and deep oil and gas reservoirs,and uranium is reduced,precipitated and enriched for mineralization. |
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