CHARACTERISTICS AND FORMATION MECHANISM OF CARBONIFEROUS BENXI FORMATION BAUXITE RESERVOIR IN NORTHEASTERN ORDOS BASIN
In recent years,significant strides have been made in gas exploration within the bauxite depos-its of the Carboniferous Taiyuan Formation in the Longdong area of the southwest Ordos Basin,marking a new frontier in gas exploration.Research indicates that there is potential for natural gas exploration in the Carboniferous Benxi Formation bauxite in the northeastern Ordos Basin.This study investigates the reser-voir characteristics and formation mechanisms of the Benxi Formation bauxite in the northeastern Ordos Basin through methods including optical thin section observation,scanning electron microscopy,energy spectrum analysis,whole rock and clay mineral X-ray diffraction,physical property analysis,and trace el-ement analysis.Research findings indicate the sedimentary sequence of Carboniferous Benxi Formation bauxite comprises ferritic bauxite and aluminous mudstone at the base,transitioning to high alumina baux-ite and alumina mudstone in the middle,and concluding with alumina mudstone at the top.The bauxite rocks predominantly exhibit structures such as pisoloidal,porous massive,compact,and clastic breccia-ted.They are composed primarily of alumino-ferric minerals,clay minerals,titanium minerals,and trace minerals.In terms of reservoir characteristics,the bauxite reservoirs in the study area are notably well-de-veloped,featuring honeycomb-like dissolution pores and intercrystalline pores as the primary reservoir types.Porosity ranges from 0.3％to 11.6％(average of 2.86％),and permeability spans from 0.002 to 21.400×10-3 μm2.These reservoirs exhibit favorable physical properties with good pore connectivity.On average,mobile fluid saturation exceeds 45％,suggesting significant reservoir potential.The controlling factors influencing the Benxi Formation bauxite reservoir in the northeast basin include early tectonic uplift movements providing diagenetic materials,an enclosed to semi-enclosed tidal flat-shore environment foste-ring diagenetic processes,and micro-paleotopography of buried pit-terraces influencing reservoir quality and preferred exploration areas.Additionally,organic acids have further modified reservoir pores during later stages.These research outcomes serve as crucial guidance for exploring new bauxite gas reservoirs in the northeast Ordos Basin.
万方数据
维普
