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鄂尔多斯盆地西缘麦垛山煤矿侏罗系煤层精细对比

Fine correlation of jurassic coal seams in Maiduoshan Coal Mine on western edge of the Ordos Basin

  • 摘要: 鄂尔多斯盆地西缘麦垛山煤矿共发育19层煤层,大部分煤层空间分布不稳定,且该区构造复杂,褶皱经过,断层众多,煤层对比困难,多年来一直困扰地质勘探与煤矿采掘设计工作。采用钻井岩心地质编录岩心观察、测井、三维地震等手段,通过井震结合高分辨率层序地层划分、沉积微相划分、地层序列识别、特殊地质标志建立以及构造控制地层的理论分析,确定鄂尔多斯盆地西缘麦垛山煤矿煤层对比方案。经研究,划分出3个长周期基准面旋回(LSQ1、LSQ2、LSQ3),较稳定厚煤层均分布于长周期基准面旋回的顶部和长周期基准面上升半旋回的顶部,在基准面上升半旋回中煤层厚度具有增加的趋势,而在基准面下降半旋回中煤层具有变薄的趋势。LSQ1、LSQ2、LSQ3中煤层分别形成于分流间湾、泛滥平原、分流河道间沉积微相,LSQ1煤层多夹在正旋回地层序列之间,LSQ2中煤层多夹于粉砂岩之间,LSQ3中煤层多夹在砂岩之间。LSQ1底部厚层平行层理砂岩、LSQ3顶部厚层块状层理砂岩、厚度较大的18煤,12煤之上厚层黑色泥岩均为典型对比标志。构造导致了煤层的重复、产状变化、厚度减小、埋深改变、顶板的裂隙增加等特征。综合性煤层对比方法为该区煤层对比提供了新的思路,提高了煤层对比的准确性,为煤田勘探与煤矿生产提供了理论依据。

     

    Abstract: The Maiduoshan coal mine on the western edge of the Ordos Basin features a total of 19 coal seams. Most of these seams exhibit unstable spatial distribution, and the area is characterized by complex structures, including folds and numerous faults, making coal seam correlation challenging and a persistent issue in geological exploration over the years. By utilizing drilling core geological logging, well logging, 3D seismic, and other techniques, and through the integration of well-seismic data with high-resolution sequence stratigraphy division, sedimentary microfacies identification, special stratigraphic sequence identification, establishment of special geological markers, and theoretical research on structure-controlled stratigraphy, a coal seam correlation scheme for the Maiduoshan Coal Mine on the western edge of the Ordos Basin has been determined. This scheme divides the area into three base-level cycles (LSQ1, LSQ2, and LSQ3). The relatively stable thick coal seams are distributed at the top of the base-level cycles and the top of the ascending half-cycle of the base level. The LSQ1 coal seams are mostly sandwiched between normal cycles, the LSQ2 coal seams are mostly sandwiched between siltstones, and the LSQ3 coal seams are mostly sandwiched between sandstones. The thick-bedded planar stratification sandstones at the bottom of LSQ1, the thick-bedded massive stratification sandstones at the top of LSQ3, the relatively thick Coal Seam 18, and the thick black mudstones above Coal Seam 12 are all typical correlation markers. At the anticlinal locations, the coal seams are laterally offset and fractured. The flower-like structures in the anticlinal areas show a steep drop in coal seam depth from bottom to top, and the thrust faults cause duplication of Coal Seam 18 at the anticlinal locations. The thrust faults also lead to an upward bending of the strata, resulting in reduced coal seam thickness, and an increase in the dip angle of the strata, causing changes in the dip direction on both sides of the flower-like structures. The comprehensive coal seam correlation method provides a new approach for coal seam correlation in the area, improves the accuracy of coal seam correlation, and provides a theoretical basis for coalfield exploration and coal mine production.

     

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