Palaoeogeographic Evolution And Coal Accumulation Pattern Under A Sequence Stratigraphy Framework Study On Jinci-Taiyuan Formation In Yangzhuang,Gujiao

Yang Zhuang exploration area is located around the Grass village, which is in the south of Gujiao city, Shan Xi province. It is estimated that there is 1.229 billion tons of resources. Lower Permian Shanxi Formation is one of the main coal-bearing strata. With the exploration degree of Yangzhuang shaft area is deepening, there is an urgent need to carry out a comprehensive study of the coal occurrence regularity in Yangzhuang shaft area.This paper researched on Taiyuan Formation sedimentary facies, sequence of division, distribution and accumulation law of seam ancient geography in Yangzhuang exploration areas under the guidance of the theory and methods of classical sequence stratigraphy, petrology, sedimentology, coal geology and other disciplines, combining the data of more than 40 drilling, the analysis of logging data in the field of Yangzhuang exploration area, and the field meticulously catalog of Y2-10 well and Y3-6 well.Studies have shown that Yangzhuang exploration area in Jinci-Taiyuan Formation period was a sea shallow tidal flat carbonate rock- barrier island- lagoon-tidal flat system, and is further divided into seven subfacies and nine microfacies. Secondly, by identifying the sequence boundaries, Jinci-Taiyuan group will be divided into four third-order sequences, eight system domain, and the region was established sequence stratigraphic framework. In SQ1 period there mainly developed a TST and HST. TST is mainly composed of carbonate rocks tidal flat and lagoon. In the eastern part there is not widely developed thickness of the Wu Jiayu limestone. The seawater is flow from the northeast. Tidal flat deposits in HST in which no seam present. In SQ2 period there only developed a TST. Sedimentary facies was mainly composed of the barrier island- lagoon- tidal flat. There was an extensive development of peat bog and thus made up of coal 8# and coal 9# that have large thickness and are widespread in this region. At the end of SQ1 period, the North China platform occurred seesaw movement and formations changed from south to north to north to south. The seawater is from the south-east. In SQ3 period, seawater intruded and back several times, and formed the Miaogou ditch and Maoer ditch limestone that contained a large number of dragonfly fossils. HST mainly included the tidal flat facies, and developed the coal seam 7# which can be regionally mined. In SQ4 period seawater intruded from the south for the last time and formed ramps limestone which is widely distributed in this region. L4 limestone is deposition of pure texture bio broken limestone debris and it is the largest product transgression throughout the late Paleozoic in North China’s. HST lagoon developed set- tidal flat sedimentary facies and tidal flat development with peat bogs and thus formed the coal seam 6# that is developing regionally. Since then the seawater has fully withdrawal from the whole territory of Shanxi.coal seam 8# developed in SQ3 period in TST. The seam distributed in a wide area and thick and the layer is stable. The structure is from simple to complex and the variation law of overall thickness is that the northwest is thick and the southeast is thin. Coal thickness contour and sulfur contour map appears in surprisingly similar, indicating that sea level changes plays an important role on the evolution of coal accumulation control. Coal seam 9# developed in TST and except for no coal in some areas, distributions in this region is stable. The semi-arc seam spread eastward opening and the changeable trends of the overall thickness is the gradual thickening of the thickness to the north and east. Terrain paleogeographic control the thickness changes of coal. In the depression of the peat bog, the underlying water is very deep with no coal exists and the coal seam is substituted by mudstone.