Sequence-paleogeographic Of The Middle Ordovicia In The North Of Tianhuan.Ordos Basin

Marine strata are widely distributed in the northern section of Tian Huan, theOrdovician, Ordos Basin, Tian Huan islocated in the Northwest,Ordos Basin, In recentyears,Found that reefs and beach,the cave-type dolomite reservoir and have broadprospects. Learn to structural geology, sedimentary geology, sequence stratigraphy as aguide,based on outcrop and drilling data, rock, the integrated results of previousstudies,studies on the stratigraphic sequence,depositional systems, rock facies andpalaeogeography of Tian Huan, Middle Ordovician,Ordos Basin, reveal thedistribution of matter in different periods of sequence stratigraphic framework, aimedat strengthening the research sedimentary microfacies in the gas-bearing formation inthe region, Provide the basis for different types of reservoir prediction. The mainresearch content and achievements have the following several aspects:Regional magma characteristics, paleogeographic evolution, biological evolutionand other research show that; Early Ordovician North Qilian ocean has been theformation of trench-arc system, the Helan Mountain region in the bcke arc basin nearthe mainland side, the Kelimoli period of structural transformation, the gradualevolution of the retroarc foreland basin, foredeep of the deposition of a gravity flow, theforebulge have uplift and the formation of central paleohigh.Based on the detailed lithofacies in the northern section of Tianhuan, and dividedinto four depositional system in the Middle Ordovician, the platform, platform margin,slope, basin, and further subdivide in sedimentary facies, subfacies, microfacies. andthe establishment of a depositional model for different periods.Focus on gas-bearing formatim, the Table-Mountain and Kelimoli group is divided,Group is divided into two of three-sequence, six of four-sequence, corresponding to thefour sections of the ancient uplift of the eastern part of the Ma4andMa5, Kelimoliwhere the group divided into a three-sequence, three four sequence and the comparisonof the four sequence to establish a sequence stratigraphic framework. On the basis of the deposition system and lithology, microfacies of the four sequencemapping unit, compilationf the North Tianhuan focus oily gas reservoir through linesedimentary microfacies map, reflecting the different periods of lithology microfaciesand the distribution of reservoir rock characteristics. And to analyzed the factors aboutlithofacies and paleogeographic evolution of the trend.