The Natural Gas Resources Potential Evaluate Of The Middle Majiagou Formation In The East Side Of The Ordos Basin

In this paper,we take the carbonatite in middle Majiagou Formation as an object of study.The research is based on previous studies,author studied in detail analyzed the characteristic of hydrocarbon source rocks,distribution of hydrocarbon source rocks and the characteristic of hydrocarbon generation capacity,by comprehensively utilizing outcrops,core observation,data of logging and drilling,Combined with the principle and methods of sedimentology,organic geochemistry and other disciplines.And evaluation of hydrocarbon resources potential by using geological analogy-probability method:The source rocks in the study area are mainly distributed in the Upper Carboniferous Benxi Formation-Lower Permian Shanxi Formation and M3?M5 members of Majiagou Formation in Ordovician.The organic matter type of the upper Paleozoic coal measure source rocks is type III and the content of organic carbon is high,which is mainly in the high-over mature stage.The carbonate source rocks of Majiagou Formation are mainly limestone and dolomite,and the content of organic carbon is low.Most of them are in the range of 0.2%~0.4%,and the organic matter types are mainly type ?.Thermal evolution degree of organic matter is in the high-mature stage.The thickness of the dark mudstone in the Upper Paleozoic is 60~100m and the thickness of the coal seam is 10~25m.The hydrocarbon source rocks of Majiagou Formation in Ordovician are mainly distributed in the five and three member of Majiagou Formation.The thickness can reach 50~100m.According to the characteristics of hydrocarbon generation and expulsion,the content of organic carbon and the reservoir characteristics of carbonate rocks in Ordos Basin,the lower limit of the organic carbon content of carbonate source rocks in Ordos Basin is 0.25%.The upper Paleozoic source rocks in the study area are widely distributed on the plane,have higher gas generating intensity,which reaches 20~30.0×10~8m~3/km2,and the hydrocarbon generating ability is strong.The hydrocarbon generation intensity of the source rocks in the Majiagou Formation is about 2.5~10×10~8m~3/km2,and the hydrocarbon generation capacity of the source rocks is generally low.The natural gas resource potential in the eastern Ordos Basin is evaluated by using the method of geological analogy-probability.The geological resources of the semi-annular natural gas accumulation zone in the eastern Ordos Basin are 6400~18700×10~8m~3.The three favorable exploration areas: the M55 block in area of Wushenqi,the M57 block in area of Hengshan-ansai,the M59 block in area of Jingbian.The total amount of three strategic objectives are 5290×10~8m~3.