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鄂尔多斯盆地北部为气源运移的指向区，具有较好的生储盖条件。下古生界气源岩为下奥陶统马家沟组碳酸盐岩，上古生界气源岩为石炭系太原组和二叠系山西组碎屑岩；下古生界储集层为马家沟组风化壳，上古生界储集层为石炭系本溪组、太原组和二叠系山西组、下石盒子组，前者以碳酸盐岩为主，后者以碎屑岩为主；下古生界风化壳气藏的区域盖层为石炭系底部的泥岩、铝土岩及铝土质泥岩，上古生界气藏的区域盖层为二叠系上石盒子组泥质岩。由于天然气聚集于两个不同的领域，其成藏各具特点，因而天然气富集控制因素就有所不同：下古生界天然气富集主要受气源、区域性岩相变化、盖层及古地貌影响，而控制上古生界天然气富集的决定因素有气源、砂岩体、局部构造的发育程度及源岩生烃期与圈闭形成期的匹配。

CONTROLLING FACTORS OF GAS RESERVOIR FORMATION IN THE NORTH OF EERDUOSI BASIN

??The north of Eerduosi Basin is the migration-oriented region of natural gas,being of fair source-reservoir caprock conditions.The gas source rocks in the Lower Paleozoic are the carbonate rocks of the Majiagou Formation,Ordovician,while those in the Upper Paleozoic are the clastic rocks of the Taiyuan Formation,Carboniferous and the Shanxi Formation,Permian.The reservoir bed in the Lower Paleozoic is the weathering crust of the Majiagou Formation,while the reservoir beds in the Upper Paleozoic are the Benxi Formation and Taiyuan Formation,Carboniferous and the Shanxi Formation and Lower Shihezi Formation,Permian;the former is the mainly carbonate rocks and the latter the clastic rocks.The regional caprocks of the gas reservoirs in the weathering crust of the Lower Paleozoic are the mudstone,bauxitite and bauxitic mudstone at the bottom of the Carboniferous,while those of the gas reservoirs in the Upper Paleozoic are the argillaceous rocks of the Upper Shihezi Formation,Permian.Because the natural gas was accumulated in two different fields and its reservoir formation is of various properties,the controlling factors of gas accumulation are different.The natural gas accumulation in the Lower Paleozoic was mainly controlled by the gas source,regional facies change,caprock and palaeogeomorphology,while the decisive factors controlling the natural gas accumulation in the Upper Paleozoic were the gas source,sand body,the development degree of regional structure,and the matching of source-rock's hydrocarbon generation period with trap formed time.