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1989年6月在鄂尔多斯盆地北部靖边县发现了我国目前面积最大的气田,现已探明含气面积达4000km~2,天然气主要储存于下奥陶统马家沟组上部的白云岩孔隙(O_1m_5~4)及其上面的古风化溶蚀带(O_1m_5~(1～2))中。上覆为晚石炭世滨海沼泽相地层,也含气。这里发育有两套气源岩:(1)下奥陶统上部马家沟组(O_1m)为碳酸盐岩,折算及。值高达2.0％～5.0％,属腐泥型过成熟气源岩;(2)上石炭统太原组(C_3t)～下二叠统山西组(P_1s)含煤地层,R_0值为1.5％～2.5％,属腐植型高成熟气源岩。由于对中部气田天然气碳同位素资料认识上的不同及混源现象的存在等,使人们对该气田的主力气源层和天然气成因类型的判识上发生了分歧。
In June 1989, the largest gas field in China was discovered in Jingbian County in the northern part of Ordos Basin. The area of gas with an area of 4,000km ~ 2 has been proven, and the natural gas is mainly stored in the dolomite pores in the upper part of the Lower Ordovician Majiagou Formation O_1m_5 ~ 4) and its paleo-erosion zone (O_1m_5 ~ (1-2)). Overlying the late Carboniferous coastal marsh facies, but also gas. There are two sets of gas source rocks developed here: (1) Upper Paleo-Ordovician Majiagou Formation (O_1m) is a carbonate rock that is converted into a carbonate rock. (2) Upper Carboniferous Taiyuan Formation (C_3t) ~ Lower Permian Shanxi Formation (P_1s) coal-bearing strata with R_0 value of 1.5% ~ 2.5 %, Is a humus-type mature source rock. Due to the difference of understanding of natural gas carbon isotope data in central gas field and the existence of mixed source phenomena, people disagree on the identification of the main gas source and gas genesis types in this gas field.