关键词: 碳酸盐岩, 烃源岩, 有机质类型, 有机碳下限, 有机碳恢复系数

Abstract: Much of the marine carbonate rocks in China are organic carbon poor (mean organic carbon content values generally <0.20%),but are still regarded as source rocks due to the conventionally proposed minimum organic carbon content required for carbonate source rocks (0.10% or even lower). No commercial accumulation was found related to these carbonate rocks after over ten years of exploration, showing the incorrectness of the above minimum organic carbon content. Obtaining such a low minimum value is caused by the unreasonable hypotheses of high hydrocarbon potential of organic matter in marine carbonate rocks and high expulsion ratio of hydrocarbon from carbonate rocks,by overestimating organic matter lost during maturation of carbonate rocks, and by omitting the hydrocarbon lost during second migration. Integrated consideration of above factors will reach the following: (ⅱ) The minimum organic carbon content for a carbonate source rock should be gained by an analogy in exploration instead of by an experiment. (ⅱ) The minimum organic carbon content values for a carbonate source rock, for a high to over mature source rock, and for a gas source rock are not necessarily lower than those for a mudstone source rock,for a mature source rock, and for an oil source rock respectively. They all should be 0.40%~0.50% at least.

Key words: carbonates, source rock, organic carbon content, China