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我国西北大部分地区在早白垩世处于挤压为主的构造环境，但共和地区处于伸展的构造环境，发育了巨厚的下白垩统湖相沉积。我们首次在共和盆地下白垩统发现了一套２５８．１５ｍ 厚的烃源岩。这一发现改变了以往西北白垩系烃源岩仅分布在祁连－秦岭以北的观点， 这对于研究我国西北地区白垩系烃源岩的分布和油气田的形成具有重大意义。共和盆地下白垩统从下到上分为万一段、万二段、万三段、万四段。万一段和万四段是炎热干旱气候条件下形成的红色沉积， 基本没有生烃能力。万二段烃源岩是一套炎热潮湿气候条件下形成的浅湖－半深湖相沉积， 烃源岩有机质丰度达到了中到好烃源岩的丰度标准， 干酪根类型以Ⅰ２ 型为主。该烃源岩在Ｋ２ 早期（９０．０１Ｍａ） 进入生油门限， 开始生油， 从Ｋ２ 晚期（７４．１１Ｍａ） 以来，一直处于大量生油的成熟阶段。下白垩统万三段沉积时期， 水体时深时浅， 暗色泥岩和红色泥岩交替出现。暗色泥岩属于中等烃源岩， 其有机质类型主要为Ⅱ型。它在晚白垩世 （７８．０２Ｍａ） 进入生油门限， 但一直到第四纪 （１．５Ｍａ） 才进入大量生油的成熟阶段。共和盆地下白垩统烃源岩发育， 具有形成中小型油气田的可能性。
Most parts of northwestern China are in the early Cretaceous crust-dominated tectonic setting, but the Republic of China is in an extensional tectonic setting and developed thick Lower Cretaceous lacustrine deposits. For the first time, we found a 258.15-m-thick source rock in the Lower Cretaceous of the Republican Basin. This finding changed the viewpoint that the Cretaceous source rocks in Northwest China distributed only to the north of the Qilian-Qinling Mountains, which is of great significance for studying the distribution of Cretaceous source rocks in Northwest China and the formation of oil and gas fields. The Lower Cretaceous in the Republican Basin is divided into ten thousand sections, ten thousand sections, three sections, and four sections of sections from bottom to top. In case that the first and the fourth sections are red sediments formed under hot and dry climatic conditions, there is basically no hydrocarbon generation capacity. The source rocks of Wan 2 Member are a set of shallow lacustrine-semi-deep lacustrine deposits formed in hot and humid climates. The organic matter abundance of source rocks reaches the abundance standard of well-to-moderate source rocks. The type of kerogen is type I 2 Mainly. The source rock entered the oil production threshold at the early stage of K2 (90.01Ma) and began to generate oil. Since the late K2 (74.11Ma), it has been in the mature stage of large oil production. During the deposition of the third member of Lower Cretaceous, shallow and dark mudstone and red mudstone alternately appear at the depth of water body. Dark mudstone belongs to moderate source rock, and its organic matter type is mainly type Ⅱ. It reached the threshold of oil generation during the Late Cretaceous (78.02Ma), but it did not enter the mature stage of large oil production until Quaternary (1.5Ma). The Lower Cretaceous source rocks in the Gonghe Basin are developed with the possibility of forming small and medium sized oil and gas fields.