罗子沟盆地下白垩统大砬子组油页岩成矿规律分析

Formation characteristics of oil shale in the Lower Cretaceous Dalazi Formation in the Luozigou basin

罗子沟盆地油页岩赋存于下白垩统大砬子组二段,埋藏浅,地层倾角缓,含油率为3.51%～14.37%。油页岩具有典型内陆湖泊成因特点,含有大量动植物化石,其成因类型为腐泥型(Ⅰ型)和腐植腐泥型(Ⅱ1型)。大砬子组为一个完整的三级层序,主要油页岩层形成在水进体系域和高水位体系域,含油率高,赋存稳定。从平面上,油页岩富矿中心在CK26、CK30、CK35、CK40孔附近,呈东西向带状分布;在纵向上,共见有29层油页岩,其中有7层为可采油页岩层,2层和3层油页岩呈层状产出,连续、稳定、含油率高,具有巨大的经济开发价值。

Oil shale of the Luozigou basin is hosted in the 2nd Member of the Lower Cretaceous Dalazi Formation. It is buried at shallow depth with a gentle dip of strata and contains 3.51 to 14.37wt% of oil equivalent. Oil shale formed in a typical inland lake environments and contains many animal and plant fossils. Its genetic types are sapropel type （ Ⅰ model） and saprolite-sapropel type （ Ⅱ1 model）. The Dalazi Formation is a complete third-order sequence and the main oil shale beds, which have a high oil content and are persistent, formed in a transgressive systems tract （TST） and a highstand systems tract （HST）. In a plan view, high-grade oil shale is located near the CK26, CK30, CK35 and CK40 holes and distributed in an E-W-trending strip. Vertically, a total of 29 oil shale beds are found, of which seven beds are extractable. Oil shale beds 2 and 3 occur as continuous and persistent beds with a high oil content. They have great economic value.