华北古生代克拉通盆地南部原生油气藏勘探前景

依据古生界烃源岩特征与烃源岩生烃史的分析,华北地区下古生界海相烃源岩虽然有机质类型好、厚度较大,但有机质丰度低,基本为差-非生油岩。加之烃源岩成熟以后,后期埋藏历史及烃源岩热演化史复杂,作为一个含油气系统的烃源岩,勘探风险较大。下古生界烃源岩仅在渤海湾南部地区具有中等-较差生烃潜力,经喜山期的深埋,在济阳坳陷、临清坳陷、东濮凹陷、黄口凹陷下古生界具备二次生烃条件,尚具有一定的勘探前景。上古生界石炭—二叠系烃源岩主要为煤系地层,厚度为150～500 m,有机质丰度属于低-中等,有机质类型为Ⅲ型。上古生界烃源岩二次生烃主要发生于晚三叠世末期和早白垩世末期,油气保存好,原生油气藏勘探前景广阔。上古生界有利勘探地区主要集中在渤海湾盆地的东濮凹陷、临南洼陷、德州凹陷南部及莘县凹陷北部二次生气强度较大的第三系凹陷内。

Prospects of exploring Palaeozoic primary oil and gas pools in southern area of North China cratonic basin

According to analyses of the features and hydrocarbon generation history of Paleozoic source rocks,the Lower Paleozoic marine source rocks in North China are basically poor source rocks to non-source rocks due to their low organic matter abundance,though they have good kerogen type and large thickness;moreover,later burial history and thermal evolution history of source rocks are complex after the source rocks getting mature.Therefore exploration risk is high when taking them as the source rocks of a petroleum system.The Lower Paleozoic source rocks have medium to poor hydrocarbon generation potentials only in the southern part of Bohai Bay.After deeply buried in Himalayan,the Lower Paleozoic would be in condition to secondary hydrocarbon generation in Jiyang depression,Linqing depression,Dongpu sag and Huangkou sag,thus certain exploration potentials exist in these areas.The Upper Paleozoic Carboniferous-Permian source rocks are mainly coal measure strata,with thickness in the range of 150～500m,low to medium organic matter abundance,and type Ⅲ kerogen.Secondary hydrocarbon generation in Upper Paleozoic source rocks had occurred mainly at the end of Late Triassic and the end of Early Cretaceous,and hydrocarbons were well preserved,thus there would be large potentials for exploration of primary oil and gas reservoirs.The Upper Paleozoic favorable exploration areas are mainly in the Tertiary sags with large secondary gas generation intensity,such as Dongpu sag,Linnan sag,the southern part of Dezhou sag and the northern part of Xinxian sag in Bohai Bay basin.