GEOCHEMICAL CHARACTERISTICS OF HYDROCARBON SOURCE ROCKS IN THE NO. 2 STRUCTURAL BELT OF THE NANPU SUBBASIN, EASTERN HEBEI OIL FIELD, AND SOURCE ROCK CORRELATION

The main oil-bearing horizons of the No.2 structural belt of the Nanpu subbasin are sandstone of the First Member of the Paleogene Dongying Formation and Ordovician limestone.Analysis of several items of organic geochemical markers of source rocks and crude oil samples from well LPN1 indicates that:the sedimentary environment of principal source rocks in the study area was a continental shallow-lake,weakly reduced environment;the source rocks of the First and Second members of the Dongying Formation are immature;and the source rocks of the Third Member of the Dongying Formation and the Shahejie Formation are mature,with a depth threshold of petroleum generation of 3100 m and a principal petroleum generation threshold below 3700 m,belonging to the Shahejie Formation.The integrated correlation of gas chromatogram and mass spectrum parameters of saturated hydrocarbons in oil and source rocks suggests that petroleum of the First Member of the Dongying Formation mainly came from source rocks of the First Member of the Shahejie Formation and formed an petroleum accumulation characterized by "generation below and accumulation above",while Ordovician petroleum was mainly derived from source rocks of the Third Member of the Shahejie Formation,forming a petroleum accumulation characterized by "generation in younger strata and accumulation in an older reservoir".