| The Dongying Depression is a Tertiary rift basin with rich petroleum resources. More than 30 years' exploration and research has been carried out in this area, and many data and important recognition on petroleum geology and geochemistry have been obtained and a number of petroleum pools have been discovered. However, with the progress of petroleum exploration in this area, exploration has become more and more difficult since the targeting areas have moved from middle -shallow strata to middle- deep strata, and types of oil pool from structures to hidden types. Thus, conventional petroleum geological investigation methods can not meet the need of exploration, which requires creative ideas and new methods to get more deep scientific information to guide exploration. From the tread of petroleum geochemistry, two aspects should be noticed. One is in the field of petroleum-generating geochemistry, new techniques and methods have been applied, and great attention has been paid to the original information of petroleum from light hydrocarbon, heavy hydrocarbon, non-hydrocarbon geochemistry, and isotopic data. Another is in the field of formation of petroleum reservoirs. Formation of oil pools and their distribution pattern in a hybrid petroleum system with multi-sources, multiphase petroleum events become a hot academic point in the world. Under this background, the petroleum system of the Northern Dongying Area has been investigated by some new methods and techniques, such as laser microprobe, Laser-induced fluorescent microscopy, MPV III microscopy, GC-MS, carbon isotopic instrument, fluid inclusion analysis technique. The following results have been achieved:1. A strong vitrinite reflectance suppression in the ES3-ES4 source rocks were found. Based on the source matter of these source rocks, a method was suggested which are used to get an equivalent VRo from the measured VRo. A model plot of VRo and depth has been established in this area.2. The crude oils can be subdivided into three types. Type I is characterized by lower Pr/Ph and Ts/Tm, relatively higher content of gammaceral and C29 sterane, and conversely, Type III by higher Pr/Ph and Ts/Tm, lower content of gammaceral parameter and C29 sterane. Type II is between both.3. The source rocks can be largely subdivided into two types based on their geochemical characteristics. Type I has the feature of lower Pr/Ph and Ts/Tm, relatively higher content of gammaceral, but Type II is with higher Pr/Ph and Ts/Tm, relatively lower content of gammaceral. The source /oil correlation based on biomarker and carbon isotopic data shown that Type I oil has a original relationship with Type I source rock, and Type III oil can be compared with Type II source rock. There are no source rocks having a obvious relationship with Type II oil, and it was believed to form from a mixture sources.4. The Northern Dongying Area forms a complete petroleum system, It is not a simple one, but belongs to a hybrid petroleum system. This petroleum system has some outstanding characteristics, such as two types of source rocks, three types of crude oils, a few sets of reservoir-cap rock combination, complicated oil pools, two petroleum events, and a round distribution of oil pools around depressions.5. The formation model of oil pools in this area was established, including three types and five models. On the basis of this, seven prospecting structures were indicated as for further important exploration areas with a total petroleum resources over than 2000 x 104 tons.
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