Characteristics Of The Source Rocks Developed In The Northern Part Of The Southwest Sag Of The Dongpu Depression And Its Hydrocarbon Generating Potential

The southwest sag of the Dongpu depression is most promising hydrocarbon exploration area with great hydrocarbon potential.The source rock is the most important element in the petroleum system that is the starting point for all the petroleum events that happened in an effective and reliable petroleum system.The characteristics(the type of the organic matter and its abundance and maturity)of different types of the source rocks together with their space distribution in the northern part of the southwest sag were studied based on the routinely source rock evaluation method.The hydrocarbon potential and the most favorable hydrocarbon exploration area were defined.The source rock is developed mainly in the third member and secondly in the first member of the Shahejie formation of the southwest sag of the Dongpu depression.The mudstone is the most prevailing source rock.Sapropel-humic and humic kerogen is found in the third member of the Shahejie formation,while sapropelic and humic-sapropel kerogen is found in the first member of the Shahejie formation.The source rock is mature to high mature according to the vitrinite reflectance and a number of other thermal history index.The maturity of source rock from the third member of the Shahejie formation is higher in the north,while that from the first member is higher in the south.Their maturity differences is controlled by early stage high heat flux before the Shahejie stage and the late stage quick subsidence and burial since Dongying period.The space distribution of the source rock is controlled by two small sags formed during rifting.The above characteristics of the source rock distribution indicate that the locations of the Fangliji,the Sangcunji and the Menju that lie in vicinity to the main source rock pod are the most favorable hydrocarbon exploration areas in the southwest sag.