The Study On Sand Body Migrating System And Hydrocarbon Acumulation In The North Slope Of Dongying Depression

By applying geological, geophysical, well-logging, well test results of more than 200 wells and geochemical theories and methods, sand body as a migration system in the North Slope of the Dongying depression is systematically analyzed in order to discuss this system and its control on hydrocarbon accumulation.Based on the analysis of geological background and sequence stratigraphy, combined with the result of sedimentary system and facies, sand body types, plane distribution and connectivity profiles of Paleocene Shahejie Formation in the north slope of Dongying depression are studied. The results show that sand bodies are well-connected from Sha2 to Upper Sha3 and delta sand body in Sha2 is best connected. These sand bodies have good lateral connectivity and are good for lateral hydrocarbon migration. Sand bodies in the south edge near uplift are developed and well-connected. The last stage of Sha4 and the middle stage of Sha3 are major developing stages for fans which have characteristics of succession and superposition distribution. Through the analysis of sand body and source rock association types, digenesis, sand body properties, and fracture characteristics etc., some influencing factors of the validity of sand body transportation are analyzed. High porosity and permeability zone in each layer is hydrocarbon's dominant path. Micro-mechanism of hydrocarbon transportation in sand body is analyzed with simulation experiments, and sand body transporting capacity is semi-quantitatively evaluated by the method of fuzzy mathematics. Some selected wells are oil-source correlated. Es3 and upper Es4 source rocks and correlated three types of oil are clarified. And the migration direction of hydrocarbon is analyzed based on physical properties and maturity index of oil. Result shows that hydrocarbon migration has the tendency of upward, from south to north, and from fault to two sides.Based on the temperature data of fluid inclusion, the period of hydrocarbon accumulation is divided into two stages: Dongying and Guantao-Minghuazhen stage. Considering fault and unconformity characteristics, three hydrocarbon accumulation models are summarized: fracture and sand type (T-type), unconformity and sand type (S-type), and hidden passage type ("—"-type). The role of connected sand bodies in hydrocarbon accumulation is pointed out.