Study On The Hydrocarbon Accumulation Law In Guantao Formation Of Southwestern Region Of Gudao Oilfield

The oil production of upper Tertiary reservoirs reached 396×10~4t/year in Gudao oilfield which is the biggest oil production factory of ShengLi oilfield. Because of persistent activity of GuNan fault, the structure in southwest of GuDao oilfield is very complex, the hydrocarbon migration conditions are difficult to analyzed and the rules of oil and gas accumulation is hard to grasp. So the degree of hydrocarbon exploration of the upper Tertiary in Guantao Formation is low. According to the information from geology, seismic and geophysical logging, associating with some data such as well drilling, testing etc, the paper firstly analyzed the distribution of sand-body and distributive characteristics of oil, gas and water in the area, further, summarized the scenario of hydrocarbon accumulation, generalized the mechanism of hydrocarbon accumulation, sumed up the lows of hydrocarbon accumulation, and finally confirmed the favorable accumulative region, so that it could be prepared for the next rolling exploration to the Guantao Formation in this area.The southwestern of Gudao is located in the east of ZhanHua area of Jiyang depression, where Guantao formation is fluvial deposits. The lower Guantao Formation is lowstand system tracts, which showed the facies of alluvial and braided stream with pebble sandstone, flag mudstone. The lithological association of low segment is positive rhythm, characterized by sand wraping mud. The structures showed on the core are through cross bedding, planar cross bedding and some parallel bedding. The upper Guantao Formation is meandering river deposits, belonging to retrograding system tracts or highstand system tract, whose lithological association varies from sandstone with mudstone to mudstone with sandstone from top to bottom.The hydrocarbon of this area is originated from the ShaHejie Formation which is located in the south of GuNan sag, which migrated upward through the fault. The light oil and gas migrated to the middle-upper part of Guantao Formation, while the heavy oil and gas stayed in the middle-lower part. Oil and gas held the eminence to accumulate in the thick and successive mudstone, showing light on the top and sticky on the bottom. At the sideway, it mainly distributed in the middle to east of the area. The reservoir-forming mechanism could be generalized: source-mixed filling, the fault conduit,the meshwork-carpeted entrapment, the mudstone sealing. It is characterized by vertical migrating along fault, lateral migrating through sandbody and reservoir-forming in the high situs.