STUDY OF THE ABNORMAL HIGH-PRESSURE IN HYDROCARBON SOURCE ROCKS-TAKING PALEOGENE IN THE DONGYING SAG, THE BOHAI BAY BASIN AS AN EXAMPLE

The abnormal high-pressure is very important to oil and gas accumulation.There is abnormal high-pressure in the 3rd and 4th member of Shahejie Formation of Paleogene all over the Dongying Sag,the Bohai Bay Basin.The main factors that lead to the pressure are under-compaction and hydrocarbon generation in the source rocks.The overpressure area is well corresponding with the thickness of source rocks.The present abnormal high-pressure is mainly distributed at a depth range 2 700 m to 3 500 m,and the range becomes bigger with increasing of the buried depth.Times of abnormal high-pressure should be considered when applying abnormal high-pressure to hydrocarbon accumulation.The present abnormal high-pressure in the source rocks has an active effect on the saving of oil and gas and it is oil source kitchen in future.The ancient abnormal high-pressure took an active part in the hydrocarbon migration in the source rocks and there is the main accumulation area of oil and gas.The main oil-gas enriched zones are located in the abnormal high-pressure after hydrocarbon generation in large scale.