The Charge Condition And Accumulation Process In Wen'an Slope Buried Hill Belt Of Baxian Sag

Buried hill structure is the most important exploration field in Huabei Oil Company.With the rising of exploration degree,the deep subtle buried hill of Baxian sag is the next exploration target.Grading evaluation of source rocks by 45 wells logging evaluation shows Baxian sag developed three sets of lacustrine source rocks including Es1,Es3 and Es4 source rocks and one set of C-P coal-measure source rock.The high heterogeneity lacustrine source rocks belong to organofacies C,D/E and F.Reconstructing thermal history with bottom hole data and paleogeothermal indicators,and applying hydrocarbon generation model proposed by Pepper(1995)to characterize source kitchen quantitatively.The source rocks with different organofacies generate hydrocarbon successively,which is a dynamic process from source kitchen to reservoir,shown as unsaturated oil expelled at early stage of source kitchen evolution accumulated at shallow to middle depth reservoirs and condensate or light oil expelled at late stage accumulated at deep reservoirs.Analysis of oil physical and geochemical features suggests that the Suqiao buried hill oil originated from Paleogene lacustrine source rocks.The characteristics of gas component and carbon isotope proved buried hill gas originated from Es4 and C-P organofacies D/E and F source rocks,which can generate humic type gas.And the buried hill hydrocarbons at south of Wen'an slope also originated from Es4 source rock.Through the charge risk evaluated and accumulating modeled of Wen'an slope buried hill belt and analyzed of typical exploration wells,the targets near the source kitchen have an advantage of hydrocarbon charge,while the targets far away from the source kitchen have a high risk of hydrocarbon charge.The hydrocarbon migrated from source kitchen affected by the faults,migrated upwards scalariformly and accumulated at shallow traps.The next exploration supposed to concentrate on the buried hill targets which are near the source kitchen.