Identification and Evaluation of Channel Type Structural and Lithological Traps in the Huagang Formation of the N Gas Field in the Central Belt Zone of the Xihu Depression
With the development of oil and gas exploration,the target gradually changes from structural reservoirs to lithological reservoirs.The fluvial reservoir of the Huagang Forma-tion in the central structural inversion zone of the Xihu Sag changes rapidly laterally to form lithological traps,which has a large potential for oil and gas exploration.Seismic sedimentol-ogy and reservoir architecture are used to analyse the planar distribution of reservoirs and connectivity of sand bodies.Variable-speed mapping is used to predict the top surface struc-ture of sand bodies.Based on the results of structural and reservoir characterization the li-thological traps are analysed.Integrated with the distribution of ancient structures and oil source faults during key reservoir formation periods,reservoir formation analysis is carried out to clarify the main controlling factors for oil and gas enrichment.The study area involves two stages of river channels,and the gas-water interface of channel 1 is lower than that of channel 2 by 37.2 m.The oil source fracture is located in the west,which has a better cou-pling relationship with the river sands and forms a river channel-type tectonic and lithological enclosure with the characteristic of"paleotectonic convergence-enrichment by near-faults-one sand,one reservoir".The southwestern flank of channel 2 is closer to the oil source frac-ture,with a high potential for reservoir formation,which is one of the important targets for the next exploration and evaluation.The characterization of lithological traps constructs the foundation,and the analysis of the main controlling factors testtifiesthe key.The concerned methods offer reference for the study of similarareas.
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