Sedimentary Construction And Lithologic Reservoir In Sequence Stratigraphic Framework Of Sha'er Layer Of Western Sag In Liaohe Basin

The Western sag of Liaohe Basin is one of the oil rich sag.That the strike slip fault forms the multistage slope break and the multistage lake level rise t provides favorable geological conditions for the formation of the tectonic lithologic oil and gas reservoirs.Early exploration is mainly concentrated in the upper part of the first slope.With the deepening of exploration and research and the demand for steady production of tens of millions of tons of oil fields,the lower part of the slope break zone and the slope area have gradually become an important area for next exploration.This study hopes that by comparing the high resolution sequence stratigraphy of Sha'er layer in Western sag of Liaohe Basin,finding out the sand body distribution on the basis of fine sequence stratigraphy and combining favorable reservoir,reservoir cover combination and reservoir analysis,we can rovide the basis for the exploration of production of the Liaohe oil field.Based on the study of sequence stratigraphy,sedimentary formation and reservoir comprehensive evaluation of the Sha'er layer of The Western sag of Liaohe Basin,the results are as follows:(1)on the basis of the classical sequence stratigraphy theory,the Shahejie formation strata of the western sag are divided into 4 three-level sequences by drilling,logging and seismic data,and the Sha'er layer is located in the LST.Then,according to the theory of high-resolution sequence stratigraphy,the Sha'er layer is divided into three parasequence sets.(2)through the paleogomorphology and seismic data analysis,the source comes from two directions of the Western gentle slope zone and the eastern steep slope zone,but thewestern direction is the main direction.Through a series of studies of core phase analysis,log phase analysis,single well phase division,across well phase division,sand body plane distribution to plane phase distribution,it is believed that the sedimentary system composed of three element sedimentary facies,including fan delta,lake and slump fan.On the plane distribution,the fan delta in the west is larger than that in the East.The fan delta front subfacies is the most developed in the study area.The lake facies is distributed in the central part of the lake basin.From bottom to top,and the scale of fan delta front sand body decreases.In the later stage of the Sha'er layer,the slump fan deposits began to appear due to the increase of unstable factors.(3)the sediment of the Sha'er layer of the study area is characterized by near source and rapid deposition.Therefore,the composition maturity and structural maturity are low,the rock type is mainly feldspar sandstone,the lithic feldspar sandstone and feldspar rock is lesser,and the lithic sandstone content is less,which belongs to low porosity,low permeability and middle pore medium permeability reservoir.The main controlling factors of the Sha'er layer reservoir include the lithofacies,burial depth and shale content.(4)in the process of comprehensive reservoir evaluation,the the Sha'er layer sand bodies in the study area are divided into 4 types,and on this basis,the lithologic favorable areas are predicted with the previous work results.The main standard is among type I and II reservoirs,and the porosity is >15%,the permeability is >10mD,and oil and gas wells is distributed around the reservoir.In particular,the favorable areas are mainly distributed in the Western gentle slope area of the sag,with the facies of the fan delta front faces and slump fans,located in the main parts of the subaqueous distributary channel and its flanks in the front of the fan delta,and are regularly located in some slump fans which in the front of fan body.