Study On Sedimentary Microfacies And Reservoir Characteristics On Chang 6 Of Zengcha Region, Wuqi Oil Field

Applied with core description,logging-data interretation,thin section identification,rese rvoir lithology and physical property analysis,and some effective theories of other subj ects such as Sedimentology,Sedimentary Petrology,Reservoir Geologyand Petroleum Ge ology,the sedimentary facies and reservoir characteristics of Chang6 oil formation of th e Yan Chang Formation of Zengcha region was studied deeply.According to the characteristics of lithological and electrical properties and marker formation,Chang 6 reservoir has been divided into sublayers Chang 61,Chang 62 and Chang 63.General thickness of 125 m ~135m.While the whole structure is west-trending and monoclinic,in local of Chang 6 reservoirs there are still many small-sized low-amplitude nose-like uplifts.According to the analysis of the facies marks,such as petrosal kinds with the features,sedimentary structure and logging facies and other criteria,combining with regional sedimentary background analysis,Chang 6 reservoir in Yanchang Formation Cengcha District were deposited in the delta front,and subdivvded into 3 microfacies,underwater distributary channal,revir mouth bar and interdistributary bay.Considering that sedimentary environments of Chang 61,62 and 63 subages have good inheritanee,which make all the sandbodies of different time spreading in the Ne dircetion on the whole.underwater distributary channals in deltaic front microfacies is the mian frame sandbodies for oil and gas reseroir of Chang 6 reservoir in Yanchang Formation Cengcha District.The reservoir sandstone is mainly made of feldspathic sandstones.Generally speaking,the reservoir is the one with low pore extra low permeability.The porosity is mainly the kind of intergranular pore and intragranular dissoved pore.The pore structure types are fine throat-small pore and mirco-fine throat-small pore.the reservoir shows stronger unhomogeneity in the study area.The porosity of Chang 6 reservoir is 7.5% and the permeability is 0.43×10-3?m2 in the study area,Chang 6 reservoir is a set of low porosity and low permeability to tight reservoir.Reservoirs classification in ?b and ?a overall,is ultra low permeability and low permeability reservoirs.Based on the study of sedimentary facies,reservoir petrological characteristics and physical properties,the main controlling factors of oil and gas distribution in the study area are analyzed,sedimentary microfacies are the basis of controlling the distribution of oil and gas,and most of the oil and gas are distributed in the sand body of the flow channel.