Research On Sedimentary Characteristics Of E₃d² In Bozhong 1/2 Area Of Bohai Bay Basin

Bozhong 1/2 area is located in the north of Bozhong depression,which is between the Shijiuyuo salient and the Shaleitian salient.In Bozhong 1/2 area,tertiary formation was developed and has large proved reserves.Especially,in the Glutenite of Dongying formation has very good oil and gas shows and industrial flows have been obtained from it.However,the work area has less number of drilling and the geological data is limited,which results in a relatively low degree of reservoir.In this thesis,I studied that the sand body distribution and development characteristics over the time and space.This thesis provides a theoretical basis for Bozhong 1/2 area to the deployment of oilfield exploration.The Dongying formation can be divided into five parts:the lower part of bottom of the E₃d²,the middle part of bottom of the E₃d²,the upper part of bottom of the E₃d² and the top of the E₃d².Each sequence can be further divided into several high-frequency-sequences?HFS?.The lower part of bottom of the E₃d²,the middle part of bottom of the E₃d²,the upper part of bottom of the E₃d²,and the top of the E₃d² were divided into ten,five,seven,and four HFS,respectively.Under the constraint of well and seismic data,I studied source-supplying direction and amount as well as the development and the distribution of sand body,and obtained the sediment characterization of each sequence.The source area was found to be alternately switching between the northeast and the southwest in the region from The lower part of bottom of the E₃d² to the upper part of Bottom of the E₃d².Each high-frequency-sequences?HFS?has Delta facies.The position and scale of all Delta facies continuously change with time.In the lower part of bottom of the E₃d² period,the main source area was in the southwestern and northwestern and progradation vertical sequence was developed.In this period,Delta plain,Delta front,the Former delta,Shallow lake and Flood plains,Flood plains all developed and in the later the Flood plain was disappeared.In the middle part of bottom of the E₃d² period,as the main source area the northeast area supplied source of sediments all the time.All deltas developed in the period had progressive delta region characteristics and also had the characteristics of product type delta.In the late of this period,the southwest and northwest of the work area developed small scale Delta facies.In this period,the sedimentary facies contained Lake,Delta,Lakeshore,Semi-deep lake,and Flooded plan facieses.The Lake facies was the main facies.In the upper part of bottom of the E₃d² period,the southwest area was the main source area,and the developed delta had large scale and good stability.The north area provided sediments in the middle and late period.The Delta in the northern part of wok area mainly had the progressive delta region characteristics,and also had the characteristics of product type delta and the trend of westward migration.Some formation suffered severe erosion,which was especially obvious in the northwest.In this period,the sedimentary facies contained Delta plain,Delta front,Semi-deep lake shore and Shallow lake.In the top of the E₃d²,the Lake surface became lower.The main sedimentary facies was Delta plain facies which was dominated by channel deposit.