Research And Application Of Seismic Sedimentology Of Lower Es₄ In The Chenguanzhuang Area

There is a set of purplish red mudstone mixed with thin sandstone deposits in the lower Es₄ in Chenguanzhuang area.After more than 50 years of exploration,dozens of wells have been seen good oil and gas shows.However,according to few wells,thin layers,many faults and complex sedimentary environment in the study area,there are controversy in sedimentary facies in the study area;Based on the newly seismic data in 2018,this thesis carries out seismic sedimentology research,depicts the distribution of sedimentary facies and predicts favorable zones,providing guidance for oil and gas exploration.Climate,as the main controlling factor,controls the change of base-level cycle and the sedimentation of sand bodies.The red beds in the lower Es₄ in the study area are the result under arid climate conditions,with the alternating action of the short-term wet flood period and the long-term drought flood intermittent period.On this basis,mainly using wavelet analysis,time-frequency analysis and other technical means,the lower Es₄ is identified and divided into two sand groups,and the stratigraphic framework of the study area is established.By using the analysis of core,logging facies and seismic facies data,the sedimentary facies types in the study area are defined.The first sand group mainly developed shallow water delta deposits and shore-shallow lake beach bar deposits,including distributary channel,beach,bar and other types.The second sand group developed food-overlake sand flat,mud flat and mixed flat deposits.On this basis,sedimentary models are established including flood period and intermittent flood period.In the isochronous stratigraphic framework,seismic sedimentology interpretation guided by sedimentary facies model is carried out.Based on the analysis of lithology type,thickness and velocity of thin sandstone,forward modeling is carried out,and the seismic response characteristics of thin sandstone in the study area are summarized.Studies have shown that40Hz seismic data is suitable for thin sandstone identification in the study area.Waveform indication inversion is carried out,and the effective prediction of 3.5 m thick sand body is realized.After comparing the application effects of various methods and combining with the actual data of the study area,the stratigraphic slices are finally extracted on the 90°phase conversion data volume,and the problem of vertical difficult to distinguish thin layers is solved by plane identification of sand bodies,and thin sand body identification and sedimentary facies characterization are completed.The facies map is drawn by combining stratigraphic slice with sandstone thickness distribution,and the sedimentary facies boundary is depicted.By analyzing the characteristics of paleogeomorphology,the direction and position of the main channel developed of flood period are inferred,and the microfacies of distributary channel are described by combining logging facies and stratigraphic slices data.The research shows that the front boundary of the shallow water delta of the first sand group develops three main waterways from the north to the Guan 4 well and the east to the Wang 662 well.The north of the Guan 4 well shows a coastal shallow lake beach bar deposit,and the south of the Guan 125 well is subjected to repeated lake waves to form local sand flat deposits;The sand flat and mud flat of sand group are distributed in strips.Finally,the oil and gas bearing properties and reservoir physical properties of different sedimentary facies are analyzed,and it is shown that shallow water delta distributary channel microfacies and flood-overlake sand flat microfacies are the most favorable facies belts,followed by shore-shallow lake beach bar facies.Combined with favorable structural conditions,four favorable areas of the first sand group and three favorable areas of the second sand group are predicted.