层序地层级次对生物碎屑灰岩沉积演化的控制作用OA北大核心CSTPCD

Based on the data of seismic,well logging,core,cast thin sections and conventional physical properties,taking the middle-lower section of Mishrif Formation in the Middle East X Oilfield as an example,the identification of sequence stratigraphic orders and the controlling effects of sequence stratigraphic orders on sedimentary evolution are studied.The results show that:(1)The Mishrif Formation is divided into 5 third-order sequences(SQ1-SQ5)and 10 fourth-order se-quences(PSS1-PSS10).The MB2—MC1 single layers in the middle-lower section of Mishrif Formation correspond to SQ2-SQ3,including 4 fourth-order sequences(PSS3-PSS6),in which multiple fifth-order and sixth-order sequences are developed.(2)Carbonate open platform-weakly rimmed platform of a sub-basin is developed in the study area,and the reservoirs mainly exist in platform margin shoals and open platform shoals.The shoal facies can be further subdivided into rudist shoal,rudist-containing bioclastic shoal,bioclastic-arene shoal,bioclastic-spherical shoal and bioclastic shoal ac-cording to bioclastic types.(3)The sixth-order sequence controls the sedimentary sequence of a single shoal body,the fifth-order controls the combination characteristics of multiple shoal bodies,the fourth-order sequence determines the evolution characteristics of sedimentary microfacies,and the third-order sequence determines the evolution characteristics of sedimentary systems.(4)In the early stage of PSS3 and PSS4 of SQ2 sequence,the two fourth-order sequences are in a platform front slope environment,with the development of lens-shaped collapsed coarse-grained sediments.In the later stage of PSS3 and PSS4,a sedimentary sequence of the platform margin intershoal→medium energy shoal is developed.The PSS5 and PSS6 of the SQ3 sequence develop a sedimentary sequence of platform margin intershoal→medium energy shoal →high energy shoal.After the completion of SQ3 sedimentation,a special incision filling sedimentation is formed.