Sedimentary Microfacies And Rhythmic Layer Characteristics Of Es28 Sandbody In The Block 28 Of Shengtuo Area

After long time years ago,the sand layer of the second member of the Shahejie Formation in the Block 28 of the Shengtuo Oilfield has entered the stage of development of ultra-high water cuts,making it more and more difficult to develop.The original small-layer division system can no longer meet the needs of the development,and the division of the rhythm layer is needed.Therefore,under the guidance of sedimentology theory and petroleum geology,the paper uses core,well logging,and logging data to divide rhythmic layer.It applys lithology,sedimentary cycles,isotropes and phase transitions and accords to isochronous and coarse-to-fine stratigraphic comparison principles to work.On the basis of stratigraphic division,they are studied that the sedimentary microfacies of the rhythmic layer and the planar distribution of the rhythm sand bodies and interlayers.Through the division and comparison of the prosody layer,the sand layer group of the study area 8 is divided into three small layers,and further divided into nine rhythm layers.1 small layer is divided into 3 rhythm small layers,2 small layers are divided into 2 rhythm small layers,and 3 small layers are divided into 4 rhythm small layers.By analyzing the lithological characteristics,sedimentary structure,grain size characteristics and electrical characteristics of the study area,the phase markers of each sedimentary facies were determined and a single well sedimentary facies map was made.It is concluded that the eight sand layers of the second member of the Shahe Formation in the study area share two sub-phase types: the delta front and the shallow lake.The sedimentary microfacies are underwater distributary channel,diversion bay,estuary dam,far sand dam,and mat sand microfacies.Based on the study of the rhythm sand body and interlayer of single well phase and continuous well profile,the law of rhythm sand body and interlayer distribution was found out.The source of the northwest part of the sand layer group in the study area is the main source area,and the thickness of the source sand body near the northwest is large,showing a clear trend from northwest to southeast.Through research,it is found that the thickness of the sand bodies of the 1,2,and 3 rhythm layers of the 3 small layers varies greatly,and the interlayer thickness between the rhythm layers is large and distributed in a contiguous manner,belonging to the type I interlayer,and the rhythm sand bodies are not connected to each other.The oil and gas barrier ability is strong,and it is an independent development unit;2 small layer1 rhythm layer has a large area of shallow lake sediment,so the interlayer between the rhythm layers in the 2 small layers is not developed,and the interlayer between the rhythm layers It is partially connected and distributed in the local well area and can be shielded.It belongs to the type II interlayer.The thickness of the three rhythm sand bodies in a small layer is thin,and the three-stage estuary dam deposition is inherited,and the thickness of the sand body changes little.The interlayer between the rhythmic layers is not developed,the interlayer thickness is thin,and most of them are scattered.