Characteristics and formation mechanisms of Chang 61 tight reservoir in Wuqi area
With the continuous exploration and development of Wuqi oilfield,the produc-tion construction proportion of low-permeability and ultra-low permeability reservoirs has been decreasing year by year,and the reserve grade continues to decline.The Chang 6 reservoir,as the main production layer series,has the characteristics of wide distribution and large thickness.However,research on the micro-characteristics of the reservoir is relatively weak,and the reasons controlling the compactness of the Chang 6 reservoir are not yet clear.Further research on reservoir characteristics is indispensable to clarify the causes of reservoir compactness and provide a basis for reservoir prediction.By comprehensively utilizing data such as well logging,cores,cast thin sections,and scanning electron microscopy,a study was conducted on the stratigraphic classification,sedimentary characteristics,and reservoir char-acteristics of the Chang 61 reservoir in Wuqi area.It is believed that the Chang 61 period in the study area belongs to the delta front subfacies sedimentation,with fine throat and poor sorting,and belongs to a low porosity ultra-low permeability reservoir.The main factors con-trolling the tight reservoir formation in this area are sedimentation,diagenesis,and tectonic processes.Sedimentary facies control the original physical properties of the reservoir,with the underwater distributary channel sand body having the best physical properties,during the diagenesis process,compaction and cementation are the main reasons for the deteriora-tion of reservoir properties,while secondary pores formed by dissolution can effectively im-prove reservoir properties,high angle fractures and vertical fractures can be seen in the area,which to some extent improve the physical properties of the reservoir.
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