Research On Connectivity Of Reservoir Sand Bodies Of The Middle Es₃ Member In Block Fan 29,Daluhu Oilfield

As the world's oil and gas exploration and development situation of increasingly serious,low permeability turbidite reservoir has got widely attention as an important type in unconventional reservoirs.Reservoir of Block Fan 29 in Daluhu Oilfield is an typical low permeability turbidite reservoir.After decades of water flooding processes,Daluhu Oilfield has already entered the high water cut development stage.The confusion of sand body connectivity has become more and more serious.In consequence,mode and degree analysis of sand body connectivity should be focused on,which is important for improving of injection production effect and seeking of the remaining oil.The research object is sand bodies of sublacustrine turbidite fan,which belongs to the4th sand bed of the Middle Es₃ member in Block Fan 29,Daluhu oilfield.Firstly,by comprehensively utilizing the logging and coring data,fine stratigraphic division and comparison to target layer are conducted.Sacondly,the boundary of single sand bodies is divided by vertical staging for periodization and lateral boundary markers,as a result 12phases of single sand bodies are identified in the target layer.Following the division and comparison,the sedimentary microfacies are studied,the middle fan subface is further divided into 5 microfacies:the main water channel,channel edge,inter channel,lobe and edge of middle fan.And then combining with sedimentary evolution and distribution characteristics of sand bodies,the vertical superimposition patterns and lateral contact patterns of sandbodies are summarized.On the basis of fine description and characterization of sand bodies,the sand body connectivity is analysed in three aspects:lateral,vertical and internal the sand bodies.Lateral connection model of sand bodies is set up for three cases:the connection among the same sand body with the same sedimentary microfacies,the connection among different sand bodies with the same sedimentary microfacies,and the connection among different sand bodies with different sedimentary microfacies.Longitudinal connectivity is related to the development characteristics and distribution of interbeds.When there is no interlayer among the sand bodies or only the third type interlayer,the longitudinal connectivity of sand bodies is good.However,when the sand bodies are separated by the first and second types of interlayers,the longitudinal connectivity is poor.For the internal connectivity of sand bodies,the heterogeneity of the permeability within the single sand bodies is summarized,and the permeability heterogeneity coefficient is calculated to study the development of interlayers in single sand body.When the interlayer developes horizontally,it has little influence on sandbody connectivity.However,when the interlayer develops obliquely,the sand body connectivity is poor.Finally,on the basis of classified research on sandbody connectivity,the relationship between sandbody connectivity and the accumulation rule of remaining oil is summarized.The remaining oil is often concentrated in the high parts within the non-connected sand bodies,which is affected and restricted by the distribution of interbeds.