The Fine Description And Three-Dimensional Characterization Of Complex Sand Body In The Late Development Of Daqing Pubei Oilfield

The Pubei oil field in Daqing has entered the late stage of high water cut development,the stage of reservoir description has reached the division of flow units in the sedimentary unit.Although the scale of reservoir research has been s uch fine,the spatial connectivity between single sand bodies is ignored in the process of development,especially ignored the sand body vertical connectivity between influence on water flooding development,as a effect,the water flooding development in the reservoir of Pubei oilfield is not high,residual oil reserves,and enrichment of remaining oil mainly in thick oil layer phenomenon.In the research area,thick oil layer mainly exists in a composite sand layer composed of multiple single sand bodies connected vertically and laterally.Therefore,in order to better excavate the remaining oil,we need to re-select the appropriate reservoir research scale and research object.The composite sand body is a sand body unit composed of single sand bod ies that are connected vertically and laterally in the same sedimentary subfacies.It is based on the detailed description of the reservoir plane,and fully considers the vertical connectivity between sand bodies,avoiding the problem that the water flooding development effect is not high due to the neglect of the vertical connectivity between the single sand bodies during the development process.This paper selected the composite sand body as the research object of the late development reservoir.The composite sand body is divided into 8 types from the characteristics of and the internal connectivity of sand body in the research area,respectively: multi period channel stack connection type,multi period channel stack locally connection type,multi period channel panconnected type,branch channel connection type,branch channel locally connection type,branch river panconnected type,narrow river connectivity and narrow river local connectivity.By using the analytic hierarchy process and reservoir 3D geological modeling technology,the composite sand bodies are described in detail according to the order of composite sand bodies,single sand bodies and thin intercalary strata.There are six different types of contact and connectivity among the single sand bodies in the composite sand of different microfacies,there are: thin note thick mining top contact type,this t ype of composite sand body connectivity;thin note thick mining central contact type,this type of composite sand body connectivity is good;thin note thick mining bottom contact type.This type of composite sand body connectivity;thick thin note mining top contact type,this type of composite sand body connectivity is poor;the thick thin note mining central contact type,this type of composite sand body connectivity is better;note thick thin mining bottom contact type,this type of composite sand body connectivity is good.The thin intercalary strata within the composite sand bod ies represent the minimum scale flood interval,which is the key and difficult point in the description of the internal structure of the composite sand body.There are 3 types of thin intercalary strata within the composite sand: muddy thin intercalary strata,thin intercalary strata of interlayer and calcareous intercalary strata,and the mainly develop muddy thin intercalary strata and thin intercalary strata of interlayer,angle less than 1 degrees,nearly horizontal,the thickness of 0.2m the most and there are some thickness of 0.1m and 0.3m developped,only a few thin intercalary strata of thickness greater than 0.3m is developed.On this basis,three-dimensional geological modeling technology and numerical simulation technology are used to discuss the three-dimensional characterization of typical composite sand bodies and the distribution of residual oil.There are 3 main types of typical structural styles for the accumulatio n of residual oil in multistage river channels: the top of the oil layer,the thick mining type and the high bend of the river.There are 2 typical structural styles in the residual oil enrichment of branch channel composite sand bodies: the superposition of the river and the branch of the river.There are mainly 3 typical structural styles for narrow strip river type composite sand bodies: superposition of river channels,curved parts of river channels and terminal types of water wells.The research results provide guidance for the exploitation of the remaining oil in the thick oil layer of No.2 fault block in Daqing oilfield.At the same time,it also has important theoretical guidance and practical significance for the remaining oil drilling in other similar fields.