Study On The Distribution Characteristics And Genesis Of Jurassic Calcareous Interlayers In The Shinan Area

At present,the research on the distribution characteristics and genesis of Jurassic calcareous interlayers in the Shinan area is very limited,and the type and distribution of interlayers in the reservoir have important controlling effects on the distribution of remaining oil,thus affecting the later stages of the oil field Development.Therefore,it is necessary to carry out in-depth research on the distribution characteristics and causes of calcareous interlayers in this block.In this paper,the second member of toutunhe formation of Jura system in the Shinan area of the junggar basin is taken as the research objective.The target area is established by analyzing the core data,logging data,and physical properties of more than 900 wells in Wells4 and 21 Stratigraphic framework;further detailed descriptions of coring wells and key wells,and the log intersection curve and log response map were drawn.Based on this,combined with the experimental results of scanning electron microscopy,cast flakes,and carbon and oxygen isotopes,the calcareous interlayers in the target area were identified and finely divided,and the distribution characteristics and causes of calcareous interlayers were clarified.The research results show that the delta front facies developed in the Toutunhe Formation can be further subdivided into four microfacies such as underwater diverted channels,river bays,underwater natural dykes,and estuary sand bars,and the calcareous interlayer is in the plane.It has a good correlation with the distribution of sedimentary microfacies,and has the same spatial distribution trend with sand bodies.The calcareous interlayer in the target area is generally developed,and it can be further divided into J2t21 top interlayer,J2t21-J2t22 interlayer and J2t22-J2t23 interlayer.There are 3 sets of interlayers and 6 sets of interlayers.The calcareous cements of the Toutunhe Formation in the Shinanjing area can be divided into three types:homogeneous calcareous cements,diagenetic calcareous cements,and epigenetic calcareous cements.In addition,calcareous cements are microscopic There are four types of speckles,lumps,layers,and uniform cementation,and the degree of calcareous cementation is affected by factors such as the cause,the permeability of the sand body,and the adequacy of calcium ion supply.The above studies can provide a geological basis for Jurassic residual oil tapping and optimization of development plans in the belly of the Junggar Basin.