Lithofacies Study Of The Triassic Baikouquan In The L Area And Its Planar Distribution

In recent years,more and more low-porosity and low-permeability oilfields have been discovered in China,and the proportion of new proven reserves of low-permeability resources is increasing.At the same time,the reservoir type of study area are the typical low-porosity and low-permeability sand-gravel reservoirs in the Triassic Baikouquan formation in Mahu Sag,Junggar Basin.The study of diagenetic facies is necessary to search for the dominant reservoir.According to the diagenetic environment,rock composition fabric and its spatial distribution characteristics in Mahu area,through the analysis of regional geological data,rock slice,casting slice and so on,it is found that the reservoir cuttings in the study area are mainly tuff,and that the reservoir cuttings in the study area are mainly tuff.This leads to the development of compaction and dissolution in reservoirs in area L generally.On the basis of previous investigation,the parameters of quantitative evaluation of diagenesis were corrected in this paper,and the quantitative evaluation of diagenesis was carried out on the basis of the corrected parameters.According to the new parameters,the reservoir genetic pore structure is systematically described.Finally,the diagenetic facies of the study area is divided by parametric diagenesis,and The reservoir in L area is divided into the following five phases:.(1)micro compacted residual pore phase residual pore is the main.(2)weakly corroded medium compacted phase characterized by inter granular dissolution.(3)weakly compacted intergranular dissolution phase characterized by inter granular dissolution and intra-granular dissolution.(4)intragranular dissolution strong compaction phase characterized by intra-granular dissolution,and the compaction is obvious,the primary pore is not developed,and the secondary pore is mainly.(5)strong compacting phase characterized by strong compaction and small Reservoir porosity,primary pores and dissolution develop weakly and often have only one or two constructive diagenesis.According to the diagenetic facies divided above,combined with logging data,we found that acoustic wave density curve and their ratio wave impedance have good response characteristics to diagenetic facies with great difference in physical properties of reservoir.The gamma curve has good response characteristics to the inter-particle erosion.So we select the gamma and wave impedance to establish the intersection diagram and use the decision tree to recognize the log feature pattern.The diagenetic facies identification and interpretation of wells in the whole area are carried out according to the identification results.Finally,the diagenetic facies distribution range and variation characteristics of Baikouquan formation in L area are obtained by comprehensive analysis and evaluation of diagenetic facies in combination with diagenetic environment.Generally speaking,the characteristics of diagenetic facies change of Baikouquan formation reservoir in L area are mainly controlled by sea level rise and fall.In the first stage and the second sand formation of the second stage in Baikouquan formation,the sea-level decline was observed.In the eastern part of the study area,Intragranular dissolution strong compaction phase is deposited in the fan delta plain environment and the relatively small Strong compacting phase reservoir is deposited in the eastern part of the study area.In the second sand formation of the second stage in Baikouquan formation,sea level began to rise rapidly,stable development of fan delta front environment in the central and eastern part of the study area by the weakly corroded medium compacted phase,with good physical properties developed in the near-water environment in the western region.In the third stage of Baikouquan formation.The distribution of diagenetic facies extends to most areas of the study area.In the western region developed in the near-water environment fan delta front far sand bar,the shallow lake and its beach and dam environment of the micro compacted residual pore phase range expanded.