Research On Multi-scale Structure Characterization And Validity Evaluation Of Continental Glutenite Bodies

With the research deepening of exploration and development of unconventional oil and gas,more and more attention has been paid to the sandy conglomerate reservoir in the steep slope zone of continental faulted basin.However,the sandy conglomerate reservoirs are characterized by diverse lithology types.The rock structure in the imaging logging,cores,thin sections and scanning electron microscopy(SEM),that is in different scales,is characterized by strong heterogeneity.It is caused the pore structure influenced by rock structure and closely related to reservoir effectiveness,is also showing a strong heterogeneity.Therefore,the multi-scale rock structure characterization study becomes the primary problem of effectiveness evaluation of reservoir.The sandy conglomerates developed in the northern steep zone of Dongying depression has excellent reservoir forming conditions,rich oil and gas resources and great exploration potential.In this paper,the sandy conglomerates of the upper sub-member of the four member of the Eocene Shahejie Formation(Es4U)in the area Y,the northern steep zone of Dongying depression are taken as the object of study,with an integrated approaches of the high resolution core scanning image,core description,casting thin-sections,scanning electron microscopy(SEM),x-ray diffraction,physical properties,oil test,mercury injection,nuclear magnetic resonance and conventional logging(including electrical imaging)data,etc.Systematically carried out deep research on the multi-scale rock structure characterization of sandy conglomerates,has been clear about the rock structure is one of the important factors affecting sandy conglomerate reservoir effectiveness.On this basis,the lower limit and the identification methods of the effective reservoir and reservoir parameter calculation are studied.Mading the following several aspects of progress and understanding:(1)Starting from rock type,rock structure and mineral composition,combining macro(imaging logging,the high resolution core scanning images and core photos)and micro(thin section and SEM)scale,the rock fabric characteristics of the sandy conglomerates are analyzed,and divided into two types,which are uniform and uneven.On this basis,the two kinds of rock structure characteristics at different scales are summarized.(2)The characteristics of mercury injection curve are analyzed,and the pore structure types of sandy conglomerates are divided into three major categories and four minor categories.And the characteristics of each pore type are analyzed by making full use of physical properties,nuclear magnetic resonance and other data.In addition,the relationships between rock fabric,pore structure and reservoir effectiveness of sandy conglomerates are analyzed.The results show that the more uniform the sandy conglomerate rock structure is,the less the interstitial material content is,the better pore structure is,and the more likely it is to become an effective reservoir.(3)Taking rock structure as bridge,a variety of experimental testing,physical properties and logging data are used to select effective reservoir samples,and the characteristics and correlation of four-properties of effective reservoir samples are analyzed.The image models of cores,thin sections(or SEM)and imaging loggings and the lower limit of four-properties are established,which laid a certain foundation for the identification and evaluation of effective reservoirs.(4)The lower limit of physical property of effective reservoir is established by using core oil-bearing production method,direct and inverse statistical method and oil-testing method.Finally,it is clear that the sandy conglomerates effective reservoir of the lower limit of physical property(Por?5.4%,Perm?0.38mD)and has uniform rock structure,and good sorting pebbly sandstone,gravel sandstone or fine conglomerate.(5)Based on core testings,physical properties and rock electric experimental data,the multi-parameter regression method is used to establish the porosity model of the sandy conglomerate by pore strcuture types,and improves the calculation precision.At the same time,based on the physical model of the two rock textures,calculate the permeability of conglomerate by rock structure.And the saturation calculation model of rock types is established by Archie formula.It provides a reliable basis for the evaluation of reservoir effectiveness of the sandy conglomerate.The series of methods established in this paper have effectively improved the accuracy of effective reservoir logging evaluation of the sandy conglomerate.The combination of rock fabric study and logging method is very helpful to use geological and logging information to divide effective reservoir and evaluate reservoir effectiveness and "sweet spot" prediction.