RESEARCH AND APPLICATION OF PETROPHYSICAL FACIES IN LOW PERMEABILITY RESERVOIRS—A CASE STUDY OF CHANG 6 RESERVOIR OF JIYUAN OILFIELD IN ORDOS BASIN

At this stage, China's key development targets are low-permeability and ultra-low permeability reservoirs which are poor in physical properties, strongly modified by later diagenesis, and complex in microscopic pore structure. Therefore, a comprehensive study of such reservoirs is of great significance. Petrophysical facies, which has been widely developed in recent years, is a research method for the effects of comprehensive sedimentation, diagenesis and later modification on reservoir performance. Its advantage is that it avoids the use of a single means to study the reservoir.In this paper, logging data, drilling data and core flake are used to study the sedimentary facies, diagenetic facies and fracture facies of the Chang 6 reservoir in the Jiyuan Oilfield, Ordos Basin. On this basis, the types of petrophysical facies in the study area are determined by superimposing the above three. Using the experimental data such as RQI value, high pressure mercury injection, nuclear magnetic resonance, and real sandstone simulated displacement experiment, the microscopic pore structure characteristics of the petrophysical facies are evaluated. Finally, the favorable pore infiltration development zone is predicted based on the actual production data. The research indicates that Sedimentary microfacies in the study area include subaqueous distributary channels and subaqueous diversion bays; Diagenesis is divided into constructive and destructive; Tectonic effect is reflected as locally developed and high angle oblique crack. Combining the above three, the three petrophysical facies types are summarized and the corresponding RQI values of each petrophysical facies are calculated, so that the single well is evaluated longitudinally. Finally, two small layers of the Chang 6 reservoir are taken as research objects, and the prediction of distribution of favorable pore infiltration zone in the study area is completed by dividing the plane distribution of the petrophysical facies and determining the distribution of the favorable petrophysical facies (PF1).