Logging Reservoir Evaluation Of Chang 6 Oil-bearing Formation In Ansai Pingqiao Oil Region

Ansai Pingqiao oil region locates in the mid-eastern part of Shanbei slope in Ordos basin. Recently, with the further exploration and exploitation of oil, abundant of resource of Chang 6 reservior of Yanchang formation were proved. The research result indicates that Chang 6 reservoir in Pingqiao region mainly developed lithologic encirclement deposit with development of sand body and weak physical properties mainly of low porosity and permeability, meanwhile, there are large area irregularity distribution of low resistivity reservoir. Therefore, the paper makes correct evaluation to reservoir via logging measures and constitutes a suit of logging evaluation standard and interpretation method suitable for targeted reservoir to provide evidence for sustainable development of oil field.The paper used data of logging, cores, oil testing, microscope image analysis and SEM, systematically analyzed lithology, physical property, oiliness of reservoir in the region and the logging response characteristic of low resistivity reservoir, on the basic of the research of primary geological features of Chang 6 reservoir in Pingqiao region , made a particular study on the causes and identification of low resistivity zone.The lithology of Chang 6 reservoir in Pingqiao region are mainly of grey green fine grained arkose, diagenesis had more infection to reservoir features. The reservoir have weak physical property, average property is 10.8%, average permeability is 0.29-0.83×10-3μm2 showing this is typical low property and permeability reservoir.Via research of cores, logging, physical properties and means of production, the paper systematically analyzed four properties relations characteristic of target reservoir, made clear the relationship of measured data and logging data, established interpretation of physical property chart and finally got the logging response characteristic of variety reservoirs of Chang 6 formation.Via analysis of abundant core research data and oil production commissioning information and combining with comprehensive analysis of logging data, the paper divided causes and types of low resistivity reservoir in Pingqiao region into four types: (1) Relatively low resistivity oil layers with complex reservoir pore structure; (2) Relatively low resistivity oil layers caused by higher shale content; (3) Relatively low resistivity oil layers caused by higher formation water salinity and poor oil and gas differentiation; (4) Relatively low resistivity manifestation after comparatively high oil bearing of radioactive sand.