Study On Pore Structure Character And Microcosmic Remaining Oil Distribution Of Low Permeability Glutenite Reservoirs

Currently,low permeability reservoirs are the principal part of new capacity construction and oil production,which contains a lot of sand conglomerate reservoirs.Long-term exploration and development indicates that microcosmic remaining oil distribution in low permeability reservoirs is closely related to the pore structure and the differences of pore structure may often determine the production and development of reservoirs in the macro effect.Therefore on the basis of further study of the characteristics of pore structure,micro analysis of remaining oil distribution has an important significance in effective and economical development of low permeability glutenite reservoirs.The paper takes the case of low permeability glutenite reservoirs of Mabei and its peripheral area in Baikouquan formation.Taking advantage of casting thin sections and scanning electron microcosmic technology,the paper analyzes types,size,distribution and mutual relations of pore and throat,then analyzes various characteristic parameters of pore structure and capillary pressure curve according to the conventional mercury injection data.Ultimately to determine the porosity,permeability,displacement pressure,maximum pore diameter,average pore throat radius and sorting coefficient as the basis of classification,and combined with the characteristics of the pore type and the characteristics of capillary pressure curve,the paper divides low permeability sandstone reservoir into three types:type I,II and III.Among the three types of pore structure,type I is rare,while type II and type III develop more.By choosing the type II and type III pore structure reservoir specimens,columnar core flooding experiment is conducted and combined with the nuclear magnetic resonance test and oil fluorescence analysis technology.Then the paper summarizes the microcosmic remaining oil distribution characteristics of type II and type III pore structure.Experimental results show that there is basically no remaining oil enrichment in large pores of II type pore structure,the vast majority of the remaining oil as types of pore half-filling and dispersed droplets distribute in small pore interval,and the distribution of remaining oil in micro pore network mostly is "zone of dead oil",and II type pore structure develops pore-throat filling and pore half filling type of remaining oil.In addition,there are a few crack stranded remaining oil and a relatively high proportion of throat stranded and corner remaining oil in II type pore structure;the remaining oil in type III pore structure mainly distributed in the small pore interval,but the medium-large pore interval remained some pore and throat filling type and hole half-filling residual oil,and relative to the II type,the content of throat stranded type,corner and dispersed droplets remaining oil is low.