Research On Controlling Gas In Tight Sand Reservoir Of Upper Paleozoic In The North Of Ordos Basin

On the basis of previous studies and guided by the theory of sedimentology, reservoirgeology, reservoir characteristics of He8and Shan1, the main gas layer of Upper PaleozoicErathem in western ordos basin, have been comprehensively analyzed and researched in thispaper and beyond that, the main factors of reservoirs’ physical properties and gas controlability by the observation and analysis of core, thin sections, physical properties, gradinganalysis, cathodoluminescence, scanning electron microscopy (SEM) and testing datacombined with the permeability logging and core analysis data.In the study area, He8and Shan1, lithic quartz sandstone develops predominately; quartzsandstone takes the second place and lithic sandstone lies minimum proportion. Interstitialsubstance of the sandstone are mainly argillaceous mixed base, kaolinite, calcite andsiliceous iron with secondary solution pore and kaolinite intercrystal pore as their main poretypes. Reservoirs in the study area belong to dense reservoirs with low porosity and lowpermeability.According to reservoir characteristics, four types of reservoirs can be classified in the studyarea:Ⅰreservoir is favorable reservoir andⅡreservoir is comparatively favorable reservoir andⅢ reservoir－the medium reservoir, Ⅳ reservoir－the poor reservoir. This research suggeststhat high quality reservoirs are mainly distributed in the sand body with good physicalproperty in channel and distributary channel. Natural gas always accumulates in betterreservoir physical property and weak heterogeneity area with lithic dissolved pore andintergranular hole developed, and where gas well located in the sand body thickness greaterthan5m, but it has no apparent effects on the control of the gas concentration.