Researches About Microscopic Features And Comprehensive Evaluation Of Chang 8 Reservoir Of Banqiao-Heshui Area In Ordos Basin

Banqiang-Heshui area belongs to typical low permeability,ultra-low permeability reservoir.The recovery efficiency is low and the contradictions are obvious during the development process. Mainly reflects in, there exists big differences of reservoir characteristics between the small different layers,edimentary facies and diagenesis, the pore structure,ercolation characteristics and microscopic heterogeneity are complicated and diverse.The distribution of high-quality reservoir is hard to find. To deal with these issues,this paper mainly studys the sedimentary, diagenesis and diagenetic facies of Chang 8 reservoir;Integrated use of multi-angle, multi-parameter, multi-method, variety of experiments methods to characterize microscopic reservoir porosity and flow characteristics; Considering the macroscopic and microscopic characteristics of reservoir to evaluate reservoir.The main achievements are:(1)Chang 8 reservoir belongs to delta front facies, and underwater distributary channel,distributary bay,estuary dam sedimentary microfacies occurred in.Chang 8 reservoirs is constructed flat and stable overall,only developmentally some small nose uplift structure in the west-dipping monoclinic, oil reservoir thickness is relatively stable and better. Chang 8 reservoirs average porosity is 9.13%;Average permeability is 0.53×10-3?m2.(2)The diagenesis of Chang 8 reservoir are mainly mechanical compaction,pressure solution,cementation,dissolution and metasomatism et al. Diagenesis times mainly in the late diagenetic stage A, part into the early diagenetic stage B.Main diagenetic facies of reservoir are:chlorite cementation phase,carbonate cementation phase;hydromica cementation phase;feldspar dissolution-residual intergranular hole phase,chlorite cementation-residual intergranular hole phase. There are big differences between the diagenetic facies.(3)Chang 8 reservoir main pore type is intergranular pore, followed by feldspar solution openings, debris dissolution pore, intercrystalline pores and microcracks; main type throat is sheet,curved sheet throats,followed by pore shrinked throat; a bit necking throat, micro-fine throat. Complicated pore structure influences reservoir seepage and reservoir quality.(4)According to water driving oil test, the main sand displacement mode of Chang 8 reservoir is average waterway displacement type,flow around finger displacement type, net displacement type. The fluid flow effects are mainly affected by microscopic pore structure characteristics, microscopic heterogeneity, different experimental conditions and many other factors.(5)Utilization of the basic features of reservoir, sedimentary fades, diagenetic facies classification, taking microscopic pores,flow characteristics and other parameters into a comprehensive analysis,the reservoir evaluation is classified into four categories,from ? class to ? class, the reservoir quality deteriorates successively, the most widely distribution is ? class.