Due to complex structures and strong heterogeneity of pores,the cementation exponent ( m )is no longer a constant,thus itis difficult to quantificationally evaluate the saturation of porous carbonate reservoirs.In order to solve this problem,a high-precision m model was build.Based on lithologies of loose,medium and tight sandstones,conglomerate,tuff,breccia,basalt,andesite,daciteand rhyolite,firstly,to analyse the impact on the saturation caused by changes in m and the saturation index (n),it can be foundthat the change of m affects the saturation largely.Secondly,on the basis of the Maxwell equation,a strong linear correlation be-tween m and the difference in the effective porosity and conductive porosity was discovered.This correlation was found changeableand behaving in a linear,exponential,power or polynomial format,so a general expression between m and the effective porosity wasdeduced.A high-precision m model of Well AG-3 in a certain oilfield of Iraq was applied to dealing with the dolomite and limestonereservoirs in Well AG-3,respectively.The results were compared with those of core analysis,indicating that the high-precision m model had improved the calculation accuracy of the saturation of porous carbonate reservoirs and laid a theoretical and practical foun-dation for the quantitative evaluation of the saturation of complex porous reservoirs.
high precision m modelMaxwell equationArchie formulacarbonatesaturation
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