Three-water pore combination conductive model for low porosity and permeability shaly sand and its application to offshore oilfields

Since the reservoirs have low porosity and low permeability,complex pore structure,high capillary bound water,new conductance theory will be used to describe conductivity for the reservoirs.A three-water pore combination conductivity model is proposed for low porosity and low permeability shaly sand reservoirs based on conductivity difference equation and three-water conductance theory.The effect of cementation exponent and saturation exponent on rock conductivity predicted by the model is investigated by only changing one of them,and the result shows that resistivity index increases as exponent of clay bound water or saturation exponent increases,decrease as exponent of free water or exponent of capillary bound water increases.It shows that this model can describe conductance law in offshore low porous and permeable shaly sand reservoirs by comparing measured conductivity with calculated conductivity under reservoir temperature and pressure.Log interpretation with calculated cementation exponent,saturation exponent and capillary bound water porosity,clay bound water porosity also shows that this model is quantitatively applicable to offshore low porous and permeable shaly sand reservoirs.