Abstract: Evaluation on complex hydrocarbon-bearing shaly sand reservoirs is a difficult problem in logging technology. Since conductance mechanism in complex hydrocarbon-bearing reservoirs is different from that in common hydrocarbon-bearing reservoirs, a new conducting theory should be proposed to describe the conducting mechanism for complex hydrocarbon-bearing reservoirs. The theoretical and experimental comparison of three effective medium resistivity models in laminated and dispersed shaly sands is addressed in detail. Theoretical analysis shows that asymmetrical effective medium resistivity model comes from HB equation and parallel conductance theory, and symmetrical effective medium resistivity model is established from symmetrical theory of resistivity interpretation and parallel conductance theory, while effective medium pore combination resistivity model is derived from conductivity integration equation of mixed medium. Also symmetrical effective medium resistivity model can be applied to the multi-continuous formation with more than two continuous components; asymmetrical resistivity model and pore combination resistivity model can be used only in the formation of a continuous component of water. The asymmetrical effective medium resistivity model and effective medium pore combination resistivity model can be simplified to Archie equation, and symmetrical effective medium resistivity model can be simplified to an equation similar to Archie equation in clean sand with non-conducting matrix grains. One set data from synthetic core sample of dispersed and laminated shaly sands, two set data of the rock sample of dispersed shaly sands, and one set data of artificial sample with conducting matrix grains show that the three models can be applied to dispersed and laminated shaly sands, and their application accuracy is about the same.

Key words: laminated and dispersed shaly sand, HB equation, symmetrical conductance theory, conductivity integration equation, resistivity model