A method for petrophysical classification of low porosity and low permeability reservoirs

In order to establish a rock electrical parameters model under the condition that pore structures and petrophysical characteristics are identical,it is necessary to classify reservoirs according to petrophysical characteristics.The disparity of two macroscopic parameters,flow zone index and reservoir quality index,is contrasted by analyzing actual data,and an effective method of classifying reservoirs is proposed based on petrophysical parameters and microscopic pore structures.The mercury injection experimental data of sixty rock samples of typical low porosity and low permeability reservoirs in the Daqingzijing(Songliao basin) and Jiyuan(Ordos basin) areas are classified based on these two indexes.The result shows that the reservoir classification by reservoir quality index is more reasonable.The theoretical analysis also demonstrates that reservoir quality index is the monotone function of pore structure while flow zone index is not.Compared with flow zone index,reservoir quality index can reflect the variation of reservoir pore structures and petrophysical properties more exactly.