Tight Sandstone Pore Structure Characteristics Based On The Resistivity Logging Data

The complicated pore structure is the basical reason of difficulty to logging interpretation, and the difficulty to exploitation. At present the researches on pore structure of reservoir depend on the indoor experiment which usually is limited by the core. So currently, it is needed to be resolved urgently how to acquire the pore structure of reservoir quickly and accurately.In this article, after investigating much information, the competent sandstone electric conductivity model was deduced, based on the capillary theory of pore structure and the electric resistance network model. Based on the competent sandstone electric conductivity model, the formal was acquired which can be used to compute the pore structure parameter including throat radius, capillary tortuosity and pore structure exponent by making use of the resistivity logging data. By electricity experiment of the competent sandstone, the resistance with different water saturations can be acquired, thus the pore structure parameter can be computed; Contrast to the rock capillary pressure curve and -the thin-section analysis, the result is good. The pore structure exponent is the comprehensive performance of the throat radius and capillary tortuousity, and can be used to reflect the pore structure of reservoir.By the use of the component sandstone electric conductivity model, the effect of the pore structure characteristic parameter to cementation exponent m and saturation exponent n in the Archie formula were studied. It can be found the cementation exponent m mainly reflects the pore space size and its sizes distribution. The m is bigger, the pore space is bigger, the throat is simpler, and the reservoir is better. The saturation exponent n reflects the tortuousity of pore structure. The n is bigger, the throat is more complicated, the reservoir is worse. The electricity experiment and the capillary pressure curve analysis also prove this conclusion.The pore structure exponent P and the cementation exponent m, the saturation exponent n of competent sandstone are all affected by the pore structure characteristic. P m n can be used to divide the type of competent sandstone.From theories and experiments, it has very great advantages to research the competent sandstone pore structure by using resistivity logging data. Finally, it has good result by this method to study the pore structure of competent sandstone in an oilfield.