A novel calculation model, characteristics and applications of Archie's cementation exponent in dual porosity reservoirs with intersecting dual fractures

Fractured rock samples are difficult to use for ground conductive experiments, and there are few related simulation researches of Archie's cementation exponent in the reservoirs with intersecting dual fractures. In order to obtain the cementation index for saturation evaluation when no experiments and methods are available in such reservoirs, we focus on the researches of the cementation exponents in these reservoirs. Based on the Maxwell-Garnett mixing rule and the morphological characteristics of fractures in reservoirs, the method for obtaining the cementation exponents in reservoirs with parallel fractures at any inclination angle are first reviewed. secondly, the rock model of the dual porosity reservoirs with two intersecting fractures is constructed. The rock model is divided into four equal parts through equivalent processing, and the respective cementation exponents of the four parts can be calculated. Based on the series and parallel connection of Ohm's law, a novel calculation model of the overall cementation exponent of the rock model is established. Thirdly, using the novel model, the characteristics of cementation exponent of the rock model affected by different fracture dips, fracture porosities and included angles between the two fractures are calculated. In terms of detail and overall, the trend curves of these characteristics exhibit different nonlinear characteristics. The combined effect of the dip angles of the dual fractures, the included angle between them, the porosities of them and the porosity of matrix makes the cementation exponent characteristics more complex than that of single fracture or parallel fractures. Fourthly, the novel calculation model is used to evaluate the cementation exponent and fluid saturation of the two wells in the Chang 8 Formation in the southwest Ordos Basin, China, and the application results can demonstrate the reliability and availability of the novel model of cementation exponent in the reservoirs with intersecting dual fractures. At last, the application effect, influencing factors and applicable conditions of the novel calculation model of cementation exponent are discussed in detail. These applications and analyses show that it can provide an alternative solution for cementation exponent estimations in such fractured reservoirs, especially when ex-periments are not available.