The Influencing Factors and Calculation Methods of Rock Electrical Parameters of Carbonate Reservoirs

Abstract

The pore structure of carbonate reservoir is much more complex than that of clastic reservoir, and its rock electrical parameters m and n vary widely, which is difficult to obtain accurately, and the fixed rock electrical parameters are used to calculate the saturation of the reservoir, which cannot meet the requirements of fine evaluation. In order to solve this problem, based on the detailed analysis of conventional physical properties, cast thin sections, mercury intrusion curves and other data and the comparison of microscopic characteristics, the necessity of reservoir sample classification research is obtained, combined with the characteristics of core photos, the reservoir is divided into three types according to the pore space: matrix pores, pores-fractures, and pores-pores, and the reservoir types represented by different positions in the porosity-permeability relationship diagram and rock-electricity relationship diagram are summarized, and the differences in microscopic pore characteristics and percolation characteristics of sample points of different reservoir types are obtained. On the basis of the understanding of the conductive characteristics of various pore types, the conductive characteristics of various pore types are analyzed by using the three-pore conductivity model of carbonate reservoirs, and the influence of pore characteristics and fracture inclination changes on the m value of cementation index is analyzed, which confirmed that the m value is closely related to the pore structure of the reservoir. According to the reservoir classification of the sample points, the variation range, influencing factors and variation laws of rock and electrical parameters of various reservoirs are obtained, and the m value of each type of reservoir is obtained by fitting, and the adjustment method of the m value is given. In the process of analyzing the saturation index n, it is realized that the n value has nothing to do with the pore structure, but is closely related to the wetting characteristics of the reservoir, and the estimation method of the n value is obtained. This method lays a foundation of the log interpretation and fine evaluation of saturation for carbonate reservoirs.

Keywords

• carbonate reservoir
• rock electrical parameter
• influencing factor
• calculation method
• cementation index
• saturation