NUMERICAL SIMULATION AND CHARACTERISTICS ANALYSIS OF DUAL LATEROLOG IN CAVERNOUS RESERVOIRS ON THE BASIS OF 3D‐FEM

Cavernous carbonate formations are characterized by strong heterogeneity, which results in the complex electric logging responses and the difficulty in the logging identification and evaluation. Numerical simulation of electric logging tools is helpful to figure out the logging response characteristics in these formations and could provide theoretical support for cave recognition and evaluation. In this paper, based on three dimensional finite element methods, a local refinement technique is adopted for the accurate discretization and simulation of complex sphere caves. Then, the response characteristics and sensitivity of dual laterolog to caves around and penetrated by wellbore are analyzed, finally the differences of sensitive scope between deep and shallow laterolog are studied. The results show that the dual laterolog response decreases significantly when cave exists. Affected by cave boundary and the investigation depth of dual laterolog tool, the logging response for caves penetrated by wellbore is very complicated, however it exhibits parabolic-like characteristic for caves around wellbore. Compared with caves around wellbore, the dual laterolog is much more sensitive to caves penetrated by wellbore. For caves around wellbore, the maximum sensitive distance for deep and shallow laterolog between the cave boundary and well wall is 0.5 m and 0.3 m, respectively.