A Two-step Method for Log Correction and Its Application Effect Analysis

Sonic and density logging curves of deep zones of interest in Xihu Sag commonly appear serious distortion due to environmental conditions such as borehole and drilling fluid and mudstone collapse. The logging quality is not good enough in the wells in the early of 1990s. In this study, a two-step method was proposed for curve correction. Firstly, the empirical formulas (Faust, Ikon, Greenberg-Castagna) were used to correct the Vp, Vs and density curves distorted by borehole washouts. Secondly, Xu-White rock physical modeling method was used to estimate the curves where Vs log may not be observed or apparently bad data need to be edited. After testing, the key correction parameters were finally determined suitable for the study area. After two-step correction, the edited logging data were more reliable. The effectiveness of the method was demonstrated in the subsequent seismic inversion, and the method can be used in other future exploratory areas in Xihu Sag.