The Borehole Environment: Known and Unknown


Hamilton M. Johnson, Tulane University

3rd Formation Evaluation Symposium of the
Canadian Well Logging Society in Calgary, May 6-8, 1970



Complex quantitative analyses of the various borehole logs are increasing in use and usefulness daily but real knowledge of the physical and chemical environs of the place of measurement, i.e., the borehole and formations immediately adjacent to it, has not grown commensurately. The theory of past years (9), including such physical parameters as the mudcake, a definite flushed-zone, a varying invaded zone, a sometimes present "low zone" and the virgin formation … and their relative electrical properties … is fundamental and has proved to be of great value. However, all of this represents a static condition which holds only momentarily; in actuality, the borehole environment must be considered as a dynamic state.