About This Item
Share This Item
Well logs serve many purposes. One part of log usage is directed toward evaluation of formation parameters: porosity, permeability, water saturation, and water salinity. Another, and perhaps the most extensive, part of log usage is applied to exploratory prospect or field-development studies related to correlation, and lithologic, structural, and stratigraphic definition. A survey of analytical practices supporting these studies finds that new logging methods and techniques are providing more direct and quantitative approaches to supplement subjective experience-based practices previously available.
The non-electrical logging methods, particularly the nuclear magnetic, density, and acoustic surveys, are affording additional opportunities for correlation and lithologic analysis. Digital dipmeter logging and oriented sidewall coring appear to be excellent sources for detailed data necessary for locating faults, relating a well's structural position to the prospect, or studying stratigraphic-structural inter-relationships. Computer processing is a key part of applied practices to exploit these new methods. Uniform log preparation for correlation and stratigraphic studies, dipmeter processing for structural analysis, and log combination for lithologic determination will be possible by computer processing of digital log data.
Many factors together form a log. The logging milieu contains a geologic model with numerous physical, chemical, and electrical properties, a bore-hole which produces effects obscuring geological information, and sophisticated tools which, together with variances in their operating mode, superimpose non-geological character on the log. Although some newer logging methods respond to fewer formation variables and are freer of bore-hole effects than older systems, unfortunately others are leaving their non-geologic fingerprints on the formation patterns. These factors combine to make technical understanding of the theory and practice of modern logging systems a necessary prerequisite to finding best uses and appreciating limitations of geological analysis of well logs.
End_of_Article - Last_Page 1091------------